Aspectos da variação morfométrica em Triacanthagyna septima (Selys, 1857) (Insecta, Odonata, Aeshnidae), com notas sobre a sua taxonomia

Abstract

Triacanthagyna septima occurs from South Mexico and Greater Antilles to Southeastern Brazil. This species shows morphological variations of discrete nature in some structures of the wing venation. These variations were analyzed, using statistical methods, in 225 specimens from Southeastern Brazil. This analysis was carried out with the aim of describing the frequency patterns of the distinct character states and their correlation with quantitative body measurements of continuous nature. The occurrence of a certain number of cells in the components of the venation seems to be related to the wing dimensions. The intervals of variation in the values of the quantitative body measurements show their inferior limits in the males and the superior limits in the females, although a great deal of overlapping is observed. The statistical parameters of these variables are also greater in the females. The degree of morphometric distinction between males and females was evaluated using multivariate methodologies. The Discriminant Function Analysis showed a distinction between males and females based on a single significant axis. The significant variables were the length and width of the hindwings. Only a single significant axis was obtained in the Principal Component Analysis. The most important variables to the formation of this axis were also the length and width of the hindwings. A systematic catalogue including a great number of bibliographic references on T. septima is included in the present study. The dubious synonymy of T. Septima (Selys, 1857) and T. obscuripennis (Blanchard, 1843) was analyzed. A careful study of the original description of T. obscuripennis revealed that it is distinct from T. septima. The former species is related to the "trifida group" of Williamson (1923), while the latter does not belong to this group.