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  • 1.
    Eckerström-Liedholm, Simon
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Sowersby, Will
    Stockholm University, Faculty of Science, Department of Zoology.
    Gonzalez-Voyer, Alejandro
    Stockholm University, Faculty of Science, Department of Zoology. Universidad Nacional Autónoma de México, Mexico.
    Rogell, Björn
    Stockholm University, Faculty of Science, Department of Zoology.
    Time-limited environments affect the evolution of egg-body size allometry2017In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 71, no 7, p. 1900-1910Article in journal (Refereed)
    Abstract [en]

    Initial offspring size is a fundamental component of absolute growth rate, where large offspring will reach a given adult body size faster than smaller offspring. Yet, our knowledge regarding the coevolution between offspring and adult size is limited. In time-constrained environments, organisms need to reproduce at a high rate and reach a reproductive size quickly. To rapidly attain a large adult body size, we hypothesize that, in seasonal habitats, large species are bound to having a large initial size, and consequently, the evolution of egg size will be tightly matched to that of body size, compared to less time-limited systems. We tested this hypothesis in killifishes, and found a significantly steeper allometric relationship between egg and body sizes in annual, compared to nonannual species. We also found higher rates of evolution of egg and body size in annual compared to nonannual species. Our results suggest that time-constrained environments impose strong selection on rapidly reaching a species-specific body size, and reproduce at a high rate, which in turn imposes constraints on the evolution of egg sizes. In combination, these distinct selection pressures result in different relationships between egg and body size among species in time-constrained versus permanent habitats.

  • 2.
    Eckerström-Liedholm, Simon
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Sowersby, Will
    Kotrschal, Alexander
    Näslund, Joacim
    Stockholm University, Faculty of Science, Department of Zoology.
    Rowiński, Piotr
    Stockholm University, Faculty of Science, Department of Zoology.
    Gonzalez-Voyer, Alejandro
    Stockholm University, Faculty of Science, Department of Zoology.
    Rogell, Björn
    Stockholm University, Faculty of Science, Department of Zoology.
    Fast life-histories are associated with larger brain size in killifishesManuscript (preprint) (Other academic)
    Abstract [en]

    Comparative studies suggest a negative relationship between pace of life-history, and relative energetic investment into brain size. However, since brain size typically evolves as a correlated response to selection on body size, any lag in brain size evolution will result in a shift in relative brain size (e.g. small body – large relative brain size).Coevolution between body size and life-history hence has the potential to drive secondary associations between relative brain size and life-history, when body size is correlated with life history. However, as far as we know, the relationship between relative brain size and life-history strategy has not been examined in systems that simultaneously present marked contrasts in life-history but no concordant shifts in body size. Using a common garden approach, we test the association between relative brain size and life-history in 21 species of killifish; a study system that fulfils the aforementioned requirements. Contrary to the prediction that brain size evolves through energetic trade-offs with life-history, we found that adults, but not juveniles, of fast-living species had larger relative brain sizes. Rather than an energetic link to life-history, our results suggest that fast- and slow-living species differ in terms of how cognitively demanding environments they inhabit are, or alternatively in the ontogenetic timing of somatic vs. neural growth.

  • 3.
    Eckerström-Liedholm, Simon
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Sowersby, Will
    Stockholm University, Faculty of Science, Department of Zoology.
    Morozov, Sergey
    van der Bijl, Wouter
    Rowiński, Piotr
    Stockholm University, Faculty of Science, Department of Zoology.
    Gonzalez-Voyer, Alejandro
    Stockholm University, Faculty of Science, Department of Zoology.
    Rogell, Björn
    Stockholm University, Faculty of Science, Department of Zoology.
    Macroevolutionary evidence suggests trait-dependent coevolution between behaviour and life-historyManuscript (preprint) (Other academic)
    Abstract [en]

