Ancient globetrotters—connectivity and putative native ranges of two cosmopolitan biofouling amphipods

The geographic distributions of some coastal marine species have appeared as
cosmopolitan ever since they were first scientifically documented. In particular, for many benthic species that are associated with anthropogenic substrata, there is much mechanisms of dispersal. Here, we focused on two congeneric coastal crustaceans nearly all kinds of artificial hard substrata in temperate to warm seas. We hypothesized that shipping activities that started centuries ago. Mitochondrial DNA sequences of the CO1 fragment of specimens from distinct marine regions around the world were on putative native ranges of the two Jassa species. Populations of both species exhibited considerable genetic diversity with differing levels of geographic structure. For both species, at least two dominant haplotypes were shared among several geographic populations. Rapid demographic expansion and high migration rates between geographically distant regions support a scenario of ongoing dispersal all J. marmorata is the Northwest Atlantic, whereas the likely former native range of J. slatteryi is the Northern Pacific region. As corroborated by the genetic connectivity between populations, shipping still appears to be the more successful vector of the two species’ dispersal when compared to natural mechanisms. Historical invasion events that likely started centuries ago, along with current ongoing dispersal, confirm
these species’ identities as true “neocosmopolitans”.