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  • 1.
    Balogh, Alexandra C.V.
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Gamberale-Stille, Gabriella
    Stockholm University, Faculty of Science, Department of Zoology.
    Tullberg, Birgitta S.
    Stockholm University, Faculty of Science, Department of Zoology.
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology.
    Feature theory and the two-step hypothesis of Müllerian mimicry evolution2010In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 64, no 3, p. 810-822Article in journal (Refereed)
    Abstract [en]

    The two-step hypothesis of Müllerian mimicry evolution states that mimicry starts with a major mutational leap between adaptive peaks, followed by gradual fine-tuning. The hypothesis was suggested to solve the problem of apostatic selection producing a valley between adaptive peaks, and appears reasonable for a one-dimensional phenotype. Extending the hypothesis to the realistic scenario of multidimensional phenotypes controlled by multiple genetic loci can be problematic, because it is unlikely that major mutational leaps occur simultaneously in several traits. Here we consider the implications of predator psychology on the evolutionary process. According to feature theory, single prey traits may be used by predators as features to classify prey into discrete categories. A mutational leap in such a trait could initiate mimicry evolution. We conducted individual-based evolutionary simulations in which virtual predators both categorize prey according to features and generalize over total appearances. We found that an initial mutational leap towards feature similarity in one dimension facilitates mimicry evolution of multidimensional traits. We suggest that feature-based predator categorization together with predator generalization over total appearances solves the problem of applying the two-step hypothesis to complex phenotypes, and provides a basis for a theory of the evolution of mimicry rings.

  • 2.
    Braga, Mariana P.
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Araujo, Sabrina B. L.
    Agosta, Salvatore
    Brooks, Daniel
    Hoberg, Eric
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology.
    Janz, Niklas
    Stockholm University, Faculty of Science, Department of Zoology.
    Boeger, Walter A.
    Host use dynamics in a heterogeneous fitness landscape generates oscillations in host range and diversification2018In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 72, no 9, p. 1773-1783Article in journal (Refereed)
    Abstract [en]

    Colonization of novel hosts is thought to play an important role in parasite diversification, yet little consensus has been achieved about the macroevolutionary consequences of changes in host use. Here, we offer a mechanistic basis for the origins of parasite diversity by simulating lineages evolved in silico. We describe an individual-based model in which (i) parasites undergo sexual reproduction limited by genetic proximity, (ii) hosts are uniformly distributed along a one-dimensional resource gradient, and (iii) host use is determined by the interaction between the phenotype of the parasite and a heterogeneous fitness landscape. We found two main effects of host use on the evolution of a parasite lineage. First, the colonization of a novel host allowed parasites to explore new areas of the resource space, increasing phenotypic and genotypic variation. Second, hosts produced heterogeneity in the parasite fitness landscape, which led to reproductive isolation and therefore, speciation. As a validation of the model, we analyzed empirical data from Nymphalidae butterflies and their host plants. We then assessed the number of hosts used by parasite lineages and the diversity of resources they encompass. In both simulated and empirical systems, host diversity emerged as the main predictor of parasite species richness.

  • 3.
    de Boer, Raïssa A.
    et al.
    University of Antwerp, Belgium.
    Eens, Marcel
    Fransen, Erik
    Müller, Wendt
    Hatching asynchrony aggravates inbreeding depression in a songbird (Serinus canaria): An inbreeding–environment interaction2015In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 69, no 4, p. 1063-1068Article in journal (Refereed)
    Abstract [en]

    Understanding how the intensity of inbreeding depression is influenced by stressful environmental conditions is an important area of enquiry in various fields of biology. In birds, environmental stress during early development is often related to hatching asynchrony; differences in age, and thus size, impose a gradient in conditions ranging from benign (first hatched chick) to harsh (last hatched chick). Here, we compared the effect of hatching order on growth rate in inbred (parents are full siblings) and outbred (parents are unrelated) canary chicks (Serinus canaria). We found that inbreeding depression was more severe under more stressful conditions, being most evident in later hatched chicks. Thus, consideration of inbreeding‐environment interactions is of vital importance for our understanding of the biological significance of inbreeding depression and hatching asynchrony. The latter is particularly relevant given that hatching asynchrony is a widespread phenomenon, occurring in many bird species. The exact causes of the observed inbreeding‐environment interaction are as yet unknown, but may be related to a decrease in maternal investment in egg contents with laying position (i.e. prehatching environment), or to performance of the chicks during sibling competition and/or their resilience to food shortage (i.e. posthatching environment).

  • 4.
    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.

  • 5. Fitzpatrick, J. L.
    et al.
    Almbro, M.
    Gonzalez-Voyer, A.
    Kolm, Niclas
    Uppsala universitet, Zooekologi.
    Simmons, L. W.
    Male Contest Competition And The Coevolution Of Weaponry And Testes In Pinnipeds2012In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 66, no 11, p. 3595-3604Article in journal (Refereed)
    Abstract [en]

    Male reproductive success is influenced by competitive interactions during precopulatory and postcopulatory selective episodes. Consequently, males can gain reproductive advantages during precopulatory contest competition by investing in weaponry and during postcopulatory sperm competition by investing in ejaculates. However, recent theory predicts male expenditure on weaponry and ejaculates should be subject to a trade-off, and should vary under increasing risk and intensity of sperm competition. Here, we provide the first comparative analysis of the prediction that expenditure on weaponry should be negatively associated with expenditure on testes mass. Specifically, we assess how sexual selection influences the evolution of primary and secondary sexual traits among pinnipeds (seals, sea lions, and walruses). Using recently developed comparative methods, we demonstrate that sexual selection promotes rapid divergence in body mass, sexual size dimorphism (SSD), and genital morphology. We then show that genital length appears to be positively associated with the strength of postcopulatory sexual selection. However, subsequent analyses reveal that both genital length and testes mass are negatively associated with investment in precopulatory weaponry. Thus, our results are congruent with recent theoretical predictions of contest-based sperm competition models. We discuss the possible role of trade-offs and allometry in influencing patterns of reproductive trait evolution in pinnipeds.

