Data from: Terrestrial species adapted to sea dispersal: differences in propagule dispersal of two Caribbean mangroves

A central goal of comparative phylogeography is to understand how
species-specific traits interact with geomorphological history to govern
the geographic distribution of genetic variation within species. One key
biotic trait with an immense impact on the spatial patterns of
intraspecific genetic differentiation is dispersal. Here we quantify how
species-specific traits directly related to dispersal affect genetic
variation in terrestrial organisms with adaptations for dispersal by sea,
not land—the mangroves of the Caribbean. We investigate the phylogeography
of white mangroves (Laguncularia racemosa, Combretaceae) and red mangroves
(Rhizophora mangle, Rhizophoraceae) using chloroplast genomes and nuclear
markers (thousands of RAD-Seq loci) from individuals throughout the
Caribbean. Both coastal tree species have viviparous propagules that can
float in salt water for months, meaning they are capable of dispersing
long distances. Spatially explicit tests of the role of ocean currents on
patterning genetic diversity revealed that ocean currents act as a
mechanism for facilitating dispersal, but other means of moving genetic
material are also important. We measured pollen- versus propagule-mediated
gene flow and discovered that in white mangroves, seeds were more
important for promoting genetic connectivity between populations, but in
red mangroves, the opposite was true: pollen contributed more. This result
challenges our concept of the importance of both proximity to ocean
currents for moving mangrove seeds and the extent of long-distance pollen
dispersal. This study also highlights the importance of spatially explicit
quantification of both abiotic (ocean currents) and biotic (dispersal)
factors contributing to gene flow to understand fully the phylogeographic
histories of species.