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Journal Cover Evolution
  [SJR: 3.204]   [H-I: 161]   [147 followers]  Follow
   Partially Free Journal Partially Free Journal
   ISSN (Print) 0014-3820 - ISSN (Online) 1558-5646
   Published by John Wiley and Sons Homepage  [1589 journals]
  • Stabilizing selection on sperm number revealed by artificial selection and
           experimental evolution
    • Authors: Silvia Cattelan; Andrea Di Nisio, Andrea Pilastro
      Abstract: Sperm competition is taxonomically widespread in animals and is usually associated with large sperm production, being the number of sperm in the competing pool the prime predictor of fertilization success. Despite the strong postcopulatory selection acting directionally on sperm production, its genetic variance is often very high. This can be explained by trade-offs between sperm production and traits associated with mate acquisition or survival, that may contribute to generate an overall stabilizing selection. To investigate this hypothesis, we first artificially selected male guppies (Poecilia reticulata) for high and low sperm production for three generations, while simultaneously removing sexual selection. Then, we interrupted artificial selection and restored sexual selection. Sperm production responded to divergent selection in one generation, and when we restored sexual selection, both high and low lines converged back to the mean sperm production of the original population within two generations, indicating that sperm number is subject to strong stabilizing total sexual selection (i.e. selection acting simultaneously on all traits associated with reproductive success). We discuss the possible mechanisms responsible for the maintenance of high genetic variability in sperm production despite strong selection acting on it.This article is protected by copyright. All rights reserved
      PubDate: 2018-01-16T07:21:13.739114-05:
      DOI: 10.1111/evo.13425
  • The “unguarded-X” and the genetic architecture of lifespan: Inbreeding
           results in a potentially maladaptive sex-specific reduction of female
           lifespan in Drosophila melanogaster
    • Authors: Zahida Sultanova; Muhammed Andic, Pau Carazo
      Abstract: Sex differences in ageing and lifespan are ubiquitous in nature. The “unguarded-X” hypothesis (UXh) suggests they may be partly due to the expression of recessive mutations in the hemizygous sex chromosomes of the heterogametic sex, which could help explain sex-specific ageing in a broad array of taxa. A prediction central to the UX hypothesis is that inbreeding will decrease the lifespan of the homogametic sex more than the heterogametic sex, because only in the former does inbreeding increase the expression of recessive deleterious mutations. In this study, we test this prediction by examining the effects of inbreeding on the lifespan and fitness of male and female Drosophila melanogaster across different social environments. We found that, across social environments, inbreeding resulted in a greater reduction of female than male lifespan, and that inbreeding effects on fitness did not seem to counterbalance sex-specific effects on lifespan, suggesting the former are maladaptative. Inter- and intra-sexual correlation analyses also allowed us to identify evidence of an underlying joint genetic architecture for inbreeding effects on lifespan. We discuss these results in light of the UXh and other alternative explanations, and suggest that more attention should be paid to the possibility that the “unguarded-X” may play an important role in the evolution of sex-specific lifespan.This article is protected by copyright. All rights reserved
      PubDate: 2018-01-16T05:21:43.898094-05:
      DOI: 10.1111/evo.13426
  • Cis-regulator runaway and divergence in asexuals
    • Authors: Frédéric Fyon; Thomas Lenormand
      Abstract: With the advent of new sequencing technologies, the evolution of gene expression is becoming a subject of intensive genomic research, with sparking debates upon the role played by these kinds of changes in adaptive evolution and speciation. In this paper, we model expression evolution in species differing by their reproductive systems. We consider different rates of sexual versus asexual reproduction and the different type of parthenogenesis (apomixis and the various modes of automixis). We show that competition for expression leads to two selective processes on cis-regulatory regions that act independently to organism-level adaptation. Coevolution within regulatory networks allows these processes to occur without strongly modifying expression levels. First, cis-regulatory regions such as enhancers evolve in a runaway fashion because they automatically become associated to chromosomes purged from deleterious mutations (“Enhancer Runaway process”). Second, in clonal or nearly clonal species, homologous cis-regulatory regions tend to diverge, which leads to haploidization of expression, when they are sufficiently isolated from one another (“Enhancer Divergence process”). We show how these two processes co-occur and vary depending on the level of outcrossing, gene conversion, mitotic recombination, or recombination in automictic species. This study offers thus a baseline to understand patterns of expression evolution across the diversity of eukaryotic species.This article is protected by copyright. All rights reserved
      PubDate: 2018-01-13T07:50:21.623373-05:
      DOI: 10.1111/evo.13424
  • Modeling strategic sperm allocation: Tailoring the predictions to the
    • Authors: Biz R. Turnell; Kerry L. Shaw, H. Kern Reeve
      Abstract: Two major challenges exist when empirically testing the predictions of sperm allocation theory. First, the study species must adhere to the assumptions of the model being tested. Unfortunately, the common assumption of sperm allocation models that females mate a maximum of once or twice does not hold for many, if not most, multiply and sequentially mating animals. Second, a model's parameters, which dictate its predictions, must be measured in the study species. Common examples of such parameters, female mating frequency and sperm precedence patterns, are unknown for many species used in empirical tests. Here, we present a broadly applicable model, appropriate for multiply, sequentially mating animals, and test it in three species for which data on all the relevant parameter values are available. The model predicts that relative allocation to virgin females, compared to non-virgins, depends on the interaction between female mating rate and the sperm precedence pattern: relative allocation to virgins increases with female mating rate under first-male precedence, while the opposite is true under later-male precedence. Our model is moderately successful in predicting actual allocation patterns in the three species, including a cricket in which we measured the parameter values and performed an empirical test of allocation.This article is protected by copyright. All rights reserved
      PubDate: 2018-01-13T07:20:23.879797-05:
      DOI: 10.1111/evo.13423
  • Trait-specific processes of convergence and conservatism shape
           ecomorphological evolution in ground-dwelling squirrels
    • Authors: Bryan S. McLean; Kristofer M. Helgen, H. Thomas Goodwin, Joseph A. Cook
      Abstract: Our understanding of mechanisms operating over deep timescales to shape phenotypic diversity often hinges on linking variation in one or few trait(s) to specific evolutionary processes. When distinct processes are capable of similar phenotypic signatures, however, identifying these drivers is difficult. We explored ecomorphological evolution across a radiation of ground-dwelling squirrels whose history includes convergence and constraint, two processes that can yield similar signatures of standing phenotypic diversity. Using 4 ecologically-relevant trait datasets (body size, cranial, mandibular, and molariform tooth shape), we compared and contrasted variation, covariation, and disparity patterns in a new phylogenetic framework. Strong correlations existed between body size and 2 skull traits (allometry) and among skull traits themselves (integration). Inferred evolutionary modes were also concordant across traits (Ornstein-Uhlenbeck with 2 adaptive regimes). However, despite these broad similarities, we found divergent dynamics on the macroevolutionary landscape, with phenotypic disparity being differentially shaped by convergence and conservatism. Such among-trait heterogeneity in process (but not always pattern) reiterates the mosaic nature of morphological evolution, and suggests ground squirrel evolution is poorly captured by single process descriptors. Our results also highlight how use of single traits can bias macroevolutionary inference, affirming the importance of broader trait-bases in understanding phenotypic evolutionary dynamics.This article is protected by copyright. All rights reserved
