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  • 1.
    Andersson, Petter
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Hambäck, Peter A.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Plant patch structure influences plant fitness via antagonistic and mutualistic interactions but in different directions2016In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 180, no 4, p. 1175-1182Article in journal (Refereed)
    Abstract [en]

    Plant patch structure and environmental context can influence the outcome of antagonistic and mutualistic plant-insect interactions, leading to spatially variable fitness effects for plants. We investigated the effects of herbivory and pollen limitation on plant reproductive performance in 28 patches of the self-compatible perennial herb Scrophularia nodosa and assessed how such effects varied with plant patch size, plant density and tree cover. Both antagonistic and mutualistic interactions had strong effects on plant reproductive performance. Leaf feeding from herbivores reduced both fruit production and seed germination, and leaf herbivory increased with plant patch size. Experimentally hand-pollinated flowers produced more seeds than open-pollinated flowers, and pollen limitation was more severe in patches with fewer plants. Our study on S. nodosa is one of few which documents that plant patch structure influences the outcome of both antagonistic and mutualistic plant-insect interactions. The results thus provide an example of how variation in plant patch structure and environmental factors can lead to spatially variable fitness effects from mutualistic and antagonistic interactions.

  • 2.
    Arnell, Matilda
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Eriksson, Ove
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Local distribution patterns of fleshy-fruited woody plants - testing the orchard hypothesis2021In: Ecography, ISSN 0906-7590, E-ISSN 1600-0587, Vol. 44, no 3, p. 481-492Article in journal (Refereed)
    Abstract [en]

    Plant distribution patterns are influenced by many different factors. We examined mechanisms behind local distribution patterns of boreo-nemoral fleshy-fruited woody plants with seed dispersal mainly mediated by birds. It has been suggested that guilds of these plants develop 'orchards', i.e. locally aggregated occurrences composed of several species. We analysed spatially explicit occurrence data of different life stages of a local guild of fleshy-fruited woody plants in south-eastern Sweden, and conducted a seedling recruitment experiment for a subset of ten species. Spatial point pattern analyses showed that the guild of fleshy-fruited species was aggregated at small (< 10 m) spatial scales. Saplings were more common under canopies of heterospecific reproductive individuals than expected by chance. These results show that the local guild of fleshy-fruited species is distributed as orchards, i.e. clusters consisting of individuals of different species and life stages. We found no evidence of negative distance dependence between saplings and reproductive conspecific individuals. Results from the recruitment experiment suggest that recruitment is seed limited and generally low among the studied species. At the site-scale (circular areas with 50 m radius), there was no difference in seedling recruitment between sites with and without reproductive conspecific individuals for most species included in the recruitment experiment. This further suggests that the aggregated patterns found are not simply a result of spatial concordance in suitable habitats across life stages. Instead, we suggest that the sheer number of seeds from species in the guild deposited under the crowns of fruit bearing individuals is the main mechanism behind the build-up of orchards. Although further studies are needed to fully disentangle the processes underlying the observed patterns of local diversity, we argue that describing patterns and contrasting them to the predictions of ecologically relevant hypotheses is a useful first step.

  • 3.
    Arnell, Matilda
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Eriksson, Ove
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Reproductive success, fruit removal and local distribution patterns in the early-flowering shrub Daphne mezereum2023In: Nordic Journal of Botany, ISSN 0107-055X, E-ISSN 1756-1051, no 10, article id e03871Article in journal (Refereed)
    Abstract [en]

    In insect-pollinated, bird-dispersed plants, both investment in reproduction and reproductive success involve interactions between plants and their pollinators and dispersers. The outcome of these plant–animal interactions may be affected by the number of flowers and fruits, as well as by the plants' local environment and by spatial associations among plants. In this study we mapped the spatial distribution of individuals in a population of the early flowering, fleshy-fruited shrub Daphne mezereum, in a forest in boreo-nemoral Sweden. For all mapped individuals we collected data on numbers of flowers and fruits and fruit removal, for three consecutive years. We analysed spatial associations among individuals, and the effects on reproductive performance and fruit removal of plant height, numbers of flowers and fruits, distance to forest edge, and neighbouring flower and fruit density. Our results show that the density of D. mezereum increases with increasing proximity to forest edge. The number of flowers produced, as well as fruit set and fruit removal, show the same positive relationship with increasing proximity to forest edges. We further show that individuals are aggregated up to distances of about 10 m. The flower production of neighbouring conspecific individuals within 10 m is negatively related to fruit set whereas the fruit production of neighbours is positively related to fruit removal. Our main conclusion is that the spatial distribution of D. mezereum affects reproductive success and fruit removal, which in turn has the potential to feed back to the spatial distribution pattern. Combining studies of reproduction with spatial analyses is important to advance our understanding of the dynamics of plant populations. 

  • 4.
    Arvanitis, Leena
    et al.
    Stockholm University, Faculty of Science, Department of Botany. Växtekologi.
    Wiklund, Christer
    Department of Zoology. Ekologi.
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Botany. Växtekologi.
    Plant ploidy level influences selection by butterfly seed predators2008In: Oikos, Vol. 117, p. 1020-1025Article in journal (Refereed)
    Abstract [en]

    Polyploidization is a common route to plant diversification. Polyploids often differ from their progenitors in size, flower number, flower size and flowering phenology. Such differences may translate into differences in the intensity of interactions with animals. Here we investigated the impact of the ploidy-related differences in tetraploids and octoploids of the perennial herb Cardamine pratensis on pre-dispersal seed predation by the butterfly Anthocharis cardamines. The probability of escaping attack was lower for octoploids than for tetraploids, even after accounting for the fact that octoploids were larger and had fewer flowers than tetraploids. Flower shoot size was correlated with probability of attack in tetraploids but not in octoploids. Differences in plant traits associated with polyploidization can alter interactions with animals, and animal-mediated differences in trait selection between ploidy types can contribute to their further divergence.

  • 5. Bisang,
    et al.
    Ehrlén,
    Stockholm University, Faculty of Science, Department of Botany.
    Hedenäs,
    Are annual growth intervals independent units in the moss Pseudocalligeron trifarium (Amblystegiaceae)2008In: BryologistArticle in journal (Refereed)
  • 6. Bisang, Irene
    et al.
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Hedenäs, Lars
    Life-history characteristics and historical factors are important to explain regional variation in reproductive traits and genetic diversity in perennial mosses2023In: Annals of Botany, ISSN 0305-7364, E-ISSN 1095-8290, Vol. 132, no 1, p. 29-42Article in journal (Refereed)
    Abstract [en]

    Background and Aims Plants have evolved an unrivalled diversity of reproductive strategies, including variation in the degree of sexual vs. clonal reproduction. This variation has important effects on the dynamics and genetic structure of populations. We examined the association between large-scale variation in reproductive patterns and intraspecific genetic diversity in two moss species where sex is manifested in the dominant haploid generation and sex expression is irregular. We predicted that in regions with more frequent realized sexual reproduction, populations should display less skewed sex ratios, should more often express sex and should have higher genetic diversity than in regions with largely clonal reproduction.

    Methods We assessed reproductive status and phenotypic sex in the dioicous long-lived Drepanocladus trifarius and D. turgescens, in 248 and 438 samples across two regions in Scandinavia with frequent or rare realized sexual reproduction, respectively. In subsets of the samples, we analysed genetic diversity using nuclear and plastid sequence information and identified sex with a sex-specific molecular marker in non-reproductive samples.

    Key Results Contrary to our predictions, sex ratios did not differ between regions; genetic diversity did not differ in D. trifarius and it was higher in the region with rare sexual reproduction in D. turgescens. Supporting our predictions, relatively more samples expressed sex in D. trifarius in the region with frequent sexual reproduction. Overall, samples were mostly female. The degree of sex expression and genetic diversity differed between sexes.

    Conclusions Sex expression levels, regional sex ratios and genetic diversity were not directly associated with the regional frequency of realized sexual reproduction, and relationships and variation patterns differed between species. We conclude that a combination of species-specific life histories, such as longevity, overall degree of successful sexual reproduction and recruitment, and historical factors are important to explain this variation. Our data on haploid-dominated plants significantly complement plant reproductive biology.

  • 7. Bisang, Irene
    et al.
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Hedenäs, Lars
    Sex expression and genotypic sex ratio vary with region and environment in the wetland moss Drepanocladus lycopodioides2020In: Botanical journal of the Linnean Society, ISSN 0024-4074, E-ISSN 1095-8339, Vol. 192, no 2, p. 421-434Article in journal (Refereed)
    Abstract [en]

    Sex ratio variation is common among organisms with separate sexes. In bryophytes, sex chromosome segregation at meiosis suggests a balanced progeny sex ratio. However, most bryophyte populations exhibit female-biased phenotypic sex ratios based on the presence of reproductive structures on gametophytes. Many bryophyte populations do not form sexual organs, and genotypic sex ratio variation in such populations is mostly unknown. We tested sex expression, and phenotypic and genotypic sex ratios against environmental parameters in natural populations of the unisexual wetland moss Drepanocladus lycopodiodes at 11 sites in each of three regions in southern Sweden. We identified sex in 660 individual ramets, based on sexual structures, when present, or with a specifically designed molecular marker, when absent. All regions exhibited a female bias in phenotypic and genotypic sex ratios. Sex ratio biases and sex expression differed between regions. Sex ratios were less female-biased in larger patches. Wetter patches exhibited a stronger female bias in genotypic sex ratio and lower sex expression. This is the first evidence of environmental effects on genotypic sex ratio in mosses. A higher frequency of females in wet patches could be due to higher female resource demands for sporophyte production or higher male sensitivity to wetness. A higher incidence of females than males in moister sites aligns with female flowering plants, but differs from reproductive bryophytes in drier environments. Taken together with previous results, our data indicate that sex ratio variation and its drivers differ among species, their life histories and environments.

