The presence of a cryptic barrier in the West Pacific Ocean suggests the effect of glacial climate changes on a widespread sea-dispersed plant, Vigna marina (Fabaceae)

Ocean currents are an important driver of evolution for sea-dispersed plants, enabling them to maintain reciprocal gene flow via sea-dispersed diaspores and obtain wide distribution ranges. Although geographic barriers are known to be the primary factors shaping present genetic structure of sea-dispersed plants, cryptic barriers which form clear genetic structure within oceanic regions are poorly understood. To test the presence of a cryptic barrier, we conducted a phylogeographic study together with past demographic inference for a widespread sea-dispersed plant, Vigna marina, using 308 individuals collected from the entire Indo-West Pacific (IWP) region. Chloroplast DNA variation showed strong genetic structure that separated populations into three groups: North Pacific (NP), South Pacific (SP) and Indian Ocean (IN) (F’CT among groups = 0.954 – 1.000). According to the Approximate Bayesian computation inference, splitting time between NP and SP was approximately 20,200 years (95%HPD, ...