Avaliação morfológica e molecular do gênero Xiphopenaeus no Atlântico Ocidental e Pacifico: existe apenas uma espécie?
Data
2017-02-22
Autores
Carvalho-Batista, Abner [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
Espécies crípticas constituem um desafio ao conhecimento da biodiversidade e tem sido tema de um número cada vez maior de estudos nos últimos anos. O gênero Xiphopenaeus por 90 anos teve reconhecidamente duas espécies, Xiphopenaeus kroyeri no Atlântico e Xiphopenaeus riveti, no Pacífico. Contudo, nos últimos 20 anos, a taxonomia do gênero tem passado por grandes reviravoltas, com a sinonimização das duas espécies em 1997 com base em dados morfológicos, tornando o gênero monotípico, com X. kroyeri como a única espécie válida. E nos últimos dez anos além da revalidação de X. riveti baseada em dados moleculares, a existência de na verdade, duas espécies crípticas no Atlântico, veio a tona. Assim, o presente estudo averiguou utilizando ferramentas moleculares (os genes mitocondriais Citocromo c Oxidase Subunidade I e 16S rDNA) e morfológicas, o possível número de espécies constituintes do gênero Xiphopenaeus, e quais caracteres morfológicos podem ser utilizados na identificação destas. Foram analisados indivíduos provenientes de 16 localidades nos oceanos Atlântico e Pacífico. Foi detectada a divisão dos indivíduos analisados em cinco grupos, três no Atlântico, aqui denominadas a principio de A1, A2 e A3 e dois no Pacífico, P1 e P2, os quais pelas divergências genéticas observadas em ambos os marcadores empregados, mostraram-se constituir cinco diferentes espécies. Tal divisão foi suportada pelas demais análises empregadas (análises filogenéticas, Amova, rede de haplótipos). As fotografias obtidas por meio da microscopia eletrônica de varredura dos caracteres sexuais secundários dos machos mostraram diferenças morfológicas substâncias capazes de separar quatro das cinco espécies detectadas nas análises moleculares (uma vez que não foram encontrados machos do grupo P2). A análise comparativa com o holótipo de Xiphopenaeus kroyeri mostrou que espécie corresponde ao grupo A1 detectado no presente estudo, e que A2 e A3 são novas espécies a serem descritas. Por fim, valores significativos de Fst foram encontrados entre as populações de A1, porém sem um padrão geográfico, enquanto as demais espécies do Atlântico parecem ser panmíticas, e sinais de expansão demográfica recente e desvios da seleção neutra foram detectados nas três.
Cryptic species comprise a challenge to the knowledge of biodiversity, and they have been increasingly studied in past recent years. For 90 years, the genus Xiphopenaeus had recognized two species: Xiphopenaeus kroyeri, in the Atlantic, and Xiphopenaeus riveti, in the Pacific. In the last 20 years, however, the taxonomy of the genus has been changed; the synonymization of the species in 1997, based on morphological characters, turned the genus monotypic, with X. kroyeri as the only valid species. In the last decade, besides the revalidation of X. riveti based on molecular data, the existence of two cryptic species in the Atlantic came to light. Thus, the present study aimed to verify, using molecular (the mitochondrial genes Cytochrome Oxidase Subunit I and 16S rDNA) and morphological tools, how many species comprise the genus Xiphopenaeus, and which morphological characters can be used for their reliable identification. Individuals from 16 localities in Atlantic and Pacific oceans were analyzed. A structuration of the analyzed individuals into five groups was observed, three from the Atlantic (A1, A2 and A3) and two from the Pacific (P1 and P2). The genetic divergence observed indicates the existence of five different species. Such structuration was also supported by the phylogenetic analyzes, AMOVA and haplotype network. The images obtained by scanning electronic microscopy of secondary sexual characters of males showed morphological differences reliable enough to discriminate four of five species detected by molecular analyzes (there were no males from P2). The comparative analyzes of the holotype of Xiphopenaeus kroyeri showed that the specimen corresponds to A1 group, and A2 and A3 are new species to be described. Finally, statistically significant Fst values were found among A1 populations, although without a clear geographic pattern. The other species from Atlantic seems to be panmictic, with recent demographic expansion and deviation of neutral selection been observed for the three species.
Cryptic species comprise a challenge to the knowledge of biodiversity, and they have been increasingly studied in past recent years. For 90 years, the genus Xiphopenaeus had recognized two species: Xiphopenaeus kroyeri, in the Atlantic, and Xiphopenaeus riveti, in the Pacific. In the last 20 years, however, the taxonomy of the genus has been changed; the synonymization of the species in 1997, based on morphological characters, turned the genus monotypic, with X. kroyeri as the only valid species. In the last decade, besides the revalidation of X. riveti based on molecular data, the existence of two cryptic species in the Atlantic came to light. Thus, the present study aimed to verify, using molecular (the mitochondrial genes Cytochrome Oxidase Subunit I and 16S rDNA) and morphological tools, how many species comprise the genus Xiphopenaeus, and which morphological characters can be used for their reliable identification. Individuals from 16 localities in Atlantic and Pacific oceans were analyzed. A structuration of the analyzed individuals into five groups was observed, three from the Atlantic (A1, A2 and A3) and two from the Pacific (P1 and P2). The genetic divergence observed indicates the existence of five different species. Such structuration was also supported by the phylogenetic analyzes, AMOVA and haplotype network. The images obtained by scanning electronic microscopy of secondary sexual characters of males showed morphological differences reliable enough to discriminate four of five species detected by molecular analyzes (there were no males from P2). The comparative analyzes of the holotype of Xiphopenaeus kroyeri showed that the specimen corresponds to A1 group, and A2 and A3 are new species to be described. Finally, statistically significant Fst values were found among A1 populations, although without a clear geographic pattern. The other species from Atlantic seems to be panmictic, with recent demographic expansion and deviation of neutral selection been observed for the three species.
Descrição
Palavras-chave
Dendrobranchiata, espécies crípticas, identificação molecular, microscopia eletrônica de varredura, fluxo gênico, cryptic species, molecular identification, scanning electronic microscopy, gene flow