Estrutura genética populacional do tubarão Squalus albicaudus (Chondrichthyes: Squaliformes) no oceano Atlântico, com base em marcadores genéticos moleculares
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Data
2022-01-28
Autores
Adachi, Aisni Mayumi Corrêa de Lima
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Universidade Estadual Paulista (Unesp)
Resumo
A pesca excessiva acarretam mudanças na estratégia de vida das populações dos organismos, especialmente com relação aos tubarões e raias, organismos que compõem o grupo dos elasmobrânquios. Assim, compreender a estrutura das populações torna-se uma importante ferramenta de conservação e manejo dos estoques de peixes. O gênero Squalus (família Squalidae) é atualmente composto por 35 espécies de tubarões que são popularmente chamados de cação-bagre. Este gênero constitui um dos grupos de tubarões mais problemáticos taxonomicamente devido a grande similaridade morfológica entre as suas espécies. No oceano Atlântico existem cerca de 11 espécies do gênero Squalus; contudo, no litoral brasileiro essas espécies nunca tiveram suas populações analisadas. Em decorrência desses fatores e da escassez de dados sobre a espécie Squalus albicaudus que ocorre na região Nordeste e Sudeste do Brasil, estão atualmente classificados como “dados deficientes” na Lista Vermelha da IUCN (International Union for Conservation of Nature). Neste contexto, o presente estudo tem como objetivo principal rastrear marcadores do tipo SNPs (Polimorfismo de Nucleotídeo Único) para avaliar a diversidade genética e a estrutura populacional da espécie S. albicaudus de ocorrência nas regiões Nordeste e Sudeste do Brasil . Uma biblioteca de ddRADSeq foi gerada a partir de 31 amostras de S. albicaudus obtidas em localidades do litoral de Pernambuco (n=14), Rio de Janeiro (n=4) e São Paulo (n=13). O rastreio dos marcadores foi realizado após o sequenciamento, sendo obtidos 455 SNPs. Os índices de diversidade genética foram baixos, tanto para a heterozigosidade observada quanto para a heterozigosidade esperada e o coeficiente de endogamia (FIS) foi negativo em todas as localidades analisadas, indicando um excesso de heterozigotos; o FST pairwise variou de 0.0365 (Rio de Janeiro x São Paulo) a 0,0157 (Pernambuco x São Paulo), demonstrando ausência de estruturação populacional. As análises de STRUCTURE e DAPC indicaram que os indivíduos pertecem a um agrupamento genético que estão distribuídos nas mesmas proporções entre as localidades e que estão relacionados; sendo que um alto fluxo gênico foi detectado entre os indivíduos, calculado pela estimativa do número de migrantes. O tamanho efetivo populacional (Ne) foi baixo. Neste primeiro estudo de avaliação da diversidade genética e da estruturação populacional da espécie S. albicaudus, os resultados obtidos apresentam evidências da ocorrência de panmixia para as localidades analisadas. Considera-se, pois, as informações obtidas essenciais para o conhecimento do estoque desta espécie, além de ressaltar a necessidade de estudos para o manejo adequado e sua conservação.
Overfishing causes changes in the life strategy of populations of organisms, especially in relation to sharks and rays, organisms that make up the group of elasmobranchs. Thus, understanding the structure of populations becomes an important tool for the conservation and management of fish stocks. The genus Squalus (family Squalidae) is currently composed of 35 species of sharks that are popularly called dogfish. This genus constitutes one of the most taxonomically problematic groups of sharks due to the great morphological similarity between their species. Besides the fact in the Atlantic Ocean there are about 11 species of the genus Squalus; however, these species of this group have never had their populations analyzed in the Brazilian coast. As a result of these factors and the scarcity of data on the species Squalus albicadus that occurs in the Northeast and Southeast regions of Brazil, they are currently classified as “data deficient” on the IUCN Red List (International Union for Conservation of Nature). In this context, the main objective of the present study is to track SNPs (Single Nucleotide Polymorphism) markers to assess the genetic diversity and population structure of the species S. albicaudus occurring in the Northeast and Southeast regions of Brazil. A ddRADSeq library was generated from 31 samples of S. albicaudus obtained from coastal locations in Pernambuco (n=14), Rio de Janeiro (n=4) and São Paulo (n=13). Marker screening was performed after sequencing, and 455 SNPs were obtained. The genetic diversity indices were low for both observed and expected heterozygosity and the inbreeding coefficient (FIS) was negative in all analyzed locations, indicating an excess of heterozygotes; the pairwise FST ranged from 0.0365 (Rio de Janeiro x São Paulo) to 0.0157 (Pernambuco x São Paulo), demonstrating the absence of population structuring. The STRUCTURE and DAPC analyzes indicated that the individuals belong to a genetic grouping that are distributed in the same proportions among the localities and that they are related; and a high gene flow was detected between individuals, calculated by estimating the number of migrants. The effective population size (Ne) was low. In this first study to evaluate the genetic diversity and population structure of the species S. albicaudus, the results obtained show evidence of the occurrence of panmixia for the analyzed localities. Therefore, the information obtained is considered essential for the knowledge of the stock of this species, in addition to emphasizing the need for studies for proper management and conservation.
Overfishing causes changes in the life strategy of populations of organisms, especially in relation to sharks and rays, organisms that make up the group of elasmobranchs. Thus, understanding the structure of populations becomes an important tool for the conservation and management of fish stocks. The genus Squalus (family Squalidae) is currently composed of 35 species of sharks that are popularly called dogfish. This genus constitutes one of the most taxonomically problematic groups of sharks due to the great morphological similarity between their species. Besides the fact in the Atlantic Ocean there are about 11 species of the genus Squalus; however, these species of this group have never had their populations analyzed in the Brazilian coast. As a result of these factors and the scarcity of data on the species Squalus albicadus that occurs in the Northeast and Southeast regions of Brazil, they are currently classified as “data deficient” on the IUCN Red List (International Union for Conservation of Nature). In this context, the main objective of the present study is to track SNPs (Single Nucleotide Polymorphism) markers to assess the genetic diversity and population structure of the species S. albicaudus occurring in the Northeast and Southeast regions of Brazil. A ddRADSeq library was generated from 31 samples of S. albicaudus obtained from coastal locations in Pernambuco (n=14), Rio de Janeiro (n=4) and São Paulo (n=13). Marker screening was performed after sequencing, and 455 SNPs were obtained. The genetic diversity indices were low for both observed and expected heterozygosity and the inbreeding coefficient (FIS) was negative in all analyzed locations, indicating an excess of heterozygotes; the pairwise FST ranged from 0.0365 (Rio de Janeiro x São Paulo) to 0.0157 (Pernambuco x São Paulo), demonstrating the absence of population structuring. The STRUCTURE and DAPC analyzes indicated that the individuals belong to a genetic grouping that are distributed in the same proportions among the localities and that they are related; and a high gene flow was detected between individuals, calculated by estimating the number of migrants. The effective population size (Ne) was low. In this first study to evaluate the genetic diversity and population structure of the species S. albicaudus, the results obtained show evidence of the occurrence of panmixia for the analyzed localities. Therefore, the information obtained is considered essential for the knowledge of the stock of this species, in addition to emphasizing the need for studies for proper management and conservation.
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Palavras-chave
Elasmobrânquios, Genética populacional, Peixe, SNPs, elasmobranchs, Population genetics, Fish, SNPs