BOYER, S. L.*; GIRIBET, G.; Harvard University; Harvard University: Vicariance in the harvestman family Pettalidae (Arachnida, Opiliones, Cyphophthalmi) during the breakup of Gondwana

The theory of plate tectonics has generated many hypotheses concerning the historical causes of global distributions of organisms. The former supercontinent Gondwana has become the textbook system for historical biogeography, and the role of vicariance vs. dispersal across Gondwanan fragments has been studied in such groups as Nothofagus, chironomid midges, and Araucaria beetle herbivores. An ideal candidate for a study of vicariance across Gondwana is found in the family Pettalidae (Arachnida, Opiliones, Cyphophthalmi), a group of tiny, leaf-litter dwelling harvestmen. These cryptic arachnids are found in Chile, South Africa, Madagascar, Sri Lanka, Australia, and New Zealand. The small species ranges within this group, and the absence of these animals on any islands formed de novo by volcanoes, suggest that these organisms have very limited dispersal ability. Therefore, their Gondwanan distribution may be due solely to vicariance. We present a phylogenetic study of this family and interpret it in light of the geological history of the breakup of Gondwana.