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Chromosome variation in the mountain pocket gopher, Thomomys monticola J. A. Allen, 1893 (Rodentia: Geomyidae).
Chromosomes were analyzed from the mitotic bone marrow of nine mountain pocket gophers (Thomomys monticola J. A. Allen, 1893). All the specimens, collected from three different localities in the'Sierra Nevadas, had a diploid number (2N) of 40. Animals from two localities exhibited slight variations in chromosome morphology. Pocket gophers from Lake Tahoe possessed a fundamental number (FN) of 76 while those from Huntington Lake and Kaiser Pass Meadow had a FN of 74. The difference in the karyotypes is attrib- uted to non-Robertsonian variation: pericentric inversions and reciprocal translocations.