evolution of large body size

Anoles are well-known for their ability to convergently evolve to similar environments, e.g. anoles in the Greater Antilles have adapted to similar micro-habitats and have been placed into “ecomorph” classes discribing their behavior, habitat use, and morphology. Anolis sagrei is a trunk-ground anole, which means it is a medium-sized stocky species with long hindlimbs and poorly-developed toepads. They are usually found around 1-1.5 meters above the ground on the tree trunk¹. Although on some islands, anoles in the A. sagrei clade don’t occupy this niche space and have evolved a different phenotype. Anolis nelsoni from the Swan islands and Anolis luteosignifer from Cayman Brac are both within the A. sagrei clade, occur on islands without competitors, and have evolved significant differences in morphology.

Both of these species arrived to their respective islands from Cuba, and have independently evolved a significantly larger body size than other A. sagrei species. There is also more differentiation between the sexes on these islands (see photo below). Anthony Geneva used morphological data from A. luteosignifer, A. nelsoni, A. s. mayensis, A. s. ordinatus, and A. s. sagrei to make a principle component analysis (Figure 1).

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