      PubDate: 2018-01-10T10:50:31.999413-05:
      DOI: 10.1111/evo.13422
  • Digest: Drivers of coral diversification in a major marine biodiversity
    • Authors: Oscar Alejandro Pérez-Escobar; Susannah Cass, Steven Dodsworth
      Abstract: Coral reefs are of great ecological importance to marine ecosystems, yet their origins are still poorly understood. Using a robust phylogenetic framework, Huang et al. (2017) show that most diversity within the Indo-Pacific Coral Triangle region is driven by range expansions of lineages from outside the region, rather than rapid diversification within. This highlights the need for macroevolutionary studies to fully understand species assemblages in biodiversity hotspots, and the potential importance of adjacent areas for conservation.This article is protected by copyright. All rights reserved
      PubDate: 2018-01-10T08:20:34.063052-05:
      DOI: 10.1111/evo.13419
  • Digest: Going solo: Self-fertilization in haploid algae may not lead to
           evolutionary decline
    • Authors: Alan Maxwell Vincent
      Abstract: Does the evolution of self-fertilization elevate species extinction rates' Hanschen et al. (2017) found that volvocine algae do not fit the expected phylogenetic pattern that selfing species go extinct faster. They suggest that this outcome results from their primarily haploid life cycle, which reduces the usual cost of self-fertilization.This article is protected by copyright. All rights reserved
      PubDate: 2018-01-09T03:50:28.98679-05:0
      DOI: 10.1111/evo.13420
  • Phanerozoic survivors: Actinopterygian evolution through the
           Permo-Triassic and Triassic-Jurassic mass extinction events
    • Authors: Fiann M. Smithwick; Thomas L. Stubbs
      Abstract: Actinopterygians (ray-finned fishes) successfully passed through four of the big five mass extinction events of the Phanerozoic, but the effects of these crises on the group are poorly understood. Many researchers have assumed that the Permo-Triassic mass extinction (PTME) and end-Triassic extinction (ETE) had little impact on actinopterygians, despite devastating many other groups. Here, two morphometric techniques, geometric (body shape) and functional (jaw morphology), are used to assess the effects of these two extinction events on the group. The PTME elicits no significant shifts in functional disparity while body shape disparity increases. An expansion of body shape and functional disparity coincides with the neopterygian radiation and evolution of novel feeding adaptations in the Middle-Late Triassic. Through the ETE, small decreases are seen in shape and functional disparity, but are unlikely to represent major changes brought about by the extinction event. In the Early Jurassic, further expansions into novel areas of ecospace indicative of durophagy occur, potentially linked to losses in the ETE. As no evidence is found for major perturbations in actinopterygian evolution through either extinction event, the group appears to have been immune to two major environmental crises that were disastrous to most other organisms.This article is protected by copyright. All rights reserved
      PubDate: 2018-01-09T02:50:29.320041-05:
      DOI: 10.1111/evo.13421
  • Learning of salient prey traits explains batesian mimicry evolution
    • Authors: Baharan Kazemi; Gabriella Gamberale-Stille, Therese Wåtz, Christer Wiklund, Olof Leimar
      Abstract: 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 semi-artificial prey. Wings of hybrids of P. p. asterius and P. 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.This article is protected by copyright. All rights reserved
      PubDate: 2018-01-09T02:20:37.214666-05:
      DOI: 10.1111/evo.13418
  • A species-specific multigene family mediates differential sperm
           displacement in Drosophila melanogaster
    • Authors: Vivek Jayaswal; Jamie Jimenez, Robert Magie, Kien Nguyen, Bryan Clifton, Shudan Yeh, José M. Ranz
      Abstract: Sperm competition is a post-copulatory sexual selection mechanism in species in which females mate with multiple males. Despite its evolutionary relevance in shaping male traits, the genetic mechanisms underlying sperm competition are poorly understood. A recently originated multigene family specific to D. melanogaster, Sdic, is important for the outcome of sperm competition in doubly-mated females, although the mechanistic nature of this phenotype remained unresolved. Here we compared doubly-mated females, second mated to either Sdic knockout or non-knockout males, and directly visualize sperm dynamics in the female reproductive tract. We found that a less effective removal of first-to-mate male's sperm within the female's sperm storage organs is consistent with a reduced sperm competitive ability of the Sdic knockout males. Our results highlight the role young genes can play in driving the evolution of sperm competition.This article is protected by copyright. All rights reserved
      PubDate: 2018-01-09T01:20:26.448831-05:
      DOI: 10.1111/evo.13417
  • Issue information - Ed Board
    • Pages: 1 - 3
      PubDate: 2018-01-04T14:54:19.771681-05:
      DOI: 10.1111/evo.13344
  • Digest: Ontogenesis and evolutionary allometry shape divergent evolution
           of genitalia in female cetaceans*
    • Authors: Jia Yu Wang; Wen Bo Liao
      PubDate: 2017-12-29T15:55:25.023386-05:
      DOI: 10.1111/evo.13414
  • Convergent evolution of floral shape tied to pollinator shifts in
           Iochrominae (Solanaceae)
    • Authors: Stacey D. Smith; Ricardo Kriebel
      Abstract: Flower form is one of many floral features thought to be shaped by pollinator-mediated selection. Although the drivers of variation in flower shape have often been examined in microevolutionary studies, relatively few have tested the relationship between shape evolution and shifts in pollination system across clades. In the present study, we use morphometric approaches to quantify shape variation across the Andean clade Iochrominae and estimate the relationship between changes in shape and shifts in pollination system using phylogenetic comparative methods. We infer multiple shifts from an ancestral state of narrow, tubular flowers toward open, bowl-shaped or campanulate flowers as well as one reversal to the tubular form. These transitions in flower shape are significantly correlated with changes in pollination system. Specifically, tubular forms tend to be hummingbird-pollinated and the open forms tend to be insect-pollinated, a pattern consistent with experimental work as well as classical floral syndromes. Nonetheless, our study provides one of the few empirical demonstrations of the relationship between flower shape and pollination system at a macroevolutionary scale.This article is protected by copyright. All rights reserved
      PubDate: 2017-12-27T06:57:09.717991-05:
      DOI: 10.1111/evo.13416
  • A phylogenetic comparative method for evaluating trait coevolution across
           two phylogenies for sets of interacting species
    • Authors: Dean C. Adams; John D. Nason
      Abstract: Evaluating trait correlations across species within a lineage via phylogenetic regression is fundamental to comparative evolutionary biology, but when traits of interest are derived from two sets of lineages that co-evolve with one another, methods for evaluating such patterns in a dual-phylogenetic context remain underdeveloped. Here we extend multivariate permutation-based phylogenetic regression to evaluate trait correlations in two sets of interacting species while accounting for their respective phylogenies. This extension is appropriate for both univariate and multivariate response data, and may utilize one or more independent variables, including environmental covariates. Imperfect correspondence between species in the interacting lineages can also be accommodated, such as when species in one lineage associate with multiple species in the other, or when there are unmatched taxa in one or both lineages. For both univariate and multivariate data, the method displays appropriate type I error, and statistical power increases with the strength of the trait covariation and the number of species in the phylogeny. These properties are retained even when there is not a 1:1 correspondence between lineages. Finally, we demonstrate the approach by evaluating the evolutionary correlation between traits in fig species and traits in their agaonid wasp pollinators. R computer code is provided.This article is protected by copyright. All rights reserved
