The Evolution of Female Pattern Polymorphism

In many species of anoles, females vary in their back patterning, some gaudily adorned with saddles, diamonds, or crosses, others sporting simple lines and speckles, some sad lasses with no markings at all. Although such female pattern polymorphism has long been noted and its adaptive significance studied (for example, here), no one has compiled a list of which species exhibit it and which don’t, much less examined patterns of FPP evolution.

Until now. In a very nice paper, Paemelaere et al. have surveyed the literature and recorded the presence or absence of of FPP in 179 anole species. They find a wide variety of interesting findings. First, there is phylogenetic signal: closely-related species tend to be similar in the presence or absence of FPP. Nonetheless, second, FPP has evolved and been lost many times—overall, at least 28 evolutionary transitions, with more gains than losses. The ancestral condition, incidentally, appears to be an absence of FPP. Third, there is great biogeographical heterogeneity (see figure above). FPP is far-and-away most common among mainland anoles, and is also reasonably common in the Lesser Antilles, but much less common in the Greater Antilles. Within the mainland anoles, it is particularly members of the Norops club that have FPP; much less among dactyloids. However, Norops also occurs on Cuba and Jamaica, and there they don’t exhibit much FPP.

One additional interesting pattern not remarked upon by Paemelaere is that among Greater Antillean species, FPP occurs primarily in trunk-ground anoles, having evolved at least three times independently on different islands (in three members of the sagrei clade on Cuba; A. cristatellus on Puerto Rico; and three members of the cybotes clade on Hispaniola). In addition, it occurs in A. acutus on St. Croix and A. conspersus on Grand Cayman, both species which occur with no congeners. Combined with its prevalence in the Lesser Antilles, which never have more than two anole species, one might wonder whether occurrence in depauperate anole communities somehow promotes the evolution of FPP, at least in island settings.

The bigger question, of course, concerns the adaptive significance of FPP. Why does it evolve, and why in some species and places and not others? This, however, is a topic for future research, and the Paemelaere et al. paper nicely lays the groundwork.

About Jonathan Losos

Author and Professor at Harvard University
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1 Response to The Evolution of Female Pattern Polymorphism

  1. Pingback: Variation in Habitat Use by Females with Different Back Patterns |

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