Sea level, topography and island diversity: phylogeography of the P uerto R ican Red‐eyed C oquí, E leutherodactylus antillensis

Abstract

Quaternary climatic oscillations caused changes in sea level that altered the size, number and degree of isolation of islands, particularly in land‐bridge archipelagoes. Elucidating the demographic effects of these oscillations increases our understanding of the role of climate change in shaping evolutionary processes in archipelagoes. The P uerto R ican B ank ( PRB ) ( P uerto R ico and the E astern I slands, which comprise V ieques, C ulebra, the V irgin I slands and associated islets) in the eastern C aribbean S ea periodically coalesced during glaciations and fragmented during interglacial periods of the quaternary. To explore population‐level consequences of sea level changes, we studied the phylogeography of the frog E leutherodactylus antillensis across the archipelago. We tested hypotheses encompassing vicariance and dispersal narratives by sequencing mt DNA ( c . 552 bp) of 285 individuals from 58 localities, and four nu DNA introns (totalling c . 1633 bp) from 173 of these individuals. We found low support for a hypothesis of divergence of the E astern I slands populations prior to the start of the penultimate interglacial c . 250 kya, and higher support for a hypothesis of colonization of the E astern I slands from sources in eastern P uerto R ico during the penultimate and last glacial period, when a land bridge united the PRB . The R ío G rande de L oíza B asin in eastern P uerto R ico delineates a phylogeographic break. Haplotypes shared between the PRB and S t. C roix (an island c . 105 km south‐east of this archipelago) likely represent human‐mediated introductions. Our findings illustrate how varying degrees of connectivity and isolation influence the evolution of tropical island organisms.

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