Historical Biogeography of Caribbean Plants Revises Regional Paleogeography

Abstract

The Caribbean archipelago is the largest and most species rich insular system in the Neotropics, yet the origins of this biodiversity hotspot are poorly understood. Four main hypotheses have been proposed to explain Caribbean diversity: vicariance, GAARlandia landspan, long-distance dispersal, and in situ speciation. Here, we use phylogenetic data and historical biogeographical inferences of Caribbean endemic plants to test amongst these four hypotheses. Together with a revision of Caribbean paleogeography, we compile the colonization times, in situ speciation, and ancestral areas of Caribbean endemic lineages. We model species richness differences among endemic lineages as a function of their colonization time in the Caribbean, resulting in an estimation of the time-for-speciation effect. Our results show that plants repeatedly colonized the West Indies over the last 60 million years from continental America, especially from central and south America. Plant colonization times do not cluster during the GAARlandia timeframe and most colonization events occurred after its putative subsidence. We did not find a relationship between the number of species in each endemic clade and the estimated time when each colonized the Caribbean (no time-for-speciation effect). Published geological constraints from the Lesser Antilles and Aves Ridge fail to support the emergent land between the Antilles and south America.