      PubDate: 2017-12-27T01:20:35.190093-05:
      DOI: 10.1111/evo.13415
  • The genetics of egg retention and fertilization success in Drosophila: One
           step closer to understanding the transition from facultative to obligate
    • Authors: Barbara Horváth; Alex T. Kalinka
      Abstract: Oviparous, facultative egg retention enables Drosophila females to withhold fertilized eggs in their reproductive tracts until circumstances favor oviposition. The propensity to retain fertilized eggs varies greatly between species, and is correlated with other reproductive traits, such as egg size and ovariole number. While previous studies have described the phenomenon, no study to date has characterized within-species variation or the genetic basis of the trait. Here, we develop a novel microscope-based method for measuring egg retention in Drosophila females and determine the range of phenotypic variation in mated female egg retention in a subset of 91 Drosophila Genetic Reference Panel (DGRP) lines. We inferred the genetic basis of egg retention using a genome-wide association study (GWAS). Further, the scoring of more than 95,000 stained, staged eggs enabled estimates of fertilization success for each line. We found evidence that ovary- and spermathecae-related genes as well as genes affecting olfactory behavior, male mating behavior, male-female attraction and sperm motility may play a crucial role in post-mating physiology. Based on our findings we also propose potential evolutionary routes towards obligate viviparity. In particular, we propose that the loss of fecundity incurred by viviparity could be offset by benefits arising from enhanced mate discrimination, resource specialization, or modified egg morphology.This article is protected by copyright. All rights reserved
      PubDate: 2017-12-19T06:21:24.137715-05:
      DOI: 10.1111/evo.13411
  • Preference for conspecifics evolves earlier in males than females in a
           sexually dimorphic radiation of fishes
    • Authors: Tamra C. Mendelson; Jennifer M. Gumm, Michael D. Martin, Patrick J. Ciccotto
      Abstract: Speciation by sexual selection is generally modeled as the coevolution of female preferences and elaborate male ornaments leading to behavioral (sexual) reproductive isolation. One prediction of these models is that female preference for conspecific males should evolve earlier than male preference for conspecific females in sexually dimorphic species with male ornaments. We tested that prediction in darters, a diverse group of freshwater fishes with sexually dimorphic ornamentation. Focusing on the earliest stages of divergence, we tested preference for conspecific mates in males and females of seven closely related species pairs. Contrary to expectation, male preference for conspecific females was significantly greater than female preference for conspecific males. Males in four of the 14 species significantly preferred conspecific females; whereas, females in no species significantly preferred conspecific males. Relationships between the strength of preference for conspecifics and genetic distance revealed no difference in slope between males and females, but a significant difference in intercept, also suggesting that male preference evolves earlier than females’. Our results are consistent with other recent studies in darters and suggest that the coevolution of female preferences and male ornaments may not best explain the earliest stages of behavioral isolation in this lineage.
      PubDate: 2017-12-19T00:01:03.683707-05:
      DOI: 10.1111/evo.13406
  • Parasites driving host diversity: Incidence of disease correlated with
           Daphnia clonal turnover
    • Authors: Patrick Turko; Christoph Tellenbach, Esther Keller, Nadine Tardent, Barbara Keller, Piet Spaak, Justyna Wolinska
      Abstract: According to the Red Queen hypothesis, clonal diversity in asexual populations could be maintained by negative frequency-dependant selection by co-evolving parasites. If common clones are selected against and rare clones gain a concomitant advantage, we expect that clonal turnover should be faster during parasite epidemics than between them. We tested this hypothesis exploring field data of the Daphnia – Caullerya host-parasite system. The clonal make-up and turnover of the Daphnia host population was tracked with high temporal resolution from 1998 until 2013, using first allozyme and later microsatellite markers. Significant differences in the clonal composition between random and infected sub-samples of Daphnia populations were detected on six of seven tested occasions, confirming genetic specificity of the host-parasite interaction in this system. We used time series analysis to compare the rates of host clonal turnover to the incidence of parasitism, and found that Caullerya prevalence was significantly associated with microsatellite-based clonal turnover. As alternate hypotheses, we further tested whether turnover was related to a variety of biotic, abiotic, and host demographic parameters. Other significant correlates of turnover were cyanobacterial biomass and (weakly) temperature. Overall, parasitism seems to be a strong driver of host clonal turnover, in support of the Red Queen hypothesis.This article is protected by copyright. All rights reserved
      PubDate: 2017-12-14T01:20:34.949379-05:
      DOI: 10.1111/evo.13413
  • The consequences of sexual selection in well-adapted and maladapted
           populations of bean beetles
    • Authors: Ivain Martinossi-Allibert; Uroš Savković, Mirko Đorđević, Göran Arnqvist, Biljana Stojković, David Berger
      Abstract: Whether sexual selection generally promotes or impedes population persistence remains an open question. Intralocus sexual conflict (IaSC) can render sexual selection in males detrimental to the population by increasing the frequency of alleles with positive effects on male reproductive success but negative effects on female fecundity. Recent modelling based on fitness landscape theory, however, indicates that the relative impact of IaSC may be reduced in maladapted populations and that sexual selection therefore might promote adaptation when it is most needed. Here, we test this prediction using bean beetles that had undergone 80 generations of experimental evolution on two alternative host plants. We isolated and assessed the effect of maladaptation on sex-specific strengths of selection and IaSC by cross-rearing the two experimental evolution regimes on the alternative hosts and estimating within-population genetic (co)variance for fitness in males and females. Two key predictions were upheld: males generally experienced stronger selection compared to females and maladaptation increased selection in females. However, maladaptation consistently decreased male-bias in the strength of selection and IaSC was not reduced in maladapted populations. These findings imply that sexual selection can be disrupted in stressful environmental conditions, thus reducing one of the potential benefits of sexual reproduction in maladapted populations.This article is protected by copyright. All rights reserved
      PubDate: 2017-12-14T00:50:43.494476-05:
      DOI: 10.1111/evo.13412
  • Greater pollination generalization is not associated with reduced
           constraints on corolla shape in Antillean plants
    • Authors: Simon Joly; François Lambert, Hermine Alexandre, Julien Clavel, Étienne Léveillé-Bourret, John L. Clark