  • 8. Bisang, Irene
    et al.
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Korpelainen, Helena
    Hedenas, Lars
    No evidence of sexual niche partitioning in a dioecious moss with rare sexual reproduction2015In: Annals of Botany, ISSN 0305-7364, E-ISSN 1095-8290, Vol. 116, no 5, p. 771-779Article in journal (Refereed)
    Abstract [en]

    Background and Aims Roughly half of the species of bryophytes have separate sexes (dioecious) and half are hermaphroditic (monoecious). This variation has major consequences for the ecology and evolution of the different species. In some sexually reproducing dioecious bryophytes, sex ratio has been shown to vary with environmental conditions. This study focuses on the dioecious wetland moss Drepanocladus trifarius, which rarely produces sexual branches or sporophytes and lacks apparent secondary sex characteristics, and examines whether genetic sexes exhibit different habitat preferences, i.e. whether sexual niche partitioning occurs. Methods A total of 277 shoots of D. trifarius were randomly sampled at 214 locations and 12 environmental factors were quantified at each site. Sex was assigned to the individual shoots collected in the natural environments, regardless of their reproductive status, using a specifically designed molecular marker associated with female sex. Key Results Male and female shoots did not differ in shoot biomass, the sexes were randomly distributed with respect to each other, and environmental conditions at male and female sampling locations did not differ. Collectively, this demonstrates a lack of sexual niche segregation. Adult genetic sex ratio was female-biased, with 2.8 females for every male individual. Conclusions The results show that although the sexes of D. trifarius did not differ with regard to annual growth, spatial distribution or habitat requirements, the genetic sex ratio was nevertheless significantly female-biased. This supports the notion that factors other than sex-related differences in reproductive costs and sexual dimorphism can also drive the evolution of biased sex ratios in plants.

  • 9. Bisang, Irene
    et al.
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Persson, Christin
    Hedenas, Lars
    Family affiliation, sex ratio and sporophyte frequency in unisexual mosses2014In: Botanical journal of the Linnean Society, ISSN 0024-4074, E-ISSN 1095-8339, Vol. 174, no 2, p. 163-172Article in journal (Refereed)
    Abstract [en]

    Patterns of sex expression and sex ratios are key features of the life histories of organisms. Bryophytes are the only haploid-dominant land plants. In contrast with seed plants, more than half of bryophyte species are dioecious, with rare sexual expression and sporophyte formation and a commonly female-biased sex ratio. We asked whether variation in sex expression, sex ratio and sporophyte frequency in ten dioecious pleurocarpous wetland mosses of two different families was best explained by assuming that character states evolved: (1) in ancestors within the respective families or (2) at the species level as a response to recent habitat conditions. Lasso regression shrinkage identified relationships between family membership and sex ratio and sporophyte frequency, whereas environmental conditions were not correlated with any investigated reproductive trait. Sex ratio and sporophyte frequency were correlated with each other. Our results suggest that ancestry is more important than the current environment in explaining reproductive patterns at and above the species level in the studied wetland mosses, and that mechanisms controlling sex ratio and sporophyte frequency are phylogenetically conserved. Obviously, ancestry should be considered in the study of reproductive character state variation in plants.(c) 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 174, 163-172.

  • 10. Boalt, Elin
    et al.
    Arvanitis, Leena
    Stockholm University, Faculty of Science, Department of Botany.
    Lehtila, Kari
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Botany.
    The association among herbivory tolerance, ploidy level, and herbivory pressure in cardamine pratensis2010In: Evolutionary Ecology, ISSN 0269-7653, E-ISSN 1573-8477, Vol. 24, no 5, p. 1101-1113Article in journal (Refereed)
    Abstract [en]

    We tested whether differences in ploidy level and previous exposure to herbivory can affect plant tolerance to herbivory. We conducted a common garden experiment with 12 populations of two ploidy levels of the perennial herb Cardamine pratensis (five populations of tetraploid ssp. pratensis and seven populations of octoploid ssp. paludosa). Earlier studies have shown that attack rates by the main herbivore, the orange tip butterfly Anthocharis cardamines, are lower in populations of octoploids than in populations of tetraploids, and vary among populations. In the common garden experiment, a combination of natural and artificial damage significantly reduced seed and flower production. We measured tolerance based on four plant-performance metrics: survival, growth, seed production and clonal reproduction. For three of these measurements, tolerance of damage did not differ between ploidy levels. For clonal reproduction, the octoploids had a higher tolerance than the tetraploids, although they experience lower herbivore attack rates in natural populations. Populations from sites with high levels of herbivory had higher tolerance, measured by seed production, than populations with low levels of herbivory. We did not detect any significant costs of tolerance. We conclude that high intensity of herbivory has selected for high tolerance measured by seed production in C. pratensis.

  • 11.
    Bolinder, Kristina
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Humphreys, Aelys M.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Royal Botanic Gardens, UK.
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Alexandersson, Ronny
    Ickert-Bond, Stefanie M.
    Rydin, Catarina
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    From near extinction to diversification by means of ashift in pollination mechanism in the gymnosperm relict Ephedra (Ephedraceae, Gnetales)2016In: Botanical journal of the Linnean Society, ISSN 0024-4074, E-ISSN 1095-8339, Vol. 180, no 4, p. 461-477Article in journal (Refereed)
    Abstract [en]

    Pollination in gymnosperms is usually accomplished by means of wind, but some groups are insect-pollinated. We show that wind and insect pollination occur in the morphologically uniform genus Ephedra (Gnetales). Based on field experiments over several years, we demonstrate distinct differences between two Ephedra species that grow in sympatry in Greece in pollen dispersal and clump formation, insect visitations and embryo formation when insects are denied access to cones. Ephedra distachya, nested in the core clade of Ephedra, is anemophilous, which is probably the prevailing state in Ephedra. Ephedra foeminea, sister to the remaining species of the genus, is entomophilous and pollinated by a range of diurnal and nocturnal insects. The generalist entomophilous system of E.foeminea, with distinct but infrequent insect visitations, is in many respects similar to that reported for Gnetum and Welwitschia and appears ancestral in Gnetales. The Ephedra lineage is well documented already from the Early Cretaceous, but the diversity declined dramatically during the Late Cretaceous, possibly to near extinction around the Cretaceous-Palaeogene boundary. The clade imbalance between insect- and wind-pollinated lineages is larger than expected by chance and the shift in pollination mode may explain why Ephedra escaped extinction and began to diversify again.

  • 12. Buckley, Yvonne M.
    et al.
    Ramula, Satu
    Blomberg, Simon P.
    Burns, Jean H.
    Crone, Elizabeth E.
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Botany.
    Knight, Tiffany M.
    Pichancourt, Jean-Baptiste
    Quested, Helen
    Stockholm University, Faculty of Science, Department of Botany.
    Wardle, Glenda M.
    Causes and consequences of variation in plant population growth rate: a synthesis of matrix population models in a phylogenetic context2010In: Ecology Letters, ISSN 1461-023X, E-ISSN 1461-0248, Vol. 13, no 9, p. 1182-1197Article, review/survey (Refereed)
    Abstract [en]

    Explaining variation in population growth rates is fundamental to predicting population dynamics and population responses to environmental change. In this study, we used matrix population models, which link birth, growth and survival to population growth rate, to examine how and why population growth rates vary within and among 50 terrestrial plant species. Population growth rates were more similar within species than among species; with phylogeny having a minimal influence on among-species variation. Most population growth rates decreased over the observation period and were negatively autocorrelated between years; that is, higher than average population growth rates tended to be followed by lower than average population growth rates. Population growth rates varied more through time than space; this temporal variation was due mostly to variation in post-seedling survival and for a subset of species was partly explained by response to environmental factors, such as fire and herbivory. Stochastic population growth rates departed from mean matrix population growth rate for temporally autocorrelated environments. Our findings indicate that demographic data and models of closely related plant species cannot necessarily be used to make recommendations for conservation or control, and that post-seedling survival and the sequence of environmental conditions are critical for determining plant population growth rate.

