Population structure, long-term connectivity, and effective size of mutton snapper (Lutjanus analis) in the Caribbean Sea and Florida Keys

Genetic structure and average long-term connectivity and effective size of mutton snapper (Lutjanus analis) sampled from offshore localities in the U.S. Caribbean and the Florida Keys were assessed by using nuclear-encoded microsatellites and a fragment of mitochondrial DNA. No significant differences in allele, genotype (microsatellites), or haplotype (mtDNA) distributions were detected; tests of selective neutrality (mtDNA) were nonsignificant after Bonferroni correction. Heuristic estimates of average long-term rate of migration (proportion of migrant individuals/generation) between geographically adjacent localities varied from 0.0033 to 0.0054, indicating that local subpopulations could respond independently of environmental perturbations. Estimates of average longterm effective population sizes varied from 341 to 1066 and differed significantly among several of the localities. These results indicate that over time larval drift and interregional adult movement may not be sufficient to maintain population sustainability across the region and that there may be different demographic stocks at some of the localities studied. The estimate of long-term effective population size at the locality offshore of St. Croix was below the minimum threshold size considered necessary to maintain the equilibrium between the loss of adaptive genetic variance from genetic drift and its replacement by mutation. Genetic variability in mutton snapper likely is maintained at the intraregional level by aggregate spawning and random mating of local populations. This feature is perhaps ironic in that aggregate spawning also renders mutton snapper especially vulnerable to overexploitation

Introgressive Hybridization and the Evolution of Lake-Adapted Catostomid Fishes.

Hybridization has been identified as a significant factor in the evolution of plants as groups of interbreeding species retain their phenotypic integrity despite gene exchange among forms. Recent studies have identified similar interactions in animals; however, the role of hybridization in the evolution of animals has been contested. Here we examine patterns of gene flow among four species of catostomid fishes from the Klamath and Rogue rivers using molecular and morphological traits. Catostomus rimiculus from the Rogue and Klamath basins represent a monophyletic group for nuclear and morphological traits; however, the Klamath form shares mtDNA lineages with other Klamath Basin species (C. snyderi, Chasmistes brevirostris, Deltistes luxatus). Within other Klamath Basin taxa, D. luxatus was largely fixed for alternate nuclear alleles relative to C. rimiculus, while Ch. brevirostris and C. snyderi exhibited a mixture of these alleles. Deltistes luxatus was the only Klamath Basin species that exhibited consistent covariation of nuclear and mitochondrial traits and was the primary source of mismatched mtDNA in Ch. brevirostris and C. snyderi, suggesting asymmetrical introgression into the latter species. In Upper Klamath Lake, D. luxatus spawning was more likely to overlap spatially and temporally with C. snyderi and Ch. brevirostris than either of those two with each other. The latter two species could not be distinguished with any molecular markers but were morphologically diagnosable in Upper Klamath Lake, where they were largely spatially and temporally segregated during spawning. We examine parallel evolution and syngameon hypotheses and conclude that observed patterns are most easily explained by introgressive hybridization among Klamath Basin catostomids

Conservation genetics of cyprinid fishes in the upper Nueces River basin in central Texas

Sequences of the mitochondrial (mt) NADH dehydrogenase subunit 5 gene (ND5) were acquired to assess genetic diversity and female effective population size (Nef) of two forms of Cyprinella (C. lepida and C. sp. cf lepida) and two species of Dionda (D. serena and D. texensis) in headwaters of three rivers in the upper Nueces River basin in central Texas. As documented in prior studies, two divergent clades of haplotypes of mtDNA were found in both genera: one in the Frio and Sabinal rivers, representing C. lepida and D. serena; one in the Nueces River, representing C. sp. cf lepida and D. texensis. Levels of variation in mtDNA from C. lepida in the Sabinal River and D. serena in the Frio and Sabinal rivers were comparable to or considerably lower than values documented for populations of several threatened or endangered cyprinids. Estimates of Nef for C. lepida in the Frio River and C. sp. cf lepida in the Nueces River were low, suggesting that adaptive genetic variation through time may be compromised. Of all populations sampled, only D. texensis in the Nueces River appears at present to be genetically stable demographically. An unexpected finding was two individuals resembling C. lepida in the Frio River with a haplotype referable to C. sp. cf lepida; the origin of these individuals is unknown. Two other individuals resembling C. lepida but with haplotypes of mtDNA referable to C. venusta were found in the Frio River and presumably represent relatively recent hybrids. Results of our study indicate that C. lepida, C. sp. cf lepida, and D. serena in the upper Nueces River basin, especially in the Sabinal River drainage, are at appreciable genetic risk

Population Structure, Long-Term Connectivity, and Effective Size of Mutton Snapper (\u3ci\u3eLutjanus analis\u3c/i\u3e) In the Caribbean Sea and Florida Keys

Genetic structure and average long-term connectivity and effective size of mutton snapper (Lutjanus analis) sampled from offshore localities in the U.S. Caribbean and the Florida Keys were assessed by using nuclear-encoded microsatellites and a fragment of mitochondrial DNA. No significant differences in allele, genotype (microsatellites), or haplotype (mtDNA) distributions were detected; tests of selective neutrality (mtDNA) were nonsignificant after Bonferroni correction. Heuristic estimates of average long-term rate of migration (proportion of migrant individuals/generation) between geographically adjacent localities varied from 0.0033 to 0.0054, indicating that local subpopulations could respond independently of environmental perturbations. Estimates of average long-term effective population sizes varied from 341 to 1066 and differed significantly among several of the localities. These results indicate that over time larval drift and interregional adult movement may not be sufficient to maintain population sustainability across the region and that there may be different demographic stocks at some of the localities studied. The estimate of long-term effective population size at the locality offshore of St. Croix was below the minimum threshold size considered necessary to maintain the equilibrium between the loss of adaptive genetic variance from genetic drift and its replacement by mutation. Genetic variability in mutton snapper likely is maintained at the intraregional level by aggregate spawning and random mating of local populations. This feature is perhaps ironic in that aggregate spawning also renders mutton snapper especially vulnerable to overexploitation

