RICK FORESTER AND NORTH AMERICAN AQUIFER OSTRACODE BIOGEOGRAPHY

The groundwater fauna of oxygenated aquifer systems in North America are not well known, although much has been done in studying particular systems (e.g., the Edwards Aquifer, Texas). The limited nature of these studies is in high contrast to the extensive studies of aquifer biology and ecology completed in Europe and Australia, where the knowledge of these fauna is valuable in a range of environmental and hydrogeologic analyses. In fact, North America has several deep, oxygenated carbonate aquifers with fracture flow, and are likely habitats of endemic ostracode fauna. Rick Forester demonstrated the value of these fauna in paleohydrologic studies of Nevada and California using fossil hypogean ostracodes to mark past aquifer recharge and discharge, and formed hypotheses to be tested in a wider context of aquifer biogeography. His application of island biogeography theory to aquifer species dispersal and diversity opens new ways of examining these fauna in the context of evolutionary ecology and paleohydrology.

In the light of his work in the western U.S., we present here results of a study of aquifer and groundwater discharge species distributions from springs in the glaciated and unglaciated forested regions of the Appalachians. Species richness is higher in the unglaciated regions, where more endemics occur, and flow rate in aquifer discharge plays a significant role in number of species recovered, as does the nature of the ground water-surface water ecotone. To date there is no agreement on the age of the arrival of these ostracode species to North American aquifers, beyond the studies by Forester indicating species were present in Plio-Pleistocene time. External similarities in shell morphology of some aquifer taxa from western and eastern North America suggest a phylogenetic study would be valuable in shedding light on the origins and dispersal mechanisms of hypogean fauna. It may be that the host environment drives convergent evolutionary features in separate lineages.