Georgaphic variation in the karyotype of pocket mice (Perognathus)

(A) Distribution of Perognathus goldmani in northwestern Mexico. (B) Proposed sequence of karyotypic evolution, involving four fusions and two inversions. Note that the hypothetical ancetral karyotype is composed entirely of acrocentric chromosomes. (after Patton 1968, from Futuyma 1997)