Genetic Studies of Hatchery-Supplemented Populations of Red Drum in Four Texas Bays

Abstract.-Genetic diversity, population structure, average long-term effective population size (N e ), and average long-term genetic migration rate of red drum Sciaenops ocellatus in each of four Texas bays were assessed using variation in 13 nuclear-encoded microsatellites among samples from the 2004 and 2005 cohorts. No significant differences in genetic diversity were detected among bays. Levels of gene diversity of red drum in each bay were equal to or greater than estimates reported for microsatellites in red drum sampled previously from two of the four bays and from other bays in the southeastern USA, including some that had not yet been supplemented with hatchery-raised fish. Tests of the homogeneity of allele and genotype distributions (including analysis of molecular variance) among the four bays were nonsignificant. Estimates of the migration rate (m) between bays ranged from 0.08% to 0.15%, with the average long-term number of migrants (calculated as N e 3 m) between bays estimated to range from 1.04 to 2.37 fish/generation. Estimates of average long-term N e in the four bays ranged from 1,302 to 1,581 fish and collectively were well within the range hypothesized to support sustained, long-term persistence. The estimates of N e also were, on average, five to six times higher than comparable estimates reported for the 1986-1989 red drum cohorts sampled from seven bays across the northern Gulf of Mexico. Adjustment of long-term N e in each of the four bays relative to bay-specific spatial parameters revealed a positive relationship with red drum abundance as measured by catch-per-unit-effort statistics compiled by the Texas Parks and Wildlife Department between 1982 and 2005. The observed high levels of genetic diversity, estimates of average long-term N e , and increased N e over the past 15-20 years are consistent with the hypothesis that the Texas Parks and Wildlife Department's stock enhancement program has not genetically compromised the resident red drum subpopulations in the four bays

Introgressive Hybridization and the Evolution of Lake-Adapted Catostomid Fishes

Hybridization has been identified as a significant factor in the evolution of plants as groups of interbreeding species retain their phenotypic integrity despite gene exchange among forms. Recent studies have identified similar interactions in animals; however, the role of hybridization in the evolution of animals has been contested. Here we examine patterns of gene flow among four species of catostomid fishes from the Klamath and Rogue rivers using molecular and morphological traits. Catostomus rimiculus from the Rogue and Klamath basins represent a monophyletic group for nuclear and morphological traits; however, the Klamath form shares mtDNA lineages with other Klamath Basin species (C. snyderi, Chasmistes brevirostris, Deltistes luxatus). Within other Klamath Basin taxa, D. luxatus was largely fixed for alternate nuclear alleles relative to C. rimiculus, while Ch. brevirostris and C. snyderi exhibited a mixture of these alleles. Deltistes luxatus was the only Klamath Basin species that exhibited consistent covariation of nuclear and mitochondrial traits and was the primary source of mismatched mtDNA in Ch. brevirostris and C. snyderi, suggesting asymmetrical introgression into the latter species. In Upper Klamath Lake, D. luxatus spawning was more likely to overlap spatially and temporally with C. snyderi and Ch. brevirostris than either of those two with each other. The latter two species could not be distinguished with any molecular markers but were morphologically diagnosable in Upper Klamath Lake, where they were largely spatially and temporally segregated during spawning. We examine parallel evolution and syngameon hypotheses and conclude that observed patterns are most easily explained by introgressive hybridization among Klamath Basin catostomids.Data Availability: All relevant data are within the paper and its Supporting Information files. Representatives of SSCP haplotypes and all sequences for phylogenetic analysis were deposited in GenBank (Accession numbers KU697909-KU698077)

Variation in carbon and nitrogen concentrations among peatland categories at the global scale

Publisher Copyright: © 2022 This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.Peatlands account for 15 to 30% of the world's soil carbon (C) stock and are important controls over global nitrogen (N) cycles. However, C and N concentrations are known to vary among peatlands contributing to the uncertainty of global C inventories, but there are few global studies that relate peatland classification to peat chemistry. We analyzed 436 peat cores sampled in 24 countries across six continents and measured C, N, and organic matter (OM) content at three depths down to 70 cm. Sites were distinguished between northern (387) and tropical (49) peatlands and assigned to one of six distinct broadly recognized peatland categories that vary primarily along a pH gradient. Peat C and N concentrations, OM content, and C:N ratios differed significantly among peatland categories, but few differences in chemistry with depth were found within each category. Across all peatlands C and N concentrations in the 10-20 cm layer, were 440 ± 85.1 g kg-1 and 13.9 ± 7.4 g kg-1, with an average C:N ratio of 30.1 ± 20.8. Among peatland categories, median C concentrations were highest in bogs, poor fens and tropical swamps (446-532 g kg-1) and lowest in intermediate and extremely rich fens (375-414 g kg-1). The C:OM ratio in peat was similar across most peatland categories, except in deeper samples from ombrotrophic tropical peat swamps that were higher than other peatlands categories. Peat N concentrations and C:N ratios varied approximately two-fold among peatland categories and N concentrations tended to be higher (and C:N lower) in intermediate fens compared with other peatland types. This study reports on a unique data set and demonstrates that differences in peat C and OM concentrations among broadly classified peatland categories are predictable, which can aid future studies that use land cover assessments to refine global peatland C and N stocks.Peer reviewe