    Species with fast life-histories prioritize current over future reproduction, which ought to require greater energetic resources, but also results in a shorter time-period to realize their reproductive potential, compared to slow life-histories, which prioritize future reproduction. Hence, behaviours that increase access to both resources and mating opportunities, at a cost of increased mortality risk, are thought to coevolve with the pace of life-history. However, whether this prediction holds across species, is yet to be tested under standardized conditions. Here, we test how potentially risky behaviours, which facilitate access to resources and mating opportunities (i.e. activity, boldness and aggression), along with metabolic rate, correlates with the pace of life-history across 20 species of killifish, which present a remarkable divergence in the pace of their life-histories. We found a positive correlation between the pace of life-history and aggression, but not with any other behavioural traits or metabolic rate. Aggression is often expressed in the context of mating, while the other behaviours we measured might be more relevant for access to energetic resources. Our results therefore suggest that the trade-off between current and future reproduction plays a more prominent role in shaping mating behaviour, while behaviours related to acquisition of energetic resources may be more affected by ecological factors.

  • 4.
    Eckerström-Liedholm, Simon
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Sowersby, Will
    Stockholm University, Faculty of Science, Department of Zoology.
    Morozov, Sergey
    van der Bijl, Wouter
    Stockholm University, Faculty of Science, Department of Zoology. University of British Columbia, Canada.
    Rowiński, Piotr K.
    Stockholm University, Faculty of Science, Department of Zoology.
    Gonzalez-Voyer, Alejandro
    Stockholm University, Faculty of Science, Department of Zoology. Universidad Nacional Autónoma de México, Mexico.
    Rogell, Björn
    Stockholm University, Faculty of Science, Department of Zoology.
    Macroevolutionary evidence suggests trait-dependent coevolution between behavior and life-history2019In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 73, no 11, p. 2312-2323Article in journal (Refereed)
    Abstract [en]

    Species with fast life-histories typically prioritize current over future reproductive events, compared to species with slow life-histories. These species therefore require greater energetic input into reproduction, and also likely have less time to realize their reproductive potential. Hence, behaviors that increase access to both resources and mating opportunities, at a cost of increased mortality risk, could coevolve with the pace of life-history. However, whether this prediction holds across species, remains untested under standardized conditions. Here, we test how risky behaviors, which facilitate access to resources and mating opportunities (i.e., activity, boldness, and aggression), along with metabolic rate, coevolve with the pace of life-history across 20 species of killifish that present remarkable divergences in the pace of life-history. We found a positive association between the pace of life-history and aggression, but interestingly not with other behavioral traits or metabolic rate. Aggression is linked to interference competition, and in killifishes is often employed to secure mates, while activity and boldness are more relevant for exploiting energetic resources. Our results suggest that the trade-off between current and future reproduction plays a more prominent role in shaping mating behavior, while behaviors related to energy acquisition may be influenced by ecological factors.

  • 5.
    Hansen Wheat, Christina
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Fitzpatrick, John L.
    Stockholm University, Faculty of Science, Department of Zoology.
    Rogell, Björn
    Stockholm University, Faculty of Science, Department of Zoology.
    Temrin, Hans
    Stockholm University, Faculty of Science, Department of Zoology.
    Behavioural correlations of the domestication syndrome are decoupled in modern dog breeds2019In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 10, article id 2422Article in journal (Refereed)
    Abstract [en]

    Domestication is hypothesized to drive correlated responses in animal morphology, physiology and behaviour, a phenomenon known as the domestication syndrome. However, we currently lack quantitative confirmation that suites of behaviours are correlated during domestication. Here we evaluate the strength and direction of behavioural correlations among key prosocial (sociability, playfulness) and reactive (fearfulness, aggression) behaviours implicated in the domestication syndrome in 76,158 dogs representing 78 registered breeds. Consistent with the domestication syndrome hypothesis, behavioural correlations within prosocial and reactive categories demonstrated the expected direction-specificity across dogs. However, correlational strength varied between dog breeds representing early (ancient) and late (modern) stages of domestication, with ancient breeds exhibiting exaggerated correlations compared to modern breeds across prosocial and reactive behaviours. Our results suggest that suites of correlated behaviours have been temporally decoupled during dog domestication and that recent shifts in selection pressures in modern dog breeds affect the expression of domestication-related behaviours independently.

