Cladistic analysis of Paraphasma (Phasmatodea: Pseudophasmatidae) highlights the importance of the phallic organ for phasmid systematics

Abstract

Abstract The internal male genitalia have been poorly investigated in Phasmatodea, remaining virtually unexplored in phylogenetic studies. Here we describe and illustrate the main phallic elements in several Neotropical stick insects, with emphasis on Paraphasma (Pseudophasmatidae), and present a phylogenetic analysis of this genus. The analysis included ten terminals in the ingroup and 18 in the outgroup, and was based on 32 characters of the phallic organ and 48 of external morphology. In order to compare these datasets in terms of phylogenetic signal and level of homoplasy, the consistency and retention indices of the cladogram were calculated separately for each of them, and partial analyses were also conducted using each dataset alone. The phylogenetic reconstruction revealed Paraphasma as polyphyletic and led us to propose a new, monotypic genus, Ecuadoriphasma gen. nov., three new combinations (Ecuadoriphasma cognatum, Paraphasma trianguliferum and Tithonophasma cancellatum) and place Oestrophora as a synonym of Paraphasma. Additionally, Olcyphides hopii and Paraphasma dentatum are synonymized with Paraphasma laterale. Both external and phallic characters were determinant for the topology obtained, and the latter were less homoplastic in the phylogenetic tree. Our results highlight the usefulness of phallic morphology for inferring phylogenetic relationships in Phasmatodea, especially among closely related genera and species.