Meeting Abstract
Nine anostracan biogeographical regions are defined for North America: Appalachia/Ozark, Southwest Arid, Great Plains, Coastal Plain, Neotropical, California, Cold Deserts, Beringia/Canadian Shield, and Transmontane. These regions are quantitatively defined using species distributions compared through Jaccard’s Coefficient of Community Similarity and substrate geochemical components (%CaSO4*H2O, %CaCO3, salinity, and dominate salt cations), and in relation to climate. Relationships between these parameters and the distributions of all 63 US species were discovered. Similar relationships were found for species assemblages as well. Community assemblages are quantified using Fager’s Index of Recurring Species Groups. The average Fager’s Index for each bioregion, as well as the percentage of taxa co-occurring, generally decreases with the length of geologic time the region has been available for colonisation. The strong Fager’s Index/colonisation time availability relationship suggests that the Monopolization Hypothesis of De Meester et al. may function at larger landscape scales. Furthermore, two widespread species were found to occur in very different habitat types in different biogeographical regions. Upon closer examination, these two taxa were each found to be comprised of more than one species.