      Abstract: Flowers show important structural variation as reproductive organs but the evolutionary forces underlying this diversity are still poorly understood. In animal-pollinated species, flower shape is strongly fashioned by selection imposed by pollinators, which is expected to vary according to guilds of effective pollinators. Using the Antillean subtribe Gesneriinae (Gesneriaceae), we tested the hypothesis that pollination specialists pollinated by one functional type of pollinator have maintained more similar corolla shapes through time due to more constant and stronger selection constraints compared to species with more generalist pollination strategies. Using geometric morphometrics and evolutionary models, we showed that the corolla of hummingbird specialists, bat specialists, and species with a mixed-pollination strategy (pollinated by hummingbirds and bats; thus a more generalist strategy) have distinct shapes and that these shapes have evolved under evolutionary constraints. However, we did not find support for greater disparity in corolla shape of more generalist species. This could be because the corolla shape of more generalist species in subtribe Gesneriinae, which has evolved multiple times, is finely adapted to be effectively pollinated by both bats and hummingbirds. These results suggest that ecological generalization is not necessarily associated with relaxed selection constraints.This article is protected by copyright. All rights reserved
      PubDate: 2017-12-13T03:20:28.828372-05:
      DOI: 10.1111/evo.13410
  • Chaos and the (un)predictability of evolution in a changing environment
    • Authors: Artur Rego-Costa; Florence Débarre, Luis-Miguel Chevin
      Abstract: Among the factors that may reduce the predictability of evolution, chaos, characterized by a strong dependence on initial conditions, has received much less attention than randomness due to genetic drift or environmental stochasticity. It was recently shown that chaos in phenotypic evolution arises commonly under frequency-dependent selection caused by competitive interactions mediated by many traits. This result has been used to argue that chaos should often make evolutionary dynamics unpredictable. However, populations also evolve largely in response to external changing environments, and such environmental forcing is likely to influence the outcome of evolution in systems prone to chaos. We investigate how a changing environment causing oscillations of an optimal phenotype interacts with the internal dynamics of an eco-evolutionary system that would be chaotic in a constant environment. We show that strong environmental forcing can improve the predictability of evolution, by reducing the probability of chaos arising, and by dampening the magnitude of chaotic oscillations. In contrast, weak forcing can increase the probability of chaos, but it also causes evolutionary trajectories to track the environment more closely. Overall, our results indicate that, although chaos may occur in evolution, it does not necessarily undermine its predictability.This article is protected by copyright. All rights reserved
      PubDate: 2017-12-12T22:50:50.007751-05:
      DOI: 10.1111/evo.13407
  • Sexual imprinting and speciation in two Peromyscus species
    • Authors: E. K. Delaney; H. E. Hoekstra
      Abstract: Sexual isolation, a reproductive barrier, can prevent interbreeding between diverging populations or species. Sexual isolation can have a clear genetic basis; however, it may also result from learned mate preferences that form via sexual imprinting. Here, we demonstrate that two sympatric species of mice—the white-footed mouse (Peromyscus leucopus) and its sister species, the cotton mouse (P. gossypinus)—hybridize only rarely in the wild despite co-occurrence in the same habitat and lack of any measurable intrinsic postzygotic barriers in laboratory crosses. We present evidence that strong conspecific mating preferences in each species result in significant sexual isolation. We find that these preferences are learned in at least one species: P. gossypinus sexually imprints on its parents, but in P. leucopus, additional factors influence mating preferences. Our study demonstrates that sexual imprinting contributes to reproductive isolation that reduces hybridization between otherwise interfertile species, supporting the role for learning in mammalian speciation.This article is protected by copyright. All rights reserved
      PubDate: 2017-12-12T10:21:27.640207-05:
      DOI: 10.1111/evo.13409
  • Antagonistic pleiotropy and mutation accumulation contribute to
           age-related decline in stress response
    • Authors: Elizabeth R. Everman; Theodore J. Morgan
      Abstract: As organisms age, the effectiveness of natural selection weakens, leading to age-related decline in fitness-related traits. The evolution of age-related changes associated with senescence is likely influenced by mutation accumulation (MA) and antagonistic pleiotropy (AP). MA predicts that age-related decline in fitness components is driven by age-specific sets of alleles, non-negative genetic correlations within trait across age, and an increase in the coefficient of genetic variance. AP predicts that age-related decline in a trait is driven by alleles with positive effects on fitness in young individuals and negative effects in old individuals, and is expected to lead to negative genetic correlations within traits across age. We build on these predictions using an association mapping approach to investigate the change in additive effects of SNPs across age and among traits for multiple stress-response fitness-related traits, including cold stress with and without acclimation and starvation resistance. We found support for both MA and AP theories of aging in the age-related decline in stress tolerance. Our study demonstrates that the evolution of age-related decline in stress tolerance is driven by a combination of alleles that have age-specific additive effects, consistent with MA, as well as non-independent and antagonistic genetic architectures characteristic of AP.This article is protected by copyright. All rights reserved
      PubDate: 2017-12-07T03:50:39.381982-05:
      DOI: 10.1111/evo.13408
  • Climate-driven build-up of temporal isolation within a recently formed
           avian hybrid zone
    • Authors: Päivi M. Sirkiä; S. Eryn McFarlane, William Jones, David Wheatcroft, Murielle Ålund, Jakub Rybinski, Anna Qvarnström
      Abstract: Divergence in the onset of reproduction can act as an important source of reproductive isolation (i.e. allochronic isolation) between co-occurring young species, but evidence for the evolutionary processes leading to such divergence is often indirect. While advancing spring seasons strongly affect the onset of reproduction in many taxa, it remains largely unexplored whether contemporary spring advancement directly affects allochronic isolation between young species. We examined how increasing spring temperatures affected onset of reproduction and thereby hybridization between pied and collared flycatchers (Ficedula spp.) across habitat types in a young secondary contact zone. We found that both species have advanced their timing of breeding in 14 years. However, selection on pied flycatchers to breed earlier was weaker, resulting in a slower response to advancing springs compared to collared flycatchers and thereby build-up of allochronic isolation between the species. We argue that a pre-adaptation to a broader niche use (diet) of pied flycatchers explains the slower response to raising spring temperature, but that reduced risk to hybridize may contribute to further divergence in the onset of breeding in the future. Our results show that minor differences in the response to environmental change of co-occurring closely related species can quickly cause allochronic isolation.This article is protected by copyright. All rights reserved
      PubDate: 2017-12-06T23:22:45.774787-05:
      DOI: 10.1111/evo.13404
  • Maternal effects and parent-offspring conflict
    • Authors: Bram Kuijper; Rufus A. Johnstone