  • 6.
    Herbert-Read, James E.
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. Uppsala University, Sweden.
    Rosén, Emil
    Szorkovszky, Alex
    Ioannou, Christos C.
    Rogell, Björn
    Stockholm University, Faculty of Science, Department of Zoology.
    Perna, Andrea
    Ramnarine, Indar W.
    Kotrschal, Alexander
    Stockholm University, Faculty of Science, Department of Zoology.
    Kolm, Niclas
    Stockholm University, Faculty of Science, Department of Zoology.
    Krause, Jens
    Sumpter, David J. T.
    How predation shapes the social interaction rules of shoaling fish2017In: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 284, no 1861, article id 20171126Article in journal (Refereed)
    Abstract [en]

    Predation is thought to shape the macroscopic properties of animal groups, making moving groups more cohesive and coordinated. Precisely how predation has shaped individuals' fine-scale social interactions in natural populations, however, is unknown. Using high-resolution tracking data of shoaling fish (Poecilia reticulata) from populations differing in natural predation pressure, we show how predation adapts individuals' social interaction rules. Fish originating from high predation environments formed larger, more cohesive, but not more polarized groups than fish from low predation environments. Using a new approach to detect the discrete points in time when individuals decide to update their movements based on the available social cues, we determine how these collective properties emerge from individuals' microscopic social interactions. We first confirm predictions that predation shapes the attraction-repulsion dynamic of these fish, reducing the critical distance at which neighbours move apart, or come back together. While we find strong evidence that fish align with their near neighbours, we do not find that predation shapes the strength or likelihood of these alignment tendencies. We also find that predation sharpens individuals' acceleration and deceleration responses, implying key perceptual and energetic differences associated with how individuals move in different predation regimes. Our results reveal how predation can shape the social interactions of individuals in groups, ultimately driving differences in groups' collective behaviour.

  • 7. Kotrschal, Alexander
    et al.
    Rogell, Björn
    Uppsala universitet, Zooekologi.
    Bundsen, Andreas
    Svensson, Beatrice
    Zajitschek, Susanne
    Brännström, Ioana
    Immler, Simone
    Maklakov, Alexei A.
    Kolm, Niclas
    Uppsala universitet, Zooekologi.
    The benefit of evolving a larger brain: big-brained guppies perform better in a cognitive task2013In: Animal Behaviour, ISSN 0003-3472, E-ISSN 1095-8282, Vol. 86, no 4, p. e4-e6Article in journal (Refereed)
    Abstract [en]

    We previously selected for large and small brain size in guppies. Large-brained females outperformed small-brained females in a learning task. Healy and Rowe challenged our interpretations of larger brains = better learning. Here we argue why we think they are mistaken.

  • 8.
    Kotrschal, Alexander
    et al.
    Uppsala universitet, Zooekologi.
    Rogell, Björn
    Uppsala universitet, Zooekologi.
    Bundsen, Andreas
    Svensson, Beatrice
    Zajitschek, Susanne
    Uppsala universitet, Evolutionsbiologi.
    Brännström, Ioana Onut
    Uppsala universitet, Evolutionsbiologi.
    Immler, Simone
    Maklakov, Alexei A.
    Kolm, Niclas
    Uppsala universitet, Zooekologi.
    Artificial selection on relative brain size in the guppy reveals costs and benefits of evolving a larger brain2013In: Current Biology, ISSN 0960-9822, E-ISSN 1879-0445, Vol. 23, no 2, p. 168-171Article in journal (Refereed)
    Abstract [en]

