Population Structure and Conservation Genetics of the Oregon Spotted Frog, Rana Pretiosa

The Oregon spotted frog (Rana pretiosa) is one of the most threatened amphibians in the Pacific Northwest. Here we analyzed data from 13 microsatellite loci and 298 bp of mitochondrial DNA in frogs collected from 23 of the remaining R. pretiosa populations in order to (1) assess levels of genetic diversity within populations of R. pretiosa, (2) identify the major genetic groups in the species, (3) estimate levels of genetic differentiation and gene flow among populations within each major group, and (4) compare the pattern of differentiation among R. pretiosa populations with that among populations of R. cascadae, a non-endangered congener that also occurs in Oregon and Washington. There is a strong, hierarchical genetic structure in R. pretiosa. That structure includes six major genetic groups, one of which is represented by a single remaining population. R. pretiosa populations have low genetic diversity (average He = 0.31) compared to R. cascadae (average He = 0.54) and to other ranid frogs. Genetic subdivision among populations is much higher in R. pretiosa than in R. cascadae, particularly over the largest geographic distances (hundreds of kilometers). A joint analysis of migration rates among populations and of effective sizes within populations (using MIGRATE) suggests that both species have extremely low migration rates, and that R. pretiosa have slightly smaller effective sizes. However, the slight difference in effective sizes between species appears insufficient to explain the large difference in genetic diversity and in large-scale genetic structure. We therefore hypothesize that low connectivity among the more widely-spaced R. pretiosa populations (owing to their patchier habitat), is the main cause of their lower genetic diversity and higher among-population differentiation. Conservation recommendations for R. pretiosa include maintaining habitat connectivity to facilitate gene flow among populations that are still potentially connected, and either expanding habitat or founding additional \u27backup\u27 populations to maintain diversity in the isolated populations. We recommend that special consideration be given to conservation of the Camas Prairie population in Northern Oregon. It is the most geographically isolated population, has the lowest genetic diversity (He = 0.14) and appears to be the only remaining representative of a major genetic group that is now almost extinct. Finally, because the six major groups within R. pretiosa are strongly differentiated, occupy different habitat types, and are geographically separate, they should be recognized as evolutionarily significant units for purposes of conservation planning

Comparative Analyses of Effective Population Size Within and Among Species: Ranid Frogs as a Case Study

It has recently become practicable to estimate the effective sizes (N e) of multiple populations within species. Such efforts are valuable for estimating N e in evolutionary modeling and conservation planning. We used microsatellite loci to estimate N e of 90 populations of four ranid frog species (20-26 populations per species, mean n per population = 29). Our objectives were to determine typical values of N e for populations of each species, compare N e estimates among the species, and test for correlations between several geographic variables and N e within species. We used single-sample linkage disequilibrium (LD), approximate Bayesian computation (ABC), and sibship assignment (SA) methods to estimate contemporary N e for each population. Three of the species-Rana pretiosa, R. luteiventris, and R. cascadae- have consistently small effective population sizes (\u3c50). N e in Lithobates pipiens spans a wider range, with some values in the hundreds or thousands. There is a strong east-to-west trend of decreasing N e in L. pipiens. The smaller effective sizes of western populations of this species may be related to habitat fragmentation and population bottlenecking

Forest in Sicily

The Sicilian forestal landscape is part of an agro-forestal environment where wood stations, often spatially organized on grazing, alternate to scrublands and cultivated areas. In Roman times, the island\u2019s forest surface amounted to about one million hectares, but the deforestation practices carried out to give room to agriculture, along the centuries, reduced this surface to about a third. Forests are still well preserved on mountains and above all on the Sicani, Madonie, and Nebrodi ranges and on Mt. Etna. On the remaining territory, the forest landscape is quite irregular and characterized by small stations within agricultural and grazing territories. On the basis of the last Regional Forests Inventory, today the total forestal surface amounts to 512 thousand hectares, but only 274 thousand are real woods; the remaining surface is made of maquis, shrublands, and grounds evolving into woods. The presence of so many areas evolving into woods is due to the fact that, on these areas, cultivation, and above all grazing, have been abandoned. Sicilian forests have been classified into 14 forest categories (9 of broadleaf trees, 3 of conifers, 2 of maquis and shrublands), subdivided into 58 forest Types; these forest categories have been defined on a physiognomic basis according to the prevailing species and then subdivided into types according to the vegetation dynamics