  • 13. Burns, Jean H.
    et al.
    Blomberg, Simon P.
    Crone, Elizabeth E.
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Botany.
    Knight, Tiffany M.
    Pichancourt, Jean-Baptiste
    Ramula, Satu
    Wardle, Glenda M.
    Buckley, Yvonne M.
    Empirical tests of life-history evolution theory using phylogenetic analysis of plant demography2010In: Journal of Ecology, ISSN 0022-0477, E-ISSN 1365-2745, Vol. 98, no 2, p. 334-344Article in journal (Refereed)
    Abstract [en]

    1. A primary goal of evolutionary ecology is to understand factors selecting for the diversity of life histories. Life-history components, such as time-to-reproduction, adult survivorship and fecundity, might differ among species because of variation in direct and indirect benefits of these life histories in different environments or might have lower-than-expected variability because of phylogenetic constraints. Here, we present a phylogenetic examination of demography and life histories using a data base of 204 terrestrial plant species. 2. Overall, statistical models without phylogeny were preferred to models with phylogeny for vital rates and elasticities, suggesting that they lacked phylogenetic signal and are evolutionarily labile. However, the effect of phylogeny was significant in models including sensitivities, suggesting that sensitivities exhibit greater phylogenetic signal than vital rates or elasticities. 3. Species with a greater age at first reproduction had lower fecundity, consistent with a cost of delayed reproduction, but only in some habitats (e.g. grassland). We found no evidence for an indirect benefit of delayed reproduction via a decrease in variation in fecundity with age to first reproduction. 4. The greater sensitivity and lower variation in survival than in fecundity was consistent with buffering of more important vital rates, as others have also found. This suggests that studies of life-history evolution should include survival, rather than only fecundity, for the majority of species. 5. Synthesis. Demographic matrix models can provide informative tests of life-history theory because of their shared construction and outputs and their widespread use among plant ecologists. Our comparative analysis suggested that there is a cost of delayed reproduction and that more important vital rates exhibit lower variability. The absolute importance of vital rates to population growth rates (sensitivities) exhibited phylogenetic signal, suggesting that a thorough understanding of life-history evolution might require an understanding of the importance of vital rates, not just their means, and the role of phylogenetic history.

  • 14.
    Christiansen, Ditte M.
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Stockholm University, Faculty of Science, The Bolin Centre for Climate Research (together with KTH & SMHI).
    Römer, Gesa
    Dahlgren, Johan P.
    Borg, Malin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Jones, Owen R.
    Merinero, Sonia
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Stockholm University, Faculty of Science, The Bolin Centre for Climate Research (together with KTH & SMHI).
    Hylander, Kristoffer
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Stockholm University, Faculty of Science, The Bolin Centre for Climate Research (together with KTH & SMHI).
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Stockholm University, Faculty of Science, The Bolin Centre for Climate Research (together with KTH & SMHI).
    High-resolution data are necessary to understand the effects of climate on plant population dynamics of a forest herb2024In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 105, no 1, article id e4191Article in journal (Refereed)
    Abstract [en]

    Climate is assumed to strongly influence species distribution and abundance. Although the performance of many organisms is influenced by the climate in their immediate proximity, the climate data used to model their distributions often have a coarse spatial resolution. This is problematic because the local climate experienced by individuals might deviate substantially from the regional average. This problem is likely to be particularly important for sessile organisms like plants and in environments where small-scale variation in climate is large. To quantify the effect of local temperature on vital rates and population growth rates, we used temperature values measured at the local scale (in situ logger measures) and integral projection models with demographic data from 37 populations of the forest herb Lathyrus vernus across a wide latitudinal gradient in Sweden. To assess how the spatial resolution of temperature data influences assessments of climate effects, we compared effects from models using local data with models using regionally aggregated temperature data at several spatial resolutions (≥1 km). Using local temperature data, we found that spring frost reduced the asymptotic population growth rate in the first of two annual transitions and influenced survival in both transitions. Only one of the four regional estimates showed a similar negative effect of spring frost on population growth rate. Our results for a perennial forest herb show that analyses using regionally aggregated data often fail to identify the effects of climate on population dynamics. This emphasizes the importance of using organism-relevant estimates of climate when examining effects on individual performance and population dynamics, as well as when modeling species distributions. For sessile organisms that experience the environment over small spatial scales, this will require climate data at high spatial resolutions. 

  • 15.
    Christiansen, Ditte Marie
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Lønsmann Iversen, Lars
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Hylander, Kristoffer
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Changes in forest structure drive temperature preferences of boreal understorey plant communities2022In: Journal of Ecology, ISSN 0022-0477, E-ISSN 1365-2745, Vol. 110, no 3, p. 631-643Article in journal (Refereed)
    Abstract [en]
    1. The local climate in forest understories can deviate substantially from ambient conditions. Moreover, forest microclimates are often characterized by cyclic changes driven by management activities such as clear-cutting and subsequent planting. To understand how and why understorey plant communities change, both ambient climate change and temporal variation in forest structure have to be considered.
    2. We used inventories from 11,436 productive forest sites in Sweden repeated every 10th year 1993–2017 to examine how variation in forest structure influences changes in the average value of minimum and maximum temperature preferences of all species in a community, that is, community temperature indices (CTIs). We then evaluated to what extent these changes were driven by local extinctions and colonizations, respectively, and to what extent the difference in CTI value between two inventories was related to changes in forest density and in macroclimate. Lastly, we tested whether effects on CTI change by these two drivers were modified by topography, soil moisture and tree species composition.
    3. CTI values of the understorey plant communities increased after clear-cutting, and decreased during periods when the forest grew denser. During the period immediately after clear-cutting, changes were predominately driven by colonizations of species with a preference for higher temperatures. During the forest regeneration phase, both colonizations by species preferring lower temperatures and local extinctions of species preferring higher temperatures increased. The change in understorey CTI over 10-year periods was explained more by changes in forest density, than by changes in macroclimate. Soil moisture, topography and forest tree species composition modified to some extent the effects of changes in forest density and in macroclimate on understorey CTI values.
    4. Synthesis. Via stand manipulation, forest management impacts the effects of regional climate on understorey plant communities. This implies that forest management by creating denser stands locally even can counterbalance the effects of regional changes in climate. Consequently, interpretations of changes in the mean temperature preference of species in forest understorey communities should take forest management regimes into account.
  • 16.
    Christiansen, Ditte Marie
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Stockholm University, Faculty of Science, The Bolin Centre for Climate Research (together with KTH & SMHI).
    Strydom, Tanya
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Université de Montréal, Canada; Québec Centre for Biodiversity Sciences, Canada.
    Greiser, Caroline
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Stockholm University, Faculty of Science, The Bolin Centre for Climate Research (together with KTH & SMHI). Stockholm University, Faculty of Science, Department of Physical Geography.
    McClory, Ryan
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. University of Reading, UK.
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Stockholm University, Faculty of Science, The Bolin Centre for Climate Research (together with KTH & SMHI).
    Hylander, Kristoffer
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Stockholm University, Faculty of Science, The Bolin Centre for Climate Research (together with KTH & SMHI).
    Effects of past and present microclimates on northern and southern plant species in a managed forest landscape2023In: Journal of Vegetation Science, ISSN 1100-9233, E-ISSN 1654-1103, Vol. 34, no 4, article id e13197Article in journal (Refereed)
    Abstract [en]

    Questions: Near-ground temperatures can vary substantially over relatively short distances, enabling species with different temperature preferences and geographical distributions to co-exist within a small area. In a forest landscape, the near-ground temperatures may change due to management activities that alter forest density. As a result of such management activities, current species distributions and performances might not only be affected by current microclimates, but also by past conditions due to time-lagged responses.

    Location: Sweden.

    Methods: We examined the effects of past and current microclimates on the distributions and performances of two northern, cold-favoured, and two southern, warm-favoured, plant species in 53 managed forest sites. Each pair was represented by one vascular plant and one bryophyte species. We used temperature logger data and predictions from microclimate models based on changes in basal area to relate patterns of occurrence, abundance, and reproduction to current and past microclimate.

    Results: The two northern species were generally favoured by microclimates that were currently cold, characterised by later snowmelt and low accumulated heat over the growing season. In contrast, the two southern species were generally favoured by currently warm microclimates, characterised by high accumulated heat over the growing season. Species generally had higher abundance in sites with a preferred microclimate both in the past and present, and lower abundance than expected from current conditions, if the past microclimate had changed from warm to cold or vice versa, indicating time-lags in abundance patterns of the species.

    Conclusions: Our results show a potential importance of past and present microclimate heterogeneity for the co-existence of species with different temperature preferences in the same landscape and highlight the possibility to manage microclimates to mitigate climate change impacts on forest biodiversity.

  • 17. Crone, Elizabeth E.
    et al.
    Ellis, Martha M.
    Morris, William F.
    Stanley, Amanda
    Bell, Timothy
    Bierzychudek, Paulette
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Botany.
    Kaye, Thomas N.
    Knight, Tiffany M.
    Lesica, Peter
    Oostermeijer, Gerard
    Quintana-Ascencio, Pedro F.
    Ticktin, Tamara
    Valverde, Teresa
    Williams, Jennifer L.
    Doak, Daniel F.
    Ganesan, Rengaian
    Mceachern, Kathyrn
    Thorpe, Andrea S.
    Menges, Eric S.
    Ability of Matrix Models to Explain the Past and Predict the Future of Plant Populations2013In: Conservation Biology, ISSN 0888-8892, E-ISSN 1523-1739, Vol. 27, no 5, p. 968-978Article in journal (Refereed)
    Abstract [en]

