Introgression between two cutthroat trout subspecies with substantial karyotypic, nuclear and mitochondrial genomic divergence
Gyllensten, U.; Leary, R.F.; Allendorf, F.W.; Wilson, A.C.
Genetics 111(4): 905-915
1985
ISSN/ISBN: 0016-6731 PMID: 4065545 Document Number: 256887
Allozymes encoded by nuclear genes, and restriction enzyme analysis of mitochondrial DNA (mtDNA), were used to study secondary contact between westslope (Salmo clarki lewisi) and Yellowstone cutthroat trout (Salmo clarki bouvieri) in Forest Lake, Montana. 11 diagnostic allozyme loci identified this as a random-mating hybrid swarm. No parental 1st-generation hybrid or backcross genotypes were detected in the 33 fish sampled, and genotype distributions at all the variable loci conformed to binomial expectations. Little linkage disequilibrium was found between the diagnostic loci, indicating that the nuclear genomes of the 2 subspecies are largely randomly associated. The allozymes and mtDNA gave identical estimates of the proportional genetic contribution of each subspecies. Thus, malemale from both subspecies have contributed equally to this hybrid swarm. Although these subspecies have accumulated substantial genetic divergence between their nuclear and mitochondrial genomes, this has not resulted in a genetic barrier to exchange between them.