Comparative Analyses Of Effective Population Size Within And Among Species: Ranid Frogs As A Case Study

It has recently become practicable to estimate the effective sizes (N e) of multiple populations within species. Such efforts are valuable for estimating N e in evolutionary modeling and conservation planning. We used microsatellite loci to estimate N e of 90 populations of four ranid frog species (20-26 populations per species, mean n per population = 29). Our objectives were to determine typical values of N e for populations of each species, compare N e estimates among the species, and test for correlations between several geographic variables and N e within species. We used single-sample linkage disequilibrium (LD), approximate Bayesian computation (ABC), and sibship assignment (SA) methods to estimate contemporary N e for each population. Three of the species-Rana pretiosa, R. luteiventris, and R. cascadae- have consistently small effective population sizes (\u3c50). N e in Lithobates pipiens spans a wider range, with some values in the hundreds or thousands. There is a strong east-to-west trend of decreasing N e in L. pipiens. The smaller effective sizes of western populations of this species may be related to habitat fragmentation and population bottlenecking. © 2011 The Author(s). Evolution © 2011 The Society for the Study of Evolution

Data from: Dispersal ability and habitat requirements determine landscape-level genetic patterns in desert aquatic insects

Species occupying the same geographic range can exhibit remarkably different population structures across the landscape, ranging from highly diversified to panmictic. Given limitations on collecting population-level data for large numbers of species, ecologists seek to identify proximate organismal traits—such as dispersal ability, habitat preference and life history—that are strong predictors of realized population structure. We examined how dispersal ability and habitat structure affect the regional balance of gene flow and genetic drift within three aquatic insects that represent the range of dispersal abilities and habitat requirements observed in desert stream insect communities. For each species, we tested for linear relationships between genetic distances and geographic distances using Euclidean and landscape-based metrics of resistance. We found that the moderate-disperser Mesocapnia arizonensis (Plecoptera: Capniidae) has a strong isolation-by-distance pattern, suggesting migration–drift equilibrium. By contrast, population structure in the flightless Abedus herberti (Hemiptera: Belostomatidae) is influenced by genetic drift, while gene flow is the dominant force in the strong-flying Boreonectes aequinoctialis (Coleoptera: Dytiscidae). The best-fitting landscape model for M. arizonensis was based on Euclidean distance. Analyses also identified a strong spatial scale-dependence, where landscape genetic methods only performed well for species that were intermediate in dispersal ability. Our results highlight the fact that when either gene flow or genetic drift dominates in shaping population structure, no detectable relationship between genetic and geographic distances is expected at certain spatial scales. This study provides insight into how gene flow and drift interact at the regional scale for these insects as well as the organisms that share similar habitats and dispersal abilities

Rana cascadae microsatellite data

GENEPOP input file

Rana pretiosa microsatellite data

GENEPOP input file

Lithobates (Rana) pipiens microsatellite data

Lithobates (Rana) pipiens microsatellite dat

Rana luteiventris microsatellite data

GENEPOP input file

Appendix B. Additional description of landscape resistance methods and tables describing landscape resistance values and source data, correlation coefficients between resistance/distance values, mixed-effects modeling results for major genetic clusters of canyon treefrogs and Mexican spadefoots, and results of multiple regression with distance matrices.

Additional description of landscape resistance methods and tables describing landscape resistance values and source data, correlation coefficients between resistance/distance values, mixed-effects modeling results for major genetic clusters of canyon treefrogs and Mexican spadefoots, and results of multiple regression with distance matrices