Cladistic analysis of the Brazilian troglobitic harvestmen genus Iandumoema Pinto-da-Rocha (Opiliones : Gonyleptidae) with the description of three new species: a brief exercise over the use of troglomorphisms in cladistic analysis

Abstract

From an ecological and evolutionary standpoint, troglobitic organisms are of special interest because they have evolved in, and are restricted to, the subterranean environment. Iandumoema Pinto-da-Rocha, 1997 stands out for being the only Brazilian harvestmen genus with more than one troglobitic species, with three species described from caves in Minas Gerais state. Traditionally, testing the monophyly of troglobitic groups is more challenging than testing groups that do not include troglobites. Many of their shared features might be the result of convergence or parallelism imposed by the cave environment, such as the absence of light, limited and infrequent availability of food resources and low population density, among others. In the case of Iandumoema, this becomes even more difficult because the genus is currently included in the species-rich and polyphyletic subfamily Pachylinae. This study tested the monophyly of this troglobitic genus and proposed the first phylogenetic hypothesis for Iandumoema based on cladistic analysis using morphological data. The analysis included all described species of Iandumoema and three new troglobitic species: I. cuca, sp. nov. (type locality: Itacarambi, Gruta da Água do João Ferreira); I. gollum, sp. nov. (type locality: Presidente Juscelino, Lapa D’Água); and I. stygia, sp. nov. (type locality: Montes Claros, Gruta do Cedro). The matrix comprises 79 characters and 28 terminal taxa: six species of Iandumoema; 14 of Pachylinae; six from other Gonyleptidae subfamilies; one species of Cosmetidae; and one of Metasarcidae. The cladistic analysis resulted in one parsimonious tree (339 steps, consistency index = 0.35, retention index = 0.56). Iandumoema is a monophyletic and well supported genus, nestled among Brazilian ‘Pachylinae’. Three new species are described and an identification key and ecological remarks for all six species of the genus Iandumoema is provided.