Environmental correlates of phenotypic evolution in ecologically diverse Liolaemus lizards

Evolutionary correlations between phenotypic and environmental traits characterize adaptive radiations. However, the lizard genus Liolaemus, one of the most ecologically diverse terrestrial vertebrate radiations on earth, has so far shown limited or mixed evidence of adaptive diversification in phenotype. Restricted use of comprehensive environmental data, incomplete taxonomic representation and not considering phylogenetic uncertainty may have led to contradictory evidence. We compiled a 26‐taxon dataset for the Liolaemus gracilis species group, representing much of the ecological diversity represented within Liolaemus and used environmental data to characterize how environments occupied by species'' relate to phenotypic evolution. Our analyses, explicitly accounting for phylogenetic uncertainty, suggest diversification in phenotypic traits toward the present, with body shape evolution rapidly evolving in this group. Body shape evolution correlates with the occupation of different structural habitats indicated by vegetation axes suggesting species have adapted for maximal locomotory performance in these habitats. Our results also imply that the effects of phylogenetic uncertainty and model misspecification may be more extensive on univariate, relative to multivariate analyses of evolutionary correlations, which is an important consideration in analyzing data from rapidly radiating adaptive radiations.     

Comparative myology of the forelimb of Liolaemus sand lizards (Liolaemidae)

The lizard genus Liolaemus includes numerous constituent clusters of putatively related taxa, one of which is the Liolaemus boulengeri group, which in turn includes the sand lizards (of the Liolaemus wiegmannii subgroup). Members of the sand lizard group exhibit three different modes of burying into sand. The general morphology of the forelimb muscles of those Liolaemus species is analysed. Herein, we present a study of the forelimb musculature of all species considered by Halloy et al. (1998). This study has three principal goals. First, we are seeking myological characters that will be useful in formulating phylogenetic hypothesis about the species of Liolaemus. With these characters, we also wish to compile morphological data that represent the morphological space implied in the diverse locomotor behaviours of these animals. Second, we are looking for derived features that reflect functional changes in the use of forelimb. Third, we wish to provide a cladistic analysis that can be used to test phylogenetic hypothesis derived from other sources of data. We present 48 characters in a data set and analyse it cladistically. We obtained a hypothesis of relationships of the Liolaemus species and compared this with previous hypotheses based on other characters. The trees obtained are not congruent with previously proposed phylogenies. We were unable to identify in our trees nodes that are based on structures reflecting functional changes in the use of the forelimb. The morphological similarities in the forelimb musculature of all species analysed seems to conform a very conservative general anatomical pattern with which Liolaemus sand lizards perform most of their locomotor behaviours.     

Evolutionary dynamics of a sexual ornament in the house sparrow (Passer domesticus): the role of indirect selection within and between sexes

The relative contribution of sexual and natural selection to evolution of sexual ornaments has rarely been quantified under natural conditions. In this study we used a long-term dataset of house sparrows in which parents and offspring were matched genetically to estimate the within- and across-sex genetic basis for variation and covariation among morphological traits. By applying two-sex multivariate "animal models" to estimate genetic parameters, we estimated evolutionary changes in a male sexual ornament, badge size, from the contribution of direct and indirect selection on correlated traits within males and females, after accounting for overlapping generations and age-structure. Indirect natural selection on genetically correlated traits in males and females was the major force causing evolutionary change in the male ornament. Thus, natural selection on female morphology may cause indirect evolutionary changes in male ornaments. We observed however no directional phenotypic change in the ornament size of one-year-old males during the study period. On the other hand, changes were recorded in other morphological characters of both sexes. Our analyses of evolutionary dynamics in sexual characters require application of appropriate two-sex models to account for how selection on correlated traits in both sexes affects the evolutionary outcome of sexual selection.     

Sex‐specific selection and sexual size dimorphism in the waterstrider Aquarius remigis

We estimated selection on adult body size for two generations in two populations of Aquarius remigis, as part of a long‐term study of the adaptive significance of sexual size dimorphism (SSD). Net adult fitness was estimated from the following components: prereproductive survival, daily reproductive success (mating frequency or fecundity), and reproductive lifespan. Standardized selection gradients were estimated for total length and for thorax, abdomen, genital and mesofemur lengths. Although selection was generally weak and showed significant temporal and spatial heterogeneity, patterns were consistent with SSD. Prereproductive survival was strongly influenced by date of eclosion, but size (thorax and genital lengths in females; total and abdomen lengths in males) played a significant secondary role. Sexual selection favoured smaller males with longer external genitalia in one population. Net adult fitness was not significantly related to body size in females, but was negatively related to size (thorax and total length) in males.     

