Phylogeny of the spider genus IxchelaHuber, 2000 (Araneae: Pholcidae) based on morphological and molecular evidence (CO1 and 16S), with a hypothesized diversification in the Pleistocene

Abstract

The genus IxchelaHuber is composed of 20 species distributed from north-eastern Mexico to Central America, including the five new species described here from Mexico: Ixchela azteca sp. nov., Ixchela jalisco sp. nov., Ixchela mendozai sp. nov., Ixchela purepecha sp. nov. and Ixchela tlayuda sp. nov. We test the monophyly and investigate the phylogenetic relationships among species of the genus Ixchela using morphological and molecular data. Parsimony (PA) analysis of 24 taxa and 40 morphological characters with equal and implied weights supported the monophyly of Ixchela with eight morphological synapomorphies. The PA analyses with equal and implied weights, and separate Bayesian inference (BI) analyses for the CO1 gene (506 characters), concatenated gene fragments CO1+16S (885 characters), morphology+CO1 (546 characters) and the combined evidence data set (morphology+CO1+16S) (925 characters) support the monophyly of Ixchela. Our preferred topology shows two large clades; clade 1 has a natural distribution in the Mesoamerican biotic component, whereas clade 2 predominates in the Mexican Montane biotic component. The genus Ixchela diverged in the late Miocene, and the divergence between the internal clades in the genus occurred in the late Pliocene; by contrast, most of the speciation events seem to have occurred mainly during the Pleistocene, where climatic changes brought on by repeated glaciations played an important role in the diversification of the genus.