Phylogenomic species delimitation in the ants of the Temnothorax salvini group (Hymenoptera: Formicidae): an integrative approach

摘要

The members of the Temnothorax salvini (Forel) species group are rarely collected, arboreally nesting ants of Central American forests. Previously thought to consist of two broadly dispersed species, recent collections have revealed a diversity of specimens that defy the two-species salvini group concept, but these are difficult to distinguish from each other based solely on morphology. I contrast several model-based approaches to species delimitation based on target-enriched genomic data. With molecular data from thousands of ultraconserved elements (UCEs), mitochondrial genome sequences and morphometric data, I use an integrated approach to species delimitation within the salvini group. Morphometric data were analysed using cluster analysis of principal component analysis (PCA) output. I use several popular methods of molecular species delimitation, including bPTP, BPP and STACEY, using a novel approach to filtering UCE data based on posterior predictive checks of nucleotide substitution model adequacy. In addition, I use iBPP to integrate morphometric PCA data and filtered UCE data in a 'total evidence' analysis. I use geographical range data for an independent contrast to discriminate among competing species delimitation hypotheses. Furthermore, I investigate the evolutionary timescale and biogeographical history of the group and find that it arose roughly 13 Ma ago in habitats associated with present day mid-to-high elevations of the mountain complex spanning southern Mexico to northern Nicaragua. In addition, dispersal of the salvini group into the Southern Sierra Madre in Mexico, lowland habitats and the southern Central American cordilleras in Costa Rica and Panama subsequent to mountain building in southern Central America 5-8 Ma ago appears to follow a taxon-cycle dynamic, with the lowland-adapted T. aztecus representing the most recent expansion phase. I find that the salvini group, which previously contained two named species, is composed of nine, all of which are morphologically diagnosable a posteriori.