    The large variation in brain size that exists in the animal kingdom has been suggested to have evolved through the balance between selective advantages of greater cognitive ability and the prohibitively high energy demands of a larger brain (the "expensive-tissue hypothesis" [1]). Despite over a century of research on the evolution of brain size, empirical support for the trade-off between cognitive ability and energetic costs is based exclusively on correlative evidence [2], and the theory remains controversial [3, 4]. Here we provide experimental evidence for costs and benefits of increased brain size. We used artificial selection for large and small brain size relative to body size in a live-bearing fish, the guppy (Poecilia reticulata), and found that relative brain size evolved rapidly in response to divergent selection in both sexes. Large-brained females outperformed small-brained females in a numerical learning assay designed to test cognitive ability. Moreover, large-brained lines, especially males, developed smaller guts, as predicted by the expensive-tissue hypothesis [1], and produced fewer offspring. We propose that the evolution of brain size is mediated by a functional trade-off between increased cognitive ability and reproductive performance and discuss the implications of these findings for vertebrate brain evolution.

  • 9.
    Kotrschal, Alexander
    et al.
    Uppsala universitet, Zooekologi.
    Rogell, Björn
    Uppsala universitet, Zooekologi.
    Maklakov, Alexei A.
    Uppsala universitet, Zooekologi.
    Kolm, Nichlas
    Uppsala universitet, Zooekologi.
    Sex-specific plasticity in brain morphology depends on social environment of the guppy, Poecilia reticulata2012In: Behavioral Ecology and Sociobiology, ISSN 0340-5443, E-ISSN 1432-0762, Vol. 66, no 11, p. 1485-1492Article in journal (Refereed)
    Abstract [en]

    The vertebrate brain is a remarkably plastic organ, which responds quickly to environmental changes. However, to date, studies investigating plasticity in brain morphology have focused mostly on the physical properties of the surrounding environment, and little is known about brain plasticity in response to the social environment. Moreover, sex differences in brain plasticity remain virtually unexplored. Here, we tested how the social environment influenced brain morphology in adult males and females using experimental manipulation of the sex composition of social pairs (same sex vs. mixed sex) in the guppy (Poecilia reticulata). We detected substantial sex-specific plasticity in both the overall brain size (controlling for body size) and separate brain structures. The brain size was larger in males that interacted with females, and female optic tectum was larger in female-only groups. Overall, females had larger olfactory bulbs and cerebellum in comparison to males. While net sexual dimorphism in the brain structure can be explained in light of the known differences in boldness and foraging behaviour between the sexes, our results also support that cognitive demands associated with courtship behaviour can lead to plastic changes in the brain size. Our findings demonstrate that not only social environment can generate rapid, plastic responses in the vertebrate brain but also that such responses can depend strongly on sex.

  • 10. Kotrschal, Alexander
    et al.
    Trombley, Susanne
    Rogell, Björn
    Brännström, Ioana
    Foconi, Eric
    Schmitz, Monika
    Kolm, Niclas
    Stockholm University, Faculty of Science, Department of Zoology. Uppsala University, Sweden.
    The mating brain: early maturing sneaker males maintain investment into the brain also under fast body growth in Atlantic salmon (Salmo salar)2014In: Evolutionary Ecology, ISSN 0269-7653, E-ISSN 1573-8477, Vol. 28, no 6, p. 1043-1055Article in journal (Refereed)
    Abstract [en]

