Disparate patterns of population genetic structure and population history in two sympatric penaeid shrimp species (Farfantepenaeus aztecus and Litopenaeus setiferus) in the eastern United States.

Analysing the population genetic structures of sympatric species provides opportunities to compare patterns of population genetic structure and phylogeography in order to gain insight into the factors that influence the development of the observed patterns. In this study, we compared the population genetic structures and phylogeographies of brown shrimp (Farfantepenaeus aztecus) and white shrimp (Litopenaeus setiferus), two sympatric penaeid shrimp species that inhabit the waters of the eastern USA, using sequence analysis of the mitochondrial DNA control region. Brown shrimp showed no significant phylogenetic structure or population subdivision, and closely related haplotypes were geographically dispersed. Mismatch analysis indicated that brown shrimp experienced a late-Pleistocene era sudden population expansion. In contrast, white shrimp had a complex haplotype phylogeny consisting of two distinct lineages and two less well-defined sublineages, and the haplotypes and lineages were geographically structured. Mismatch analysis for white shrimp also showed evidence of sudden population expansion, albeit for each lineage separately and more recently than in the brown shrimp. These disparate patterns may have developed as a result of species-specific differences in physiological tolerances and habitat preferences that caused greater fluctuations in white shrimp population sizes and reductions in long-term effective population size relative to that of the brown shrimp, and thereby increased the susceptibility of the white shrimp populations to stochastic genetic change.

Methodologies for conservation assessments of the genetic biodiversity of aquatic macro-organisms

International organizations and biodiversity scientists recognize three levels of biodiversity: genetic, species, and ecosystem. However, most studies with the goal of assessing biodiversity collect data at only a single level -- that of the species. Even when multiple levels of biodiversity are considered, usually only ecosystem diversity is also evaluated. Genetic diversity is virtually never considered. Yet, genetic diversity is essential for the maintenance of populations and species over ecological and evolutionary time periods. Moreover, because components of genetic diversity are independent of either species or ecosystem diversity, genetic diversity can provide a unique measure by which to assess the value of regions for conservation. Regions can be valuable for conservation of their genetic resources regardless of their levels of species or ecosystem uniqueness or diversity. In general, the same methods and statistical programs that are used to answer questions about population genetics and phylogenetics are applicable to conservation genetics. Thus, numerous genetic techniques, laboratory methods, and statistical programs are available for assessing regional levels of genetic diversity for conservation considerations. Here, we provide the rationale, techniques available, field and laboratory protocols, and statistical programs that can be used to estimate the magnitude and type of genetic diversity in regions. We also provide information on how to obtain commonly utilized statistical programs and the type of analyses that they include. The guide that we present here can be used to conduct investigations of the genetic diversity of regions under consideration for conservation of their natural resources.

Organizações internacionais e pesquisadores da biodiversidade reconhecem três níveis de biodiversidade: da genética, de espécies e de ecossistemas. Entretanto, muitos estudos desenvolvidos com o objetivo de estimar a biodiversidade coletam dados somente em um único nível -- o de espécies -- e, mesmo quando diferentes níveis da biodiversidade são considerados, usualmente apenas a diversidade de ecossistema é avaliada, sendo que a diversidade genética raramente é avaliada. No entanto, o conhecimento da diversidade genética é essencial para a manutenção das populações e das espécies em períodos ecológicos e evolutivos. Além disso, como seus componentes são independentes de outras espécies ou da diversidade de ecossistemas, a diversidade genética pode fornecer uma medida pela qual pode-se estimar o valor das regiões para conservação. As regiões podem ser valiosas para a conservação de seus recursos genéticos independente de seus níveis de espécies, ecossistema ou diversidade. Em geral, o método e o programa estatístico utilizados para responder questões sobre genética de populações e sobre filogenética são aplicáveis para conservação genética. Assim, numerosas técnicas genéticas, métodos laboratoriais e programas estatísticos estão disponíveis para estimar os níveis regionais da diversidade genética para conservação. Neste trabalho são apresentadas as razões, as técnicas disponíveis, os protocolos de campo e laboratório e os programas estatísticos que podem ser empregados para estimar a magnitude e o tipo de diversidade genética nas regiões. Também são dadas informações sobre como obter os programas estatísticos comumente utilizados e as formas de análises que eles incluem. O roteiro apresentado pode ser utilizado para conduzir investigações da diversidade genética de regiões em estudo visando à conservação de seus recursos naturais.

Methodologies for conservation assessments of the genetic biodiversity of aquatic macro-organisms

International organizations and biodiversity scientists recognize three levels of biodiversity: genetic, species, and ecosystem. However, most studies with the goal of assessing biodiversity collect data at only a single level -- that of the species. Even when multiple levels of biodiversity are considered, usually only ecosystem diversity is also evaluated. Genetic diversity is virtually never considered. Yet, genetic diversity is essential for the maintenance of populations and species over ecological and evolutionary time periods. Moreover, because components of genetic diversity are independent of either species or ecosystem diversity, genetic diversity can provide a unique measure by which to assess the value of regions for conservation. Regions can be valuable for conservation of their genetic resources regardless of their levels of species or ecosystem uniqueness or diversity. In general, the same methods and statistical programs that are used to answer questions about population genetics and phylogenetics are applicable to conservation genetics. Thus, numerous genetic techniques, laboratory methods, and statistical programs are available for assessing regional levels of genetic diversity for conservation considerations. Here, we provide the rationale, techniques available, field and laboratory protocols, and statistical programs that can be used to estimate the magnitude and type of genetic diversity in regions. We also provide information on how to obtain commonly utilized statistical programs and the type of analyses that they include. The guide that we present here can be used to conduct investigations of the genetic diversity of regions under consideration for conservation of their natural resources

Methodologies for conservation assessments of the genetic biodiversity of aquatic macro-organisms.

International organizations and biodiversity scientists recognize three levels of biodiversity: genetic, species, and ecosystem. However, most studies with the goal of assessing biodiversity collect data at only a single level--that of the species. Even when multiple levels of biodiversity are considered, usually only ecosystem diversity is also evaluated. Genetic diversity is virtually never considered. Yet, genetic diversity is essential for the maintenance of populations and species over ecological and evolutionary time periods. Moreover, because components of genetic diversity are independent of either species or ecosystem diversity, genetic diversity can provide a unique measure by which to assess the value of regions for conservation. Regions can be valuable for conservation of their genetic resources regardless of their levels of species or ecosystem uniqueness or diversity. In general, the same methods and statistical programs that are used to answer questions about population genetics and phylogenetics are applicable to conservation genetics. Thus, numerous genetic techniques, laboratory methods, and statistical programs are available for assessing regional levels of genetic diversity for conservation considerations. Here, we provide the rationale, techniques available, field and laboratory protocols, and statistical programs that can be used to estimate the magnitude and type of genetic diversity in regions. We also provide information on how to obtain commonly utilized statistical programs and the type of analyses that they include. The guide that we present here can be used to conduct investigations of the genetic diversity of regions under consideration for conservation of their natural resources.