THE BIOGEOGRAPHIC SIGNIFICANCE OF ANTARCTIC NEOGENE INSECTS

Fossils from the Neogene Meyer Desert Formation (Sirius Group), exposed on the Beardmore Glacier, 500 km from the South Pole, are the basis for reassessing the role of Antarctica in insect evolution. The fossils of broad-nosed weevils in the subtribe Listroderina and a fly in the subfamily Cyclorrhapha are of more highly evolved insects than those described from Jurassic deposits. The weevils, with living relatives in South America, indicate that considerable divergence must have occurred in the Curculionidae after the family first appeared in the Cretaceous and before the isolation of Antarctica, between 34-22 Ma, prevented genetic exchange. The most plausible interpretation for the insects, which together with plants and freshwater mollusks represent a tundra assemblage, is that they are the descendants of an Antarctic biota that continued to exist on the continent for millions of years after the final break-up of Gondwana. Ultimately, most species in the tundra biota became extinct with the change to the ultracold and ultraxeric climate that today supports polar deserts. The occurrence of fossils of ‘modern insects’ in Antarctica during the Neogene supports Brundin’s interpretation that Antarctica, as part of Gondwana, could have been an important center for insect evolution and radiation. Research supported by NSF OPP 0230696.