  • 6. Fitzpatrick, John L
    et al.
    Baer, Boris
    Polyandry reduces sperm length variation in social insects.2011In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 65, no 10Article in journal (Refereed)
    Abstract [en]

    Postcopulatory sexual selection, either in the form of sperm competition or cryptic female choice, is an important selective force that is thought to have generated the enormous variation in sperm morphology observed interspecifically. However, the evolutionary significance of intraspecific variation in sperm morphology, and the role that postcopulatory sexual selection plays in influencing this variation, remains poorly investigated in invertebrates. Here, we tested the hypothesis that postcopulatory sexual selection reduces variation in sperm morphology, both between and within males, in 27 species of eusocial ants and bees. These eusocial species offer an unusual opportunity to assess how selection acts on variance in sperm morphology, as haploid males produce clonal, haploid sperm that does not experience haploid-diploid conflict. We provide solid evidence that males of polyandrous ant and bee species indeed produce less-variable sperm, indicating that sperm competition selected for sperm of superior quality. Our results offer a mechanistic explanation for the evolution of high-quality sperm and provide comprehensive evidence that sperm morphology of social insects is influenced by sexual selection.

  • 7.
    Fogarty, Laurel
    et al.
    University of St Andrews, Centre for Social Learning and Cognitive Evolution, School of Biology.
    Strimling, Pontus
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution.
    Laland, Kevin Neville
    University of St Andrews, Centre for Social Learning and Cognitive Evolution, School of Biology.
    THE EVOLUTION OF TEACHING2011In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 65, no 10, p. 2760-2770Article in journal (Refereed)
    Abstract [en]

    Teaching, alongside imitation, is widely thought to underlie the success of humanity by allowing high-fidelity transmission of information, skills, and technology between individuals, facilitating both cumulative knowledge gain and normative culture. Yet, it remains a mystery why teaching should be widespread in human societies but extremely rare in other animals. We explore the evolution of teaching using simple genetic models in which a single tutor transmits adaptive information to a related pupil at a cost. Teaching is expected to evolve where its costs are outweighed by the inclusive fitness benefits that result from the tutor's relatives being more likely to acquire the valuable information. We find that teaching is not favored where the pupil can easily acquire the information on its own, or through copying others, or for difficult to learn traits, where teachers typically do not possess the information to pass on to relatives. This leads to a narrow range of traits for which teaching would be efficacious, which helps to explain the rarity of teaching in nature, its unusual distribution, and its highly specific nature. Further models that allow for cumulative cultural knowledge gain suggest that teaching evolved in humans because cumulative culture renders otherwise difficult-to-acquire valuable information available to teach.

  • 8.
    Forsman, Anders
    et al.
    Department of Biology and Environmental Science, University of Kalmar.
    Hagman, Mattias
    School of Biological Sciences A08, University of Sydney, NSW 2006, Australia.
    Calling is an honest indicator of paternal genetic quality in male poison frogs2006In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 60, no 10, p. 2148-2157Article in journal (Refereed)
    Abstract [en]

    Several competing hypotheses have been put forward to explain why females of many species mate preferentially with males possessing the most conspicuous signals (e.g., ornaments, displays, or songs). We performed a laboratory experiment using two species of poison frogs, Dendrobates leucomelas and Epipedobates tricolor, to test the hypothesis that male calling performance is an honest indicator of parental quality. Our analyses are based on data from behavioral observations of mating activities of captive-reared individuals (and their offspring) that were housed in terraria for four consecutive breeding seasons. Male mating success increased with male calling rate and chirp duration in both species, suggesting that females preferred males with more elaborate calls. Because calling performance improved with age in D. leucomelas, female poison frogs that prefer males with more elaborate calls in the wild may end up mating with older males that have already proven their ability to survive. Females that mated with good callers obtained higher quality offspring. Eggs fertilized by males with high calling rates and long chirp durations had higher hatching success and produced tadpoles that were more likely to metamorphose into surviving frogs. As a consequence, females that mated with males with high calling performance obtained more surviving offspring per egg, compared to females that mated with poor callers. Collectively, our findings comply with the notion that female poison frogs prefer to mate with good callers because calling performance is a reliable predictor of offspring quality. The possible influence of maternal allocation and reasons for the strong effect size compared to previous studies are discussed.

