Biogeography of spiders (Araneae: Arachnida) on the islands of the Southern Ocean

The araneofauna of the extreme Southern Hemisphere is highly impoverished and disharmonic. Four dead anthropogenic immigrant spiders have been collected from Antarctica while only 115 verified species from 26 families are reported on the islands of the Southern Ocean. Cluster analysis of the verified Southern Ocean species distribution data identifies a weak, but distinct, Neotropical/South Atlantic association together with robust South Indian and South Pacific biogeographic clusters. These groupings, largely attributed to vicariance and/or endemism, contain little evidence of post-Pleistocene dispersal. Indeed the 14 records of anthropogenic origin suggest that the pace of recent human-mediated introduction has been at least 30 times more rapid than that of Holocene natural dispersal.