evolution of large body size

Investigating the genetic component of large body size evolution in the Anolis sagrei clade

Anolis sagrei. Photo from wikipedia.

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.

Anolis sagrei from Conception Bank. Photo by Anthony Geneva.

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).

A male and female Anolis luteosignifer mating on Cayman Brac. Note how much larger the male is compared to the female. Photo by Anthony Geneva.
Figure 1. PCA based on morphological data from 5 A. sagrei populations.

References

  1. Losos JB. 2009. Lizards in an Evolutionary Tree: Ecology and Adaptive Radiation of Anoles. Berkeley and Los Angeles (CA): Univeristy of California Press. 507p.