    Uncertainty associated with ecological forecasts has long been recognized, but forecast accuracy is rarely quantified. We evaluated how well data on 82 populations of 20 species of plants spanning 3 continents explained and predicted plant population dynamics. We parameterized stage-based matrix models with demographic data from individually marked plants and determined how well these models forecast population sizes observed at least 5 years into the future. Simple demographic models forecasted population dynamics poorly; only 40% of observed population sizes fell within our forecasts' 95% confidence limits. However, these models explained population dynamics during the years in which data were collected; observed changes in population size during the data-collection period were strongly positively correlated with population growth rate. Thus, these models are at least a sound way to quantify population status. Poor forecasts were not associated with the number of individual plants or years of data. We tested whether vital rates were density dependent and found both positive and negative density dependence. However, density dependence was not associated with forecast error. Forecast error was significantly associated with environmental differences between the data collection and forecast periods. To forecast population fates, more detailed models, such as those that project how environments are likely to change and how these changes will affect population dynamics, may be needed. Such detailed models are not always feasible. Thus, it may be wiser to make risk-averse decisions than to expect precise forecasts from models. Habilidad de los Modelos Matriciales para Explicar el Pasado y Predecir el Futuro de las Poblaciones de Plantas Resumen La incertidumbre asociada con el pronostico ecologico ha sido reconocida durante un largo tiempo pero rara vez se cuantifica su seguridad. Evaluamos que tan bien la informacion de 82 poblaciones de 20 especies de plantas a lo largo de 3 continentes explica y predice la dinamica de poblacion de las plantas. Realizamos parametros con modelos matriciales con base en estadios con datos demograficos a partir de plantas marcadas individualmente y determinamos que tan bien estos modelos pronostican el tamano de las poblaciones al menos 5 anos en el futuro. Los modelos demograficos simples pronosticaron pobremente las dinamicas de poblacion; solamente el 40% de las poblaciones observadas cayo dentro de los limites de confianza de 85% de nuestros pronosticos. Estos modelos sin embargo explicaron la dinamica de poblacion a lo largo de los anos en los que se colectaron datos; los cambios observados en el tamano de la poblacion durante el periodo de colecta de datos estuvieron positivamente correlacionados con la tasa de crecimiento de la poblacion. Asi, estos modelos son por lo menos una manera segura de cuantificar el estado de la poblacion. Los pronosticos debiles no estuvieron asociados con el numero de plantas individuales o con los anos de datos. Probamos si las tasas vitales dependian de la densidad y encontramos que existe dependencia hacia la densidad tanto positiva como negativa, sin embargo la dependencia de densidad no se asocio con el error de pronostico. El error de pronostico estuvo significativamente asociado con diferencias ambientales entre la recoleccion de datos y los periodos de pronostico. Para predecir el destino de las poblaciones se necesitan modelos mas detallados, como aquellos que proyectan los cambios probables en el ambiente y como estos cambios afectaran a la dinamica de las poblaciones. Tales modelos tan detallados no siempre son factibles. Por ello puede ser mejor tomar decisiones aversas a riesgos que esperar pronosticos precisos de los modelos.

  • 18. Crone, Elizabeth E.
    et al.
    Menges, Eric S.
    Ellis, Martha M.
    Bell, Timothy
    Bierzychudek, Paulette
    Ehrlen, Johan
    Stockholm University, Faculty of Science, Department of Botany.
    Kaye, Thomas N.
    Knight, Tiffany M.
    Lesica, Peter
    Morris, William F.
    Oostermeijer, Gerard
    Quintana-Ascencio, Pedro F.
    Stanley, Amanda
    Ticktin, Tamara
    Valverde, Teresa
    Williams, Jennifer L.
    How do plant ecologists use matrix population models?2011In: Ecology Letters, ISSN 1461-023X, E-ISSN 1461-0248, Vol. 14, no 1, p. 1-8Article in journal (Refereed)
    Abstract [en]

    P>Matrix projection models are among the most widely used tools in plant ecology. However, the way in which plant ecologists use and interpret these models differs from the way in which they are presented in the broader academic literature. In contrast to calls from earlier reviews, most studies of plant populations are based on < 5 matrices and present simple metrics such as deterministic population growth rates. However, plant ecologists also cautioned against literal interpretation of model predictions. Although academic studies have emphasized testing quantitative model predictions, such forecasts are not the way in which plant ecologists find matrix models to be most useful. Improving forecasting ability would necessitate increased model complexity and longer studies. Therefore, in addition to longer term studies with better links to environmental drivers, priorities for research include critically evaluating relative/comparative uses of matrix models and asking how we can use many short-term studies to understand long-term population dynamics.

  • 19.
    Dahlberg, C. Johan
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Christiansen, Ditte Marie
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Meineri, Eric
    Hylander, Kristoffer
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Correlations between plant climate optima across different spatial scales2020In: Environmental and Experimental Botany, ISSN 0098-8472, E-ISSN 1873-7307, Vol. 170, article id 103899Article in journal (Refereed)
    Abstract [en]

    Identifying the factors determining the abundance and distribution of species is a fundamental question in ecology. One key issue is how similar the factors determining species' distributions across spatial scales are (here we focus especially on spatial extents). If the factors are similar across extents, then the large scale distribution pattern of a species may provide information about its local habitat requirements, and vice versa. We assessed the relationships between landscape and national optima as well as landscape and continental optima for growing degree days, maximum temperature and minimum temperature for 96 bryophytes and 50 vascular plants. For this set of species, we derived landscape optima from abundance weighted temperature data using species inventories in central Sweden and a fine-grained temperature model (50 m), national optima from niche centroid modelling based on GBIF data from Sweden and the same fine-grained climate model, and continental optima using the same method as for the national optima but from GBIF data from Europe and Worldclim temperatures (c. 1000 m). The landscape optima of all species were positively correlated with national as well as continental optima for maximum temperature (r = 0.45 and 0.46, respectively), weakly so for growing degree days (r = 0.30 and r = 0.28), but sometimes absent for minimum temperature (r = 0.26 and r = 0.04). The regression slopes of national or continental optima on local optima did not differ between vascular plants and bryophytes for GDD and Tmax. However, the relationship between the optima of Tmin differed between groups, being positive in vascular plants but absent in bryophytes. Our results suggest that positive correlations between optima at different spatial scales are present for some climatic variables but not for others. Moreover, our results for vascular plants and bryophytes suggest that correlations might differ between organism groups and depend on the ecology of the focal organisms. This implies that it is not possible to routinely up- or downscale distribution patterns based on environmental correlations, since drivers of distribution patterns might differ across spatial extents.

  • 20.
    Dahlberg, C. Johan
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Hylander, Kristoffer
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Performance of Forest Bryophytes with Different Geographical Distributions Transplanted across a Topographically Heterogeneous Landscape2014In: PLOS ONE, E-ISSN 1932-6203, Vol. 9, no 11, article id e112943Article in journal (Refereed)
    Abstract [en]

    Most species distribution models assume a close link between climatic conditions and species distributions. Yet, we know little about the link between species’ geographical distributions and the sensitivity of performance to local environmental factors. We studied the performance of three bryophyte species transplanted at south- and north-facing slopes in a boreal forest landscape in Sweden. At the same sites, we measured both air and ground temperature. We hypothesized that the two southerly distributed species Eurhynchium angustirete and Herzogiella seligeri perform better on south-facing slopes and in warm conditions, and that the northerly distributed species Barbilophozia lycopodioides perform better on north-facing slopes and in relatively cool conditions. The northern, but not the two southern species, showed the predicted relationship with slope aspect. However, the performance of one of the two southern species was still enhanced by warm temperatures. An important reason for the inconsistent results can be that microclimatic gradients across landscapes are complex and influenced by many climate-forcing factors. Therefore, comparing only north- and south-facing slopes might not capture the complexity of microclimatic gradients. Population growth rates and potential distributions are the integrated results of all vital rates. Still, the study of selected vital rates constitutes an important first step to understand the relationship between population growth rates and geographical distributions and is essential to better predict how climate change influences species distributions.

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  • 21.
    Dahlberg, C. Johan
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Hylander, Kristoffer
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Population dynamics of moss transplants across microclimatic gradientsManuscript (preprint) (Other academic)
    Abstract [en]

    In order to determine the response of a species to climatic change it is important to study how climatic factors influence its vital rates and population growth rate across climatic gradients. We investigated how microclimate influence the population dynamics of transplants from northern and more southern populations of the forest bryophyte Hylocomiastrum umbratum. We predicted that its population growth rate is favored by moist microclimates with colder maximum temperatures, longer snow cover duration and less evaporation, and that annual shoots (segments) will be shorter under drier conditions. We also predicted that northern populations will have higher population growth rate and larger segments than southern populations when transplanted to the northern range. We placed transplants from three northern and three southern populations of H. umbratum at 30 forested sites in central Sweden differing in microclimate. We marked and followed the growth of individual shoots during two years, and calculated population growth rates and stable stage distributions of segment size classes using transition matrix models for northern and southern transplants, respectively, at each locality. Population growth rate was lower and shorter segments developed at sites with higher evaporation, corresponding to our hypothesis. There were no significant difference in population growth rate and stable stage segment length between southern and northern populations. Higher evaporation during the summer result in lower population growth rates of H. umbratum by affecting vital rates, in terms of less segment growth. Both climate change and forestry may alter evaporation conditions across the landscape and, thus, the future distribution of the species.

  • 22.
    Dahlberg, C. Johan
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Meineri, Eric
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Plant landscape climatic optima correlate with their continental range optimaManuscript (preprint) (Other academic)
    Abstract [en]

    Aim

    Factors determining species’ distributions at smaller scales may inform us about larger scale distributions, and vice versa. We predicted that landscape and continental climatic optima for plants are positively correlated, and that species that have their optima outside a given focal landscape will cluster at the warmest or coldest landscape patches. Also, we predicted that the correlations of temperature optima are stronger for vascular plants than for bryophytes, since bryophytes may be regulated also by air moisture.

