A common approach to investigating species' niches is to examine relationships between spatial variation in environmental conditions and contemporary species occurrences, using species distribution models (SDM or niche models). The relationships between past species distributions and environmental variation over time are less commonly explored. One way to examine effects on species changes over time is to use paleo-datasets to parameterize niche models, where the use of temporal variation allows for making more direct links between past species and environmental conditions through records of past changes. We examined the impact of five environmental variables (temperature, incidence of external nutrient input, local [within bog] moisture, incidence of regionally dry periods, and fire activity) on temporal variation in peatland species composition, occurrences, and abundances (Sphagnum, Eriophorum, Carex, and Ericaceous dwarf shrubs) using a high-resolution peat macrofossil paleo-record spanning the last ~10,000 years from the Store Mosse bog (south-central Sweden). Our results showed that species composition was affected by external nutrient input, local moisture conditions and incidence of regionally dry conditions. The presence and abundance of different species groups were mainly affected by external nutrient input and the incidence of regionally dry periods. Moreover, hummock Sphagna benefited from external nutrient input and low moisture, and in one species, warmer temperatures. Intermediate Sphagna from cooler temperatures with no external nutrient input, and hollow Sphagna from cooler temperatures and external nutrient input. Lastly, our results showed that environmental effects differed between the successional stages of the peatland in one case. Overall, the observed species' responses imply that peatland carbon dynamics will shift with future changes in climate. By examining links between climate and species responses of the past, this study demonstrates that the paleo-data approach in SDMs can contribute to a better understanding of the environmental effects influencing species distributions on longer time scales, thereby providing a valuable tool to improve predictions of future climate change effects.

Premise: In plants, within-individual trait variation might result from mechanisms related to ontogenetic contingency, i.e., to the position of a particular structure within the plant, previous developmental events, and/or the developmental environment. Flower position within inflorescences as well as inflorescence position within plants can influence resource provisioning, phenology, biotic interactions, and reproductive success. Despite the potential implications of within-individual variation in plant reproductive phenotypes, its causes and effects on reproductive success are still little explored. Methods: We assessed how reproductive success, in terms of fruit and seed set, and seed predation of 5883 flowers in Lathyrus vernus were influenced by their position within and among racemes, to what extent relationships between flower position and reproductive success and seed predation were mediated by phenology, and if positional effects on reproductive success depended on the external environment. Results: In three years, basal flowers and racemes opened earlier and had higher fruit set than distal. Basal flowers also experienced higher seed predation. Differences among racemes in fruit and seed set were largely related to phenology, while differences in fruit set, seed set, and seed predation within racemes were not. In one year, differences in fruit set among flowers at different positions depended on flowering duration. Conclusions: Our results highlight the important role of ontogenetic contingency for within-individual variation in phenology and reproductive success. As the spatial distribution of reproductive structures affects both within-plant trait distributions and fitness, it is a likely target for natural selection.

Questions How do local forest conditions and characteristics at the forest patch - scale and landscape - scale affect plot-scale plant diversity in Europe? Do these patterns vary between forest specialists and generalists? Do community saturation patterns differ between forests varying in their surrounding landscape type?

Location: Deciduous forests sampled along a European gradient from southwest to northeast comprising eight regions in five countries (France, Belgium, Germany, Sweden, Estonia).

Methods: We examined the effects of local conditions assessed by means of Ellenberg indicator values (soil moisture, soil nitrogen, soil pH, light availability), patch-scale characteristics (patch-scale plant diversity, forest patch age, forest patch size) and a landscape-scale variable (representing low and high connectivity of forest patches) on plot-scale plant diversity, separately for forest specialist and generalist species. Additionally, we ran regression models to examine community saturation patterns.

Results: We found patterns of niche partitioning among forest specialists and generalists. Low light availability and medium soil moisture favored forest specialists, while generalists were mostly present at higher light availability and medium and high soil moisture. In general, we found the highest plot-scale diversity at medium soil pH. Patch-scale diversity showed a positive impact on plot-scale diversity and plots in the high-connectivity landscape had a higher diversity than plots in the low-connectivity landscape. Further, we observed a high degree of community saturation in both landscape types.

Conclusion: The positive impact of a high connectivity of forest patches on local plant diversity emphasizes the importance of small semi-natural habitats like tree lines, unused field margins and hedgerows to enhance the potential dispersal of forest plants across agricultural landscapes. Community saturation patterns revealed the increasing relevance of local conditions and processes for plot-scale diversity when patch-scale diversity increases.

