Detecting morphological limits between parapatric species: cranial variation in Cerradomys (Cricetidae: Sigmodontinae) from northeastern Brazil

摘要: The advent of molecular and cytogenetic methodologies has improved our ability to recognize taxonomically distinctive, but morphologically cryptic forms. However, data are often based on small geographically restricted samples, hampering an objective evaluation alternative hypotheses such as limited and/or uneven sampling leading character discontinuity. It is important investigate this possibility, especially when it concerns species distributed parapatrically with confusing geographical limits. In study, we analyze patterns qualitative quantitative variation in cranial morphology a series Cerradomys samples from northeastern Brazil. These form north–south transect through region, where 2 parapatric distributions, C. vivoi langguthi , currently recognized. Our results show that characters regarded diagnostic for each vary gradually along the and, despite overall similarities among morphometric analysis reveals increase size gradual modification skull shape northern southern samples. findings indicate that, although distinction between supported by available karyological variation, these cannot be confidently distinguished only morphology, particularly those intermediate regions transect. We propose intensification regions, integrated use cytogenetic, molecular, morphological data, attempt refine resolution discontinuities population access limits recognized genus. O desenvolvimento de metodos analise citogenetica e tem determinado um aumento da resolucao na distincao taxonomica entre formas cripticas. Entretanto, dados moleculares geneticos sao geralmente oriundos amostras pequenas geograficamente restritas, frequentemente dificultando uma avaliacao objetiva hipoteses alternativas taxonomica, como que diferencas resultem, fato, falhas amostragem levando descontinuidade caracteres. E importante investigar essa possibilidade, especialmente quando envolve especies com distribuicao parapatrica limites geograficos confusos. Nesse trabalho, analisamos padroes variacao qualitativa quantitativa morfologia craniana em populacionais do Nordeste Brasil. Essas amostram transecto norte-sul atraves dessa regiao, onde parapatrica, C . atualmente reconhecidas. Nossos resultados mostram os caracteres qualitativos considerados diagnosticos para cada especie variam gradualmente ao longo transecto; mesma forma, apesar similaridade geral amostras, analises morfometricas revelaram no tamanho modificacao forma crânio das norte direcao sul. Apesar ser suportada pela cariologica disponivel, esses sugerem nao podem confiavelmente distintas somente base informacoes morfologicas, particularmente concerne regioes intermediarias transecto. Propomos essas regioes, alem uso integrado morfologicos, cariologicos moleculares, modo possibilitar deteccao descontinuidades assim acessar reconhecidas desse genero.