Genetic interactions among three chromosomal races of the Geomys bursarius complex (Rodentia: Geomyidae)

Abstract

Genetic relationships among three races of the plains pocket gopher, (Geomys bursarius complex) were determined using data from chromosome banding, meiotic analysis, and protein electrophoresis. Race E (2n = 74, FN = 72) interacts with races F (2n = 70, FN = 74) and G (2n = 70, FN = 72) at a small area in Burleson Co. Of 67 pocket gophers collected there, three (3.8%) represented F1 hybrids, and none were backcross or F2 individuals. Races F and G interact over a broad area of Burleson and Milam counties, with hybrids being collected over a distance of 85 km. Backcross and F2 animals cannot be distinguished from F1 hybrids between these races, but the lack of pocket gophers with parental race G karyotypes in the northeastern end of the contact zone suggests that hybrid production in that area includes backcross individuals and/or F2 hybrids. G-band chromosomal analysis reveals that races F and G differ from race E by two centric fission-fusion events. The presence of further chromosomal rearrangements distinguishing race E from races F and G are indicated by G-band analysis, but the specific rearrangements cannot be identified. One multivalent is identifiable in pachytene and diakinesis from an F1 hybrid male between races E and G. C-banding reveals constitutive heterochromatin to be concentrated at or near the centromeres in race E, whereas race G has large heterochromatic regions on 14 pairs of autosomes. Race F differs from race G by the presence of a heterochromatic long arm on a small acrocentric of race G and a paracentric inversion in one of the larger chromosomes. A loop configuration at pachytene in F x G hybrids corresponds in size and position to the inversion identified in G-banded chromosomes. ...