    It has been suggested that mating behaviours require high levels of cognitive ability. However, since investment into mating and the brain both are costly features, their relationship is likely characterized by energetic trade-offs. Empirical data on the subject remains equivocal. We investigated if early sexual maturation was associated with brain development in Atlantic salmon (Salmo salar), in which males can either stay in the river and sexually mature at a small size (sneaker males) or migrate to the sea and delay sexual maturation until they have grown much larger (anadromous males). Specifically, we tested how sexual maturation may induce plastic changes in brain development by rearing juveniles on either natural or ad libitum feeding levels. After their first season we compared brain size and brain region volumes across both types of male mating tactics and females. Body growth increased greatly across both male mating tactics and females during ad libitum feeding as compared to natural feeding levels. However, despite similar relative increases in body size, early maturing sneaker males maintained larger relative brain size during ad libitum feeding levels as compared to anadromous males and females. We also detected several differences in the relative size of separate brain regions across feeding treatments, sexes and mating strategies. For instance, the relative size of the cognitive centre of the brain, the telencephalon, was largest in sneaker males. Our data support that a large relative brain size is maintained in individuals that start reproduction early also during fast body growth. We propose that the cognitive demands during complex mating behaviours maintain a high level of investment into brain development in reproducing individuals.

  • 11. Marzal, Julia Carolina Segami
    et al.
    Rudh, Andreas
    Rogell, Björn
    Stockholm University, Faculty of Science, Department of Zoology.
    Ödeen, Anders
    Lovlie, Hanne
    Rosher, Charlotte
    Qvarnström, Anna
    Cryptic female Strawberry poison frogs experience elevated predation risk when associating with an aposematic partner2017In: Ecology and Evolution, ISSN 2045-7758, E-ISSN 2045-7758, Vol. 7, no 2, p. 744-750Article in journal (Refereed)
    Abstract [en]

    Population divergence in sexual signals may lead to speciation through prezygotic isolation. Sexual signals can change solely due to variation in the level of natural selection acting against conspicuousness. However, directional mate choice (i.e., favoring conspicuousness) across different environments may lead to gene flow between populations, thereby delaying or even preventing the evolution of reproductive barriers and speciation. In this study, we test whether natural selection through predation upon mate-choosing females can favor corresponding changes in mate preferences. Our study system, Oophaga pumilio, is an extremely color polymorphic neotropical frog with two distinctive antipredator strategies: aposematism and crypsis. The conspicuous coloration and calling behavior of aposematic males may attract both cryptic and aposematic females, but predation may select against cryptic females choosing aposematic males. We used an experimental approach where domestic fowl were encouraged to find digitized images of cryptic frogs at different distances from aposematic partners. We found that the estimated survival time of a cryptic frog was reduced when associating with an aposematic partner. Hence, predation may act as a direct selective force on female choice, favoring evolution of color assortative mating that, in turn, may strengthen the divergence in coloration that natural selection has generated.

  • 12.
    Rogell, Björn
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. Swedish University of Agricultural Sciences, Sweden.
    Dowling, Damian K.
    Husby, Arild
    Controlling for body size leads to inferential biases in the biological sciences2019In: Evolution letters, E-ISSN 2056-3744Article in journal (Refereed)
    Abstract [en]

    Many traits correlate with body size. Studies that seek to uncover the ecological factors that drive evolutionary responses in traits typically examine these responses relative to associated changes in body size using multiple regression analysis. However, it is not well appreciated that in the presence of strongly correlated variables, the partial (i.e., relative) regression coefficients often change sign compared to the original coefficients. Such sign reversals are difficult to interpret in a biologically meaningful way, and could lead to erroneous evolutionary inferences if the true mechanism underlying the sign reversal differed from the proposed mechanism. Here, we use simulations to demonstrate that sign reversal occurs over a wide range of parameter values common in the biological sciences. Further, as a case-in-point, we review the literature on brain size evolution; a field that explores how ecological traits relate to the evolution of relative brain size (brain size relative to body size). We find that most studies show sign reversals and thus that the inferences of many studies in this field may be inconclusive. Finally, we propose some approaches to mitigating this issue.

