Chromosomal variation in pocket gophers (Geomys) detected by sequential G-, R-, and C-band analyses.

The chromosomes of six taxa, representing five species of Geomys (G. attwateri, G. breviceps, G. personatus, G. texensis, G. bursarius) were analysed for variation in G-band, R-band, sequential R-/DAPI-AMD, and sequential R-/C-band patterns. Eleven chromosomes had structural rearrangements resulting from deletion/addition events. Fission/fusion rearrangements occurred in two chromosomes, and a pericentric inversion was confirmed in only one chromosome. Eighteen of 34 autosomes had constitutive heterochromatin, with variation in its presence or absence, position, and quantity. The heterochromatic differences were seen both among species and between two subspecies of G. personatus. Chromomycin A3 fluorescent staining identified G-C rich regions in 31 of the autosomes with 29 showing variation in their presence or absence, position, and quantity, and identified a high degree of cryptic variation. The X chromosome was highly variable, with differences attributable to structural rearrangements and variation in chromomycin bright-staining regions.