Color Polymorphism is a Driver of Diversification in the Lizard Family Lacertidae

Abstract

Color polymorphism – two or more heritable color phenotypes maintained within a single breeding population – is an extreme type of intra-specific 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-standing theoretical expectations that color polymorphism is a driver of diversification.

WITHDRAWN: Mimicry promotes morphological diversification but not speciation in mimetic swallowtail butterflies

“…Sexually dichromatic and monochromatic clades of ray-finned fish on the whole have similar diversification rates, although diversification rates are elevated in the context of either sexual dimorphism or monomorphism at family levels [11]. In birds and lizards, colour polymorphic clades have higher speciation rates compared to monomorphic clades [12,13].…”

Colour polymorphism and conspicuousness do not increase speciation rates in Lacertids

“…We also wish to stress a previously neglected inherent difficulty with the detection of the morphic speciation model through comparative methods in empirical datasets. The diversification analyses used by us or by Brock et al (2021) test for differences in diversification rates associated with the presence of polymorphism. Yet, the morphic species model predict that "polymorphic lineages should be ancestral and monomorphic lineages should be derived" (Corl et al 2010b), as morphic speciation generates monomorphic species from polymorphic species.…”

“…They found that polymorphic populations were often ancestral, and that populations that lost a morph after colonizing a new environment showed reproductive incompatibilities with the ancestral population and rapid phenotypic changes. At macroevolutionnary scale, two studies found that polymorphism increased speciation rates in birds and in lacertid lizards (Hugall and Stuart-Fox 2012; Brock et al 2021). Taken together, these findings support the hypothesis of increased speciation rates in polymorphic species.…”

The Angolan bushveld lizards, genus Heliobolus Fitzinger, 1843 (Squamata: Lacertidae): Integrative taxonomy and the description of two new species

“…It is interesting to note that one of the few consistent physical features differentiating the three Angolan Heliobolus species is their coloration patterns, not only of the adults but also of the juveniles. Although coloration in lacertids has traditionally been disregarded as a good diagnostic character for closely related taxa, especially due to the high prevalence of color polymorphism in the family Lacertidae (see Brock et al 2022) and for the difficulty of objectively differentiating between subtle coloration differences, most recent descriptions of southern African lacertids (all backed by molecular phylogenies) have relied on coloration differences to diagnose the newly described species (Conradie et al 2012;Branch et al 2019b;Childers et al 2021;Parrinha et al 2021). This situation agrees with the results of Brock et al (2022) that color polymorphism can be a driver of speciation.…”

“…Although coloration in lacertids has traditionally been disregarded as a good diagnostic character for closely related taxa, especially due to the high prevalence of color polymorphism in the family Lacertidae (see Brock et al 2022) and for the difficulty of objectively differentiating between subtle coloration differences, most recent descriptions of southern African lacertids (all backed by molecular phylogenies) have relied on coloration differences to diagnose the newly described species (Conradie et al 2012;Branch et al 2019b;Childers et al 2021;Parrinha et al 2021). This situation agrees with the results of Brock et al (2022) that color polymorphism can be a driver of speciation. More interestingly in this case is the fact that we report here for the first time a clear and diagnostic difference in the coloration of the juvenile specimens.…”