Natural selection on traits expressed repeatedly by individuals is usually investigated with a focus on mean values, although within-individual trait distributions often differ also in other aspects, such as their spread and shape. In plants producing multiple flowers during a season, there might not be a single optimal flowering time, but rather an optimal distribution of flower opening dates. This optimal distribution might depend on both resource allocation patterns and interactions with the abiotic and biotic environment. In this study, we quantified mean, variance, skewness and kurtosis of 495 individual flowering schedules (5287 flowers) over 3 years, and assessed phenotypic selection on these aspects of the within-individual distribution of opening dates in the perennial herb Lathyrus vernus. We also explored how selection on within-individual variation in flowering schedules was related to effects on two fitness components: fruit set and the proportion of seeds escaping pre-dispersal predation. Within-individual variation in phenology was larger than, or at least similar to, among-individual variation in all years. We found phenotypic selection on several aspects of individual flowering schedules. In 1 year, selection favoured plants with higher variance in opening dates, and this coincided with a higher fruit set in plants with an increased spread of the flowering schedule. In two of the study years, selection favoured a higher asymmetry of the flowering schedule, and plants with more right-skewed distributions had higher fruit set and higher proportions of seeds escaping predation. Both fruit set and seed predation increased with an earlier mean flowering, resulting in no net selection on mean flowering date. Synthesis: Our results suggest that phenotypic selection on the spread and shape of flower opening date distributions might be at least as important as selection on the mean flowering date. In a broad sense, this implies that we should consider the entire trait distribution if we aim to understand the evolution of traits that are expressed multiple times within individuals.

Many landscapes worldwide are characterized by the presence of a mosaic of forest patches with contrasting age and size embedded in a matrix of agricultural land. However, our understanding of the effects of these key forest patch features on the soil nutrient status (in terms of nitrogen, carbon, and phosphorus) and soil pH is still limited due to a lack of large-scale data. To address this research gap, we analyzed 830 soil samples from nearly 200 forest patches varying in age (recent versus ancient forests) and size (small versus larger patches) along a 2500-km latitudinal gradient across Europe. We also considered environmental covariates at multiple scales to increase the generality of our research, including variation in macroclimate, nitrogen deposition rates, forest cover in a buffer zone, basal area and soil type. Multiple linear mixed-effects models were performed to test the combined effects of patch features and environmental covariates on soil nutrients and pH. Recent patches had higher total soil phosphorus concentrations and stocks in the mineral soil layer, along with a lower nitrogen to phosphorus ratio within that layer. Small patches generally had a higher mineral soil pH. Mineral soil nitrogen stocks were lower in forest patches with older age and larger size, as a result of a significant interactive effect. Additionally, environmental covariates had significant effects on soil nutrients, including carbon, nitrogen, phosphorus, and their stoichiometry, depending on the specific covariates. In some cases, the effect of patch age on mineral soil phosphorus stocks was greater than that of environmental covariates. Our findings underpin the important roles of forest patch age and size for the forest soil nutrient status. Long-term studies assessing edge effects and soil development in post-agricultural forests are needed, especially in a context of changing land use and climate.

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. 

In seasonal environments, a high responsiveness of development to increasing temperatures in spring can infer benefits in terms of a longer growing season, but also costs in terms of an increased risk of facing unfavourable weather conditions. Still, we know little about how climatic conditions influence the optimal plastic response. Using 22 years of field observations for the perennial forest herb Lathyrus vernus, we assessed phenotypic selection on among-individual variation in reaction norms of flowering time to spring temperature, and examined if among-year variation in selection on plasticity was associated with spring temperature conditions. We found significant among-individual variation in mean flowering time and flowering time plasticity, and that plants that flowered earlier also had a more plastic flowering time. Selection favoured individuals with an earlier mean flowering time and a lower thermal plasticity of flowering time. Less plastic individuals were more strongly favoured in colder springs, indicating that spring temperature influenced optimal flowering time plasticity. Our results show how selection on plasticity can be linked to climatic conditions, and illustrate how we can understand and predict evolutionary responses of organisms to changing environmental conditions.

