Investigação de variação morfológica alar em populações de borboletas gregárias e não-gregárias pertencentes a Tribo Ithomiini (Nymphalidae:Danainae)

Abstract

The order Lepidoptera covers insects of the holometabolic cycle, and host moths and butterflies. Currently, it is the second largest group of Hexapoda, with an estimated 180,000 species distributed almost all over the planet. Butterflies belonging to the Ithomiini tribe are known to be urban and occur in most tropics within forest galleries and near water courses. Some species of this tribe have a notable characteristic: during the dry season, they aggregate in areas within forests, which possibly comes from an adaptation to deal with adverse conditions, such as the frequency of low temperatures and low relative humidity of dry season. Due to this habit, Ithomiini butterflies are important bioindicators of preserved forests. This work aims to evaluate the existence and magnitude of sexual dimorphism on the alar form in Mechanitys polymnia, Hypothyris ninonia, Epityches eupompe and Mcclungia cymo, intending to test the hypothesis of sexual selection on these species. The animals were collected in the west of São Paulo, the wings were detached from the animals' thorax, bathed in a series of chemical solutions, photographed and analyzed. 13 to 21 landmarks were marked on the wings of the individuals. To quantify the shapes of the wings without the allometric effect, the multivariate regression of the Procrustes superposition was applied and, thus, the Cartesian coordinates were submitted to the Analysis of Discriminant between females and males, isolating factors that might influence the results as: taxa, phenological events, position and wing orientation. Posterior wings have the highest indexes for Mahalanobis distance, with values such as 20.2207; P = 0.0015 for Mechanitis polymnia, while, anterior wings although shows lower indexes in magnitude, still performs dissimilarity, in Hypothyris ninonia it is observed 7.4867 Md; P= <0,0001. The literature suggests that the effect of genera- specific have driven the shape of the wings to maximize flight in disparate cases. Thus, the findings of this study suggest sexual dimorphism for all tested species although plasticity is observed in terms of magnitude.