  • 9.
    Gamberale-Stille, Gabriella
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Balogh, Alexandra C. V.
    Stockholm University, Faculty of Science, Department of Zoology.
    Tullberg, Birgitta S.
    Stockholm University, Faculty of Science, Department of Zoology.
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology.
    FEATURE SALTATION AND THE EVOLUTION OF MIMICRY2012In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 66, no 3, p. 807-817Article in journal (Refereed)
    Abstract [en]

    In Batesian mimicry, a harmless prey species imitates the warning coloration of an unpalatable model species. A traditional suggestion is that mimicry evolves in a two-step process, in which a large mutation first achieves approximate similarity to the model, after which smaller changes improve the likeness. However, it is not known which aspects of predator psychology cause the initial mutant to be perceived by predators as being similar to the model, leaving open the question of how the crucial first step of mimicry evolution occurs. Using theoretical evolutionary simulations and reconstruction of examples of mimicry evolution, we show that the evolution of Batesian mimicry can be initiated by a mutation that causes prey to acquire a trait that is used by predators as a feature to categorize potential prey as unsuitable. The theory that species gain entry to mimicry through feature saltation allows us to formulate scenarios of the sequence of events during mimicry evolution and to reconstruct an initial mimetic appearance for important examples of Batesian mimicry. Because feature-based categorization by predators entails a qualitative distinction between nonmimics and passable mimics, the theory can explain the occurrence of imperfect mimicry.

  • 10.
    Gonzalez-Voyer, Alejandro
    et al.
    Uppsala universitet, Institutionen för ekologi och evolution.
    Fitzpatrick, John L.
    Kolm, Niclas
    Uppsala universitet, Institutionen för ekologi och evolution.
    Sexual selection determines parental care patterns in cichlid fishes2008In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 62, no 8, p. 2015-2026Article in journal (Refereed)
    Abstract [en]

    Despite a massive research effort, our understanding of why, in most vertebrates, males compete for mates and females care for offspring remains incomplete. Two alternative hypotheses have been proposed to explain the direction of causality between parental care and sexual selection. Traditionally, sexual selection has been explained as a consequence of relative parental investment, where the sex investing less will compete for the sex investing more. However, a more recent model suggests that parental care patterns result from sexual selection acting on one sex favoring mating competition and lower parental investment. Using species-level comparative analyses on Tanganyikan cichlid fishes we tested these alternative hypotheses employing a proxy of sexual selection based on mating system, sexual dichromatism, and dimorphism data. First, while controlling for female reproductive investment, we found that species with intense sexual selection were associated with female-only care whereas species with moderate sexual selection were associated with biparental care. Second, using contingency analyses, we found that, contrary to the traditional view, evolutionary changes in parental care type are dependent on the intensity of sexual selection. Hence, our results support the hypothesis that sexual selection determines parental care patterns in Tanganyikan cichlid fishes.

  • 11.
    Gonzalez-Voyer, Alejandro
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. Estación Biológica de Donana (EBD-CSIC), Spain; Universidad Nacional Autónoma de México, México.
    Gonzalez-Suarez, Manuela
    Vila, Carles
    Revilla, Eloy
    Larger brain size indirectly increases vulnerability to extinction in mammals2016In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 70, no 6, p. 1364-1375Article in journal (Refereed)
    Abstract [en]

    Although previous studies have addressed the question of why large brains evolved, we have limited understanding of potential beneficial or detrimental effects of enlarged brain size in the face of current threats. Using novel phylogenetic path analysis, we evaluated how brain size directly and indirectly, via its effects on life history and ecology, influences vulnerability to extinction across 474 mammalian species. We found that larger brains, controlling for body size, indirectly increase vulnerability to extinction by extending the gestation period, increasing weaning age, and limiting litter sizes. However, we found no evidence of direct, beneficial, or detrimental effects of brain size on vulnerability to extinction, even when we explicitly considered the different types of threats that lead to vulnerability. Order-specific analyses revealed qualitatively similar patterns for Carnivora and Artiodactyla. Interestingly, for Primates, we found that larger brain size was directly (and indirectly) associated with increased vulnerability to extinction. Our results indicate that under current conditions, the constraints on life history imposed by large brains outweigh the potential benefits, undermining the resilience of the studied mammals. Contrary to the selective forces that have favored increased brain size throughout evolutionary history, at present, larger brains have become a burden for mammals.

  • 12.
    Gonzalez-Voyer, Alejandro
    et al.
    Uppsala universitet, Zooekologi.
    Winberg, Svante
    Uppsala universitet, Fysiologi.
    Kolm, Niclas
    Uppsala universitet, Zooekologi.
    Distinct Evolutionary Patterns of Brain and Body Size During Adaptive Radiation2009In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 63, no 9, p. 2266-2274Article in journal (Refereed)
    Abstract [en]

    Morphological traits are often genetically and/or phenotypically correlated with each other and such covariation can have an important influence on the evolution of individual traits. The strong positive relationship between brain size and body size in vertebrates has attracted a lot of interest, and much debate has surrounded the study of the factors responsible for the allometric relationship between these two traits. Here, we use comparative analyses of the Tanganyikan cichlid adaptive radiation to investigate the patterns of evolution for brain size and body size separately. We found that body size exhibited recent bursts of rapid evolution, a pattern that is consistent with divergence linked to ecological specialization. Brain weight on the other hand, showed no bursts of divergence but rather evolved in a gradual manner. Our results thus show that even highly genetically correlated traits can present markedly different patterns of evolution, hence interpreting patterns of evolution of traits from correlations in extant taxa can be misleading. Furthermore, our results suggest, contrary to expectations from theory, that brain size does not play a key role during adaptive radiation.

