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

Abstract

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 sexbiased 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.

Geographic influences on fine-scale, hierarchical population structure in northern Canadian populations of anadromous Arctic Char (Salvelinus alpinus)

“…Arctic fishes provide rich opportunities for studying the factors responsible for organizing spatial genetic structure among populations, the majority of which were impacted by historical events such as isolation in distinct glacial refugia where, in many cases, secondary contact has ensued following dispersal from these areas (e.g., Lindsay and McPhail 1986;Turgeon and Bernatchez 2001a, b;Elmer et al 2012). Furthermore, north temperate and Arctic fish species exhibit remarkable amounts of morphological and ecotypic polymorphisms stemming from divergence following the colonization of previously unexploited habitats that became available after the ice-sheets receded subsequent to the most recent glaciation events (Schluter 1996).…”

Sampling schemes and drift can bias admixture proportions inferred by structure

“…Most simulation studies have assumed equal admixture rates between parental populations in their experimental designs, making this pattern impossible to detect. This pattern poses a problem for empirical studies as highly asymmetric admixture events are common in natural and domestic populations (Elmer, Recknagel, Thompson, & Meyer, 2012; Muranishi, Tamaki, Setsuko, & Tomaru, 2013; Papa & Gepts, 2003). structure’ s admixture proportions are often used as a hybrid index to build clines in hybrid zone analyses (Arntzen et al., 2016; Dufresnes et al., 2018; Wielstra et al., 2017).…”

Genetic diversity and population structure of burbot Lota lota in Germany: Implications for conservation and management

“…Most studies of burbot population genetic structure have examined populations from North America (e.g. Elmer, Recknagel, Thompson, & Meyer, 2012;Elmer, Van Houdt, Meyer, & Volckaert, 2008;Powell, Paragamian, & Dunnigan, 2008;Underwood et al, 2016), China (Fang, Zhang, Song, Qian, & Gao, 2013) and Russia (Van Houdt, Cleyn, Perretti, & Volckaert, 2005;Van Houdt et al, 2003). Only three studies (Barluenga, Sanetra, & Meyer, 2006;Van Houdt et al, 2005, 2003 included a limited number of German sampling sites (Lake Constance and the rivers Isar and Elbe).…”