      Abstract: Maternal effects can provide offspring with reliable information about the environment they are likely to experience, but also offer scope for maternal manipulation of young when interests diverge between parents and offspring. To predict the impact of parent-offspring conflict, we model the evolution of maternal effects on local adaptation of young. We find that parent-offspring conflict strongly influences the stability of maternal effects; moreover, the nature of the disagreement between parents and young predicts how conflict is resolved: when mothers favor less extreme mixtures of phenotypes relative to offspring (i.e., when mothers stand to gain by hedging their bets), mothers win the conflict by providing offspring with limited amounts of information. When offspring favor overproduction of one and the same phenotype across all environments compared to mothers (e.g., when offspring favor a larger body size), neither side wins the conflict and signaling breaks down. Only when offspring favor less extreme mixtures relative to their mothers (something no current model predicts), offspring win the conflict and obtain full information about the environment. We conclude that a partial or complete breakdown of informative maternal effects will be the norm rather than the exception in the presence of parent-offspring conflict.This article is protected by copyright. All rights reserved
      PubDate: 2017-12-06T05:20:33.727615-05:
      DOI: 10.1111/evo.13403
  • Digest: The effect of the pollinator composition and abundance on
           pollen-related floral traits
    • Authors: Camille Madec
      Abstract: Is variation in pollen-related floral traits linked to variation in the composition and abundance of pollinators present in an area' Parker et al. (2017) found that, in the wildflower Claytonia virginica, pollen release by anthers was slower and more staggered at northern sites dominated by a pollen-foraging bee than at southern sites where the main pollinator is a nectar-collecting bee fly. Their findings suggest that C. virginica populations may be adapted to their local pollinator environment.This article is protected by copyright. All rights reserved
      PubDate: 2017-12-06T02:50:21.341568-05:
      DOI: 10.1111/evo.13405
  • The origin and evolution of coral species richness in a marine
           biodiversity hotspot
    • Authors: Danwei Huang; Emma E. Goldberg, Loke Ming Chou, Kaustuv Roy
      Abstract: The Coral Triangle region of the Indo-Pacific realm harbors an extraordinary number of species, with richness decreasing away from this biodiversity hotspot. Despite multiple competing hypotheses, the dynamics underlying this regional diversity pattern remain poorly understood. Here we use a time-calibrated evolutionary tree of living reef coral species, their current geographic ranges, and model-based estimates of regional rates of speciation, extinction, and geographic range shifts to show that origination rates within the Coral Triangle are lower than in surrounding regions, a result inconsistent with the long-standing center of origin hypothesis. Furthermore, endemism of coral species in the Coral Triangle is low, and the Coral Triangle endemics are older than relatives found outside this region. Overall, our model results suggest that the high diversity of reef corals in the Coral Triangle is largely due to range expansions into this region of species that evolved elsewhere. These findings strongly support the notion that geographic range shifts play a critical role in generating species diversity gradients. They also show that preserving the processes that gave rise to the striking diversity of corals in the Coral Triangle requires protecting not just reefs within the hotspot, but also those in the surrounding areas.This article is protected by copyright. All rights reserved
      PubDate: 2017-11-27T02:18:02.246378-05:
      DOI: 10.1111/evo.13402
  • Digest: Evolution of sperm size and number in external fertilizers
    • Authors: Pedram Samani
      Abstract: Ejaculate evolution in externally fertilizing species is influenced by competition among sperm as well as the rate at which sperm and eggs encounter one another. Liao et al. (2017) found that ejaculate evolution in external fertilizers depended on spawning conditions. In anurans, gametes are released very close to eggs and are relatively protected from dispersal by water currents, thus sperm competition is more important. However, in fish, sperm-egg encounter rate plays a much more important role in ejaculate evolution because gametes may be easily dispersed when released into the aquatic environment.This article is protected by copyright. All rights reserved
      PubDate: 2017-11-21T06:20:33.444076-05:
      DOI: 10.1111/evo.13400
  • Digest: Room for geckos of all shapes and sizes
    • Authors: H. Christoph Liedtke
      Abstract: Closely related lineages co-existing geographically are expected to show morphological divergence via character displacement. Moritz et al. (2017) use high-throughput sequencing to uncover cryptic diversity in a complex of Australian geckos and, with the resulting phylogeny, discern patterns of morphological evolution in relation to patterns of geographic overlap. They found that divergence in body size is greater in species pairs occurring in sympatry than in parapatry, which is consistent with the idea that body size divergence facilitates sympatry.This article is protected by copyright. All rights reserved
      PubDate: 2017-11-21T06:20:30.851328-05:
      DOI: 10.1111/evo.13401
  • The evolutionary dynamics of adaptive virginity, sex-allocation and
           altruistic helping in haplodiploid animals
    • Authors: Petri Rautiala; Heikki Helanterä, Mikael Puurtinen
      Abstract: In haplodiploids, females can produce sons from unfertilized eggs without mating. However, virgin reproduction is usually considered to be a result of a failure to mate, rather than an adaptation. Here we build an analytical model for evolution of virgin reproduction, sex-allocation, and altruistic female helping in haplodiploid taxa. We show that when mating is costly (e.g. when mating increases predation risk), virginity can evolve as an adaptive female reproductive strategy. Furthermore, adaptive virginity results in strongly divergent sex-ratios in mated and virgin queen nests (‘split sex ratios’), which promotes the evolution of altruistic helping by daughters in mated queen nests. However, when helpers evolve to be efficient and increase nest production significantly, virgin reproduction is selected against. Our results suggest that adaptive virginity could have been an important stepping stone on the pathway to eusociality in haplodiploids. We further show that virginity can be an adaptive reproductive strategy also in primitively social haplodiploids if workers bias the sex ratio toward females. By remaining virgin, queens are free to produce sons, the more valuable sex in a female-biased population. Our work brings a new dimension to the studies linking reproductive strategies with social evolution.This article is protected by copyright. All rights reserved
      PubDate: 2017-11-21T06:20:28.173532-05:
      DOI: 10.1111/evo.13399
  • Males that drop a sexually selected weapon grow larger testes
    • Authors: Paul N. Joseph; Zachary Emberts, Daniel A. Sasson, Christine W. Miller
      Abstract: Costly sexually selected weapons are predicted to trade off with postcopulatory traits, such as testes. Although weapons can be important for achieving access to females, individuals of some species can permanently drop (i.e. autotomize) their weapons, without regeneration, to escape danger. We capitalized on this natural behavior to experimentally address whether the loss of a sexually selected weapon leads to increased testes investment in the leaf-footed cactus bug, Narnia femorata Stål (Hemiptera: Coreidae). In a second experiment, we measured offspring production for males that lost a weapon during development. As predicted, males that dropped a hind limb during development grew significantly larger testes than the control treatments. Hind-limb autotomy did not result in the enlargement of other nearby traits. Our results are the first to experimentally demonstrate that males compensate for natural weapon loss by investing more in testes. In a second experiment we found that females paired with males that lost a hind limb had 40% lower egg hatching success than females paired with intact males, perhaps because of lower mating receptivity to males with a lost limb. Importantly, in those cases where viable offspring were produced, males missing a hind limb produced 42% more offspring than males with intact limbs. These results suggest that the loss of a hind-limb weapon can, in some cases, lead to greater fertilization success.
