Color polymorphism is a driver of diversification

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, we estimate an ancient origin of color polymorphism (111 MYA) 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.颜色多态性（Color polymorphism）——指在单个繁殖种群中维持两种及以上可遗传颜色表型的现象——是一类极端的种内多样性形式，广泛分布于整个生命之树中。颜色多态性被假说为物种形成的核心驱动力：当某一物种内不同颜色形态发生丢失或分化时，会催生新支系的快速演化，因此颜色多态支系预计会表现出更高的多样化速率。蜥蜴科（Lacertidae）中有多个物种存在颜色多态性，使其成为研究该性状演化历史及其对宏观演化影响的理想类群。本研究构建了蜥蜴科（Lacertidae）全面的物种水平系统发育树，以重建颜色多态性的演化历史，并验证颜色多态性是否为物种多样化的驱动因素。考虑到系统发育不确定性，本研究估算出颜色多态性在蜥蜴亚科（Lacertinae）的Lacertini族内具有古老的起源，时间可追溯至1.11亿年前（111 MYA）。颜色多态性在蜥蜴科中大概率仅演化出现过数次，且其丢失速率远高于获得速率。向颜色多态性的演化转变，与该蜥蜴科类群净多样化速率的提升显著相关。综上，本研究的实证结果验证了长期以来的理论预期：颜色多态性是物种多样化的驱动因素。