Testing the adaptive significance of sex‐specific mating tactics in collared lizards (Crotaphytus collaris)

We tested whether territorial defence is adaptive in male collared lizards by examining the extent to which territory owners monopolize females. We also tested whether females benefit by mating with multiple males using alternative tactics when local sex ratios varied. Surprisingly, neither the number of offspring that males sired, nor the number of females that males mated with varied as a consequence of highly variable local sex ratios. Moreover, both the number of offspring sired and the number of female mates were independent of male social status. Courtship frequency was under positive directional sexual selection for mating success for territorial males. None of the phenotypic traits that we examined were targets of sexual selection in nonterritorial males. Although offspring survivorship decreased with the degree of multiple mating, females mated multiply with similar numbers of territorial and nonterritorial males during all three seasons. Females did not obtain material or genetic benefits that balanced the apparent offspring survival cost imposed by mating with multiple males. Instead, females appeared to be ‘making the best of a bad job’, perhaps because the abundance of hiding places used by subordinate males makes it difficult for females to avoid male harassment. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 115 , 423–436.     

Ecological consequences of ontogenetic changes in head shape and bite performance in the Jamaican lizard Anolis lineatopus

It has been documented extensively that body size affects the physiology and musculoskeletal function of organisms. However, less well understood is how body size affects the ecology of organisms through its effects on physiology and performance. We explored the effects of body size on morphology and performance in different ontogenetic classes and sexes of a common Anolis lizard ( A. lineatopus ). Next, we tested whether these morphological and performance differences may affect functional aspects of the diet such as prey size and prey hardness. Our data showed that males, females and juveniles differ significantly in head size, head shape and bite force. Multiple regression models indicated that head shape and bite force are significantly correlated to prey size and hardness. Yet juveniles had relatively large heads and bit disproportionately hard for their size, allowing them to eat prey as large as those of females. However, for a given prey size, males and females ate more robust prey than did juveniles. Additionally, males ate relatively harder prey than did juveniles. These data suggest that: (1) body size affects the dietary ecology of animals through its effect on head size and bite force; (2) changes in head morphology independent of changes in overall size also have important effects on performance and diet.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 89 , 443–454.     

Sex‐specific effects of inbreeding in wild‐caught Drosophila melanogaster under benign and stressful conditions

In animal populations, sib mating is often the primary source of inbreeding depression (ID). We used recently wild‐caught Drosophila melanogaster to test whether such ID is amplified by environmental stress and, in males, by sexual selection. We also investigated whether increased ID because of stress (increased larval competition) persisted beyond the stressed stage and whether the effects of stress and sexual selection interacted. Sib mating resulted in substantial cumulative fitness losses (egg to adult reproduction) of 50% (benign) and 73% (stressed). Stress increased ID during the larval period (23% vs. 63%), but not during post‐stress reproductive stages (36% vs. 31%), indicating larval stress may have purged some adult genetic load (although ID was uncorrelated across stages). Sexual selection exacerbated inbreeding depression, with inbred male offspring suffering a higher reproductive cost than females, independent of stress (57% vs. 14% benign, 49% vs. 11% stress).     

Morphological divergence of North‐European nine‐spined sticklebacks (Pungitius pungitius): signatures of parallel evolution

