Abstract
Summary
Chromosomes were analyzed from the bone marrow of 4 specimens of Spermophilus richardsonii nevadensis. Comparison of chromosomal characters from the 3 geographically isolated subspecies of S. richardsonii demonstrates that S. r. nevadensis and S. r. elegans both have a diploid number of 34 and similar karyotypes whereas S. r. richardsonii has a diploid number of 36 and a different karyotype. The nevadensis and elegans karyotypes probably evolved from the chromosomally more ancestral richardsonii karyotype by means of a chromosomal polymorphism. The data also suggest that S. r. nevadensis and S. r. elegans are more closely related to one another than either is to S. r. richardsonii.
The author wishes to thank Mr. Ray Alcorn for providing the specimens examined in this study.
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