boa convergence

It’s not anoles but at least it’s about convergent evolution!

A recent study by Damien Esquerre and Scott Keogh published in Ecology Letters found that pythons and boas, the two famous constrictor snake families, have evolved convergent head shapes. The study was based on over 1,000 specimens and including most of the species. Pythons and boas that occupy the same micro-habitat or ecology (i.e. arboreal, terrestrial, semi-aquatic, semi-fossorial) look more like each other than to other snakes in their own family. This is exciting because it highlights how important ecology and adaptation is in shaping biological diversity.

Abstract:

Pythons and boas are globally distributed and distantly related radiations with remarkable phenotypic and ecological diversity. We tested whether pythons, boas and their relatives have evolved convergent phenotypes when they display similar ecology. We collected geometric morphometric data on head shape for 1073 specimens representing over 80% of species. We show that these two groups display strong and widespread convergence when they occupy equivalent ecological niches and that the history of phenotypic evolution strongly matches the history of ecological diversification, suggesting that both processes are strongly coupled. These results are consistent with replicated adaptive radiation in both groups. We argue that strong selective pressures related to habitat-use have driven this convergence. Pythons and boas provide a new model system for the study of macro-evolutionary patterns of morphological and ecological evolution and they do so at a deeper level of divergence and global scale than any well-established adaptive radiation model systems.

Reference:

Esquerré, D & J S Keogh. 2016. Parallel selective pressures drive convergent diversification of phenotypes in pythons and boas. Ecology Letters, 19(7): 800-809.

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