  • 13.
    Hagman, Mattias
    et al.
    Department of Biology and Environmental Sciences, Kalmar University.
    Forsman, Anders
    Department of Biology and Environmental Sciences, Kalmar University.
    Correlated evolution of conspicuous colouration and body size in the poison frog family Dendrobatidae2003In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 57, no 12, p. 2904-2910Article in journal (Refereed)
    Abstract [en]

    Conspicuous coloration is often used in combination with chemical defenses to deter predators from attacking. Experimental studies have shown that the avoidance inducing effect of conspicuous prey coloration increases with increasing size of pattern elements and with increasing body size. Here we use a comparative approach to test the prediction from these findings, namely that conspicuous coloration will evolve in tandem with body size. In our analysis, we use a previously published mitochondrial DNA-based phylogeny and comparative analysis of independent contrasts to examine if evolutionary shifts in color pattern have been associated with evolutionary changes in body size in aposematic poison frogs (Anura: Dendrobatidae). Information on body size (snout to vent length) and coloration were obtained from the literature. Two different measures of conspicuousness were used, one based on rankings by human observers and the other based on computer analysis of digitized photographs. The results from comparative analyses using either measure of coloration indicated that avoidance inducing coloration and body size have evolved in concert in poison frogs. Results from reconstruction of character change further indicate that the correlated evolution of size and coloration has involved changes in both directions within each of the different clades of the phylogenetic tree. This finding is consistent with the hypothesis that selection imposed by visually guided predators has promoted the evolution of larger body size in species with conspicuous coloration, or enhanced evolution of conspicuous coloration in larger species.

  • 14.
    Hughes, P. William
    Max Planck Institute for Plant Breeding Research, Germany; University of Cologne, Germany.
    How universal is the evolution of senescence?2017In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 71, no 7, p. 1919-1921Article in journal (Refereed)
  • 15.
    Janz, Niklas
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Braga, Mariana P
    Stockholm University, Faculty of Science, Department of Zoology.
    Wahlberg, Niklas
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology.
    On oscillations and flutterings - A reply to Hamm and Fordyce2016In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 70, no 5, p. 1150-1155Article in journal (Refereed)
    Abstract [en]

    The diversification of plant-feeding insects is seen as a spectacular example of evolutionary radiation. Hence, developing hypotheses to explain this diversification, and methods to test them, is an important undertaking. Some years ago, we presented the oscillation hypothesis as a general process that could drive diversification of this and similar interactions, through repeated expansions and contractions of host ranges. Hamm and Fordyce recently presented a study with the outspoken intention of testing this hypothesis where they concluded that the oscillation hypothesis was not supported. We point out several problems with their study, owing both to a misrepresentation of our hypothesis and to the methods. We provide a clarifying description of the oscillation hypothesis, and detail some predictions that follow from it. A reanalysis of the data demonstrated a troubling sensitivity of the "SSE" class of models to small changes in model specification, and we caution against using them for tests of trait-based diversification. Future tests of the hypothesis also need to better acknowledge the processes behind the host range oscillations. We suspect that doing so will resolve some of the apparent conflicts between our hypothesis and the view presented by Hamm and Fordyce.

  • 16.
    Kazemi, Baharan
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Gamberale-Stille, Gabriella
    Stockholm University, Faculty of Science, Department of Zoology.
    Wåtz, Therese
    Stockholm University, Faculty of Science, Department of Zoology.
    Wiklund, Christer
    Stockholm University, Faculty of Science, Department of Zoology.
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology.
    Learning of salient prey traits explains Batesian mimicry evolution2018In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 72, no 3, p. 531-539Article in journal (Refereed)
    Abstract [en]

    Batesian mimicry evolution involves an initial major mutation that produces a rough resemblance to the model, followed by smaller improving changes. To examine the learning psychology of this process, we applied established ideas about mimicry in Papilio polyxenes asterius of the model Battus philenor. We performed experiments with wild birds as predators and butterfly wings as semiartificial prey. Wings of hybrids of P. p. asterius and Papilio machaon were used to approximate the first mutant, with melanism as the hypothesized first mimetic trait. Based on previous results about learning psychology and imperfect mimicry, we predicted that: melanism should have high salience (i.e., being noticeable and prominent), meaning that predators readily discriminate a melanistic mutant from appearances similar to P. machaon; the difference between the first mutant and the model should have intermediate salience to allow further improvement of mimicry; and the final difference in appearance between P. p. asterius and B. philenor should have very low salience, causing improvement to level off. Our results supported both the traditional hypothesis and all our predictions about relative salience. We conclude that there is good agreement between long-held ideas about how Batesian mimicry evolves and recent insights from learning psychology about the role of salience in mimicry evolution.

  • 17.
    Kivela, Sami M.
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. University of Oulu.
    Valimaki, Panu
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology.
    SEASONALITY MAINTAINS ALTERNATIVE LIFE-HISTORY PHENOTYPES2013In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 67, no 11, p. 3145-3160Article in journal (Refereed)
    Abstract [en]

    Many organisms express discrete alternative phenotypes (polyphenisms) in relation to predictable environmental variation. However, the evolution of alternative life-history phenotypes remains poorly understood. Here, we analyze the evolution of alternative life histories in seasonal environments by using temperate insects as a model system. Temperate insects express alternative developmental pathways of diapause and direct development, the induction of a certain pathway affecting fitness through its life-history correlates. We develop a methodologically novel and holistic simulation model and optimize development time, growth rate, body size, reproductive effort, and adult life span simultaneously in both developmental pathways. The model predicts that direct development should be associated with shorter development time (duration of growth) and adult life span, higher growth rate and reproductive effort, smaller body size as well as lower fecundity compared to the diapause pathway, because the two generations divide the available time unequally. These predictions are consistent with many empirical data. Our analysis shows that seasonality alone can explain the evolution of alternative life histories.