    Location

    Ångermanland, Sweden (landscape scale); Europe (continental scale).

    Methods

    We derived landscape optima from fine-grained temperature models (50 m) and species inventories, and continental optima from MaxEnt niche modelling based on GBIF occurrences and Worldclim temperatures (c. 1000 m), for 96 bryophytes and 50 vascular plants. Optima were derived for growing degree days, and maximum and minimum temperature.

    Results

    The landscape and continental optima of all species were positively correlated for growing degree days and maximum temperature (r = 0.19 and r = 0.44), but not for minimum temperature (r = -0.010). Species with their continental optima outside the focal landscape did not clearly cluster in the most extreme parts of the landscape. For vascular plants the correlation was positive for both growing degree days and maximum temperature (r = 0.50 and r = 0.64), but for bryophytes only for maximum temperature (r = 0.34).

    Main conclusions

    The optima correlations for maximum temperature and growing degree days indicate that we can infer large scale distribution patterns of plants from their local scale distributions, and suggest in which environments species occur if we only know their continental scale optima. The lack of clustering of southern and northern species limits the possibility for conservation actions targeting microrefugia. Lastly, the correlations indicate that the distributions of vascular plants were more influenced by temperature than bryophytes.

  • 23.
    Dahlgren, Johan
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Ehrlen, Johan
    Stockholm University, Faculty of Science, Department of Botany.
    Incorporating environmental change over succession in an integral projection model of population dynamics of a forest herb2011In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 120, no 8, p. 1183-1190Article in journal (Refereed)
    Abstract [en]

    Despite seemingly obvious effects of environmental drivers, mechanisms behind long-term changes in plant population sizes over time are often poorly known. We investigated how soil potassium concentration and seed predation are likely to change over time as a result of succession from deciduous forest to spruce forest, and how this affects population trajectories of Actaea spicata. Observations and addition experiments showed that high soil potassium concentration increased individual growth rates. Among-site comparisons showed that soil potassium concentration was lower where proportion spruce was higher. Incorporation of a gradual increase in spruce over time in an integral projection model where individual growth depended on potassium suggested a net decrease in A. spicata population sizes over forest succession. This result suggests that small changes in factors with small effects on individual performance can influence patterns of species occupancy along successional gradients. We incorporated also density independent and density dependent effects of pre-dispersal seed predation over succession into the same model. Seed predation influenced the tree composition at which A. spicata population growth was positive. However, significant effects of A. spicata population size on seed predation intensity did not translate into important feedback effects on population growth trajectories over succession. Our results illustrate how demographic models can be used to gain understanding of the mechanisms behind effects of environmental change on species abundances and distributions by the simultaneous inclusion of changing abiotic and biotic factors.

  • 24.
    Dahlgren, Johan
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Botany.
    Linking environmental variation to population dynamics of a forest herb2009In: Journal of Ecology, ISSN 0022-0477, E-ISSN 1365-2745, Vol. 97, no 4, p. 666-674Article in journal (Refereed)
    Abstract [en]

    . Although necessary for understanding and predicting population dynamics, abiotic and biotic interactions have only rarely been coupled to demography and population dynamics.

    2. We estimated effects of 11 environmental factors on survival, growth and fertility of the perennial herb Actaea spicata and incorporated significant factors into integral projection models to assess their effect on population dynamics.

    3. Statistical models suggested that high soil potassium concentration increased individual growth and that seed predation and, to a lesser extent, canopy cover reduced seed production.

    4. Demographic models showed that both soil potassium concentration and pre-dispersal seed predation could reverse population growth from positive to negative. The observed range of soil potassium concentration corresponded to growth rates (lambda) between 0.96 and 1.07, at mean observed seed predation intensity. At observed mean potassium concentration, growth rate ranged from 0.99 to 1.02 over observed seed predation intensities.

    5. Sensitivity of population growth rate to different vital rates strongly influenced the relative effects of the two factors. Elasticity analysis suggested that proportional changes in soil potassium concentration result in seven times larger effects on population growth rate than changes in seed predation.

    6. Synthesis. We conclude that relatively weak associations between environmental factors and vital rates can have substantial long-term effects on population growth. Approaches based on detailed demographic models, that simultaneously assess abiotic and biotic effects on population growth rate, constitute important tools for establishing the links between the environment and dynamics of populations and communities.

  • 25. Dahlgren, Johan P.
    et al.
    Bengtsson, Karin
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    The demography of climate-driven and density-regulated population dynamics in a perennial plant2016In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 97, no 4, p. 899-907Article in journal (Refereed)
    Abstract [en]

    Identifying the internal and external drivers of population dynamics is a key objective in ecology, currently accentuated by the need to forecast the effects of climate change on species distributions and abundances. The interplay between environmental and density effects is one particularly important aspect of such forecasts. We examined the simultaneous impact of climate and intraspecific density on vital rates of the dwarf shrub Fumana procumbens over 20 yr, using generalized additive mixed models. We then analyzed effects on population dynamics using integral projection models. The population projection models accurately captured observed fluctuations in population size. Our analyses suggested the population was intrinsically regulated but with annual fluctuations in response to variation in weather. Simulations showed that implicitly assuming variation in demographic rates to be driven solely by the environment can overestimate extinction risks if there is density dependence. We conclude that density regulation can dampen effects of climate change on Fumana population size, and discuss the need to quantify density dependence in predictions of population responses to environmental changes.

  • 26.
    Dahlgren, Johan P.
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Garcia, Maria B.
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Botany.
    Nonlinear relationships between vital rates and state variables in demographic models2011In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 92, no 5, p. 1181-1187Article in journal (Refereed)
    Abstract [en]

    To accurately estimate population dynamics and viability, structured population models account for among-individual differences in demographic parameters that are related to individual state. In the widely used matrix models, such differences are incorporated in terms of discrete state categories, whereas integral projection models (IPMs) use continuous state variables to avoid artificial classes. In IPMs, and sometimes also in matrix models, parameterization is based on regressions that do not always model nonlinear relationships between demographic parameters and state variables. We stress the importance of testing for nonlinearity and propose using restricted cubic splines in order to allow for a wide variety of relationships in regressions and demographic models. For the plant Borderea pyrenaica, we found that vital rate relationships with size and age were nonlinear and that the parameterization method had large effects on predicted population growth rates, lambda (linear IPM, 0.95; nonlinear IPMs, 1.00; matrix model, 0.96). Our results suggest that restricted cubic spline models are more reliable than linear or polynomial models. Because even weak nonlinearity in relationships between vital rates and state variables can have large effects on model predictions, we suggest that restricted cubic regression splines should be considered for parameterizing models of population dynamics whenever linearity cannot be assumed.

  • 27.
    Dahlgren, Johan P.
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. University of Southern Denmark, Denmark.
    Östergård, Hannah
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Local environment and density-dependent feedbacks determine population growth in a forest herb2014In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 176, no 4, p. 1023-1032Article in journal (Refereed)
    Abstract [en]

    Linking spatial variation in environmental factors to variation in demographic rates is essential for a mechanistic understanding of the dynamics of populations. However, we still know relatively little about such links, partly because feedbacks via intraspecific density make them difficult to observe in natural populations. We conducted a detailed field study and investigated simultaneous effects of environmental factors and the intraspecific density of individuals on the demography of the herb Lathyrus vernus. In regression models of vital rates we identified effects associated with spring shade on survival and growth, while density was negatively correlated with these vital rates. Density was also negatively correlated with average individual size in the study plots, which is consistent with self-thinning. In addition, average plant sizes were larger than predicted by density in plots that were less shaded by the tree canopy, indicating an environmentally determined carrying capacity. A size-structured integral projection model based on the vital rate regressions revealed that the identified effects of shade and density were strong enough to produce differences in stable population sizes similar to those observed in the field. The results illustrate how the local environment can determine dynamics of populations and that intraspecific density may have to be more carefully considered in studies of plant demography and population viability analyses of threatened species. We conclude that demographic approaches incorporating information about both density and key environmental factors are powerful tools for understanding the processes that interact to determine population dynamics and abundances.

  • 28.
    Dahlgren, Johan
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    von Zeipel, Hugo
    Stockholm University, Faculty of Science, Department of Botany.
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Botany. växtekologi.
    Variation in vegetative and flowering phenology in a forest herb caused by environmental heterogeneity2007In: AMERICAN JOURNAL OF BOTANY, Vol. 94, no 9, p. 1570-1576Article in journal (Refereed)
  • 29.
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Selection on flowering time in a life-cycle context2015In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 124, no 1, p. 92-101Article in journal (Refereed)
    Abstract [en]

    The main way in which plants can exert control over their local environment is by the timing of different events within their life cycles. Regarding timing of flowering as an integrated part of both the annual cycle and of the whole life cycle, rather than as an isolated event, has important implications for how we assess selection on timing of reproduction and interpret existing phenological patterns in perennial plants. I argue that: 1) we have little unequivocal evidence of pollinator-mediated selection on flowering time, but perhaps more evidence of antagonist-mediated selection; 2) much of selection on flowering time might occur before flowers have developed and after reproduction; 3) vital rates of non-flowering individuals can influence the strength and direction of selection on flowering time, and 4) differences in the direction of selection on flowering date between years might well correspond to consistent selection on the mechanisms determining flowering time. Overall, a life cycle perspective on timing of flowering is likely to facilitate the identification of selective agents and the understanding of the complex mechanisms underlying spatial and temporal variation in selection as well as to enable more accurate predictions of responses to environmental change.

