The effects of gene flow and population isolation on the genetic structure of␣reintroduced wild turkey populations: Are genetic signatures of source populations retained?

The number and size of tiger populations continue to decline owing to habitat loss, habitat fragmentation and poaching of tigers and their prey. As a result, tiger populations have become small and highly structured. Current populations have been isolated since the early 1970s or for approximately seven generations. The objective of this study is to explore how inbreeding may be affecting the persistence of remaining tiger populations and how dispersal, either natural or artificial, may reduce the potentially detrimental effect of inbreeding depression. We developed a tiger simulation model and used published levels of genetic load in mammals to simulate inbreeding depression. Following a 50 year period of population isolation, we introduced one to four dispersing male tigers per generation to explore how gene flow from nearby populations may reduce the negative impact of inbreeding depression. For the smallest populations, even four dispersing male tigers per generation did not increase population viability, and the likelihood of extinction is more than 90% within 30 years. Unless habitat connectivity is restored or animals are artificially introduced in the next 70 years, medium size wild populations are also likely to go extinct, with only four to five of the largest wild tiger populations likely to remain extant in this same period without intervention. To reduce the risk of local extinction, habitat connectivity must be pursued concurrently with efforts to increase population size (e.g. enhance habitat quality, increase habitat availability). It is critical that infrastructure development, dam construction and other similar projects are planned appropriately so that they do not erode the extent or quality of habitat for these populations so that they can truly serve as future source populations.

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Hierarchical Analysis of Genetic Structure in Native Fire Ant Populations: Results From Three Classes of Molecular Markers

Genetics ◽

10.1093/genetics/147.2.643 ◽

1997 ◽

Vol 147 (2) ◽

pp. 643-655 ◽

Cited By ~ 3

Author(s):

Kenneth G Ross ◽

Michael J B Krieger ◽

D DeWayne Shoemaker ◽

Edward L Vargo ◽

Laurent Keller

Keyword(s):

Gene Flow ◽

Genetic Structure ◽

Solenopsis Invicta ◽

Large Scale ◽

Fire Ant ◽

Nuclear Markers ◽

Social Forms ◽

Native Populations ◽

Nest Level ◽

Nuclear Differentiation

We describe genetic structure at various scales in native populations of the fire ant Solenopsis invicta using two classes of nuclear markers, allozymes and microsatellites, and markers of the mitochondrial genome. Strong structure was found at the nest level in both the monogyne (single queen) and polygyne (multiple queen) social forms using allozymes. Weak but significant microgeographic structure was detected above the nest level in polygyne populations but not in monogyne populations using both classes of nuclear markers. Pronounced mitochondrial DNA (mtDNA) differentiation was evident also at this level in the polygyne form only. These microgeographic patterns are expected because polygyny in ants is associated with restricted local gene flow due mainly to limited vagility of queens. Weak but significant nuclear differentiation was detected between sympatric social forms, and strong mtDNA differentiation also was found at this level. Thus, queens of each form seem unable to establish themselves in nests of the alternate type, and some degree of assortative mating by form may exist as well. Strong differentiation was found between the two study regions usinga all three sets of markers. Phylogeographic analyses of the mtDNA suggest that recent limitations on gene flow rather than longstanding barriers to dispersal are responsible for this large-scale structure.

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Geographic Structure of Mitochondrial and Nuclear Gene Polymorphisms in Australian Green Turtle Populations and Male-Biased Gene Flow

Genetics ◽

10.1093/genetics/147.4.1843 ◽

1997 ◽

Vol 147 (4) ◽

pp. 1843-1854 ◽

Cited By ~ 8

Author(s):

Nancy N FitzSimmons ◽

Craig Moritz ◽

Colin J Limpus ◽

Lisa Pope ◽

Robert Prince

Keyword(s):

Gene Flow ◽

Genetic Structure ◽

Green Turtle ◽

Nuclear Dna ◽

Nuclear Gene ◽

Chelonia Mydas ◽

Single Copy ◽

Microsatellite Data ◽

Ecological Data ◽

Infinite Allele Model

Abstract The genetic structure of green turtle (Chelonia mydas) rookeries located around the Australian coast was assessed by (1) comparing the structure found within and among geographic regions, (2) comparing microsatellite loci vs. restriction fragment length polymorphism analyses of anonymous single copy nuclear DNA (ascnDNA) loci, and (3) comparing the structure found at nuclear DNA markers to that of previously analyzed mitochondrial (mtDNA) control region sequences. Significant genetic structure was observed over all regions at both sets of nuclear markers, though the microsatellite data provided greater resolution in identifying significant genetic differences in pairwise tests between regions. Inferences about population structure and migration rates from the microsatellite data varied depending on whether statistics were based on the stepwise mutation or infinite allele model, with the latter being more congruent with geography. Estimated rates of gene flow were generally higher than expected for nuclear DNA (nDNA) in comparison to mtDNA, and this difference was most pronounced in comparisons between the northern and southern Great Barrier Reef (GBR). The genetic data combined with results from physical tagging studies indicate that the lack of nuclear gene divergence through the GBR is likely due to the migration of sGBR turtles through the courtship area of the nGBR population, rather than male-biased dispersal. This example highlights the value of combining comparative studies of molecular variation with ecological data to infer population processes.

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