Broad‐ to fine‐scale population genetic patterning in the smallmouth bassMicropterus dolomieuacross the Laurentian Great Lakes and beyond: an interplay of behaviour and geography

Abstract

Analysis of population genetic relationships reveals the signatures of current processes such as spawning behaviour and migration, as well as those of historical events including vicariance and climate change. This study examines these signatures through testing broad- to fine-scale genetic patterns among smallmouth bass Micropterus dolomieu spawning populations across their native Great Lakes range and outgroup areas, with fine-scale concentration in Lake Erie. Our primary hypotheses include whether genetic patterns result from behavioural and/or geographical isolation, specifically: (i) Are spawning groups in interconnected waterways genetically separable? (ii) What is the degree of isolation across and among lakes, basins, and tributaries? (iii) Do genetic divergences correspond to geographical distances? and (iv) Are historical colonization patterns from glacial refugia retained? Variation at eight nuclear microsatellite DNA loci are analysed for 666 smallmouth bass from 28 locations, including 425 individuals in Lake Erie; as well as Lakes Superior, Huron, and Ontario, and outgroups from the Mississippi, Ohio, St. Lawrence, and Hudson River drainages. Results reveal marked genetic differences among lake and river populations, as well as surprisingly high divergences among closely spaced riverine sites. Results do not fit an isolation-by-geographical-distance prediction for fine-scale genetic patterns, but show weak correspondence across large geographical scales. Genetic relationships thus are consistent with hypotheses regarding divergent origins through vicariance in glacial refugia, followed by colonization pathways establishing modern-day Great Lakes populations, and maintenance through behavioural site fidelity. Conservation management practices thus should preserve genetic identity and unique characters among smallmouth bass populations.

A multi-scale comparison of trait linkages to environmental and spatial variables in fish communities across a large freshwater lake

“…This may be due to the nature of our coastal sampling sites: many of these shallow nearshore areas would freeze over in winter and be less accessible, thus promoting an annual recolonization of sites. Also, some coastal fishes show high nest fidelity and can have substantial genetic divergence within the same lake, despite the absence of geographic barriers (Stepien et al 2007), which implies that dispersal may be limiting for some coastal species. Although we might expect that small-bodied species are possibly more dispersal limited because of a lower mobility and smaller home range size, the ratio of abundance of small-bodied to large-bodied fishes was not related to the amount of independent spatial variation explained (R 2 = 0.10).…”

Movement of smallmouth bass within the Beaver Island Archipelago, northern Lake Michigan

“…A Lake Erie smallmouth bass genetics study showed that migration rates may be higher in lake-spawning, as opposed to lotic-spawning, smallmouth bass (Stepien et al, 2007). Findings from this study and other evidence from Lake Erie (Stepien et al, 2007) may indicate that this population is more "open", with some individuals leaving the Archipelago. Therefore, northern Lake Michigan may need to be considered one management unit for smallmouth bass.…”

A geographical genetics framework for inferring homing reproductive behavior in fishes

“…If this structure is a consequence of high-level population differentiation, which may be caused for example by a long-term historical divergence (i.e., the species was subdivided), then a multivariate analysis of genetic divergence will show distinct population clusters with no clear pattern of variation among the waterheads within these clusters. This alternative again relies on supporting prediction 1.2 at the ''correct'' hierarchical level within the same reproductive units (e.g., Telles and Diniz-Filho 2005; see also Stepien et al 2007). If this pattern of long-term differentiation is known a priori and these regions can be inferred independently such as from ecological or limnological data, then the magnitude of genetic variation that can be attributed to each of these levels can be measured by a hierarchical model such as nested ANOVA.…”

“…1.1 Under homing behavior, a high genetic variability is expected to exist among waterheads because individuals reproducing within each one will tend to mate successively within a subsample of the total population (e.g., Stepien and Faber 1998;Waters et al 2000;Exadactylos et al 2003;Hoffman et al 2005;Stepien et al 2007;Pereira et al 2009;Abreu et al 2009;Waldman et al 2008 andGoodman et al 2008 for an inverted reasoning using this type of data-i.e., low levels of population differentiation is indicative of the absence of strong homing behavior). Likewise, kinship (i.e., co-ancestry) among individuals within waterheads will be higher than among individuals belonging to different waterheads.…”