  • 18.
    Kivelä, Sami M.
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. University of Oulu, Finland.
    Svensson, Beatrice
    Stockholm University, Faculty of Science, Department of Zoology.
    Tiwe, Alma
    Stockholm University, Faculty of Science, Department of Zoology.
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology.
    Thermal plasticity of growth and development varies adaptively among alternative developmental pathways2015In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 69, no 9, p. 2399-2413Article in journal (Refereed)
    Abstract [en]

    Polyphenism, the expression of discrete alternative phenotypes, is often a consequence of a developmental switch. Physiological changes induced by a developmental switch potentially affect reaction norms, but the evolution and existence of alternative reaction norms remains poorly understood. Here, we demonstrate that, in the butterfly Pieris napi (Lepidoptera: Pieridae), thermal reaction norms of several life history traits vary adaptively among switch-induced alternative developmental pathways of diapause and direct development. The switch was affected both by photoperiod and temperature, ambient temperature during late development having the potential to override earlier photoperiodic cues. Directly developing larvae had higher development and growth rates than diapausing ones across the studied thermal gradient. Reaction norm shapes also differed between the alternative developmental pathways, indicating pathway-specific selection on thermal sensitivity. Relative mass increments decreased linearly with increasing temperature and were higher under direct development than diapause. Contrary to predictions, population phenology did not explain trait variation or thermal sensitivity, but our experimental design probably lacks power for finding subtle phenology effects. We demonstrate adaptive differentiation in thermal reaction norms among alternative phenotypes, and suggest that the consequences of an environmentally dependent developmental switch primarily drive the evolution of alternative thermal reaction norms in P. napi.

  • 19.
    Korall, Petra
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Schuettpelz, Eric
    Pryer, Kathleen M.
    ABRUPT DECELERATION OF MOLECULAR EVOLUTION LINKED TO THE ORIGIN OF ARBORESCENCE IN FERNS2010In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 64, no 9, p. 2786-2792Article in journal (Refereed)
    Abstract [en]

    Molecular rate heterogeneity, whereby rates of molecular evolution vary among groups of organisms, is a well-documented phenomenon. Nonetheless, its causes are poorly understood. For animals, generation time is frequently cited because longer-lived species tend to have slower rates of molecular evolution than their shorter-lived counterparts. Although a similar pattern has been uncovered in flowering plants, using proxies such as growth form, the underlying process has remained elusive. Here, we find a deceleration of molecular evolutionary rate to be coupled with the origin of arborescence in ferns. Phylogenetic branch lengths within the ""tree fern"" clade are considerably shorter than those of closely related lineages, and our analyses demonstrate that this is due to a significant difference in molecular evolutionary rate. Reconstructions reveal that an abrupt rate deceleration coincided with the evolution of the long-lived tree-like habit at the base of the tree fern clade. This suggests that a generation time effect may well be ubiquitous across the green tree of life, and that the search for a responsible mechanism must focus on characteristics shared by all vascular plants. Discriminating among the possibilities will require contributions from various biological disciplines, but will be necessary for a full appreciation of molecular evolution.

  • 20.
    Kotrschal, Alexander
    et al.
    Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    Corral-Lopez, Alberto
    Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    Szidat, Soenke
    Kolm, Niclas
    Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    The effect of brain size evolution on feeding propensity, digestive efficiency, and juvenile growth2015In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 69, no 11, p. 3013-3020Article in journal (Refereed)
    Abstract [en]

    One key hypothesis in the study of brain size evolution is the expensive tissue hypothesis; the idea that increased investment into the brain should be compensated by decreased investment into other costly organs, for instance the gut. Although the hypothesis is supported by both comparative and experimental evidence, little is known about the potential changes in energetic requirements or digestive traits following such evolutionary shifts in brain and gut size. Organisms may meet the greater metabolic requirements of larger brains despite smaller guts via increased food intake or better digestion. But increased investment in the brain may also hamper somatic growth. To test these hypotheses we here used guppy (Poecilia reticulata) brain size selection lines with a pronounced negative association between brain and gut size and investigated feeding propensity, digestive efficiency (DE), and juvenile growth rate. We did not find any difference in feeding propensity or DE between large-and small-brained individuals. Instead, we found that large-brained females had slower growth during the first 10 weeks after birth. Our study provides experimental support that investment into larger brains at the expense of gut tissue carries costs that are not necessarily compensated by a more efficient digestive system.