Climatic conditions can influence plant reproduction directly, but also via changes in plant traits, interactions with animals, and the surrounding environment. Such indirect effects can often be complex and involve multiple steps including climatic effects on interacting species, and on the context in which these interactions occur. The joint effects of climatic variation and indirect effects in terms of plant-animal interactions have sometimes been assessed at larger spatial scales. However, less is known about how microclimatic variation affects within-population variation in reproductive performance, in spite of that it is becoming increasingly clear that variation in climatic conditions can occur over very short distances. We studied the direct and indirect effects of microclimate on withinpopulation variation in reproductive performance of the plant Gentiana pneumonanthe in presence of the myrmecophagous and seed predator butterfly Phengaris alcon. We found that microclimatic effects on plant performance were mainly indirect, and that effects of temperature and moisture were interactive. The number of seeds per flower of G. pneumonanthe decreased in cold and moist microsites, and these effects were mediated by an increased oviposition by P. alcon in these microsites. The effects of soil temperature and moisture on the incidence of oviposition and plant performance were mediated by effects on plant phenology, density and phenology of neighbouring host plants, and host ant abundance. Plants that flowered earlier and where host ants were more abundant, and especially plants surrounded by fewer and later-flowering neighbours, produced fewer seeds per flower because of a higher incidence of oviposition. Our results demonstrate that effects of microclimatic variation on plant reproductive performance can be mostly indirect and largely mediated by species interactions. These findings highlight that among individual variation in small-scale environmental conditions within populations can cause variation in individual plant performance through multiple pathways.

Premise: In high-latitude environments, plastic responses of phenology to increasing spring temperatures allow plants to extend growing seasons while avoiding late frosts. However, evolved plasticity might become maladaptive if climatic conditions change and spring temperatures no longer provide reliable cues for conditions important for fitness. Maladaptative phenological responses might be related to both abiotic factors and mismatches with interacting species. When mismatches arise, we expect selection to favor changes in phenology.

Methods: We combined observations along a soil temperature gradient in a geothermally heated area with pollen and prey supplementation experiments and examined how phenotypic selection on flowering time in the carnivorous plant Pinguicula vulgaris depends on soil temperature, and pollen and prey availability.

Results: Flowering advanced and fitness decreased with increasing soil temperature. However, in pollen-supplemented plants, fitness instead increased with soil temperature. In heated soils, there was selection favoring later flowering, while earlier flowering was favored in unheated soils. This pattern remained also after artificially increasing pollen and prey availability.

Conclusions: Plant–pollinator mismatches can be an important reason why evolved plastic responses of flowering time to increasing spring temperatures become maladaptive under novel environmental conditions, and why there is selection to delay flowering. In our study, selection for later flowering remained after artificially increasing pollen availability, suggesting that abiotic factors also contribute to the observed selection. Identifying the factors that make evolved phenological responses maladaptive under novel conditions is fundamental for understanding and predicting evolutionary responses to climate warming.

Aim: The spatio-temporal connectivity of forest patches in lowland agricultural landscapes and their age matter to explain current biodiversity patterns across regional as well as biogeographical extents, to the point that their effect exceeds the one of macroclimate for plant diversity in the understorey of temperate forests. Whether this remains true for other taxonomic groups is still largely unknown. Yet, this relative influence has important consequences for ecosystem functioning and the delivery of ecosystem services. Focusing on carabid beetle assemblages, we assessed the relative importance of macroclimatic, landscape and patch attributes in driving local species richness (alpha-diversity) and species dissimilarity between patches (beta-diversity).

Location: Deciduous forest patches in seven regions along a 2,100-km-long latitudinal gradient across the European temperate forest biome, from southern France to central Sweden.

Methods: We sampled 221 forest patches in two 5-km x 5-km landscape windows with contrasting management intensities. Carabid beetles were classified into four habitat-preference guilds: forest-specialist, forest-generalist, eurytopic and open-habitat species. We quantified the multi-level environmental influence using mixed-effects models and variation partitioning analysis.

Results: We found that both alpha- and beta-diversity were primarily determined by macroclimate, acting as a large-scale ecological filter on carabid assemblages among regions. Forest-patch conditions, including biotic and abiotic heterogeneity as well as patch age (but not patch size), increased alpha-diversity of forest species. Landscape management intensity weakly influenced alpha-diversity of forest species, but increased the number of non-forest species in forest patches. Beta diversity of non-forest species increased with patch heterogeneity and decreased with landscape management intensity.

Main conclusions: Our results highlight the leading role of broad macroclimatic gradients over local and landscape factors in determining the composition of local carabid communities, thereby shedding light on macroecological patterns of arthropod assemblages. This study emphasizes the urgent need for preserving ancient forest patches embedded in agricultural landscapes, even the small and weakly connected ones.