149 



Fig.96: Composite distribution for the ranges of species of Phoxinus in Eurasia (data summarized 

 from Berg 1949, Banarescu 1964, Yang & Huang 1964). 



curs in the northern portion of North America. Some isolated populations are present in 

 central Wisconsin (Green 1935), South Dakota (Evermann & Cox 1896a, Churchill & 

 Over 1938), Nebraska, Colorado, and Wyoming (Bailey & Allum 1962). (See the species 

 account of P. neogaeus below.) The isolated populations indicate P. neogaeus used to have 

 a much broader geographic range. These isolated populations might be the descend from 

 glacial populations that failed to expand following the deglaciation (Underhill 1957), or 

 due to the similar causes for the isolated populations of P. erythrogaster discussed by 

 Cross (1970) (see below). Mahy (1975c) interpreted the present distribution of P. neogae- 

 us as northern dispersal of the species from its refuge. 



The Pleistocene glaciation in North America during which ice covered the area to 40° (N. 

 lat.) played an important role in the current geographical distribution of the North Ame- 

 rican freshwater fishes (Underhill 1957, McPhail 1963, Cross 1970). During the glacial 

 advances, the range of fishes in the area covered by the ice were forced to southward, ex- 

 cept some may have persisted in refuge that remained ice-free. The current geographical 



