An understanding of the relative roles of historical and contemporary factors in structuring genetic variation is a fundamental, but understudied aspect of geographic variation. We examined geographic variation in microsatellite DNA allele frequencies in bull trout (Salvelinus confluentus, Salmonidae) to test hypotheses concerning the relative roles of postglacial dispersal (historical) and current landscape features (contemporary) in structuring genetic variability and population differentiation. Bull trout exhibit relatively low intrapopulation microsatellite variation (average of 1.9 alleles per locus, average He = 0.24), but high levels of interpopulation divergence (F(ST) = 0.39). We found evidence of historical influences on microsatellite variation in the form of a decrease in the number of alleles and heterozygosities in populations on the periphery of the range relative to populations closer to putative glacial refugia. In addition, one region of British Columbia that was colonized later during deglaciation and by more indirect watershed connections showed less developed and more variable patterns of isolation by distance than a similar region colonized earlier and more directly from refugia. Current spatial and drainage interconnectedness among sites and the presence of migration barriers (falls and cascades) within individual streams were found to be important contemporary factors influencing historical patterns of genetic variability and interpopulation divergence. Our work illustrates the limited utility of equilibrium models to delineate population structure and patterns of genetic diversity in recently founded populations or those inhabiting highly heterogeneous environments, and it highlights the need for approaches incorporating a landscape context for population divergence. Substantial microsatellite DNA divergence among bull trout populations may also signal divergence in traits important to population persistence in specific environments.

An understanding of the relative roles of historical and contemporary factors in structuring genetic variation is a fundamental, but understudied aspect of geographic variation. We examined geographic variation in microsatellite DNA allele frequencies in bull trout (Salvelinus confluentus, Salmonidae) to test hypotheses concerning the relative roles of postglacial dispersal (historical) and current landscape features (contemporary) in structuring genetic variability and population differentiation. Bull trout exhibit relatively low intrapopulation microsatellite variation (average of 1.9 alleles per locus, average H e ϭ 0.24), but high levels of interpopulation divergence (F ST ϭ 0.39). We found evidence of historical influences on microsatellite variation in the form of a decrease in the number of alleles and heterozygosities in populations on the periphery of the range relative to populations closer to putative glacial refugia. In addition, one region of British Columbia that was colonized later during deglaciation and by more indirect watershed connections showed less developed and more variable patterns of isolation by distance than a similar region colonized earlier and more directly from refugia. Current spatial and drainage interconnectedness among sites and the presence of migration barriers (falls and cascades) within individual streams were found to be important contemporary factors influencing historical patterns of genetic variability and interpopulation divergence. Our work illustrates the limited utility of equilibrium models to delineate population structure and patterns of genetic diversity in recently founded populations or those inhabiting highly heterogeneous environments, and it highlights the need for approaches incorporating a landscape context for population divergence. Substantial microsatellite DNA divergence among bull trout populations may also signal divergence in traits important to population persistence in specific environments.