  • 13.
    Rowiński, Piotr K.
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Rogell, Björn
    Stockholm University, Faculty of Science, Department of Zoology.
    Environmental stress correlates with increases in both genetic and residual variances: A meta-analysis of animal studies2017In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 71, no 5, p. 1339-1351Article in journal (Refereed)
    Abstract [en]

    Adaptive evolutionary responses are determined by the strength of selection and amount of genetic variation within traits, however, both are known to vary across environmental conditions. As selection is generally expected to be strongest under stressful conditions, understanding how the expression of genetic variation changes across stressful and benign environmental conditions is crucial for predicting the rate of adaptive change. Although theory generally predicts increased genetic variation under stress, previous syntheses of the field have found limited support for this notion. These studies have focused on heritability, which is dependent on other environmentally sensitive, but nongenetic, sources of variation. Here, we aim to complement these studies with a meta-analysis in which we examine changes in coefficient of variation (CV) in maternal, genetic, and residual variances across stressful and benign conditions. Confirming previous analyses, we did not find any clear direction in how heritability changes across stressful and benign conditions. However, when analyzing CV, we found higher genetic and residual variance under highly stressful conditions in life-history traits but not in morphological traits. Our findings are of broad significance to contemporary evolution suggesting that rapid evolutionary adaptive response may be mediated by increased evolutionary potential in stressed populations.

  • 14.
    Rowiński, Piotr
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Laurila, Anssi
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology.
    Sowersby, Will
    Stockholm University, Faculty of Science, Department of Zoology.
    Lind, Martin
    Richter-Boix, Alex
    Eckerström-Liedholm, Simon
    Stockholm University, Faculty of Science, Department of Zoology.
    Rogell, Björn
    Stockholm University, Faculty of Science, Department of Zoology.
    Thermally induced parental effects influence life history traits and covary with an environmental cline in common frog populationsManuscript (preprint) (Other academic)
    Abstract [en]

    Across latitudinal clines, the juvenile developmental rates of ectotherms often covary with the length of the growing season, due to life-history trade-offs imposed by time-constrained environments. However, as the start of the growing season often varies substantially across years, adaptive parental effects on juvenile developmental rates may mediate the costs of a delayed spring. By employing a meta-analysis, we tested whether larval developmental rates across a latitudinal cline of common frogs (Rana temporaria) are affected by fluctuating onsets of breeding, across years. We predicted that larval developmental rate will be inversely related to the onset of breeding, and that northern populations will be more prone to shorten their developmental rate in response to late breeding, as the costs of delayed metamorphosis should be highest in areas with a shorter growing season. We found that the larval period of both northern and southern populations responded to parental environmental conditions to similar degree in absolute terms, but in different directions. In northern populations, a late season start correlated with decreased development time, suggesting that the evolution of parental effects aid population persistence in time-constrained environments. In southern populations, late season start correlated with increased development time, which could potentially be explained as a predator avoidance strategy. Our findings suggest that local ecological variables can induce adaptive parental effects, but responses are complex, and likely trade-off with other ecological factors.

  • 15.
    Rowiński, Piotr
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Näslund, Joacim
    Stockholm University, Faculty of Science, Department of Zoology.
    Sowersby, Will
    Stockholm University, Faculty of Science, Department of Zoology.
    Eckerström-Liedholm, Simon
    Stockholm University, Faculty of Science, Department of Zoology.
    Rogell, Björn
    Stockholm University, Faculty of Science, Department of Zoology.
    The evolution of a placenta is not linked to increased brain size in poeciliid fishesManuscript (preprint) (Other academic)
    Abstract [en]

