Importance of long distance dispersal in colonization processes of sub-Antarctic islands

BORN C.* ; MC GEOCH M.A. ; SHAW J. ; BERGSTROM D. ; LEBOUVIER M. ; CHOWN S.L. PEAT H. ; CONVEY P. ; UPSON R. PADIN A. ; GROSFELD J. AND JANSEN VAN VUUREN B.

Bariloche

Congreso; VI Southern Connection Congress; 2010

Southern Connection

Vicariance and long-distance dispersal (LDD) are commonly invoked to explain the disjunct distribution of related taxa among Gondwanian landmasses. The relative importance of each process remains problematic to disentangle, mostly because LDD remains challenging to quantify. In this study, we focus on the sub-Antarctic region, including magellanic South America, Malvinas/Falkland Islands and islands for which historical biogeography strictly relies on LDD. Our aim is to evaluate the importance of dispersal throughout the Southern Ocean. Both chloroplast and nuclear genetic markers were sequenced to compare phylogeographic patterns of two perennial plant species, Acaena magellanica and Azorella selago. For both species phylogeographic patterns are very similar notwithstanding different modes of dispersal. Phylogeographic patterns also reveal a strong relatedness between Tierra del Fuego and most sub-Antarctic islands lineages, with only little divergence among islands. In contrast, our results show that Malvinas/Falkland Islands and Macquarie Island are very divergent from other lineages. These results show that the presence of both species on Malvinas/ Falkland Islands may predate the Gondwana breakup. The propagules responsible for the early colonization of sub-Antarctic islands may originate from Tierra del Fuego. Finally, the absence of divergence among islands shows the importance of gene flow between most sub-Antarctic islands, with the exception of Macquarie Island.