How Geography Influences Animal Evolution: The Story of a Caribbean Lizard

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Why are some animal bigger than other? Is evolution only influenced by genes? Does colder and hotter environment have an impact on animal differences? These are some of the common questions that have been bogging the mind of great scientists for the past 150 years. Bergmann’s rule — the tendency for warm-blooded animal body size to increase in colder environments — has long been controversial with debate around whether it applies to cold-blooded animals and how the rule applies within or among species.

However, a new research, collaboration between Nottingham and Harvard Universities’ seeking to determine if it is inter-specific (external factors) or intra-specific (internal species factors) that cause the differences observed in animal sizes. Their study was centered on the Anolis lizard living on the Cuba and Hispaniola islands. These are high altitude islands with climatically different factors.


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In their statement after the research they stated that “Our results suggest that restricted analyses to either the intra-specific or inter-specific levels can miss important patterns.” Stating further “We found that the similar body size gradients in the lizards on both islands are constructed in very different ways. Even though lizards are smaller at high elevations on both islands, these body size patterns are underlain by very different processes. On Hispaniola, inter-specific processes dominate, while on Cuba, intra-specific processes drive the pattern.”

So does geography influence differing animal sizes even within the same species? The researchers believe this new research is leading the way in understanding how far it does.

Read: Untangling intra- and interspecific effects on body size clines reveals divergent processes structuring convergent patterns in Anolis lizards

Those wishing to explore the data can download it from Dryad.  The text file contains measurements of body size, locality, and elevation data for all individual lizards used in this study.

A pallid stout anole (Anolis whitemani), a low to mid-elevation species from Hispaniola. (Photo by Miguel A. Landestoy)
A pallid stout anole (Anolis whitemani), a low to mid-elevation species from Hispaniola.
(Photo by Miguel A. Landestoy)

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