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Genetic estimates of contemporary effective population size in an endangered butterfly indicate a possible role for genetic compensation.

ABSTRACT: The effective population size (N e ) is a critical evolutionary and conservation parameter that can indicate the adaptive potential of populations. Robust estimates of N e of endangered taxa have been previously hampered by estimators that are sensitive to sample size. We estimated N e on two remaining populations of the endangered Miami blue butterfly, a formerly widespread taxon in Florida. Our goal was to determine the consistency of various temporal and point estimators on inferring N e and to determine the utility of this information for understanding the role of genetic stochasticity. We found that recently developed 'unbiased estimators' generally performed better than some older methods in that the former had more realistic N e estimates and were more consistent with what is known about adult population size. Overall, N e /N ratios based on census point counts were high. We suggest that this pattern may reflect genetic compensation caused by reduced reproductive variance due to breeding population size not being limited by resources. Assuming N e and N are not heavily biased, it appears that the lack of gene flow between distant populations may be a greater genetic threat in the short term than the loss of heterozygosity due to inbreeding.

SUBMITTER: Saarinen EV

PROVIDER: S-EPMC3352457 | biostudies-literature | 2010 Jan

REPOSITORIES: biostudies-literature

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Genetic estimates of contemporary effective population size in an endangered butterfly indicate a possible role for genetic compensation.

Saarinen Emily V EV Austin James D JD Daniels Jaret C JC

Evolutionary applications 20090810 1

The effective population size (N e ) is a critical evolutionary and conservation parameter that can indicate the adaptive potential of populations. Robust estimates of N e of endangered taxa have been previously hampered by estimators that are sensitive to sample size. We estimated N e on two remaining populations of the endangered Miami blue butterfly, a formerly widespread taxon in Florida. Our goal was to determine the consistency of various temporal and point estimators on inferring N e and ...[more]

PMID: 25567901

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Project description:Understanding historical range shifts and population size variation provides an important context for interpreting contemporary genetic diversity. Methods to predict changes in species distributions and model changes in effective population size (N e) using whole genomes make it feasible to examine how temporal dynamics influence diversity across populations. We investigate N e variation and climate-associated range shifts to examine the origins of a previously observed latitudinal heterozygosity gradient in the bumble bee Bombus vancouverensis Cresson (Hymenoptera: Apidae: Bombus Latreille) in western North America. We analyze whole genomes from a latitude-elevation cline using sequentially Markovian coalescent models of N e through time to test whether relatively low diversity in southern high-elevation populations is a result of long-term differences in N e. We use Maxent models of the species range over the last 130,000 years to evaluate range shifts and stability. N e fluctuates with climate across populations, but more genetically diverse northern populations have maintained greater N e over the late Pleistocene and experienced larger expansions with climatically favorable time periods. Northern populations also experienced larger bottlenecks during the last glacial period, which matched the loss of range area near these sites; however, bottlenecks were not sufficient to erode diversity maintained during periods of large N e. A genome sampled from an island population indicated a severe postglacial bottleneck, indicating that large recent postglacial declines are detectable if they have occurred. Genetic diversity was not related to niche stability or glacial-period bottleneck size. Instead, spatial expansions and increased connectivity during favorable climates likely maintain diversity in the north while restriction to high elevations maintains relatively low diversity despite greater stability in southern regions. Results suggest genetic diversity gradients reflect long-term differences in N e dynamics and also emphasize the unique effects of isolation on insular habitats for bumble bees. Patterns are discussed in the context of conservation under climate change.

Project description:Eradication or local extinction of the human parasite Schistosoma mansoni is a goal for many control programs. Population genetic analyses are helping to evaluate and guide these efforts, yet what to sample, how to sample and how densely to sample is not well established. We determined the S. mansoni allele frequency profile of nearly all infected inhabitants in two small Brazilian communities and created sub-samples representing 5-50% of all detected human infections (infrapopulations). Samples were selected at random with replacement, and each size class was replicated 100 times. Mean pairwise differentiation for all infrapopulations (Di) and the variance effective population size (Ne) were calculated for each sample. Prior to community-wide treatment, the true mean Di was moderate (0.095-0.123) and Ne large (>30,000). Most samples of <50% of those infected produced estimates outside of 5% of the true value. For estimates within 10%, sample sizes of >15% of all infrapopulations were required. At the 3 year follow-up after treatment, the Di increased and Ne was reduced by >15 fold. At this time sampling of >30-45% was needed to achieve the same accuracy. Following a second treatment and 4 years from baseline, the Di further increased and Ne decreased with little change in the sampling effort required. Extensive sampling is required for accurate estimates of these important population parameters. Characteristics such as population census size, infection prevalence, the community's treatment history and the degree of infrapopulation differentiation should be taken into account. The intensity of infection was weakly correlated with the ability of a single infrapopulation to represent the component population (Dic), indicating a tendency toward random acquisition of parasite genotypes. This also suggests that targeted sampling from those most heavily infected will better represent the genetic diversity of the whole community than a random sample of infrapopulations.

Dataset Information

Genetic estimates of contemporary effective population size in an endangered butterfly indicate a possible role for genetic compensation.

Publications

Genetic estimates of contemporary effective population size in an endangered butterfly indicate a possible role for genetic compensation.

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