  • 21.
    Kotrschal, Alexander
    et al.
    Department of Ecology & Genetics/Animal Ecology, Uppsala University, Sweden.
    Lievens, Eva J. P.
    Dahlbom, Josefin
    Bundsen, Andreas
    Semenova, Svetlana
    Sundvik, Maria
    Maklakov, Alexei A.
    Winberg, Svante
    Panula, Pertti
    Kolm, Niclas
    Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    Artificial selection on relative brain size reveals a positive genetic correlation between brain size and proactive personality in the guppy2014In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 68, no 4, p. 1139-1149Article in journal (Refereed)
    Abstract [en]

    Animal personalities range from individuals that are shy, cautious, and easily stressed (a reactive personality type) to individuals that are bold, innovative, and quick to learn novel tasks, but also prone to routine formation (a proactive personality type). Although personality differences should have important consequences for fitness, their underlying mechanisms remain poorly understood. Here, we investigated how genetic variation in brain size affects personality. We put selection lines of large- and small-brained guppies (Poecilia reticulata), with known differences in cognitive ability, through three standard personality assays. First, we found that large-brained animals were faster to habituate to, and more exploratory in, open field tests. Large-brained females were also bolder. Second, large-brained animals excreted less cortisol in a stressful situation (confinement). Third, large-brained animals were slower to feed from a novel food source, which we interpret as being caused by reduced behavioral flexibility rather than lack of innovation in the large-brained lines. Overall, the results point toward a more proactive personality type in large-brained animals. Thus, this study provides the first experimental evidence linking brain size and personality, an interaction that may affect important fitness-related aspects of ecology such as dispersal and niche exploration.

  • 22.
    Kotrschal, Alexander
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Zeng, Hong-Li
    van der Bijl, Wouter
    Stockholm University, Faculty of Science, Department of Zoology.
    Öhman-Mägi, Caroline
    Kotrschal, Kurt
    Pelckmans, Kristiaan
    Kolm, Niclas
    Stockholm University, Faculty of Science, Department of Zoology.
    Evolution of brain region volumes during artificial selection for relative brain size2017In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 71, no 12, p. 2942-2951Article in journal (Refereed)
    Abstract [en]

    The vertebrate brain shows an extremely conserved layout across taxa. Still, the relative sizes of separate brain regions vary markedly between species. One interesting pattern is that larger brains seem associated with increased relative sizes only of certain brain regions, for instance telencephalon and cerebellum. Till now, the evolutionary association between separate brain regions and overall brain size is based on comparative evidence and remains experimentally untested. Here, we test the evolutionary response of brain regions to directional selection on brain size in guppies (Poecilia reticulata) selected for large and small relative brain size. In these animals, artificial selection led to a fast response in relative brain size, while body size remained unchanged. We use microcomputer tomography to investigate how the volumes of 11 main brain regions respond to selection for larger versus smaller brains. We found no differences in relative brain region volumes between large- and small-brained animals and only minor sex-specific variation. Also, selection did not change allometric scaling between brain and brain region sizes. Our results suggest that brain regions respond similarly to strong directional selection on relative brain size, which indicates that brain anatomy variation in contemporary species most likely stem from direct selection on key regions.

  • 23.
    Lindenfors, Patrik
    et al.
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Dalén, Love
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    A monophyletic origin of delayed implantation and its implications2003In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 57, p. 1952-1956Article in journal (Refereed)
  • 24. Marhounová, Lucie
    et al.
    Kotrschal, Alexander
    Stockholm University, Faculty of Science, Department of Zoology. Wageningen University & Research, Netherlands.
    Kverková, Kristina
    Kolm, Niclas
    Stockholm University, Faculty of Science, Department of Zoology.
    Nemec, Pavel
    Artificial selection on brain size leads to matching changes in overall number of neurons2019In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646Article in journal (Refereed)
    Abstract [en]

    Neurons are the basic computational units of the brain, but brain size is the predominant surrogate measure of brain functional capacity in comparative and cognitive neuroscience. This approach is based on the assumption that larger brains harbor higher numbers of neurons and their connections, and therefore have a higher information-processing capacity. However, recent studies have shown that brain mass may be less strongly correlated with neuron counts than previously thought. Till now, no experimental test has been conducted to examine the relationship between evolutionary changes in brain size and the number of brain neurons. Here, we provide such a test by comparing neuron number in artificial selection lines of female guppies (Poecilia reticulata) with >15% difference in relative brain mass and numerous previously demonstrated cognitive differences. Using the isotropic fractionator, we demonstrate that large-brained females have a higher overall number of neurons than small-brained females, but similar neuronal densities. Importantly, this difference holds also for the telencephalon, a key region for cognition. Our study provides the first direct experimental evidence that selection for brain mass leads to matching changes in number of neurons and shows that brain size evolution is intimately linked to the evolution of neuron number and cognition.

  • 25. Martínez-Abadías, Neus
    et al.
    Esparza, Mireia
    Sjøvold, Torstein
    Stockholm University, Faculty of Humanities, Osteology Unit.
    González-José, Rolando
    Santos, Mauro
    Hernández, Miquel
    Klingenberg, Christian Peter
    PERVASIVE GENETIC INTEGRATION DIRECTS THE EVOLUTION OF HUMAN SKULL SHAPE2012In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 66, no 4, p. 1010-1023Article in journal (Refereed)
    Abstract [en]

    It has long been unclear whether the different derived cranial traits of modern humans evolved independently in response to separate selection pressures or whether they resulted from the inherent morphological integration throughout the skull. In a novel approach to this issue, we combine evolutionary quantitative genetics and geometric morphometrics to analyze genetic and phenotypic integration in human skull shape. We measured human skulls in the ossuary of Hallstatt (Austria), which offer a unique opportunity because they are associated with genealogical data. Our results indicate pronounced covariation of traits throughout the skull. Separate simulations of selection for localized shape changes corresponding to some of the principal derived characters of modern human skulls produced outcomes that were similar to each other and involved a joint response in all of these traits. The data for both genetic and phenotypic shape variation were not consistent with the hypothesis that the face, cranial base, and cranial vault are completely independent modules but relatively strongly integrated structures. These results indicate pervasive integration in the human skull and suggest a reinterpretation of the selective scenario for human evolution where the origin of any one of the derived characters may have facilitated the evolution of the others.