Parallel evolution is characterised by repeated, independent occurrences of similar phenotypes in a given habitat type, in different parts of the species distribution area. We studied body shape and body armour divergence between five marine, four lake, and ten pond populations of nine‐spined sticklebacks [Pungitius pungitius (Linnaeus, 1758)] in Fennoscandia. We hypothesized that marine and lake populations (large water bodies, diverse fish fauna) would be similar, whereas sticklebacks in isolated ponds (small water bodies, simple fish fauna) would be divergent. We found that pond fish had deeper bodies, shorter caudal peduncles, and less body armour (viz. shorter/absent pelvic spines, reduced/absent pelvic girdle, and reduced number of lateral plates) than marine fish. Lake fish were intermediate, but more similar to marine than to pond fish. Results of our common garden experiment concurred with these patterns, suggesting a genetic basis for the observed divergence. We also found large variation among populations within habitat types, indicating that environmental variables other than those related to gross habitat characteristics might also influence nine‐spined stickleback morphology. Apart from suggesting parallel evolution of morphological characteristics of nine‐spined sticklebacks in different habitats, the results also show a number of similarities to the evolution of three‐spined stickleback (Gasterosteus aculeatus Linnaeus, 1758) morphology. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101 , 403–416.     

Evolutionary relationships between morphology, performance and habitat openness in the lizard genus Niveoscincus (Scincidae: Lygosominae)

Correlations between an animal's morphology and ecological parameters such as habitat characteristics emphasize the intimate link between phenotype and the environment, but are often difficult to interpret because the functional consequences of morphological variation are frequently unknown. We provide one of the few studies relating limb morphology, functional capabilities, and habitat in reptiles. We tested the hypothesis that species occupying open microhabitats would possess relatively longer limbs and faster sprint speeds than those occurring in more closed microhabitats. A number of morphological characteristics relevant to locomotion were quantified, including the length of the bones of the fore- and hindlimbs and body size. A phylogenetic analysis was then used to examine the evolutionary relationships between morphology, locomotor performance and microhabitat openness in seven species of Niveoscincus and one species of the closely related genus Pseudemoia. A significant evolutionary relationship was established between sprinting ability, morphology, and the openness of the microhabitat occupied by a species. The phylogenetic analysis demonstrated an evolutionary trend in Niveoscincus of species occupying open microhabitats (e.g. N. greeni, N ocellatus) being large with long limbs and high sprinting ability, while those occupying closed microhabitats (e.g. N coventryi, P. entrecasteauxii) art smaller with short limbs and much slower maximum sprint speeds.     

Connecting behaviour and performance: the evolution of biting behaviour and bite performance in bats

Variation in behaviour, performance and ecology are traditionally associated with variation in morphology. A neglected part of this ecomorphological paradigm is the interaction between behaviour and performance, the ability to carry out tasks that impact fitness. Here we investigate the relationship between biting behaviour and performance (bite force) among 20 species of ecologically diverse bats. We studied the patterns of evolution of plasticity in biting behaviour and bite force, and reconstructed ancestral states for behaviour and its plasticity. Both behavioural and performance plasticity exhibited accelerating evolution over time, and periods of rapid evolution coincided with major dietary shifts from insect‐feeding to plant‐feeding. We found a significant, positive correlation between behavioural plasticity and bite force. Bats modulated their performance by changing their biting behaviour to maximize bite force when feeding on hard foods. The ancestor of phyllostomids was likely a generalist characterized by high behavioural plasticity, a condition that also evolved in specialized frugivores and potentially contributed to their diversification.     

Evolution of a sexually dimorphic trait in a broadly distributed topminnow (Fundulus olivaceus)

Understanding the interaction between sexual and natural selection within variable environments is crucial to our understanding of evolutionary processes. The handicap principle predicts females will prefer males with exaggerated traits provided those traits are indicators of male quality to ensure direct or indirect female benefits. Spatial variability in ecological factors is expected to alter the balance between sexual and natural selection that defines the evolution of such traits. Male and female blackspotted topminnows (Fundulidae: Fundulus olivaceus) display prominent black dorsolateral spots that are variable in number across its broad range. We investigated variability in spot phenotypes at 117 sites across 13 river systems and asked if the trait was sexually dimorphic and positively correlated with measures of fitness (condition and gonadosomatic index [GSI]). Laboratory and mesocosm experiments assessed female mate choice and predation pressure on spot phenotypes. Environmental and community data collected at sampling locations were used to assess predictive models of spot density at the individual, site, and river system level. Greater number of spots was positively correlated with measures of fitness in males. Males with more spots were preferred by females and suffered greater mortality due to predation. Water clarity (turbidity) was the best predictor of spot density on the drainage scale, indicating that sexual and natural selection for the trait may be mediated by local light environments.     

