BIOGEOGRAPHICAL ORIGIN OF CARIBBEAN PALMS: Did palms colonize the Caribbean through GAARlandia?

Abstract

The biogeography of the Caribbean islands is an ongoing mystery, with many possible explanations to how biota colonized the region. One hypothesis is the Greater Antilles and Aves Ridge (GAARlandia), which acted as a landbridge and connected the Caribbean and South America 35-32 million years ago. The palm family is an excellent taxonomic group to examine this and other hypotheses since palms are well established in the region and have a rich evolutionary history. A dated phylogenetic tree of all palms with distribution records for all species mapped on the tree was used to explore the hypotheses. Ancestral state reconstruction was performed for the phylogeny under different models. The statistically best fitting model was selected by comparing the AIC values for the models. Colonization by most Caribbean palms occurred either in a different time period from when GAARlandia existed or originated from regions that are not indicative of GAARlandia. However, one genus of Caribbean palms, Acrocomia, supports the existence of GAARlandia. The existence of GAARlandia can not be proven by Acrocomia alone. More biota in the Caribbean need to be analyzed in order to determine the existence of GAARlandia. Our mixed findings can at least provide a clue to the complex biogeographical history of the Caribbean and reflect the importance of conservation in the Caribbean Biodiversity Hotspot.