chapter  17
Historical Biogeography of Pacifastacus Crayfi shes and their Branchiobdellidan and Entocytherid Ectosymbionts in Western
ByNorth America
Pages 44

Western North America is not rich in crayfi sh species relative to high diversity regions like the southeastern United States or eastern Australia. Only fi ve species, three subspecies, and a fossil record of the crayfi sh genus Pacifastacus are endemic to this region. Yet western North America is a representative microcosm of many challenges in contemporary crayfi sh conservation and management. One Pacifastacus species has gone extinct since European colonization of the west, whereas a second is listed under the United States (US) Endangered Species Act (ESA). Declines of both of these endemic crayfi sh have been attributed in part to human introductions of an additional Pacifastacus species, which is also a globally successful invader in Asia and Europe —as well as a species of high economic and recreational value. For these reasons, western North America may be of broad interest to crayfi sh researchers concerned with the patterns and processes of range expansion (invasion) and extinction in crayfi shes.