Partitioning diversity across geographic scales in artesian springs of the Bonneville Basin, USA: Patterns and processes

An important goal of ecology is to understand the factors that determine the spatial distribution of diversity ranging from local sites (α diversity) to the regional species pool (γ diversity).  We partitioned the β-diversity of invertebrates in artesian springs into contributions by different sites nested within habitats (springs, channels, and marshes), habitat types within spring wetlands, wetlands within valleys, and valleys nested within the Bonneville Basin of Utah.  We identified 288 taxa from 280 sites.  Fifty percent of the taxa were collected from six or fewer sites, whereas 20% were collected from a single site.  Factors operating at large scales had the greatest effect on the regional distribution of diversity.  Fifty percent of the regional diversity was attributed to differences between valleys, 20% to differences between wetlands within valleys and the remainder to differences between habitats within wetlands (10%), locations within habitats (10%) and alpha richness within locations (10%).  Springs in different valleys contained a different complement of species many of which are unique to individual springs. Historical biogeography associated with the drying of ancient Lake Bonneville, habitat heterogeneity, stochastic historical events, and dispersal limitations between valleys were the most important processes determining patterns of β-diversity.