Here, we describe a new species of Eusarcus and reconstruct the geographical evolution of its species group based on biogeographical event-based analysis. Eusarcus dandara sp. nov. has been recorded from Alagoas state, in northeastern Brazil, which represents an important range extension of the genus to the northern Atlantic Rainforest. We performed a cladistic morphological analysis based on new data and data from a previous systematic review of the genus to reconstruct the phylogenetic placement of the new species. This analysis resulted in six most parsimonious cladograms. We performed the biogeographical reconstruction using the Treefitter 1.3B1 algorithm for the clade of eight species that includes E. dandara sp. nov., and we tested the significance of the reconstructions. We found two alternative reconstructions depended on the differences in species relationships; both were significant (0.002 ≤ p ≤ 0.019). The phylogenetic placement of the new species is consistent with some expectations based on previous biogeographical studies of Atlantic Rainforest harvestmen. Reconstructions reveal the origin of the species group in the northeast region, in the Atlantic Rainforest plus interior and dry biomes, such as the Caatinga xeric shrubland and Cerrado savanna, with subsequent dispersal to the southeast region. Harvestmen are good models to study the historical biogeography of the Atlantic Rainforest, especially those species that are endemic, like most Eusarcus. We have demonstrated a complex history of the spatial evolution of the group and the importance of the adjacent drier biomes in the evolution of endemic organisms of the Atlantic Rainforest.
Opiliones are highly diverse in the Neotropics. Because of biological constraints, most harvestmen communities are associated with humid forests, exhibiting a high species diversity and endemism in these habitats. Drier formations, such as the Caatinga biome in northeastern Brazil, are less diverse and still considered under-sampled for the order. This study represents an effort to examine the aforementioned diversity by describing a new Gonyleptidae genus, Sertanejagen. nov., comprising two new species from Ceará state, Sertaneja bicuspidatasp. nov. and Sertaneja crassitibialissp. nov., and one new species from Rio Grande do Norte state, Sertaneja falcatasp. nov. A morphological cladistic analysis consisting of 20 terminals and 72 characters was performed to evaluate monophyly of the new genus and relate it to other Gonyleptidae. The analysis resulted in a single most parsimonious tree, corroborating Sertanejagen. nov. monophyly and relatedness to Gyndoides springmanni Soares & Soares, 1947, which in turn is the sister group to the DRMN clade. Taking into account the morphological traits and phylogenetic placement of Sertanejagen. nov., we chose to place the new genus in Pachylinae despite its polyphyletic status, given that the Sertanejagen. nov. clade is closely related to one of the Brazilian Pachylinae lineage. A resolution to the Pachylinae conundrum is needed to further explain the subfamily intricacies. Future research requires a larger scope, but currently, based on the new genus monophyly, support, and relatedness, we formally propose its creation and hope to shed light on the possible evolutionary scenarios for the subfamily.
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