New species of the long-horned caddisfly Oecetis McLachlan, 1877 (Trichoptera: Leptoceridae) from the Atlantic Forest, Brazil and their evolutionary relationship

Abstract

Asymmetrical genitalia are reported from major Trichoptera subgroups and evolved multiple times independently. In Oecetis, it is a characteristic of the insconpicua group. However, certain species in other species groups also evolved an asymmetrical spiny projection on the phallotheca. Here, two new species with an asymmetric projection are described in the falicia group from the Brazilian Atlantic Forest, Espírito Santo state. Their phylogenetic relationships were investigated through a Bayesian analysis combining COI and morphological data. Additionally, we provide new records of Oecetis connata, O. inconspicua and O. paranensis from the Espírito Santo state, and O. connata and O. flinti from Minas Gerais state. Oecetis capixaba sp. nov. is placed with low support as the sister species of O. acanthostema, both presenting stout spine-like setae on the inner surface of the inferior appendage; the new species is diagnosed by the long spine-like setae on the inferior appendage, the narrow dorsolateral process of segment IX, and the phallic apparatus without apical projections. Oecetis ruschii sp. nov. is placed as a sister group of the clade including O. facilia and O. furcata, both presenting forked dorsolateral processes of segment IX; the new species is diagnosed by the dorsolateral process of segment IX with a lateral branching and the apex of inferior appendage wide and triangular. While the phylogenetic results should be considered preliminary and interpreted with caution, they indicate that the asymmetric projection evolved multiple times convergently in the avara, punctata, and falicia groups. The asymmetric genitalia in the falicia group seems to have evolved only in males since no correspondent asymmetry is described for females. The function of the asymmetrical projection remains unknown.