Asymmetric admixture and morphological variability at a suture zone: parapatric burbot subspecies (Pisces) in the Mackenzie River basin, Canada

• Published in: Hydrobiologia
• Main Authors: Elmer, Kathryn R., Recknagel, Hans, Thompson, Amy, Meyer, Axel
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Springer Netherlands 2012
• Subjects: Canada; Great Slave Lake; Mackenzie River; Burbot; Lota lota; Mackenzie river; lota
• Online Access: https://eprints.gla.ac.uk/99128/

The burbot (Lota lota L.) is a northern freshwater fish with a circumpolar distribution. Two subspecies diverged due to isolation during glacial maxima: Lota lota lota is the Eurasian-Beringian subspecies and Lota lota maculosa the North American subspecies. We sampled burbot from the Great Slave Lake and Mackenzie River area, Canada, the only known contact zone of these two lineages. Using molecular methods (microsatellite loci and mtDNA sequence) we found that the subspecies’ distributions abut in the Mackenzie River delta, with L. l. lota in the lower delta and L. l. maculosa in all upstream rivers and lakes. Admixture between subspecies was minimal, decreased with increasing geographic distance, and was asymmetrical: mitochondrial and nuclear genetic introgression was from L. l. lota into L. l. maculosa but not the reverse. Within subspecies, there was low inter-population genetic differentiation, no isolation-by-distance, and no evidence for sex-biased dispersal. We did not identify a difference in body length between subspecies per se, though mean lengths differed among localities. Thus, genetic data demonstrate that burbot subspecies are reproductively isolated though the extent to which morphologically variability relates to local versus subspecific variation remains unclear.