  • 30.
    Ehrlén, Johan
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Borg-Karlson, Anna-Karin
    Kolb, Annette
    Selection on plant optical traits and floral scent: Effects via seed development and antagonistic interactions2012In: Basic and Applied Ecology, ISSN 1439-1791, E-ISSN 1618-0089, Vol. 13, no 6, p. 509-515Article in journal (Refereed)
    Abstract [en]

    Evolutionary explanations of plant reproductive traits have usually emphasized optical characteristics of plants and selection mediated by pollinators. In recent years, studies have been broadened by incorporating also interactions with antagonists and by studying plant fragrant cues. Here, we examined if optical and fragrance traits of the perennial herb Primula veris correlated with reproductive success, in terms of fruit and seed set, and with avoidance of seed predators. Selection path analysis showed that both optical and fragrance traits influenced total seed production, and effects occurred both via fruit and seed set and via predator avoidance. In one case the same trait, inflorescence height, influenced total seed production both positively and negatively through effects on different components of fitness. Our results lend support to the notion that selection by mutualists and antagonists simultaneously acts on optical and fragrance traits.

  • 31.
    Ehrlén, Johan
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Morris, William F.
    Predicting changes in the distribution and abundance of species under environmental change2015In: Ecology Letters, ISSN 1461-023X, E-ISSN 1461-0248, Vol. 18, no 3, p. 303-314Article, review/survey (Refereed)
    Abstract [en]

    Environmental changes are expected to alter both the distribution and the abundance of organisms. A disproportionate amount of past work has focused on distribution only, either documenting historical range shifts or predicting future occurrence patterns. However, simultaneous predictions of abundance and distribution across landscapes would be far more useful. To critically assess which approaches represent advances towards the goal of joint predictions of abundance and distribution, we review recent work on changing distributions and on effects of environmental drivers on single populations. Several methods have been used to predict changing distributions. Some of these can be easily modified to also predict abundance, but others cannot. In parallel, demographers have developed a much better understanding of how changing abiotic and biotic drivers will influence growth rate and abundance in single populations. However, this demographic work has rarely taken a landscape perspective and has largely ignored the effects of intraspecific density. We advocate a synthetic approach in which population models accounting for both density dependence and effects of environmental drivers are used to make integrated predictions of equilibrium abundance and distribution across entire landscapes. Such predictions would constitute an important step forward in assessing the ecological consequences of environmental changes.

  • 32.
    Ehrlén, Johan
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Morris, William F.
    von Euler, Tove
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Dahlgren, Johan P.
    Advancing environmentally explicit structured population models of plants2016In: Journal of Ecology, ISSN 0022-0477, E-ISSN 1365-2745, Vol. 104, no 2, p. 292-305Article in journal (Refereed)
    Abstract [en]

    The relationship between the performance of individuals and the surrounding environment is fundamental in ecology and evolutionary biology. Assessing how abiotic and biotic environmental factors influence demographic processes is necessary to understand and predict population dynamics, as well as species distributions and abundances. We searched the literature for studies that have linked abiotic and biotic environmental factors to vital rates and, using structured demographic models, population growth rates of plants. We found 136 studies that had examined the environmental drivers of plant demography. The number of studies has been increasing rapidly in recent years. Based on the reviewed studies, we identify and discuss several major gaps in our knowledge of environmentally driven demography of plants. We argue that some drivers may have been underexplored and that the full potential of spatially and temporally replicated studies may not have been realized. We also stress the need to employ relevant statistical methods and experiments to correctly identify drivers. Moreover, assessments of the relationship between drivers and vital rates need to consider interactive, nonlinear and indirect effects, as well as effects of intraspecific density dependence.Synthesis. Much progress has already been made by using structured population models to link the performance of individuals to the surrounding environment. However, by improving the design and analyses of future studies, we can substantially increase our ability to predict changes in plant population dynamics, abundances and distributions in response to changes in specific environmental drivers. Future environmentally explicit demographic models should also address how genetic changes prompted by selection imposed by environmental changes will alter population trajectories in the face of continued environmental change and investigate the reciprocal feedback between plants and their biotic drivers.

  • 33.
    Ehrlén, Johan
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Münzbergova, Zuzana
    Timing of flowering - opposed selection on different fitness components and trait covariation2009In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 173, p. 819-830Article in journal (Refereed)
  • 34.
    Ehrlén, Johan
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Raabova, Jana
    Dahlgren, Johan P.
    Flowering schedule in a perennial plant; life-history trade-offs, seed predation, and total offspring fitness2015In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 96, no 8, p. 2280-2288Article in journal (Refereed)
    Abstract [en]

    Optimal timing of reproduction within a season may be influenced by several abiotic and biotic factors. These factors sometimes affect different components of fitness, making assessments of net selection difficult. We used estimates of offspring fitness to examine how pre-dispersal seed predation influences selection on flowering schedule in an herb with a bimodal flowering pattern, Actaea spicata. Within individuals, seeds from flowers on early terminal inflorescences had a higher germination rate and produced larger seedlings than seeds from flowers on late basal inflorescences. Reproductive value, estimated using demographic integral projection models and accounting for size-dependent differences in future performance, was two times higher for intact seeds from early flowers than for seeds from late flowers. Fruits from late flowers were, however, much more likely to escape seed predation than fruits from early flowers. Reproductive values of early and late flowers balanced at a predation intensity of 63%. Across 15 natural populations, the strength of selection for allocation to late flowers was positively correlated with mean seed predation intensity. Our results suggest that the optimal shape of the flowering schedule, in terms of the allocation between early and late flowers, is determined by the trade-off between offspring number and quality, and that variation in antagonistic interactions among populations influences the balancing of this trade-off. At the same time they illustrate that phenotypic selection analyses that fail to account for differences in offspring fitness might be misleading.

  • 35.
    Ehrlén, Johan
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Valdés, Alicia
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Climate drives among-year variation in natural selection on flowering time2020In: Ecology Letters, ISSN 1461-023X, E-ISSN 1461-0248, Vol. 23, no 4, p. 653-662Article in journal (Refereed)
    Abstract [en]

    To predict long-term responses to climate change, we need to understand how changes in temperature and precipitation elicit both immediate phenotypic responses and changes in natural selection. We used 22 years of data for the perennial herb Lathyrus vernus to examine how climate influences flowering phenology and phenotypic selection on phenology. Plants flowered earlier in springs with higher temperatures and higher precipitation. Early flowering was associated with a higher fitness in nearly all years, but selection for early flowering was significantly stronger in springs with higher temperatures and lower precipitation. Climate influenced selection through trait distributions, mean fitness and trait-fitness relationships, the latter accounting for most of the among-year variation in selection. Our results show that climate both induces phenotypic responses and alters natural selection, and that the change in the optimal phenotype might be either weaker, as for spring temperature, or stronger, as for precipitation, than the optimal response.

  • 36.
    Ehrlén, Johan
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Stockholm University, Faculty of Science, The Bolin Centre for Climate Research (together with KTH & SMHI).
    Valdés, Alicia
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Stockholm University, Faculty of Science, The Bolin Centre for Climate Research (together with KTH & SMHI).
    Helmutsdóttir, Vigdís F.
    Marteinsdóttir, Bryndís
    Maladaptive plastic responses of flowering time to geothermal heating2023In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 104, no 10, article id e4121Article in journal (Refereed)
    Abstract [en]

    Phenotypic plasticity might increase fitness if the conditions under which it evolved remain unaltered, but becomes maladaptive if the environment no longer provides reliable cues for subsequent conditions. In seasonal environments, timing of reproduction can respond plastically to spring temperature, maximizing the benefits of a long season while minimizing the exposure to unfavorable cold temperatures. However, if the relationship between early spring temperatures and later conditions changes, the optimal response might change. In geothermally heated ecosystems, the plastic response of flowering time to springtime soil temperature that has evolved in unheated areas is likely to be non-optimal, because soil temperatures are higher and decoupled from air temperatures in heated areas. We therefore expect natural selection to favor a lower plasticity and a delayed flowering in these areas. Using observational data along a natural geothermal warming gradient, we tested the hypothesis that selection on flowering time depends on soil temperature and favors later flowering on warmer soils in the perennial Cerastium fontanum. In both study years, plants growing in warmer soils began flowering earlier than plants growing in colder soils, suggesting that first flowering date (FFD) responds plastically to soil temperature. In one of the two study years, selection favored earlier flowering in colder soils but later flowering in warmer soils, suggesting that the current level of plastic advance of FFD on warmer soils may be maladaptive in some years. Our results illustrate the advantages of using natural experiments, such as geothermal ecosystems, to examine selection in environments that recently have undergone major changes. Such knowledge is essential to understand and predict both ecological and evolutionary responses to climate warming. 

