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Hickman - Geologic and Evolutionary context of Land Snail diversity on Oceanic Islands

Geologic and Evolutionary Context of Land Snail Diversity on Oceanic Islands

Carole S. Hickman

Department of Integrative Biology, University of California, Berkeley, CA 94720-3140

Linear, age progressive chains of basalt islands and seamounts are the geological hallmark of a long history of active intraplate volcanism as the Pacific plate has passed over discrete hotspots. Multibeam sonor seafloor mapping, records of seismic and magmatic activity, subsurface geophysical data, and geochronology reveal a repeated geologic sequence that constrains the evolutionary life of the biota of any one island to less than 5 Ma. The geologic model for origin and evolution of island archipelagos provides a unique opportunity to investigate repeated patterns of infrequent colonization followed by intra-island speciation and evolutionary radiation. The Hawaiian and Society Island archipelagos are the best examples of hotspot chains and are also the most intensively studied, both geologically and biologically. Endemism is a pervasive pattern in land snails. Four entire families (Endodontidae, Partulidae, Amastridae, Achitenellidae) are endemic to Pacific Islands. Subfamilies and genera commonly are endemic to individual archipelagos or single islands, while species typically are confined to single islands. Six additional families (Succineidae, Pupillidae, Diplommatinidae, Helicinidae, Assimineidae, and Helicarionidae) have undergone significant Pacific island radiations. Accurate reconstructions of geologic history and phylogenetic relationships are of equal importance in explaining modern geographic distributions. Hominid-induced extinctions seriously depleted island land snail diversity before most of it could be documented. Unstudied museum collections and a largely undocumented fossil record are key to resolving major gaps in our current understanding.

Next: Holland & Cowie - Up: Special Symposium - Pacific Previous: Hadfield - Progress in
Peter Roopnarine 2005-04-12