Systematics of the Subterranean Amphipod Genus Stygobromus (Crangonyctidae), Part II: Species of the Eastern United States. Smithsonian Contributions to Zoology, Number 266

摘要

The amphipod genus Stygobromus is widespread in the subterranean waters of the United States and is recorded from a variety of groundwater habitats. A revised diagnosis of the genus is given and a tentative division into three subgeneric groups is proposed. The recently proposed synonymy of Stygonectes and Apocrangonyx with Stygobromus is reaffirmed. Forty-eight described species are herein recognized from the Appalachian and Coastal Plain regions of the eastern United States, of which 30 are newly described, three are completely redescribed, and new systematic data are given for the remainder. In addition, six populations are provisionally recognized as distinct species but are not described because of lack of adequate material. On the basis of morphology and geographic distribution, 12 species groups are recognized in the eastern United States, eight of these being newly established herein. Ancestral stygobromids are now believed to have occurred earlier in the freshwater environment than originally suggested. Species of Stygobromus occupy a diversity of groundwater and groundwater-related habitats in the eastern United States, including primarily cave pools and streams, phreatic reservoirs and the hypotelminorheic media of seeps and small springs.