Great Basin Naturalist


Evidence from the morphology, genetics, and biogeography of a rare endemic from western Nevada, Erigonum robustum, is presented to determine the most accurate taxonomic classification. Previous authors have classified E. robustrum Greene both as a species and as a variety E. lobbii Torrey & Gray. However, results of a morphometric comparison for 9 characters establish that significant morphological differentiation exists between E. robustum and E. lobbii. In addition, results of a genetic study using protein electrophoresis indicated that genetic differentiation may exist between these 2 taxa. Furthermore, the 2 taxa are geographically, ecologically, and reproductively isolated. Finally, the selective pressures that act on E. robustum in a narrowly restricted cold-desert environment are different from those that act on E. lobbii in subalpine environment. Thus, all available data support a species-level taxonomic classification for E. robustum.