RESUMO
Speciation in arthropods is usually coupled with marked changes in genital morphology, which explains the usefulness of genitalia in distinguishing closely related species. The present paper describes specimens that are assigned to separate species based on extreme size differences and colour pattern differences, but the shape of the genitalia is essentially identical. We argue that such cryptic species may be more common than currently assumed, but if marked morphological (non-genital) differences are missing, traditional taxonomic methodology is biased against discovering them. The two new species from the Brazilian Atlantic Forest are tentatively assigned to the genus Psilochorus: Psilochorus itaguyrussu n. sp. and Psilochorus ybytyriguara n. sp.
Assuntos
Animais , Aranhas/classificação , Especificidade da Espécie , BrasilRESUMO
The observation that genitalia, rather than other characters, are useful in distinguishing species has resulted in the statement that genitalia evolve relatively rapidly. In this paper we claim that relatively rapid evolution of genitalia may often be restricted to the shapes, numbers, and sizes of individual structures. In contrast, the more basic pattern, including the presence or absence of structures and their interrelationships (the bauplan), does not seem to evolve more rapidly than other (nongenital) aspects of morphology. We document this idea by contrasting two litter-dwelling pholcid species, Metagonia petropolis sp. n. and M. paranapiacaba sp. n., with their mostly leaf-dwelling congeners. Significant differences occur with regard to nongenital aspects of morphology as well as shapes of individual genital structures, but the bauplan of their genitalia is basically the same.