  • 37.
    Elmhagen, Bodil
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Destouni, Georgia
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Borgström, Sara
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Boyd, Emily
    Stockholm University, Faculty of Science, Stockholm Resilience Centre. University of Reading, England.
    Cousins, Sara A. O.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Dalen, Love
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Physical Geography. Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Ermold, Matti
    Hambäck, Peter A.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Hedlund, Johanna
    Stockholm University, Faculty of Science, Department of Zoology.
    Hylander, Kristoffer
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Jaramillo, Fernando
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Lagerholm, Vendela K.
    Stockholm University, Faculty of Science, Department of Zoology. Swedish Museum of Natural History, Sweden.
    Lyon, Steve W.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Moor, Helen
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Nykvist, Björn
    Stockholm University, Faculty of Science, Stockholm Resilience Centre. Stockholm University, Stockholm Environment Institute.
    Pasanen-Mortensen, Marianne
    Stockholm University, Faculty of Science, Department of Zoology.
    Plue, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Prieto, Carmen
    Stockholm University, Faculty of Science, Department of Physical Geography.
    van der Velde, Ype
    Stockholm University, Faculty of Science, Department of Physical Geography. Wageningen University & Research Center, Netherlands.
    Lindborg, Regina
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Interacting effects of change in climate, human population, land use, and water use on biodiversity and ecosystem services2015In: Ecology & Society, E-ISSN 1708-3087, Vol. 20, no 1, article id UNSP 23Article in journal (Refereed)
    Abstract [en]

    Human population growth and resource use, mediated by changes in climate, land use, and water use, increasingly impact biodiversity and ecosystem services provision. However, impacts of these drivers on biodiversity and ecosystem services are rarely analyzed simultaneously and remain largely unknown. An emerging question is how science can improve the understanding of change in biodiversity and ecosystem service delivery and of potential feedback mechanisms of adaptive governance. We analyzed past and future change in drivers in south-central Sweden. We used the analysis to identify main research challenges and outline important research tasks. Since the 19th century, our study area has experienced substantial and interlinked changes; a 1.6 degrees C temperature increase, rapid population growth, urbanization, and massive changes in land use and water use. Considerable future changes are also projected until the mid-21st century. However, little is known about the impacts on biodiversity and ecosystem services so far, and this in turn hampers future projections of such effects. Therefore, we urge scientists to explore interdisciplinary approaches designed to investigate change in multiple drivers, underlying mechanisms, and interactions over time, including assessment and analysis of matching-scale data from several disciplines. Such a perspective is needed for science to contribute to adaptive governance by constantly improving the understanding of linked change complexities and their impacts.

  • 38.
    Eriksson, Ove
    et al.
    Stockholm University, Faculty of Science, Department of Botany. Växtekologi.
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Botany. Växtekologi.
    Seedling recruitment and population ecology2008In: Seedling Ecology and Evolution, Cambridge University Press, Cambridge , 2008, p. 239-254Chapter in book (Refereed)
  • 39. Fernández-Fernández, P.
    et al.
    Sanczuk, P.
    Vanneste, T.
    Brunet, J.
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Hedwall, P.-O.
    Hylander, Kristoffer
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Van Den Berge, S.
    Verheyen, K.
    De Frenne, P.
    Different effects of warming treatments in forests versus hedgerows on the understorey plant Geum urbanum2022In: Plant Biology, ISSN 1435-8603, E-ISSN 1438-8677, Vol. 24, no 5, p. 734-744Article in journal (Refereed)
    Abstract [en]
    • The effectiveness of hedgerows as functional corridors in the face of climate warming has been little researched. Here we investigated the effects of warming temperatures on plant performance and population growth of Geum urbanum in forests versus hedgerows in two European temperate regions.
    • Adult individuals were transplanted in three forest–hedgerow pairs in each of two different latitudes, and an experimental warming treatment using open-top chambers was used in a full factorial design. Plant performance was analysed using mixed models and population performance was analysed using Integral Projection Models and elasticity analyses.
    • Temperature increases due to open-top chamber installation were higher in forests than in hedgerows. In forests, the warming treatment had a significant negative effect on the population growth rate of G. urbanum. In contrast, no significant effect of the warming treatment on population dynamics was detected in hedgerows. Overall, the highest population growth rates were found in the forest control sites, which was driven by a higher fecundity rather than a higher survival probability.
    • Effects of warming treatments on G. urbanum population growth rates differed between forests and hedgerows. In forests, warming treatments negatively affected population growth, but not in hedgerows. This could be a consequence of the overall lower warming achieved in hedgerows. We conclude that maintenance of cooler forest microclimates coul, at least temporarily, moderate the species response to climate warming.
  • 40.
    Fogelström, Elsa
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Dahlberg, Johan
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Hylander, Kristoffer
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Population differentiation of flowering time in Lathyrus vernusManuscript (preprint) (Other academic)
  • 41.
    Fogelström, Elsa
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Phenotypic but not genotypic selection for earlier flowering in a perennial herb2019In: Journal of Ecology, ISSN 0022-0477, E-ISSN 1365-2745, Vol. 107, no 6, p. 2650-2659Article in journal (Refereed)
    Abstract [en]

    1. Timing of reproduction affects the outcome of interactions between plants and their pollinators, grazers and seed predators, as well as with their local abiotic environment. In seasonal environments, phenotypic selection has often been shown to favour early flowering. Yet, we still know little about the agents driving selection in natural populations and whether observed phenotypic selection corresponds to genotypic selection – a prerequisite for evolutionary change.

    2. In this study, we experimentally assessed phenotypic and genotypic selection for flowering time in a natural population of the perennial herb Lathyrus vernus. We transplanted sibling individuals, obtained through controlled crosses, to their source population and found net phenotypic selection for earlier flowering in the field.

    3. Despite a higher susceptibility to roe deer grazing, early‐flowering plants had higher fruit set and more seeds per fruit than late‐flowering plants. We found no support for genotypic selection on flowering time, and heritability for first flowering day was very low.

    4. Synthesis: Our results suggest that commonly observed patterns of higher fitness in early‐flowering plants do not always correspond to selection on genotypic values and are thus not necessarily expected to result in evolutionary change even if the relationship between flowering time and fitness is causal. This finding should be important to understand how species phenology might respond to changing environmental conditions.

  • 42.
    Fogelström, Elsa
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Guasconi, Daniela
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Dahlgren, Johan P.
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Flowering status and individual condition affects phenology in a perennial herbManuscript (preprint) (Other academic)
  • 43.
    Fogelström, Elsa
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Olofsson, Martin
    Stockholm University, Faculty of Science, Department of Zoology.
    Posledovich, Diana
    Stockholm University, Faculty of Science, Department of Zoology.
    Wiklund, Christer
    Stockholm University, Faculty of Science, Department of Zoology.
    Dahlgren, Johan P.
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Plant-herbivore synchrony and selection on plant flowering phenology2017In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 98, no 3, p. 703-711Article in journal (Refereed)
    Abstract [en]

    Temporal variation in natural selection has profound effects on the evolutionary trajectories of populations. One potential source of variation in selection is that differences in thermal reaction norms and temperature influence the relative phenology of interacting species. We manipulated the phenology of the butterfly herbivore Anthocharis cardamines relative to genetically identical populations of its host plant, Cardamine pratensis, and examined the effects on butterfly preferences and selection acting on the host plant. We found that butterflies preferred plants at an intermediate flowering stage, regardless of the timing of butterfly flight relative to flowering onset of the population. Consequently, the probability that plant genotypes differing in timing of flowering should experience a butterfly attack depended strongly on relative phenology. These results suggest that differences in spring temperature influence the direction of herbivore-mediated selection on flowering phenology, and that climatic conditions can influence natural selection also when phenotypic preferences remain constant.

  • 44.
    Fogelström, Elsa
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Zacchello, Giulia
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Simultaneous selection on vegetative and reproductive phenology in a perennial herb2022In: Ecology and Evolution, E-ISSN 2045-7758, Vol. 12, no 2, article id e8610Article in journal (Refereed)
    Abstract [en]

    The timing of different life-history events is often correlated, and selection might only rarely be exerted independently on the timing of a single event. In plants, phenotypic selection has often been shown to favor earlier flowering. However, little is known about to what extent this selection acts directly versus indirectly via vegetative phenology, and if selection on the two traits is correlational. We estimated direct, indirect, and correlational phenotypic selection on vegetative and reproductive phenology over 3 years for flowering individuals of the perennial herb Lathyrus vernus. Direct selection favored earlier flowering and shorter timespans between leaf-out and flowering in all years. However, early flowering was associated with early leaf-out, and the direction of selection on leaf-out day varied among years. As a result, selection on leaf-out weakened selection for early flowering in one of the study years. We found no evidence of correlational selection. Our results highlight the importance of including temporally correlated traits when exploring selection on the phenology of seasonal events. 

  • 45.
    Fogelström, Elsa
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Zacchello, Giulia
    Guasconi, Daniela
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Dahlgren, Johan P.
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Spring and autumn phenology in an understory herb are uncorrelated and driven by different factors2022In: American Journal of Botany, ISSN 0002-9122, E-ISSN 1537-2197, Vol. 109, no 2, p. 226-236Article in journal (Refereed)
    Abstract [en]

    Premise: Climate warming has altered the start and end of growing seasons in temperate regions. Ultimately, these changes occur at the individual level, but little is known about how previous seasonal life-history events, temperature, and plant-resource state simultaneously influence the spring and autumn phenology of plant individuals.

    Methods: We studied the relationships between the timing of leaf-out and shoot senescence over 3 years in a natural population of the long-lived understory herb Lathyrus vernus and investigated the effects of spring temperature, plant size, reproductive status, and grazing on spring and autumn phenology.

