Samples of the forest‐dwelling mouse Abrothrix olivaceus and the steppe‐dwelling A. xanthorhinus across a transect between 45 and 47° S in southern Chile were analysed using the mitochondrial cytochrome b (cyt b ) sequence, substantially adding to the data presented previously for these taxa from Argentina and Chile. The level of variation in the cyt b sequence throughout the entire olivaceus/xanthorhinus complex is comparable...

Mitochondrial DNA (mtDNA) variation in the cytochrome b gene was determined for two divergent taxa of pocket gophers, Thomomys bottae actuosus and T. b. ruidosae . These two taxa hybridize in a narrow contact zone, but introgression of nuclear markers such as allozymes or chromosomes does not extend much beyond the hybrid zone (Patton et al. 1979). We found that despite their distinctness, the two subspecies shared very simila...