A new species of Liolaemus related to L. nigroviridis from the Andean highlands of Central Chile (Iguania,Liolaemidae)

The Liolaemus nigroviridis group is a clade of highland lizards endemic to Chile. These species are distributed from northern to central Chile, and currently there are no cases of sympatric distribution. This study describes a new species, Liolaemus uniformis sp. n., from this group, and provides a detailed morphological characterization and mitochondrial phylogeny using cytochrome-b. Liolaemus uniformis was found in sympatry with Liolaemus nigroviridis but noticeably differed in size, scalation, and markedly in the color pattern, without sexual dichromatism. This new species has probably been confused with Liolaemus monticola and Liolaemus bellii, both of which do not belong to the nigroviridis group. The taxonomic issues of this group that remain uncertain are also discussed.     

Differential predation on sexes affects colour polymorphism of the isopod Idotea baltica (Pallas)

Variable selection, including spatio-temporal variation, frequency-dependent selection and differential selection due to habitat choice, may maintain polymorphism in heterogeneous environments. We studied predation as a selective agent on colour polymorphism of the aquatic isopod I baltica. Variable predation on this species can arise from at least three sources. First, apostatic selection was studied by testing the formation of preferences on colour morphs in the perch, a common predator of I baltica. Such acquired preferences should induce apostatic selection. While our results indicate some acquired preferences, there was significant heterogeneity in the behaviour of predator individuals. Second, temporal variation in selection can arise due to habitat shift from the green algae juvenile habitat to the bladderwrack adult habitat, and the consequent change in the crypsis of the morphs. Different crypsis between sexes probably promoted high predation mortality among females in the juvenile habitat. The high rate of male mortality during the breeding period, on the other hand, was presumably due to their high mate-searching activity. Third, the sex-dependent habitat choice of I baltica leads to sexual differences in the susceptibility of morphs to predation. Predators preferred the white-spotted morph over the uniform one in males but not in females, supporting the 'dimorphic niche' hypothesis as an explanation of sexual differences in morph frequencies. Finally, no evidence was found that the colouration patterns were under sexual selection. We therefore conclude diat variable predation is the most promising explanation for the maintenance of polymorphism in I. baltica.     

How the length of genital parts affects copulation performance in a carabid beetle: implications for correlated genital evolution between the sexes

To identify factors leading to the correlated evolution of exaggerated male and female genitalia, we studied the effects of the variable dimensions of corresponding functional genital parts (male copulatory piece and female vaginal appendix) on copulatory performance in the polygamous carabid beetle Carabus (Ohomopterus) maiyasanus. We used mating pairs of individuals from two populations to increase the variances in genital dimensions and determined the copulation performance (insemination and spermatophore replacement, and copulation time) in single‐ and double‐mating situations. In single mating, insemination success was not affected by genital dimensions, although the copulation time was significantly shorter when the male aedeagus was longer. In the double‐mating experiment, insemination and replacement of spermatophores by the second male succeeded more frequently when the copulatory piece was shorter and the vaginal appendix was longer, and when the difference between the length of the copulatory piece and the vaginal appendix was smaller. Thus, a matching of the corresponding genital parts between the sexes increases the male's reproductive success in sperm competition, but elongation of the copulatory piece cannot be explained simply by the improvement in male reproductive success. We discuss possible factors for the elongation of genital parts in terms of sexual conflict and reproductive interference through interspecific copulation.     

Sex‐biased dispersal,kin selection and the evolution of sexual conflict

There is growing interest in resolving the curious disconnect between the fields of kin selection and sexual selection. Rankin's (2011, J. Evol. Biol. 24 , 71–81) theoretical study of the impact of kin selection on the evolution of sexual conflict in viscous populations has been particularly valuable in stimulating empirical research in this area. An important goal of that study was to understand the impact of sex‐specific rates of dispersal upon the coevolution of male‐harm and female‐resistance behaviours. But the fitness functions derived in Rankin's study do not flow from his model's assumptions and, in particular, are not consistent with sex‐biased dispersal. Here, we develop new fitness functions that do logically flow from the model's assumptions, to determine the impact of sex‐specific patterns of dispersal on the evolution of sexual conflict. Although Rankin's study suggested that increasing male dispersal always promotes the evolution of male harm and that increasing female dispersal always inhibits the evolution of male harm, we find that the opposite can also be true, depending upon parameter values.     