      PubDate: 2017-11-20T12:20:29.09033-05:0
      DOI: 10.1111/evo.13387
  • Phenotypic and genetic integration of personality and growth under
           competition in the sheepshead swordtail, Xiphophorus birchmanni
    • Authors: K. Boulton; C.A. Walling, A.J. Grimmer, G.G. Rosenthal, A.J. Wilson
      Abstract: Competition for resources including food, physical space, and potential mates is a fundamental ecological process shaping variation in individual phenotype and fitness. The evolution of competitive ability, in particular social dominance, depends on genetic (co)variation among traits causal (e.g., behaviour) or consequent (e.g. growth) to competitive outcomes. If dominance is heritable, it will generate both direct and indirect genetic effects (IGE) on resource dependent traits. The latter are expected to impose evolutionary constraint because winners necessarily gain resources at the expense of losers. We varied competition in a population of sheepshead swordtails, Xiphophorus birchmanni, to investigate effects on behaviour, size, growth, and survival. We then applied quantitative genetic analyses to determine (i) whether competition leads to phenotypic and/or genetic integration of behaviour with life history and (ii) the potential for IGE to constrain life history evolution. Size, growth and survival were reduced at high competition. Male dominance was repeatable and dominant individuals show higher growth and survival. Additive genetic contributions to phenotypic covariance were significant, with the G matrix largely recapitulating phenotypic relationships. Social dominance has a low but significant heritability and is strongly genetically correlated with size and growth. Assuming causal dependence of growth on dominance, hidden IGE will therefore reduce evolutionary potential.This article is protected by copyright. All rights reserved
      PubDate: 2017-11-17T07:50:25.953948-05:
      DOI: 10.1111/evo.13398
  • Signatures of selection in embryonic transcriptomes of lizards adapting in
           parallel to cool climate
    • Authors: Nathalie Feiner; Alfredo Rago, Geoffrey M. While, Tobias Uller
      Abstract: Populations adapting independently to the same environment provide important insights into the repeatability of evolution at different levels of biological organization. In the 20th century, common wall lizards (Podarcis muralis) from southern and western Europe were introduced to England, north of their native range. Non-native populations of both lineages have adapted to the shorter season and lower egg incubation temperature by increasing the absolute rate of embryonic development. Here we tested if this adaptation is accompanied by signatures of directional selection in the transcriptomes of early embryos and, if so, if non-native populations show adaptive convergence. Embryos from non-native populations exhibited gene expression profiles consistent with directional selection following introduction, but different genes were affected in the two lineages. Despite this, the functional enrichment of genes that changed their expression following introduction showed substantial similarity between lineages, and was consistent with mechanisms that should promote developmental rate. Moreover, the divergence between non-native and native populations was enriched for genes that were temperature-responsive in native populations. These results indicate that small populations are able to adapt to new climatic regimes, but the means by which they do so may largely be determined by founder effects and other sources of genetic drift.This article is protected by copyright. All rights reserved
      PubDate: 2017-11-16T05:50:36.664202-05:
      DOI: 10.1111/evo.13397
  • Convergent selection pressures drive the evolution of rhodopsin kinetics
           at high altitudes via non-parallel mechanisms
    • Authors: Gianni M. Castiglione; Ryan K. Schott, Frances E. Hauser, Belinda S. W. Chang
      Abstract: Convergent evolution in response to similar selective pressures is a well-known phenomenon in evolutionary biology. Less well understood is how selection drives convergence in protein function, and the underlying mechanisms by which this can be achieved. Here we investigate functional convergence in the visual system of two distantly related lineages of high-altitude adapted Andean and Himalayan catfishes. Statistical analyses revealed in the two high-altitude lineages, a parallel acceleration of evolutionary rates in rhodopsin, the dim-light visual pigment. However, the elevated rates were found to be accompanied by substitutions at different sites in the protein. Experiments substituting Andean- or Himalayan-specific residues significantly accelerated the kinetic rates of rhodopsin, destabilizing the ligand-bound forms. As found in cold-adapted enzymes, this phenotype likely compensates for a cold-induced decrease in kinetic rates, properties of rhodopsin mediating rod sensitivity and visual performance. Our study suggests that molecular convergence in protein function can be driven by parallel shifts in evolutionary rates but via non-parallel molecular mechanisms. Signatures of natural selection may therefore be a powerful guide for identifying complex instances of functional convergence across a wider range of protein systems.This article is protected by copyright. All rights reserved
      PubDate: 2017-11-16T02:51:13.979303-05:
      DOI: 10.1111/evo.13396
  • The evolution of genital shape variation in female cetaceans
    • Authors: Dara N. Orbach; Brandon Hedrick, Bernd Würsig, Sarah L. Mesnick, Patricia LR Brennan
      Abstract: Male genital diversification is likely the result of sexual selection. Female genital diversification may also result from sexual selection, although it is less well studied and understood. Female genitalia are complex among whales, dolphins, and porpoises, especially compared to other vertebrates. The evolutionary factors affecting the diversity of vaginal complexity could include ontogeny, allometry, phylogeny, sexual selection, and natural selection. We quantified shape variation in female genitalia using 2-D geometric morphometric analysis, and validated the application of this method to study soft tissues. We explored patterns of variation in the shape of the cervix and vagina of 24 cetacean species (n = 61 specimens), and found that genital shape varies primarily in the relative vaginal length and overall aspect ratio of the reproductive tract. Extensive genital shape variation was partly explained by ontogenetic changes and evolutionary allometry among sexually mature cetaceans, while phylogenetic signal, relative testis size, and neonate size were not significantly associated with genital shape. Female genital shape is diverse and evolves rapidly even among closely related species, consistent with predictions of sexual selection models and with findings in invertebrate and vertebrate taxa. Future research exploring genital shape variation in 3-D will offer new insights into evolutionary mechanisms since internal vaginal structures are variable and can form complex spirals.This article is protected by copyright. All rights reserved
      PubDate: 2017-11-14T02:51:08.653074-05:
      DOI: 10.1111/evo.13395
  • Microbial expansion-collision dynamics promote cooperation and coexistence
           on surfaces
    • Authors: Shuang Xu; J. David Dyken
      Abstract: Microbes colonizing a surface often experience colony growth dynamics characterized by an initial phase of spatial clonal expansion followed by collision between neighboring colonies to form potentially genetically heterogeneous boundaries. For species with life cycles consisting of repeated surface colonization and dispersal, these spatially-explicit “expansion-collision dynamics” generate periodic transitions between two distinct selective regimes, “expansion competition” and “boundary competition”, each one favoring a different growth strategy. We hypothesized that this dynamic could promote stable coexistence of expansion- and boundary-competition specialists by generating time-varying, negative frequency-dependent selection that insulates both types from extinction. We tested this experimentally in budding yeast by competing an exo-enzyme secreting “cooperator” strain (expansion-competition specialists) against non-secreting “defectors” (boundary-competition specialists). As predicted, we observed cooperator-defector coexistence or cooperator dominance with expansion-collision dynamics, but only defector dominance otherwise. Also as predicted, the steady-state frequency of cooperators was determined by colonization density (the average initial cell-cell distance) and cost of cooperation. Lattice-based spatial simulations give good qualitative agreement with experiments, supporting our hypothesis that expansion-collision dynamics with costly public goods production is sufficient to generate stable cooperator-defector coexistence. This mechanism may be important for maintaining public-goods cooperation-and-conflict in microbial pioneer species living on surfaces.This article is protected by copyright. All rights reserved