Partitioning within-species genetic diversity is fundamental to conservation of the bioheritage, current viability, and evolutionary potential of individual taxa. We conducted a hierarchical analysis of genetic diversity in Dolly Varden (Salvelinus malma) and bull trout (Salvelinus confluentus) involving analysis of hybrid zones between Dolly Varden and bull trout, analysis of phylogenetic structure within species across their native ranges using mitochondrial DNA, and a microsatellite DNA survey of population subdivision of bull trout within single watersheds. Our analyses documented hybridization and some introgression between Dolly Varden and bull trout across a geographically widespread zone of secondary contact between the two species. Both species were subdivided into two major mtDNA lineages, and one lineage in Dolly Varden may have arisen through introgression with bull trout. Bull trout have low levels of microsatellite diversity within populations, but there was substantial interpopulation variation in allele frequencies. Allele frequency distributions suggested that recent, severe bottlenecks occur frequently in some bull trout populations. Our results illustrate partitioning of genetic variation at distinct levels of biological organization (species, phylogeographic lineages, local populations), and we address how such nested variation is fundamental to conservation of biodiversity.Résumé : La compartimentation de la diversité génétique intraspécifique est une opération essentielle pour la conservation de l'héritage biologique, de la viabilité actuelle et du potentiel évolutif de taxons particuliers. Nous avons procédé à une analyse hiérarchique de la diversité génétique de la Dolly Varden (Salvelinus malma) et de l'Omble à tête plate (Salvelinus confluentus) qui comprend une étude des zones d'hybrides entre les deux espèces, une analyse basée sur l'ADN mitochondrial de la structure phylogénétique des espèces sur toute leur répartition géographique d'origine et un inventaire des microsatellites de l'ADN dans les subdivisions de populations de l'Omble à tête plate à l'intérieur de bassins hydrographiques particuliers. Nos analyses révèlent l'existence d'hybridation et d'introgression dans une large zone géographique de contact secondaire entre les deux espèces. Chacune des espèces se divise en deux lignées principales d'après son ADNmt; l'une des lignées de la Dolly Varden est peut-être apparue par introgression avec l'Omble à tête plate. L'Omble à tête plate possède une faible diversité des microsatellites à l'intérieur des populations, mais il y a une importante variation des fréquences d'allèles entre les populations. Les distributions de fréquence des allèles laissent croire que d'importants goulots d'étranglement récents se sont produits à plusieurs reprises dans quelques populations d'Omble à tête plate. Notre étude est un exemple de la compartimentation de la variation génétique à plusieurs niveaux distincts de l'organisation biologique (espèce, lignées phylogénétiques, populations locales); nou...

Nonnative salmonids have been intentionally introduced in North America for over a century and are now implicated in the decline of native aquatic species. Current management objectives for some national parks are to remove invasive species, where feasible. We evaluated the use of mechanical methods (gill nets and electrofishing) to eliminate a naturalized population of nonnative Brook Trout Salvelinus fontinalis in a subalpine headwater basin. We required a total of 1,383 continuous net nights/ha (net nights = number of nets × number of nights) over 5 years to completely eradicate 1,527 Brook Trout from both Lower (9.7 ha; 6 m maximum depth) and Middle (23.1 ha; 25 m maximum depth) Devon Lakes, Alberta, Canada. Electrofishing along the shoreline of both lakes resulted in the capture of 301 Brook Trout over 4 years. We required a total of 52.1 h/km of electrofishing over 5 years to completely remove 3,288 Brook Trout from the upper 4.5 km of the Clearwater River. We verified the absence of fish in the lakes with 1,558 net nights/ha of sampling over 4 years and in the river with 13.6 h/km over 2 years. This project confirms that mechanical methods are a viable option for removing introduced fish, even in relatively large (up to 20 ha) and deep (up to 25 m) mountain lakes. We surmised that our success (relative to that of projects described in the literature) was due to (1) the relatively simple alpine habitat, in which river and lake margins were clear of macrophytes, suspended sediment, and overhanging riparian vegetation, and (2) the sheer magnitude of our effort.

The objective of this study was to estimate Argia vivida (Odonata: Coenagrionidae) populations, identify breeding habitat, and investigate movement of adults within Banff National Park, Alberta, Canada, during the summer of 2003. Mark-recapture techniques and standardized dip-net surveys were used to monitor Argia vivida at various life stages. A reproductive index identified which sites Argia vivida recognized as suitable breeding habitat, and exuvia surveys confirmed breeding sites. The basic structure of emergent and surrounding vegetation was measured to investigate the importance of available ovipositing or roosting sites and the condition of the matrix habitat. Data was recorded for Amphiagrion abbreviatum and Ischnura cervula (both Odonata: Coenagrionidae) to determine if these spring-associated damselflies were successfully breeding within Banff National Park. Comparisons were made between the highly protected Middle Springs and the heavily altered Cave & Basin Springs. Additional surveys at the Vermilion Lake cool spring and Middle Springs Bog investigated their use as breeding habitat for Amphiagrion abbreviatum and Argia vivida, respectively. Results suggest the ecological value of thermal springs extends beyond their origin to outflows and downstream pools. Conservation of Argia vivida must recognize the value of unobstructed thermal outflows, and consider the condition of the forested habitat surrounding springs with regard to its potential use as nocturnal roosts and dispersal corridors. Amphiagrion abbreviatum was confirmed breeding within Banff National Park, while no sign of breeding activity was recorded for Ischnura cervula.