  • 26.
    Nylin, Sören
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Slove, Jessica
    Stockholm University, Faculty of Science, Department of Zoology.
    Janz, Niklas
    Stockholm University, Faculty of Science, Department of Zoology.
    HOST PLANT UTILIZATION, HOST RANGE OSCILLATIONS AND DIVERSIFICATION IN NYMPHALID BUTTERFLIES: A PHYLOGENETIC INVESTIGATION2014In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 68, no 1, p. 105-124Article in journal (Refereed)
    Abstract [en]

    It has been suggested that phenotypic plasticity is a major factor in the diversification of life, and that variation in host range in phytophagous insects is a good model for investigating this claim. We explore the use of angiosperm plants as hosts for nymphalid butterflies, and in particular the evidence for past oscillations in host range and how they are linked to host shifts and to diversification. At the level of orders of plants, a relatively simple pattern of host use and host shifts emerges, despite the 100 million years of history of the family Nymphalidae. We review the evidence that these host shifts and the accompanying diversifications were associated with transient polyphagous stages, as suggested by the oscillation hypothesis. In addition, we investigate all currently polyphagous nymphalid species and demonstrate that the state of polyphagy is rare, has a weak phylogenetic signal, and a very apical distribution in the phylogeny; we argue that these are signs of its transient nature. We contrast our results with data from the bark beetles Dendroctonus, in which a more specialized host use is instead the apical state. We conclude that plasticity in host use is likely to have contributed to diversification in nymphalid butterflies.

  • 27. Outomuro, David
    et al.
    Angel-Giraldo, Pedro
    Corral-López, Alberto
    Stockholm University, Faculty of Science, Department of Zoology.
    Realpe, Emilio
    Multitrait aposematic signal in Batesian mimicry2016In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 70, no 7, p. 1596-1608Article in journal (Refereed)
    Abstract [en]

    Batesian mimics can parasitize Mullerian mimicry rings mimicking the warning color signal. The evolutionary success of Batesian mimics can increase adding complexity to the signal by behavioral and locomotor mimicry. We investigated three fundamental morphological and locomotor traits in a Neotropical mimicry ring based on Ithomiini butterflies and parasitized by Polythoridae damselflies: wing color, wing shape, and flight style. The study species have wings with a subapical white patch, considered the aposematic signal, and a more apical black patch. The main predators are VS-birds, visually more sensitive to violet than to ultraviolet wavelengths (UVS-birds). The white patches, compared to the black patches, were closer in the bird color space, with higher overlap for VS-birds than for UVS-birds. Using a discriminability index for bird vision, the white patches were more similar between the mimics and the model than the black patches. The wing shape of the mimics was closer to the model in the morphospace, compared to other outgroup damselflies. The wing-beat frequency was similar among mimics and the model, and different from another outgroup damselfly. Multitrait aposematic signals involving morphology and locomotion may favor the evolution of mimicry rings and the success of Batesian mimics by improving signal effectiveness toward predators.

  • 28. Qvarnström, Anna
    et al.
    Rudh, Andreas
    Edström, Torkel
    Ödeen, Anders
    Løvlie, Hanne
    Stockholm University, Faculty of Science, Department of Zoology. Linkoping University, Sweden.
    Tullberg, Birgitta S.
    Stockholm University, Faculty of Science, Department of Zoology.
    COARSE DARK PATTERNING FUNCTIONALLY CONSTRAINS ADAPTIVE SHIFTS FROM APOSEMATISM TO CRYPSIS IN STRAWBERRY POISON FROGS2014In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 68, no 10, p. 2793-2803Article in journal (Refereed)
    Abstract [en]

    Ecological specialization often requires tight coevolution of several traits, which may constrain future evolutionary pathways and make species more prone to extinction. Aposematism and crypsis represent two specialized adaptations to avoid predation. We tested whether the combined effects of color and pattern on prey conspicuousness functionally constrain or facilitate shifts between these two adaptations. We combined data from 17 natural populations of strawberry poison frogs, Oophaga pumilio with an experimental approach using digitalized images of frogs and chickens as predators. We show that bright coloration often co-occurs with coarse patterning among the natural populations. Dull green frogs with coarse patterning are rare in nature but in the experiment they were as easily detected as bright red frogs suggesting that this trait combination represents a transient evolutionary state toward aposematism. Hence, a gain of either bright color or coarse patterning leads to conspicuousness, but a transition back to crypsis would be functionally constrained in populations with both bright color and coarse patterning by requiring simultaneous changes in two traits. Thus, populations (or species) signaling aposematism by conspicuous color should be less likely to face an evolutionary dead end and more likely to radiate than populations with both conspicuous color and coarse patterning.

  • 29.
    Rowinski, 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.

