Ice Age effects on genetic divergence of the American crocodile (Crocodylus acutus) in Panama: reconstructing limits of gene flow and environmental ranges: a reply to O'Dea et al.

This article focuses on the genetic divergence and gene flow of the American crocodile (Crocodylus acutus) populations across the Central American Isthmus in Panama, examining the influence of Pleistocene sea-level changes. The authors clarify that while an error was made in reconstructing sea levels during the last interglacial period (LIG, 118–130 thousand years ago), their primary hypothesis concerns restricted gene flow during periods of low sea levels, particularly the last glacial maximum (LGM, 19–26.5 ka) and the preceding 50,000 years when sea levels were significantly lower. They argue that the broad environmental tolerance of C. acutus makes paleoclimate changes less likely to explain genetic divergence, whereas sea-level drops likely transformed the Isthmus from a semi-permeable to an impermeable barrier to gene flow. The study emphasizes the importance of incorporating Ice Age sea-level dynamics into evolutionary research of Neotropical species and suggests that further sampling is needed to confirm these conclusions.