Abstract
Dispersal is a crucial mechanism to living beings, allowing them to
reach new resources such that populations and species can explore new
environments. However, directly observing the dispersal mechanisms of
widespread species can be costly or even impracticable, which is the
case for mangrove trees. The influence of ocean currents on the
mangroves’ propagules’ movement has been increasingly evident; however,
few studies mechanistically relate the patterns of population
distribution with the dispersal by oceanic currents under an integrated
framework. Here, we evaluate the role of oceanic currents on dispersal
and connectivity of Rhizophora mangle along the Southwest
Atlantic. We inferred population genetic structure and migration rates
based on single nucleotide polymorphisms, simulated the displacement of
propagules along the region and tested our hypotheses with Mantel tests
and redundancy analysis. We observed a two populations structure, north
and south, which is corroborated by other studies with Rhizophora
and other coastal plants. The inferred recent migration rates do not
indicate gene flow between the sampled sites. Conversely, long-term
migration rates were low across groups and contrasting dispersal
patterns within each one, which is consistent with long-distance
dispersal events. Our hypothesis tests suggests that both isolation by
distance and isolation by oceanography (derived from the oceanic
currents) can explain the neutral genetic variation of R. mangle
in the region. Our findings expand current knowledge of mangrove
connectivity and highlight how the association of molecular methods with
oceanographic simulations improve the interpretation power of the
dispersal process, which has ecological and evolutionary implications.