A portrait of a sucker using landscape genetics: how colonization and life history undermine the idealized dendritic metapopulation

Abstract

Dendritic metapopulations have been attributed unique properties by in silico studies, including an elevated genetic diversity relative to a panmictic population of equal total size. These predictions have not been rigorously tested in nature, nor has there been full consideration of the interacting effects among contemporary landscape features, colonization history and life history traits of the target species. We tested for the effects of dendritic structure as well as the relative importance of life history, environmental barriers and historical colonization on the neutral genetic structure of a longnose sucker (Catostomus catostomus) metapopulation in the Kogaluk watershed of northern Labrador, Canada. Samples were collected from eight lakes, genotyped with 17 microsatellites, and aged using opercula. Lakes varied in differentiation, historical and contemporary connectivity, and life history traits. Isolation by distance was detected only by removing two highly genetically differentiated lakes, suggesting a lack of migration-drift equilibrium and the lingering influence of historical factors on genetic structure. Bayesian analyses supported colonization via the Kogaluk's headwaters. The historical concentration of genetic diversity in headwaters inferred by this result was supported by high historical and contemporary effective sizes of the headwater lake, T-Bone. Alternatively, reduced allelic richness in headwaters confirmed the dendritic structure's influence on gene flow, but this did not translate to an elevated metapopulation effective size. A lack of equilibrium and upstream migration may have dampened the effects of dendritic structure. We suggest that interacting historical and contemporary factors prevent the achievement of the idealized traits of a dendritic metapopulation in nature.

Small fish, large river: Surprisingly minimal genetic structure in a dispersal‐limited, habitat specialist fish

“…Heightened upstream genetic structure and DIGD is particularly pronounced in organisms inhabiting dendritic systems with many confluences and larger ranges (Crispo, Bentzen, Reznick, Kinnison, & Hendry, ; Ginson et al, ; Salisbury, McCracken, Keefe, Perry, & Ruzzante, ; Thomaz et al, ); however, linear river systems do not typically show strong signals of reduced upstream gene flow (Kanno et al, ; Paz‐Vinas et al, ; Thomaz et al, ). Thomaz et al () found a signal of DIGD in linear systems, but their models are based on a total range of 1,000 km, which suggests that a detectable signal of downstream‐biased dispersal (and the associated effects of DIGD and higher genetic differentiation in upstream areas) may not exist at smaller spatial scales such as that of E. lemniscatum (~38 km).…”

Extensive secondary contact among three glacial lineages of Arctic Char (Salvelinus alpinus) in Labrador and Newfoundland

“…Access to this watershed may have been enhanced by significant runoff from the paleolake Naskaupi, which drained through the Kogaluk between 7,500 and 6,000 years BP (Barnett & Peterson, ; Jansson & Kleman, ). Alternatively, many lakes within the Kogaluk River drainage are connected via shallow streams which could facilitate the occasional migration between lakes as it has for lake trout (McCracken, Perry, Keefe, & Ruzzante, ) and longnose suckers ( Catostomus catostomus ) (Salisbury, McCracken, Keefe, Perry, & Ruzzante, ) in this system. Migration may have countered genetic drift (Tallmon, Luikart, & Waples, ), maintaining both Arctic and Atlantic lineage haplotypes in these lakes.…”

River network architecture, genetic effective size and distributional patterns predict differences in genetic structure across species in a dryland stream fish community

“…Nonequilibrium metapopulation dynamics and colonization history may also exert stronger influence over species genetic patterns than network architecture (in fish Salisbury et al . ; salamanders Cosentino et al . ).…”