“Sex” is often used to describe a suite of phenotypic and genotypic traits of an organism related to reproduction. However, these traits—gamete type, chromosomal inheritance, physiology, morphology, behavior, etc.—are not necessarily coupled, and the rhetorical collapse of variation into a single term elides much of the complexity inherent in sexual phenotypes. We argue that consideration of “sex” as a constructed category operating at multiple biological levels opens up new avenues for inquiry in our study of biological variation. We apply this framework to three case studies that illustrate the diversity of sex variation, from decoupling sexual phenotypes to the evolutionary and ecological consequences of intrasexual polymorphisms. We argue that instead of assuming binary sex in these systems, some may be better categorized as multivariate and nonbinary. Finally, we conduct a meta-analysis of terms used to describe diversity in sexual phenotypes in the scientific literature to highlight how a multivariate model of sex can clarify, rather than cloud, studies of sexual diversity within and across species. We argue that such an expanded framework of “sex” better equips us to understand evolutionary processes, and that as biologists, it is incumbent upon us to push back against misunderstandings of the biology ofmore »
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Multivariate Models of Animal Sex: Breaking Binaries Leads to a Better Understanding of Ecology and Evolution
Variation in color morph behavior is an important factor in the maintenance of color polymorphism. Alternative anti-predator behaviors are often associated with morphological traits such as coloration, possibly because predator-mediated viability selection favors certain combinations of anti-predator behavior and color. The Aegean wall lizard,
Podarcis erhardii, is color polymorphic and populations can have up to three monochromatic morphs: orange, yellow, and white. We investigated whether escape behaviors differ among coexisting color morphs, and if morph behaviors are repeatable across different populations with the same predator species. Specifically, we assessed color morph flight initiation distance (FID), distance to the nearest refuge (DNR), and distance to chosen refuge (DR) in two populations of Aegean wall lizards from Naxos island. We also analyzed the type of refugia color morphs selected and their re-emergence behavior following a standardized approach. We found that orange morphs have different escape behaviors from white and yellow morphs, and these differences are consistent in both populations we sampled. Orange morphs have shorter FIDs, DNRs, and DRs; select different refuge types; and re-emerge less often after being approached compared to white and yellow morphs. Observed differences in color morph escape behaviors support the idea that morphs have evolved alternative behavioral strategiesmore » Significance statement
Color polymorphic species often differ in behaviors related to reproduction, but differences in other behaviors are relatively underexplored. In this study, we use an experimental approach in two natural populations of color populations of color polymorphic lizards to determine that color morphs have diverged in their escape behaviors. By conducting our experiments in two different populations with similar predator regimes, we show for the first time that behavioral differences among intra-specific color morphs are repeatable across populations, suggesting that alternative behavioral strategies have evolved in this species. Using this experimental approach, we demonstrate that the brightest orange morph stays closer to refuge than other morphs, uses a different refuge type (vegetation) more often than other morphs (wall crevices), and take much longer to emerge from refuge after a simulated predation event than other morphs. Thus, selective pressures from visual predators may differ between morphs and play a role in the evolution and maintenance of color polymorphisms in these types of systems. Our study species,
Podarcis erhardii, belongs to a highly color polymorphic genus (19/23 spp. are color polymorphic) that contains the same three color morphs, thus we believe our results may be relevant to more than just P. erhardii.
Eaton, Deren (Ed.)Abstract Color polymorphism—two or more heritable color phenotypes maintained within a single breeding population—is an extreme type of intraspecific diversity widespread across the tree of life. Color polymorphism is hypothesized to be an engine for speciation, where morph loss or divergence between distinct color morphs within a species results in the rapid evolution of new lineages, and thus, color polymorphic lineages are expected to display elevated diversification rates. Multiple species in the lizard family Lacertidae are color polymorphic, making them an ideal group to investigate the evolutionary history of this trait and its influence on macroevolution. Here, we produce a comprehensive species-level phylogeny of the lizard family Lacertidae to reconstruct the evolutionary history of color polymorphism and test if color polymorphism has been a driver of diversification. Accounting for phylogenetic uncertainty with multiple phylogenies and simulation studies, we estimate an ancient origin of color polymorphism (111 Ma) within the Lacertini tribe (subfamily Lacertinae). Color polymorphism most likely evolved few times in the Lacertidae and has been lost at a much faster rate than gained. Evolutionary transitions to color polymorphism are associated with shifts in increased net diversification rate in this family of lizards. Taken together, our empirical results support long-standingmore »