Phylogenetic placement of the ant Lasius atopus with implications for the evolution and subgeneric classification of the genus

Lasius is a conspicuous ant genus distributed throughout northern temperate regions, comprising over 100 currently recognized species. Its members have been widely studied from ecological and evolutionary perspectives, with special interest regarding the evolution of social parasitism and the ability to culture fungi.
Following rediscovery of the rare and morphologically aberrant species Lasius atopus, we infer the first phylogeny of the genus based on multiple protein-coding genes. Previous attempts at estimating the phylogeny of Lasius have relied on morphology or ribosomal and mitochondrial loci. We sampled representatives of all major clades within the genus for a total of 15 ingroup species. To analyze the data we took advantage of the latest developments in model-based phylogenetic inference, including objective selection of partitioning schemes, model averaging, and assessment of gene tree-species tree conflict.
Significantly, we recover a phylogeny that is different from those presented in earlier studies. Despite the novel topology, we confirm an earlier result of both social parasitism and fungiculture evolving twice within the group. Lasius atopus is revealed to be only distantly related to other members of the subgenus in which it was originally placed based on morphology and we find strong support for non-monophyly of two out of six Lasius subgenera. We discuss the utility of the current subgeneric classification. Our work provides the most robust framework for comparative approaches to studying the evolution and ecology of the genus to date, and will facilitate further research on the taxonomy and diversity of this important group of ants.