    Results: The timing of leaf-out and senescence were consistent within individuals among years. Leaf-out and senescence were not correlated with each other within years. Larger plants leafed out and senesced later, and size had no effect on growing season length. Reproductive plants leafed out earlier and had longer growing seasons than nonreproductive plants. Grazing had no detectable effects on phenology. Colder spring temperatures delayed senescence in two of three study years.

    Conclusions: The timing of seasonal events, such as leaf-out and senescence in plants can be expressed largely independently within and among seasons and are influenced by different factors. Growing season start and length can often be dependent on plant condition and reproductive status. Knowledge about the drivers of growing season length of individuals is essential to more accurately predict species and community responses to environmental variation.

  • 46. Garcia,
    et al.
    Pico,
    Ehrlén,
    Stockholm University, Faculty of Science, Department of Botany.
    Life span correlates with population dynamics in perennial herbaceous plants2008In: American Journal of BotanyArticle in journal (Refereed)
  • 47. Garcia, Maria B.
    et al.
    Dahlgren, Johan P.
    Stockholm University, Faculty of Science, Department of Botany.
    Ehrlen, Johan
    Stockholm University, Faculty of Science, Department of Botany.
    No evidence of senescence in a 300-year-old mountain herb2011In: Journal of Ecology, ISSN 0022-0477, E-ISSN 1365-2745, Vol. 99, no 6, p. 1424-1430Article in journal (Refereed)
    Abstract [en]

    1. Understanding how vital rates and reproductive value change with age is fundamental to demography, life history evolution and population genetics. The universality of organism senescence has been questioned on both theoretical and empirical grounds, and the prevalence and strength of senescence remain a controversial issue. Plants are particularly interesting for studies of senescence since individuals of many species have been reported to reach very high ages. 2. In this study, we examined whether the herb Borderea pyrenaica, known to reach ages of more than 300 years, experiences senescence. We collected detailed demographic information from male and female individuals in two populations over 5 years. An unusual morphological feature in this species enabled us to obtain exact age estimates for each of the individuals at the end of the demographic study. 3. We used restricted cubic regression splines and generalized linear models to determine nonlinear effects of age and size on vital rates. We then incorporated the effects of age and size in integral projection models of demography for determining the relationship between age and reproductive value. As the species is dioecious, we performed analyses separately for males and females and examined also the hypothesis that a larger reproductive effort in females comes at a senescence cost. 4. We found no evidence for senescence. Recorded individuals reached 260 years, but growth and fecundity of female and male individuals did not decrease at high ages, and survival and reproductive value increased with age. The results were qualitatively similar also when accounting for size and among-individual vital rate heterogeneity, with the exception that male flowering probability decreased with age when accounting for size increases. 5. Synthesis. Overall, our results show that performance of both male and female plants of B. pyrenaica may increase rather than decrease at ages up to several centuries, and they support the notion that senescence may be negligible in long-lived modular organisms. This highlights the need to explore mechanisms that enable some species to maintain high reproductive values also at very high ages and to identify the evolutionary reasons why some organisms appear to experience no or negligible senescence.

  • 48. García, María B.
    et al.
    Domingo, Darío
    Pizarro, Manuel
    Font, Xavier
    Gómez, Daniel
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Rocky habitats as microclimatic refuges for biodiversity. A close-up thermal approach2020In: Environmental and Experimental Botany, ISSN 0098-8472, E-ISSN 1873-7307, Vol. 170, article id 103886Article in journal (Refereed)
    Abstract [en]

    In the present scenario of climatic change, climatic refugia will be of paramount importance for species persistence. Topography can generate a considerable climatic heterogeneity over short distances, which is often disregarded in macroclimatic predictive models. Here we investigate the role of rocky habitats as microclimatic refugia by combining two different analyses: exploring a thermal mechanism whereby rocky habitats might serve as refugia, and examining if the biogeographic pattern shows a high abundance of relict, endemic and peripheral species. The thermal profile of two populations of relict and endemic plant species occurring in Pyrenean cliffs was investigated by infrared images and in situ temperature data-loggers. Despite occurring in crevices of a south oriented slope, Androsace cylindrica showed a narrower daily range of temperature than the surrounding matrix, thereby avoiding extreme high temperatures. Borderea chouardii, of tropical ancestors, also occurred in patches where temperatures were buffered during the growth season, experiencing lower mean temperatures than the surrounding matrix and nearby areas during the warmer part of the day, and similar temperatures during the colder. The rocky habitats of both species, therefore, reduced temperature ranges and exposition to extreme climatic events. Compared to other habitats, the rocky ones also harboured a very high fraction of both endemics and peripheral plant populations according to the largest vegetation dataset available in the Pyrenees (18,800 plant inventories and 400,000 records). Our results suggest an association between the habitats of relicts, endemics and species at their distribution limit, driven by a stabilizing effect of rocky habitats on extreme temperatures. Given the important role of rocky habitats as hotspots of singular and unique plants, their characterization seems a sensible first step to identify potential refugia in the context of climate change.

  • 49. Graae, Bente J.
    et al.
    Vandvik, Vigdis
    Armbruster, W. Scott
    Eiserhardt, Wolf L.
    Svenning, Jens-Christian
    Hylander, Kristoffer
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Speed, James D. M.
    Klanderud, Kari
    Brathen, Kari Anne
    Milbau, Ann
    Opedal, Oystein H.
    Alsos, Inger G.
    Ejrnaes, Rasmus
    Bruun, Hans Henrik
    Birks, H. John B.
    Westergaard, Kristine B.
    Birks, Hilary H.
    Lenoir, Jonathan
    Stay or go - how topographic complexity influences alpine plant population and community responses to climate change2018In: Perspectives in plant ecology, evolution and systematics, ISSN 1433-8319, E-ISSN 1618-0437, Vol. 30, p. 41-50Article in journal (Refereed)
    Abstract [en]

    In the face of climate change, populations have two survival options - they can remain in situ and tolerate the new climatic conditions (stay), or they can move to track their climatic niches (go). For sessile and small-stature organisms like alpine plants, staying requires broad climatic tolerances, realized niche shifts due to changing biotic interactions, acclimation through plasticity, or rapid genetic adaptation. Going, in contrast, requires good dispersal and colonization capacities. Neither the magnitude of climate change experienced locally nor the capacities required for staying/going in response to climate change are constant across landscapes, and both aspects may be strongly affected by local microclimatic variation associated with topographic complexity. We combine ideas from population and community ecology to discuss the effects of topographic complexity in the landscape on the immediate stay or go opportunities of local populations and communities, and on the selective pressures that may have shaped the stay or go capacities of the species occupying contrasting landscapes. We demonstrate, using example landscapes of different topographical complexity, how species' thermal niches could be distributed across these landscapes, and how these, in turn, may affect many population and community ecological processes that are related to adaptation or dispersal. Focusing on treeless alpine or Arctic landscapes, where temperature is expected to be a strong determinant, our theorethical framework leads to the hypothesis that populations and communities of topographically complex (rough and patchy) landscapes should be both more resistant and more resilient to climate change than those of topographically simple (flat and homogeneous) landscapes. Our theorethical framework further points to how meta-community dynamics such as mass effects in topographically complex landscapes and extinction lags in simple landscapes, may mask and delay the long-term outcomes of these landscape differences under rapidly changing climates.

  • 50.
    Greiser, Caroline
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Luoto, Miska
    Meineri, Eric
    Merinero, Sonia
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Swedish University of Agricultural Sciences, Sweden.
    Willman, Benny
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Hylander, Kristoffer
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Warm range margin of boreal bryophytes and lichens not directly limited by temperatures2021In: Journal of Ecology, ISSN 0022-0477, E-ISSN 1365-2745, Vol. 109, no 10, p. 3724-3736Article in journal (Refereed)
    Abstract [en]

    Species at their warm range margin are potentially threatened by higher temperatures, but may persist in microrefugia. Whether such microsites occur due to more suitable microclimate or due to lower biotic pressure from, for example competitive species, is still not fully resolved. We examined whether boreal bryophytes and lichens show signs of direct climate limitation, that is whether they perform better in cold and/or humid microclimates at their warm range margin. We transplanted a moss, a liverwort and a lichen to 58 boreal forest sites with different microclimates at the species' southern range margin in central Sweden. Species were grown in garden soil patches to control the effects of competitive exclusion and soil quality. We followed the transplanted species over three growing seasons (2016-2018) and modelled growth and vitality for each species as a function of subcanopy temperature, soil moisture, air humidity and forest type. In 2018, we also recorded the cover of other plants having recolonized the garden soil patches and modelled this potential future competition with the same environmental variables plus litter. Species performance increased with warmer temperatures, which was often conditional on high soil moisture, and at sites with more conifers. Soil moisture had a positive effect, especially on the moss in the last year 2018, when the growing season was exceptionally hot and dry. The lichen was mostly affected by gastropod grazing. Recolonization of other plants was also faster at warmer and moister sites. The results indicate that competition, herbivory, shading leaf litter and water scarcity might be more important than the direct effects of temperature for performance at the species' warm range margin. Synthesis. In a transplant experiment with three boreal understorey species, we did not find signs of direct temperature limitation towards the south. Forest microrefugia, that is habitats where these species could persist regional warming, may instead be sites with fewer competitors and enemies, and with sufficient moisture and more conifers in the overstorey.

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