Abstract of Dunham, A. E., G. R. Smith, and J.N. Taylor. 1979. Evidence for ecological character displacement in western American catostomid fishes. Evolution 33:877-896.

Sympatric sucker species are divergent from each other in gill raker size and numbers; allopatric forms have intermediate (more generalized) numbers, hypothesized to to be caused by absence of competition. Ecological character displacement is demonstrated by multiple linear regression of the gill raker characters along with an index of sympatry and other possible variables that could cause heritable or ecophenotypic shifts in meristic numbers.