A new paper from the American Journal of Botany explores how Red Mangroves reestablished their populations in the Caribbean after the last glacial maximum (~19,000 years ago). The authors determined that there are actually 3 distinct genetic clusters of Red Mangrove:  Caribbean Mainland (Belize and Panama, Caribbean Islands (The Bahamas, St. Kitts, Puerto Rico) and Florida. Interestingly, they found that the Caribbean Island cluster was also genetically similar to Northwest Africa. This finding demonstrates that long distance dispersal of mangrove propagules occurred from Northwest Africa to some Caribbean Islands (mainly St. Kitts and Puerto Rico).

They also found that regional ocean currents were important in dispersing propagules, and therefore genetic material, throughout the Caribbean Islands and Florida, especially from the Caribbean Mainland (Belize and Panama). Specifically, they found that Florida was recolonized via the mainland pathway (see figure) and that The Bahamas may have been colonized via the Antilles Island pathway (see figure). However, they found that The Bahamas are quite different genetically from the Islands they were clustered with. This suggests that genetic differentiation occurred fairly rapidly after colonization likely as a result of geographic isolation that Island chains typically experience.

Reference:

Kennedy, J. P., M. W. Pil, C. E. Proffitt, W. A. Boeger, A. M. Stanford, and D. J. Devlin. 2016. Postglacial expansion pathways of red mangrove, Rhizophora mangle, in the Caribbean Basin and Florida. Am J Bot 103:260-276.