Phylogenetic Relationships of Palaearctic Formica Species (Hymenoptera, Formicidae) Based on Mitochondrial Cytochrome b Sequences

Anna V Goropashnaya,Vadim B Fedorov,Bernhard Seifert,Pekka Pamilo

doi:10.1371/journal.pone.0041697

Abstract

Ants of genus Formica demonstrate variation in social organization and represent model species for ecological, behavioral, evolutionary studies and testing theoretical implications of the kin selection theory. Subgeneric division of the Formica ants based on morphology has been questioned and remained unclear after an allozyme study on genetic differentiation between 13 species representing all subgenera was conducted. In the present study, the phylogenetic relationships within the genus were examined using mitochondrial DNA sequences of the cytochrome b and a part of the NADH dehydrogenase subunit 6. All 23 Formica species sampled in the Palaearctic clustered according to the subgeneric affiliation except F. uralensis that formed a separate phylogenetic group. Unlike Coptoformica and Formica s. str., the subgenus Serviformica did not form a tight cluster but more likely consisted of a few small clades. The genetic distances between the subgenera were around 10%, implying approximate divergence time of 5 Myr if we used the conventional insect divergence rate of 2% per Myr. Within-subgenus divergence estimates were 6.69% in Serviformica, 3.61% in Coptoformica, 1.18% in Formica s. str., which supported our previous results on relatively rapid speciation in the latter subgenus. The phylogeny inferred from DNA sequences provides a necessary framework against which the evolution of social traits can be compared. We discuss implications of inferred phylogeny for the evolution of social traits.

Highlights

Large scale molecular studies have recently focused on the phylogeny of ant subfamilies [1,2]
The subgenus Raptiformica includes slave-making species, and the subgenera Formica s. str. and Coptoformica use temporary parasitism as a mode of founding new colonies, while the species of the subgenus Serviformica are used as slaves
The present study aims to explore the phylogenetic relationships of the Palaearctic subgenera within genus Formica

Summary

Introduction

Large scale molecular studies have recently focused on the phylogeny of ant subfamilies [1,2]. Distinctions in morphological characters used for taxonomy of the genus often tend to be clear in local faunas but vague and imprecise when closely related species are studied on a large geographical scale. The previous allozyme study on 13 Formica species of four European subgenera [20] agreed with the subgeneric division based on morphological and behavioral characters with some exceptions. Due to a low level of allozyme variation in Formica ants, the resolution of the relationships of the species was poor with these data and the phylogeny of the genus remained unclear [20]. The present study aims to explore the phylogenetic relationships of the Palaearctic subgenera within genus Formica. The species are geographically widely distributed and show, even within a single species, a wide variation of social structures from monogynous societies to large supercolonies which resemble those in invasive ants The results from the F. rufa group suggest recent radiation and we want to compare this pattern with that in the other subgenera

Materials and Methods

Results and Discussion

Serviformica