    Maternal investment traits are considered to have a direct influence on the size of energetically costly organs, including the brain. In placental organisms, offspring are supplied with nutrients during pre-natal development, which in turn may modulate brain size evolution. While this hypothesis has received some support in mammals (i.e. in the marsupial/placental transition), how the evolution of the placenta affects brain size in other taxa is largely unknown.Here, we use eight poeciliid fish species to test if species with placental transferred nutrients, invest more resources into offspring brain development than species with no placental structures. We predicted that the evolution of the placenta would be associated with larger relative brain size in fry, and possibly also shallower ontogenetic brain size allometry, if cognitive demands are similar in adults across placental and non-placental species. We tested these hypotheses by taking non-invasive brain size measurements during the first four weeks of life, and relating these to corresponding somatic growth. Contrary to our expectations, we did not find any differences in brain size between the two maternal strategies. Furthermore, we did not find any differences in how relative brain size changed over ontogenetic development between placental and non-placental species. Elsewhere, maternal investment traits have been commonly linked to brain size, however the species investigated here only exhibit pre-natal provisioning, which may reduce the potential for maternal investment into brain size. Our results suggest that coevolution between placental structures and juvenile brain size is not a general pattern.

  • 16.
    Rowiński, Piotr
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Sowersby, Will
    Stockholm University, Faculty of Science, Department of Zoology.
    Näslund, Joacim
    Stockholm University, Faculty of Science, Department of Zoology.
    Eckerström-Liedholm, Simon
    Stockholm University, Faculty of Science, Department of Zoology.
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology.
    Rogell, Björn
    Stockholm University, Faculty of Science, Department of Zoology.
    Variation in developmental rates is not linked to environmental unpredictability in annual killifishesManuscript (preprint) (Other academic)
    Abstract [en]

    Comparative evidence suggests that adaptive plasticity may evolve as a response to predictable environmental variation. However, receiving less attention is unpredictable environmental variation, which is considered to affect evolutionary trajectories by increasing phenotypic variation (bet-hedging). If increased variance in development time evolved as an adaptation to unpredictable environmental conditions, we would expect species inhabiting locations with unpredictable conditions to have a higher variance in development time. Here, we examine the occurrence of bet-hedging in egg developmental rate in seven species of annual killifish, originating from a gradient of precipitation rate variation, under three different incubation temperatures (21°C, 23°C, and 25°C). These fish species persist as dormant eggs buried in the soil, in seasonal environments with regular habitat desiccation. At the onset of the rainy season, the eggs must be sufficiently developed in order to hatch, and complete their life-cycle. We found substantial differences among species in both mean and variation of egg development rates, as well as species-specific plastic temperature responses. However, there was no clear relationship between variation in egg development time and variation in precipitation (environmental predictability). Hence, if species specific variances are adaptive, they do not diverge in accordance with simple linear relationship to variation in precipitation.

  • 17. Sowersby, Will
    et al.
    Eckerström-Liedholm, Simon
    Stockholm University, Faculty of Science, Department of Zoology.
    Rowiński, Piotr
    Stockholm University, Faculty of Science, Department of Zoology.
    Balogh, Julia
    Eiler, Stefan
    Upstone, Joseph
    Gonzalez-Voyer, Alejandro
    Stockholm University, Faculty of Science, Department of Zoology.
    Rogell, Björn
    Stockholm University, Faculty of Science, Department of Zoology.
    Costly sexual ornaments coevolve with fast life-histories in killifishesManuscript (preprint) (Other academic)
    Abstract [en]

    Sexually selected ornaments constitute an important investment into reproduction, increasing current mating success, at a potential cost to survival. Theory suggests that exaggerated sexual ornaments may coevolve with the life-history trade-off between current and future reproduction, however this hypothesis has remained unexplored. Here, we determine how the size of secondary sexual traits coevolves with the pace of life-histories (slow or fast), using a clade of killifishes, where independent adaptations to ephemeral environments have resulted in substantial divergences in life-history strategy. In addition, we assess costs to swimming performance driven by enlarged, ornamental fins. We predict that killifishes with fast life-histories, which inhabit time-limited environments and prioritize current reproduction, will have a greater tendency to evolve enlarged fins, compared to killifishes with slow life-histories. Indeed, we found that species with fast life-histories had more pronounced sexual size dimorphism, with males from these species having exaggerated dorsal and anal fins, compared to species with slow life-histories. Furthermore, males from species with fast life-histories and larger ornaments exhibited lower swimming performances compared to both conspecific females, and individuals from species with slow life-histories. Our results indicate that the trade-off between current and future reproduction, can be an evolutionary driver of costly sexual ornaments.