  • 30. Simmons, Leigh W.
    et al.
    Fitzpatrick, John L.
    Stockholm University, Faculty of Science, Department of Zoology.
    Sperm competition and the coevolution of pre- and postcopulatory traits: Weapons evolve faster than testes among onthophagine dung beetles2016In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 70, no 5, p. 998-1008Article in journal (Refereed)
    Abstract [en]

    Reproductive competition generates episodes of both pre- and postcopulatory sexual selection. Theoretical models of sperm competition predict that as the fitness gains from expenditure on the weapons of male combat increase, males should increase their expenditure on weapons and decrease their expenditure on traits that contribute to competitive fertilization success. Although traits subject to sexual selection are known to have accelerated evolutionary rates of phenotypic divergence, it is not known whether the competing demands of investment into pre- and postcopulatory traits affect their relative rates of evolutionary divergence. We use a comparative approach to estimate the rates of divergence in pre-and postcopulatory traits among onthophagine dung beetles. Weapons evolved faster than body size while testes mass and sperm length evolved more slowly than body size, suggesting that precopulatory competition is the stronger episode of sexual selection acting on these beetles. Although horns evolved faster than testes, evolutionary increases in horn length were not associated with evolutionary reductions in testes mass. Our data for onthophagines support the notion that in taxa where males are unable to monopolize paternity, expenditure on both weapons and testes should both be favored.

  • 31. Tsuboi, Masahito
    et al.
    Husby, Arild
    Kotrschal, Alexander
    Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    Hayward, Alexander
    Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    Buechel, Severine D.
    ETH Zürich Institute of Integrative Biology (IBZ), Switzerland.
    Zidar, Josefina
    Lovlie, Hanne
    Kolm, Niclas
    Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    Comparative support for the expensive tissue hypothesis: Big brains are correlated with smaller gut and greater parental investment in Lake Tanganyika cichlids2015In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 69, no 1, p. 190-200Article in journal (Refereed)
    Abstract [en]

    The brain is one of the most energetically expensive organs in the vertebrate body. Consequently, the energetic requirements of encephalization are suggested to impose considerable constraints on brain size evolution. Three main hypotheses concerning how energetic constraints might affect brain evolution predict covariation between brain investment and (1) investment into other costly tissues, (2) overall metabolic rate, and (3) reproductive investment. To date, these hypotheses have mainly been tested in homeothermic animals and the existing data are inconclusive. However, there are good reasons to believe that energetic limitations might play a role in large-scale patterns of brain size evolution also in ectothermic vertebrates. Here, we test these hypotheses in a group of ectothermic vertebrates, the Lake Tanganyika cichlid fishes. After controlling for the effect of shared ancestry and confounding ecological variables, we find a negative association between brain size and gut size. Furthermore, we find that the evolution of a larger brain is accompanied by increased reproductive investment into egg size and parental care. Our results indicate that the energetic costs of encephalization may be an important general factor involved in the evolution of brain size also in ectothermic vertebrates.

  • 32. Tsuboi, Masahito
    et al.
    Kotrschal, Alexander
    Stockholm University, Faculty of Science, Department of Zoology.
    Hayward, Alexander
    Stockholm University, Faculty of Science, Department of Zoology.
    Buechel, Severine Denise
    Stockholm University, Faculty of Science, Department of Zoology.
    Zidar, Josefina
    Lovlie, Hanne
    Kolm, Niclas
    Stockholm University, Faculty of Science, Department of Zoology.
    Evolution of brain-body allometry in Lake Tanganyika cichlids2016In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 70, no 7, p. 1559-1568Article in journal (Refereed)
    Abstract [en]

    Brain size is strongly associated with body size in all vertebrates. This relationship has been hypothesized to be an important constraint on adaptive brain size evolution. The essential assumption behind this idea is that static (i.e., within species) brain-body allometry has low ability to evolve. However, recent studies have reported mixed support for this view. Here, we examine brain-body static allometry in Lake Tanganyika cichlids using a phylogenetic comparative framework. We found considerable variation in the static allometric intercept, which explained the majority of variation in absolute and relative brain size. In contrast, the slope of the brain-body static allometry had relatively low variation, which explained less variation in absolute and relative brain size compared to the intercept and body size. Further examination of the tempo and mode of evolution of static allometric parameters confirmed these observations. Moreover, the estimated evolutionary parameters indicate that the limited observed variation in the static allometric slope could be a result of strong stabilizing selection. Overall, our findings suggest that the brain-body static allometric slope may represent an evolutionary constraint in Lake Tanganyika cichlids.

  • 33. 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.

  • 34. Yu, Xin
    et al.
    Zhong, Mao Jun
    Li, Da Yong
    Jin, Long
    Liao, Wen Bo
    Kotrschal, Alexander
    Stockholm University, Faculty of Science, Department of Zoology.
    Large-brained frogs mature later and live longer2018In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 72, no 5, p. 1174-1183Article in journal (Refereed)
    Abstract [en]

    Brain sizes vary substantially across vertebrate taxa, yet, the evolution of brain size appears tightly linked to the evolution of life histories. For example, larger brained species generally live longer than smaller brained species. A larger brain requires more time to grow and develop at a cost of exceeded gestation period and delayed weaning age. The cost of slower development may be compensated by better homeostasis control and increased cognitive abilities, both of which should increase survival probabilities and hence life span. To date, this relationship between life span and brain size seems well established in homoeothermic animals, especially in mammals. Whether this pattern occurs also in other clades of vertebrates remains enigmatic. Here, we undertake the first comparative test of the relationship between life span and brain size in an ectothermic vertebrate group, the anuran amphibians. After controlling for the effects of shared ancestry and body size, we find a positive correlation between brain size, age at sexual maturation, and life span across 40 species of frogs. Moreover, we also find that the ventral brain regions, including the olfactory bulbs, are larger in long-lived species. Our results indicate that the relationship between life history and brain evolution follows a general pattern across vertebrate clades.

1 - 34 of 34
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