Meeting Abstract
Explanations of the origins of disjunct populations in dispersing species include 1) hidden population connectivity, 2) contraction of relict distributions and 3) recent long-distance expansion. The onuphid polychaete Diopatra biscayensis has its northern contiguous population limit at la Trinité-sur-Mer in the Bay of Biscay, and separated by ~500 coastal km is a disjunct population in the English Channel near Mont-Saint-Michel. We tested the following hypotheses. H1a: the population is actually connected by an unexplored population. This is false because subtidal and intertidal populations share the same geographic range limit in the Bay of Biscay, thus there are unlikely to be hidden populations that provide connectivity. H1b: the disjunct population is within the dispersal range of larvae. This is false because ocean transport modeling indicates that the maximum dispersal distance is less than 50km. H2: the disjunct population is a relict of more permissive times. This is false because hindcasts of geographic distributions of metapopulations indicate that the English Channel population could not have persisted during the shifting climate of the past 1200 years. H3: this disjunct population is relatively new and is associated with long-distance human-assisted transport. This is supported by genetic analysis using a SNP-based RAD tag approach to look at connectivity among populations over the geographic range of the species.