  • 18. Stocks, Michael
    et al.
    Dean, Rebecca
    Rogell, Björn
    Stockholm University, Faculty of Science, Department of Zoology.
    Friberg, Urban
    Sex-specific Trans-regulatory Variation on the Drosophila melanogaster X Chromosome2015In: PLOS Genetics, ISSN 1553-7390, E-ISSN 1553-7404, Vol. 11, no 2, article id e1005015Article in journal (Refereed)
    Abstract [en]

    The X chromosome constitutes a unique genomic environment because it is present in one copy in males, but two copies in females. This simple fact has motivated several theoretical predictions with respect to how standing genetic variation on the X chromosome should differ from the autosomes. Unmasked expression of deleterious mutations in males and a lower census size are expected to reduce variation, while allelic variants with sexually antagonistic effects, and potentially those with a sex-specific effect, could accumulate on the X chromosome and contribute to increased genetic variation. In addition, incomplete dosage compensation of the X chromosome could potentially dampen the male-specific effects of random mutations, and promote the accumulation of X-linked alleles with sexually dimorphic phenotypic effects. Here we test both the amount and the type of genetic variation on the X chromosome within a population of Drosophila melanogaster, by comparing the proportion of X linked and autosomal trans-regulatory SNPs with a sexually concordant and discordant effect on gene expression. We find that the X chromosome is depleted for SNPs with a sexually concordant effect, but hosts comparatively more SNPs with a sexually discordant effect. Interestingly, the contrasting results for SNPs with sexually concordant and discordant effects are driven by SNPs with a larger influence on expression in females than expression in males. Furthermore, the distribution of these SNPs is shifted towards regions where dosage compensation is predicted to be less complete. These results suggest that intrinsic properties of dosage compensation influence either the accumulation of different types of trans-factors and/or their propensity to accumulate mutations. Our findings document a potential mechanistic basis for sex-specific genetic variation, and identify the X as a reservoir for sexually dimorphic phenotypic variation. These results have general implications for X chromosome evolution, as well as the genetic basis of sex-specific evolutionary change.

  • 19. Yee, Winston K. W.
    et al.
    Rogell, Björn
    Stockholm University, Faculty of Science, Department of Zoology. Monash University, Australia.
    Lemos, Bernardo
    Dowling, Damian K.
    Intergenomic interactions between mitochondrial and Y-linked genes shape male mating patterns and fertility in Drosophila melanogaster2015In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 69, no 11, p. 2876-2890Article in journal (Refereed)
    Abstract [en]

    Under maternal inheritance, mitochondrial genomes are prone to accumulate mutations that exhibit male-biased effects. Such mutations should, however, place selection on the nuclear genome for modifier adaptations that mitigate mitochondrial-incurred male harm. One gene region that might harbor such modifiers is the Y-chromosome, given the abundance of Y-linked variation for male fertility, and because Y-linked modifiers would not exert antagonistic effects in females because they would be found only in males. Recent studies in Drosophila revealed a set of nuclear genes whose expression is sensitive to allelic variation among mtDNA-and Y-haplotypes, suggesting these genes might be entwined in evolutionary conflict between mtDNA and Y. Here, we test whether genetic variation across mtDNA and Y haplotypes, sourced from three disjunct populations, interacts to affect male mating patterns and fertility across 10 days of early life in D. melanogaster. We also investigate whether coevolved mito-Y combinations outperform their evolutionarily novel counterparts, as predicted if the interacting Y-linked variance is comprised of modifier adaptations. Although we found no evidence that coevolved mito-Y combinations outperformed their novel counterparts, interactions between mtDNA and Y-chromosomes affected male mating patterns. These interactions were dependent on male age; thus male reproductive success was shaped by G x G x E interactions.

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