USING LANDSCAPE GENETICS TO FORM A PORTRAIT OF A SUCKER: AN ARGUMENT FOR THE CONSIDERATION OF MULTIPLE FACTORS TO CAPTURE THE WHOLE PICTURE OF A SUBARCTIC DENDRITIC METAPOPULATION

Abstract

I tested the relative importance of life history, environmental barriers, dendritic structure, and historical colonization on the neutral genetic structure of a longnose sucker (Catostomus catostomus) metapopulation in the Kogaluk River of northern Labrador. Samples were collected from eight lakes, genotyped with 17 microsatellites, and aged using opercula. Lakes demonstrated varying migration rates and genetic differentiation. Isolation by distance was found only when the two most genetically distinct lakes were removed from the analyses, suggesting a lack of migration-drift equilibrium and the importance of historical and contemporary factors in shaping metapopulation structure. Lower allelic richness in the headwaters due to the dendritic structure of the watershed contrasted with high effective population sizes of the south-western headwaters, potentially due to their earlier colonization. Recent colonization, variable migration rates between lakes, long generation times, and upstream migration have stalled achievement of a typical dendritic metapopulation structure and its associated elevated effective size.