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.