      PubDate: 2017-11-14T02:50:38.43424-05:0
      DOI: 10.1111/evo.13393
  • Repeated evolution and reversibility of self-fertilization in the
           volvocine green algae
    • Authors: Erik R. Hanschen; Matthew D. Herron, John J. Wiens, Hisayoshi Nozaki, Richard E. Michod
      Abstract: Outcrossing and self-fertilization are fundamental strategies of sexual reproduction, each with different evolutionary costs and benefits. Self-fertilization is thought to be an evolutionary “dead-end” strategy, beneficial in the short term but costly in the long term, resulting in self-fertilizing species that occupy only the tips of phylogenetic trees. Here, we use volvocine green algae to investigate the evolution of self-fertilization. We use ancestral-state reconstructions to show that self-fertilization has repeatedly evolved from outcrossing ancestors and that multiple reversals from selfing to outcrossing have occurred. We use three phylogenetic metrics to show that self-fertilization is not restricted to the tips of the phylogenetic tree, a finding inconsistent with the view of self-fertilization as a dead-end strategy. We also find no evidence for higher extinction rates or lower speciation rates in selfing lineages. We find that self-fertilizing species have significantly larger colonies than outcrossing species, suggesting the benefits of selfing may counteract the costs of increased size. We speculate that our macroevolutionary results on self-fertilization (i.e. non-tippy distribution, no decreased diversification rates) may be explained by the haploid-dominant life cycle that occurs in volvocine algae, which may alter the costs and benefits of selfing.This article is protected by copyright. All rights reserved
      PubDate: 2017-11-14T01:20:26.885531-05:
      DOI: 10.1111/evo.13394
  • Environmental variation partitioned into separate heritable components
    • Authors: Michael Ørsted; Palle Duun Rohde, Ary Anthony Hoffmann, Peter Sørensen, Torsten Nygaard Kristensen
      Abstract: Trait variation is normally separated into genetic and environmental components, yet genetic factors also control the expression of environmental variation, encompassing plasticity across environmental gradients and within-environment responses. We defined four components of environmental variation: plasticity across environments, variability in plasticity, variation within environments, and differences in within-environment variation across environments. We assessed these components for cold tolerance across five rearing temperatures using the Drosophila melanogaster Genetic Reference Panel (DGRP). The four components were found to be heritable, and genetically correlated to different extents. By whole genome single marker regression, we detected multiple candidate genes controlling the four components and showed limited overlap in genes affecting them. Using the binary UAS-GAL4 system, we functionally validated the effects of a subset of candidate genes affecting each of the four components of environmental variation and also confirmed the genetic and phenotypic correlations obtained from the DGRP in distinct genetic backgrounds. We delineate selection targets associated with environmental variation and the constraints acting upon them, providing a framework for evolutionary and applied studies on environmental sensitivity. Based on our results we suggest that the traditional quantitative genetic view of environmental variation and genotype-by-environment interactions needs revisiting.This article is protected by copyright. All rights reserved
      PubDate: 2017-11-10T08:52:06.872904-05:
      DOI: 10.1111/evo.13391
  • A theoretical approach to the size-complexity rule
    • Authors: André Amado; Carlos Batista, Paulo R. A. Campos
      Abstract: The so-called size-complexity rule claims the existence of a positive correlation between organism size and number of cell types. In this spirit, here we address the relationship between organism size and number of potential tasks that can be performed. The modeling relies on the assumption that the states of the cells within the aggregates are such that the maximum fitness is realized, but also relies on the existence of tradeoffs among the distinct functions. For group sizes larger than the number of potential tasks, fitness maximization is attained when all cells in group specialize in a given task. Under this scenario, the number of potential tasks equals the number of cell types. We have found that the morphology and the topology of aggregates, as well as the developmental mode, strongly influence the dynamics of body formation. Particularly, it has been observed that more compact structures, such as sphere-like structures, are more likely to follow the claim of the size-complexity rule, whereas more fragile structures such as linear chains, which are more vulnerable to drastic changes due to division mechanisms, can, in a broad scenario, violate the size-complexity rule.This article is protected by copyright. All rights reserved
      PubDate: 2017-11-09T05:50:28.70332-05:0
      DOI: 10.1111/evo.13392
  • Male mate choice via cuticular hydrocarbon pheromones drives reproductive
           isolation between Drosophila species
    • Authors: Michael P. Shahandeh; Alison Pischedda, Thomas L. Turner
      Abstract: Mate discrimination is a key mechanism restricting gene flow between species. While studied extensively with respect to female mate choice, mechanisms of male mate choice between species are far less studied. Thus, we have little knowledge of the relative frequency, importance, or overall contribution of male mate discrimination to reproductive isolation. In the present study, we estimated the relative contributions of male and female choice to reproductive isolation between Drosophila simulans and D. sechellia, and show that male mate discrimination accounts for the majority of the current isolation between these species. We further demonstrate that males discriminate based on female cuticular hydrocarbon pheromones, and collect evidence supporting the hypothesis that male mate discrimination may alleviate the costs associated with heterospecific courtship and mating. Our findings highlight the potentially significant contribution of male mate choice to the formation of reproductive isolating barriers, and thus the speciation process.This article is protected by copyright. All rights reserved
      PubDate: 2017-11-03T01:50:29.19871-05:0
      DOI: 10.1111/evo.13389
  • Polygenic evolution drives species divergence and climate adaptation in
    • Authors: Noah H. Rose; Rachael A. Bay, Megan K. Morikawa, Stephen R. Palumbi
      Abstract: Closely related species often show substantial differences in ecological traits that allow them to occupy different environmental niches. For few of these systems is it clear what the genomic basis of adaptation is and whether a few loci of major effect or many genome-wide differences drive species divergence. Four cryptic species of the tabletop coral Acropora hyacinthus are broadly sympatric in American Samoa; here we show that two common species have differences in key environmental traits such as microhabitat distributions and thermal stress tolerance. We compared gene expression patterns and genetic polymorphism between these two species using RNA-Seq. The vast majority of polymorphisms are shared between species, but the two species show widespread differences in allele frequencies and gene expression, and tend to host different symbiont types. We find that changes in gene expression are related to changes in the frequencies of many gene regulatory variants, but that many of these differences are consistent with the action of genetic drift. However, we observe greater genetic divergence between species in amino acid replacement polymorphisms compared to synonymous variants. These findings suggest that polygenic evolution plays a major role in driving species differences in ecology and resilience to climate change.This article is protected by copyright. All rights reserved