Contrasting global‐scale evolutionary radiations: phylogeny,diversification, and morphological evolution in the major clades of iguanian lizards

Parallel evolutionary radiations in adjacent locations have been documented in many systems, but typically at limited geographical scales. Here, we compare patterns of evolutionary radiation at the global scale in iguanian lizards, the dominant clade of lizards. We generated a new time‐calibrated phylogeny including 153 iguanian species (based on mitochondrial and nuclear data) and obtained data on morphology and microhabitats. We then compared patterns of species diversification, morphological disparity, and ecomorphological relationships in the predominantly Old World and New World clades (Acrodonta and Pleurodonta, respectively), focusing on the early portions of these radiations. Acrodonts show relatively constant rates of species diversification and disparity over time. In contrast, pleurodonts show an early burst of species diversification and less‐than‐expected morphological disparity early in their history, and slowing diversification and increasing disparity more recently. Analyses including all species (with MEDUSA) suggest accelerated diversification rates in certain clades within both Acrodonta and Pleurodonta, which strongly influences present‐day diversity patterns. We also find substantial differences in ecomorphological relationships between these clades. Our results demonstrate that sister clades in different global regions can undergo very different patterns of evolutionary radiation over similar time frames. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ●● , ●●–●●.     

Multilocus phylogeography of the Patagonian lizard complex Liolaemus kriegi (Iguania: Liolaemini)

This study presents a detailed phylogeographical analysis of one of the most conspicuous groups of lizards in northwestern Patagonia, the Liolaemus kriegi complex. This region is geographically very complex as a result of Andean orogeny and subsequent volcanism coupled with a long history of glaciations and climatic changes. For 247 individuals we sequenced one mitochondrial gene (cytochrome b) and for a subset we sequenced another mitochondrial gene [12S ribosomal RNA (12S)] and two nuclear fragments [kinesin family member 24 (KIF24) and BA3 ribosomal RNA (BA3)]. We obtained gene trees and mitochondrial and nuclear haploytpe networks, and estimated genetic distances between the main lineages and basic molecular diversity indices. We also performed spatial analysis of molecular variance (SAMOVA) and Bayesian Skyline Plot (BSP) analyses, and concordant patterns from different lines of evidence permitted delimitation of seven lineages: two described species, Liolaemus buergeri and Liolaemus tregenzai; four candidate species, Liolaemus sp. A, Liolaemus sp. B, Liolaemus sp. C, and Liolaemus sp. D; and one lineage that includes all individuals from the geographical range of Liolaemus ceii and L. kriegi, referred to as L. kriegi + L. ceii. We discuss the evolutionary processes that may contribute to the origin of these lineages and their taxonomic and conservation implications. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113 , 256–269.     

Sex‐specific recombination rates and allele frequencies affect the invasion of sexually antagonistic variation on autosomes

The introduction and persistence of novel, sexually antagonistic alleles can depend upon factors that differ between males and females. Understanding the conditions for invasion in a two‐locus model can elucidate these processes. For instance, selection can act differently upon the sexes, or sex linkage can facilitate the invasion of genetic variation with opposing fitness effects between the sexes. Two factors that deserve further attention are recombination rates and allele frequencies – both of which can vary substantially between the sexes. We find that sex‐specific recombination rates in a two‐locus diploid model can affect the invasion outcome of sexually antagonistic alleles and that the sex‐averaged recombination rate is not necessarily sufficient to predict invasion. We confirm that the range of permissible recombination rates is smaller in the sex benefitting from invasion and larger in the sex harmed by invasion. However, within the invasion space, male recombination rate can be greater than, equal to or less than female recombination rate in order for a male‐benefit, female‐detriment allele to invade (and similarly for a female‐benefit, male‐detriment allele). We further show that a novel, sexually antagonistic allele that is also associated with a lowered recombination rate can invade more easily when present in the double heterozygote genotype. Finally, we find that sexual dimorphism in resident allele frequencies can impact the invasion of new sexually antagonistic alleles at a second locus. Our results suggest that accounting for sex‐specific recombination rates and allele frequencies can determine the difference between invasion and non‐invasion of novel, sexually antagonistic alleles in a two‐locus model.