Técnicas multivariadas de morfometria geométrica são capazes de discriminar a forma dos crânios de Trachycephalus atlas Bokermann, 1966 e Trachycephalus nigromaculatus Tschudi, 1838 (Anura, Hylidae)?
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2020-03-19
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Universidade Estadual Paulista (Unesp)
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Trachycephalus atlas e Trachycephalus nigromaculatus são espécies da família Hylidae, Ordem Anura, que são morfologicamente semelhantes entre si. Apesar de T. atlas ser relatada em sua maioria em ambientes do Bioma Caatinga e T. nigromaculatus ocorrer em regiões costeiras da Mata Atlântica e interioranas em matas de galeria do Cerrado, ambas foram registradas em ambientes com fitofisionomia vegetal de transição de Mata Atlântica e Caatinga, especialmente no estado da Bahia. Devido à sua semelhança morfológica, não existe uma característica conspícua que ajude na diagnose destas espécies. Suas diferenças aparecem no canto e no girino. Neste estudo examinamos essas duas espécies utilizando a morfometria geométrica para analisar as variações da forma do crânio e determinar se essas variações são diagnósticas, encontrando amparo em dados estatísticos robustos. A morfometria geométrica (MG) tem sido empregada para resolver uma variedade de questões do mais amplo contexto de ecologia e evolução. Foram examinados 160 exemplares de coleções representativas das espécies, perfazendo o maior número possível de localidades registradas. Os crânios dos indivíduos foram fotografados em vista dorsal e lateral e 17 marcos anatômicos (landmarks) foram selecionados e digitalizados de acordo com a representatividade em estruturas homólogas da área craniana de todos os exemplares. Para as análises de morfometria geométrica foi utilizado o método de sobreposição de Procrustes com as coordenadas dos marcos para as duas vistas e posteriormente Análise de Componentes Principais (PCA), Análise de Variáveis Canônicas (CVA) e Função Discriminante. Os resultados revelaram uma tendência de separação das espécies em ambas vistas, com significância estatística, corroborando os dados da literatura. Quanto ao dimorfismo sexual, somente T. nigromaculatus apontou diferença entre os sexos, na vista lateral, sendo que os machos tendem a apresentar alongamento na região posterior do crânio. Os dados comparativos de localidade dos exemplares de Trachycephalus atlas mostraram diferenças significativas entre o grupo da série-tipo e demais grupos da espécie, nas duas vistas. Os grupos de Trachycephalus nigromaculatus apresentaram diferenças, exceto Rio de Janeiro, que foi semelhante a todos na vista dorsal e com Espírito Santo na vista lateral. A técnica da MG foi efetiva para pontuar o quanto e onde as alterações na forma do crânio diferem entre as espécies desse estudo.
Trachycephalus atlas and Trachycephalus nigromaculatus are species of the family Hylidae, Order Anura, which are morphologically similar to each other. Although T. atlas is mostly reported in environments of the Caatinga Biome and T. nigromaculatus occurs in coastal regions of the Atlantic Forest and inlands of Cerrado, both were recorded in environments with transition vegetation phytophysiognomy of the Atlantic Forest and Caatinga, especially in the state of Bahia. Due to its morphological similarity, there is no conspicuous characteristic that helps in the diagnosis of these species. Their differences appear in the call and the tadpole. In this study we examine these two species using geometric morphometry to analyze variations in the shape of the skull and determine whether these variations are diagnostic, finding support in more robust statistical data. Geometric morphometry (GM) has been used to solve a variety of issues in the broadest context of ecology and evolution. The sample consisted of 160 specimens of representative collections of the species, sampling the largest possible number of registered locations. The skulls of the individuals were photographed in dorsal and lateral views and 17 anatomical landmarks were selected and digitized according to the representativeness in homologous structures of the cranial area of all the specimens. For the analysis of geometric morphometry, the Procrustes superimposition method with the coordinates of the milestones for the two views was used, and later Principal Component Analysis (PCA), Canonical Variables Analysis (CVA) and Discriminant Function. The results revealed a tendency of species separation in both views, with statistical significance, corroborating the literature data. As for sexual dimorphism, only T. nigromaculatus showed a difference between the sexes, in the lateral view, with males tending to be elongated in the posterior region of the skull. The comparative data of locality of the specimens of Trachycephalus atlas showed significant differences between the group of the type series and other groups of the species, in the two views. The groups of Trachycephalus nigromaculatus showed differences, except Rio de Janeiro, which was similar to all in the dorsal view and with Espírito Santo in the lateral view. The MG technique was effective in scoring how much and where changes in the shape of the skull differ between the species in this study.
Trachycephalus atlas and Trachycephalus nigromaculatus are species of the family Hylidae, Order Anura, which are morphologically similar to each other. Although T. atlas is mostly reported in environments of the Caatinga Biome and T. nigromaculatus occurs in coastal regions of the Atlantic Forest and inlands of Cerrado, both were recorded in environments with transition vegetation phytophysiognomy of the Atlantic Forest and Caatinga, especially in the state of Bahia. Due to its morphological similarity, there is no conspicuous characteristic that helps in the diagnosis of these species. Their differences appear in the call and the tadpole. In this study we examine these two species using geometric morphometry to analyze variations in the shape of the skull and determine whether these variations are diagnostic, finding support in more robust statistical data. Geometric morphometry (GM) has been used to solve a variety of issues in the broadest context of ecology and evolution. The sample consisted of 160 specimens of representative collections of the species, sampling the largest possible number of registered locations. The skulls of the individuals were photographed in dorsal and lateral views and 17 anatomical landmarks were selected and digitized according to the representativeness in homologous structures of the cranial area of all the specimens. For the analysis of geometric morphometry, the Procrustes superimposition method with the coordinates of the milestones for the two views was used, and later Principal Component Analysis (PCA), Canonical Variables Analysis (CVA) and Discriminant Function. The results revealed a tendency of species separation in both views, with statistical significance, corroborating the literature data. As for sexual dimorphism, only T. nigromaculatus showed a difference between the sexes, in the lateral view, with males tending to be elongated in the posterior region of the skull. The comparative data of locality of the specimens of Trachycephalus atlas showed significant differences between the group of the type series and other groups of the species, in the two views. The groups of Trachycephalus nigromaculatus showed differences, except Rio de Janeiro, which was similar to all in the dorsal view and with Espírito Santo in the lateral view. The MG technique was effective in scoring how much and where changes in the shape of the skull differ between the species in this study.
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Hylinae, Lophiohylini, Análise interespecífica, Morfologia, Dimorfismo sexual, Morphology, Interspecific analysis, Sexual dimorphism