      PubDate: 2017-11-02T23:51:37.4188-05:00
      DOI: 10.1111/evo.13385
  • Integrating phylogenomic and population genomic patterns in avian lice
           provides a more complete picture of parasite evolution
    • Authors: Andrew D. Sweet; Bret M. Boyd, Julie M. Allen, Scott M. Villa, Michel P. Valim, Jose L. Rivera-Parra, Robert E. Wilson, Kevin P. Johnson
      Abstract: Parasite diversity accounts for most of the biodiversity on earth, and is shaped by many processes (e.g. cospeciation, host-switching). To identify the effects of the processes that shape parasite diversity, it is ideal to incorporate both deep (phylogenetic) and shallow (population) perspectives. To this end, we developed a novel workflow to obtain phylogenetic and population genetic data from whole genome sequences of body lice parasitizing New World ground-doves. Phylogenies from these data showed consistent, highly resolved species-level relationships for the lice. By comparing the louse and ground-dove phylogenies, we found that over long-term evolutionary scales their phylogenies were largely congruent. Many louse lineages (both species and populations) also demonstrated high host-specificity, suggesting ground-dove divergence is a primary driver of their parasites’ diversity. However, the few louse taxa that are generalists are structured according to biogeography at the population level. This suggests dispersal among sympatric hosts has some effect on body louse diversity, but over deeper time scales the parasites eventually sort according to host species. Overall, our results demonstrate that multiple factors explain the patterns of diversity in this group of parasites, and that the effects of these factors can vary over different evolutionary scales. The integrative approach we employed was crucial for uncovering these patterns, and should be broadly applicable to other studies.This article is protected by copyright. All rights reserved
      PubDate: 2017-11-02T00:21:05.935923-05:
      DOI: 10.1111/evo.13386
  • Cryptic lineage diversity, body size divergence and sympatry in a species
           complex of Australian lizards (Gehyra)
    • Authors: Craig Moritz; Renae C. Pratt, Sarah Bank, Gayleen Bourke, Jason G. Bragg, Paul Doughty, J. Scott Keogh, Rebecca J. Laver, Sally Potter, Luisa C. Teasdale, Leonardo G. Tedeschi, Paul M. Oliver
      Abstract: Understanding the joint evolutionary and ecological underpinnings of sympatry among close relatives remains a key challenge in biology. This problem can be addressed through joint phylogenomic and phenotypic analysis of complexes of closely related lineages within, and across, species and hence representing the speciation continuum. For a complex of tropical geckos from northern Australia – Gehyra nana and close relatives – we combine mtDNA phylogeography, exon-capture sequencing and morphological data to resolve independently evolving lineages and infer their divergence history and patterns of morphological evolution. Gehyra nana is found to include nine divergent lineages and is paraphyletic with four other species from the Kimberley region of north-west Australia. Across these 13 taxa, 12 of which are restricted to rocky habitats, several lineages overlap geographically, including on the diverse Kimberley islands. Morphological evolution is dominated by body size shifts, and both body -size and -shape have evolved gradually across the group. However, larger body size shifts are observed among overlapping taxa than among closely related parapatric lineages of G. nana, and sympatric lineages are more divergent than expected at random. Whether elevated body size differences among sympatric lineages are due to ecological sorting or character displacement remains to be determined.This article is protected by copyright. All rights reserved
      PubDate: 2017-10-25T03:20:50.009512-05:
      DOI: 10.1111/evo.13380
  • Geographic patterns and pollination ecotypes in Claytonia virginica
    • Authors: Alison J. Parker; Neal M. Williams, James D. Thomson
      Abstract: Geographical variation in pollinators visiting a plant can produce plant populations adapted to local pollinator environments. We documented two markedly different pollinator climates for the spring ephemeral wildflower Claytonia virginica: in more northern populations, the pollen-specialist bee Andrena erigeniae dominated, but in more southern populations, A. erigeniae visited rarely and the bee-fly Bombylius major dominated. Plants in the northern populations experience faster pollen depletion than plants in southern populations. We also measured divergent pollen-related plant traits; plants in northern populations produced relatively more pollen per flower and anther dehiscence was more staggered than plants in southern populations. These plant traits might function to increase pollen dispersal via the different pollen vectors.This article is protected by copyright. All rights reserved
      PubDate: 2017-10-21T04:50:24.229355-05:
      DOI: 10.1111/evo.13381
  • Estimating diversification rates for higher taxa: BAMM can give
           problematic estimate of rates and rate shifts
    • Authors: Andreas L. S. Meyer; John J. Wiens
      Abstract: Estimates of diversification rates are invaluable for many macroevolutionary studies. Recently, an approach called BAMM (Bayesian Analysis of Macro-evolutionary Mixtures) has become widely used for estimating diversification rates and rate shifts. At the same time, several papers have concluded that estimates of net diversification rates from the method-of-moments (MS) estimators are inaccurate. Yet, no studies have compared the ability of these two methods to accurately estimate clade diversification rates. Here, we use simulations to compare their performance. We found that BAMM yielded relatively weak relationships between true and estimated diversification rates. This occurred because BAMM underestimated the number of rates shifts across each tree, and assigned high rates to small clades with low rates. Errors in both speciation and extinction rates contributed to these errors, showing that using BAMM to estimate only speciation rates is also problematic. In contrast, the MS estimators (particularly using stem group ages), yielded stronger relationships between true and estimated diversification rates, by roughly twofold. Furthermore, the MS approach remained relatively accurate when diversification rates were heterogeneous within clades, despite the widespread assumption that it requires constant rates within clades. Overall, we caution that BAMM may be problematic for estimating diversification rates and rate shifts.This article is protected by copyright. All rights reserved
      PubDate: 2017-10-21T04:20:30.762881-05:
      DOI: 10.1111/evo.13378
  • Ejaculate evolution in external fertilizers: Influenced by sperm
           competition or sperm limitation'
    • Authors: Wen Bo Liao; Yan Huang, Yu Zeng, Mao Jun Zhong, Yi Luo, Stefan Lüpold
      Abstract: The evolution of sperm quality and quantity is shaped by various selective processes, with sperm competition generally considered the primary selective agent. Particularly in external fertilizers, however, sperm limitation through gamete dispersal can also influence gamete investments, but empirical data examining this effect are limited. Here, we studied the relative importance of sperm competition and the spawning conditions in explaining the macroevolutionary patterns of sperm size and number within two taxa with external fertilization but differences in their reproductive biology. In frogs, sperm swim slowly but for up to hours as they penetrate the gelatinous egg coating, whereas fish sperm typically swim fast, are very short-lived (seconds to minutes), and often face a relatively higher risk of being moved away from the ova by currents. Our phylogenetic models and path analyses revealed different trajectories of ejaculate evolution in these two taxa. Sperm size and number responded primarily to variation in sperm competition in the anurans, but more strongly to egg number and water turbulence in the fishes. Whereas the results across anurans align with the general expectation that sexual selection is the main driver of ejaculate evolution, our findings across the fishes suggest that sperm limitation has been underappreciated.This article is protected by copyright. All rights reserved
      PubDate: 2017-10-04T00:20:41.374473-05:
      DOI: 10.1111/evo.13372
  • Corrigendum
    • PubDate: 2017-09-14T11:50:21.84191-05:0
      DOI: 10.1111/evo.13337
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