An analysis of the observed heterozygosity of lake trout

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An analysis of the observed heterozygosity of lake trout

Re-use of this article is permitted in accordance with the Creative Commons Deed, Attribution 2. This article has been cited by other articles in PMC. Abstract Resolving the genetic population structure of species inhabiting pristine, high latitude ecosystems can provide novel insights into the post-glacial, evolutionary processes shaping the distribution of contemporary genetic variation.

It appears, therefore, that contemporary ongoing dispersal and gene flow and historical historical gene flow and large founding and present-day effective population sizes factors contribute to the lack of neutral genetic structure in GBL.

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Overall, our results illustrate the importance of history e. Gene flow, glaciations, history, panmictic, Salvelinus Introduction The extent of genetic structure among, and variation within, populations of north temperate faunas is expected to be markedly different from that exhibited by populations from more southerly latitudes, which were exempt from the direct impacts of Pleistocene glaciations Hewitt Fishes in particular, given their reliance on aquatic habitats for survival, were clearly impacted by glacial events e.

For example, populations with contemporary ranges spanning areas formerly glaciated during the Pleistocene Epoch are expected to show reduced levels of genetic variation and historical effective population size NEas well as reduced levels of DNA sequence and phylogenetic divergence compared with those from unglaciated areas Hewitt ; Bernatchez and Wilson ; Hewitt Differences in patterns between geography and genetic variation are also expected.

For instance, decreases in genetic variation with increasing distance from glacial refugia have been observed in several species of fishes Stamford and Taylor ; Harris and Taylor a.

An analysis of the observed heterozygosity of lake trout

Furthermore, isolation and survival in distinct glacial refugia should result in clear phylogeographic groupings of populations Bernatchez and Dodson ; Wilson and Hebert ; Stamford and Tayloralthough these patterns can be distorted as a result of contemporary secondary contact among refugial groups Lu et al.

Evolutionary processes such as founder events associated with post-glacial dispersal and historical bottlenecks as a result of glacial cycles are offered as potential explanations for some of these observations Bernatchez et al.

Although current patterns of phylogeography, population structure, and genetic variation among and within populations of northern fishes can be largely explained by historical events, contemporary factors also contribute to these patterns.

For example, contemporary connectivity facilitating gene flow among populations will reduce genetic differentiation Dionne et al. Alternatively, recent reductions in population size, resulting from anthropogenic disturbances Stamford and Taylor ; Hanfling and Weetmanfor example, can reduce genetic variation and promote genetic divergence through genetic drift, especially in small populations Consuegra et al.

Furthermore, contemporary landscape and environmental features of aquatic ecosystems e. Disentangling the relative influences of historical and contemporary factors, such as historical gene flow versus contemporary dispersal, on population genetic structure can present formidable challenges Sobel et al.

One way to increase our understanding of the relative roles of historical and contemporary influences on genetic diversity and population structure is to use comparative methods.

The use of multi-locus data of varying evolutionary rates e. Alternatively, the mutation rate of mitochondrial DNA mtDNA is much lower than that exhibited by microsatellite loci e.

Relying solely on one approach may result in misleading conclusions, whereas combining these approaches can prove very useful for disentangling historical versus contemporary influences on population structure and genetic diversity.

Arctic systems provide unique opportunities for investigating the roles of historical and contemporary processes in shaping the genetic structure in populations of freshwater fishes.

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Virtually all Arctic populations of fishes were impacted by Pleistocene glaciation events through the displacement of populations during glacial maxima and then the recolonization of contemporary ranges when the ice-sheets receded Lindsey and McPhail ; Pielou Some groups of fishes dispersed remarkable distances across numerous watersheds post-glacially to occupy their current range Bernatchez and Dodson ; Rempel and Smith ; Wilson and Hebert ; Witt et al.

Furthermore, many Arctic systems are characterized by complex and dynamic watersheds harboring a multitude of populations, many of which exist in a meta-population framework.

This permits the study of processes such as contemporary dispersal, gene flow, and source-sink population dynamics Dias ; Palstra et al. In addition, many of these systems are virtually pristine, providing ample opportunity to study population structure in fishes that have not been anthropogenically impacted.

Arctic populations of fishes are relatively less studied than those at more southerly latitudes and therefore the evolutionary ecology of many Arctic fish populations remains unresolved e. Characterized by five distinct basins from herein referred to as armsGBL was at one time encompassed by glacial Lake McConnell Smith The lake is oligotrophic and is characterized by very low species diversity Johnson b.

Lake trout Salvelinus namaycush are one of the most abundant and widely distributed fishes in this system, found at all depths and temperatures Johnson b. The biology and evolutionary ecology of lake trout is relatively well studied in other large lakes, for example, the heavily anthropogenically impacted Laurentian Great Lakes Moore and Bronte ; Guinand et al.

Additional recent studies of lake trout in GBL have examined morphological variation and trophic resource polymorphism in this species Blackie et al.Cutthroat trout present in Lake Eva during July were defined as resident, and a two-event mark-recapture method was used to estimate that 1,± resident fish were present and had an average fork length of mm.

Shown are the number of alleles observed (A), effective number of alleles (A e), allelic richness (A r), expected heterozygosity (H e), observed heterozygosity, and the number of individuals (n) genotyped at each locus for.

In a recently bottlenecked population, the observed heterozygosity is higher than the heterozygosity expected from the observed number of alleles under the assumption of a population at mutation-drift equilibrium (Cornuet & Luikart, ).

The decline is also implied by an N e heterozygosity at or above the observed 55–60%.

An analysis of the observed heterozygosity of lake trout

The similarity of N e estimates in the two intervals suggests a gradual decline of diversity over the century, not an acute drop after dump closure. Evidence of a remnant self-sustaining strain of lake trout in the Lake Michigan basin For morphometric analysis, adult stocked lake trout were collected from Lake Michigan during summer and fall Deviations of observed and expected heterozygosity reflected in relatively high and significant positive F is were documented in lake.

An Analysis of the Observed Heterozygosity of Lake Trout Essay Words Nov 3rd, 8 Pages An analysis of the observed heterozygosity of Lake Trout populations from three lakes: Devil, Eagle, and Loughborough, inferred from microsatellite genotypes.

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