Distribution & Karyotype Variation in the Southern Pocket Gopher
(Thomomys umbrinus) (Geomyidae: Rodentia: Mammalia)

    Pocket Gophers are fossorial (tunnel-dwelling) rodents that create and inhabit extensive underground burrow systems, from which they emerge only rarely. Only certain types of soil are suitable for burrows, in consequence the ranges are highly disjunct. More than 200 subspecies of T. umbrinus have been recognized in the southwestern United States and northern Mexico. They vary widely in pelage color, typically so as to match the local soil type. Karyotypes also vary, often over a few meters, which create effective barriers to hybridization.

    The karyotypes below can be shown to be related by fission / fusion of metacentric / telocentric chromosomes, which changes the diploid chromosome number (2N) without changing the number of arms (FN, Fundamental Number) or DNA content. The pattern of G-bands allows similar reconstructions to those done with polytene chromosomes in Drosophila.