Estrutura genética populacional de Squatina guggenheim (Squatiniformes, Squatinidae), um endêmico e ameaçado cação-anjo do Atlântico Sudoeste
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Data
2020-07-23
Autores
Bunholi, Ingrid Vasconcellos
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Universidade Estadual Paulista (Unesp)
Resumo
Recursos pesqueiros compreendem importantes fontes econômicas e são essenciais em muitas regiões, porém, seu acesso não regulamentado e insustentável pode ocasionar acentuados declínios populacionais em muitas espécies. O cação-anjo Squatina guggenheim é um tubarão costeiro e endêmico do Atlântico Sudoeste e um dos principais alvos da pesca incidental. Em decorrência disso, esses tubarões apresentam fortes sinais de declínio populacional e estão atualmente classificados como “Em Perigo” na Lista Vermelha de Espécies Ameaçadas da International Union for Conservation of Nature (IUCN). A partir desse cenário, este estudo teve como objetivo avaliar os níveis de diversidade genética, estrutura populacional e aspectos demográficos de S. guggenheim no Atlântico Sudoeste, utilizando marcadores moleculares mitocondriais: Região Controle (RC), Citocromo B (CytB), Citocromo c oxidase subunidade I (COI) e o marcador molecular nuclear: internal transcribed spacer 2 (its-2). Detectamos altos índices de diversidade genética para os marcadores mitocondriais concatenados em 122 amostras (hRC+COI+CytB = 0.838; πRC+COI+CytB = 0.0017) e uma significativa estruturação populacional para os mesmos marcadores (ɸST RC+COI+CytB = 0.2992, p=0.001), enquanto o marcador nuclear demonstrou ausência de estruturação. A maior divergência genética foi observada entre as populações Sudeste do Brasil (SEBR) e Sul do Atlântico Sudoeste (SASO). As análises filogenéticas apresentam a presença de duas linhagens matrilineares simpátricas para a espécie, que divergiram 1,26 milhões de anos atrás (Mia) durante o Pleistoceno. Sinais de expansão demográfica leve foram detectadas no mesmo período geológico para ambas as populações, porém ocorridas em eventos glaciais-interglaciais diferentes. Essas descobertas refletem uma alta fragilidade desta espécie ameaçada de tubarão frente aos impactos da pesca local e fornecem informações relevantes para a elaboração de planos de conservação eficazes para preservar seu potencial evolutivo, principalmente nas regiões mais frágeis.
Fishery resources are essential economic sources and a profitable activity in many regions however its unregulated and unsustainable access can provide major population declines for many species. The angel shark Squatina guggenheim is a coastal and endemic shark from the southwestern Atlantic Ocean and has been the main victims of bycatch fishing. As a result, this shark set out high signs of population decline and is currently listed as “Endangered” by the International Union for Conservation of Nature (IUCN). In this view, the present study aimed to investigate the levels of genetic diversity, population structure and demographic aspects of S. guggenheim in the Southwest Atlantic using three mitochondrial DNA (mtDNA) molecular markers: mitochondrial control region (CR), Cytochrome b (CytB), Cytochrome c oxidase subunit I (COI) and one nuclear molecular marker: internal transcribed spacer 2 (its-2). We detected high mitochondrial genetic diversity in 122 samples for concatenated mtDNA markers hCR+COI+CytB = 0.838; πCR+COI+CytB = 0.0017 and significant population genetic structure (ɸST CR+COI+CytB = 0.2992, p=0.001), whereas no population structure was detected in the nuclear marker. The highest genetic divergence was observed between two populations: Southeast Brazil (SEBR) and South-Southwest Atlantic (SASO). Phylogenetics analyses show the presence of two sympatric matrilineal lineages, which diverged about 1.26 million years ago during the Pleistocene. Signs of smooth demographic expansion were also detected at the same geologic period for both populations but occurring during distinct glacial events. These findings reflect a high fragility for this endangered shark to local fishing impacts and provide relevant information for the elaboration of effective conservation plans to preserve its evolutionary potential mostly in the more fragile regions.
Fishery resources are essential economic sources and a profitable activity in many regions however its unregulated and unsustainable access can provide major population declines for many species. The angel shark Squatina guggenheim is a coastal and endemic shark from the southwestern Atlantic Ocean and has been the main victims of bycatch fishing. As a result, this shark set out high signs of population decline and is currently listed as “Endangered” by the International Union for Conservation of Nature (IUCN). In this view, the present study aimed to investigate the levels of genetic diversity, population structure and demographic aspects of S. guggenheim in the Southwest Atlantic using three mitochondrial DNA (mtDNA) molecular markers: mitochondrial control region (CR), Cytochrome b (CytB), Cytochrome c oxidase subunit I (COI) and one nuclear molecular marker: internal transcribed spacer 2 (its-2). We detected high mitochondrial genetic diversity in 122 samples for concatenated mtDNA markers hCR+COI+CytB = 0.838; πCR+COI+CytB = 0.0017 and significant population genetic structure (ɸST CR+COI+CytB = 0.2992, p=0.001), whereas no population structure was detected in the nuclear marker. The highest genetic divergence was observed between two populations: Southeast Brazil (SEBR) and South-Southwest Atlantic (SASO). Phylogenetics analyses show the presence of two sympatric matrilineal lineages, which diverged about 1.26 million years ago during the Pleistocene. Signs of smooth demographic expansion were also detected at the same geologic period for both populations but occurring during distinct glacial events. These findings reflect a high fragility for this endangered shark to local fishing impacts and provide relevant information for the elaboration of effective conservation plans to preserve its evolutionary potential mostly in the more fragile regions.
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Palavras-chave
Elasmobrânquios, Genética da conservação, Genética populacional, Marcadores moleculares, Peixes, Population genetics, Endemic species, Threatened species, Population genetics, Phylogeography