Insights into the evolution, biogeography and natural history of the acorn ants, genus Temnothorax Mayr (hymenoptera: Formicidae)

Matthew Prebus

doi:10.1186/s12862-017-1095-8

Abstract

BackgroundTemnothorax (Formicidae: Myrmicinae) is a diverse genus of ants found in a broad spectrum of ecosystems across the northern hemisphere. These diminutive ants have long served as models for social insect behavior, leading to discoveries about social learning and inspiring hypotheses about the process of speciation and the evolution of social parasitism. This genus is highly morphologically and behaviorally diverse, and this has caused a great deal of taxonomic confusion in recent years. Past efforts to estimate the phylogeny of this genus have been limited in taxonomic scope, leaving the broader evolutionary patterns in Temnothorax unclear. To establish the monophyly of Temnothorax, resolve the evolutionary relationships, reconstruct the historical biogeography and investigate trends in the evolution of key traits, I generated, assembled, and analyzed two molecular datasets: a traditional multi-locus Sanger sequencing dataset, and an ultra-conserved element (UCE) dataset. Using maximum likelihood, Bayesian, and summary-coalescent based approaches, I analyzed 22 data subsets consisting of 103 ingroup taxa and a maximum of 1.8 million base pairs in 2485 loci.ResultsThe results of this study suggest an origin of Temnothorax at the Eocene-Oligocene transition, concerted transitions to arboreal nesting habits in several clades during the Oligocene, coinciding with ancient global cooling, and several convergent origins of social parasitism in the Miocene and Pliocene. As with other Holarctic taxa, Temnothorax has a history of migration across Beringia during the Miocene.ConclusionsTemnothorax is corroborated as a natural group, and the notion that many of the historical subgeneric and species group concepts are artificial is reinforced. The strict form of Emery’s Rule, in which a socially parasitic species is sister to its host species, is not well supported in Temnothorax.

Highlights

Temnothorax (Formicidae: Myrmicinae) is a diverse genus of ants found in a broad spectrum of ecosystems across the northern hemisphere
The data matrix is nearly complete, with COI + COII missing for the outgroups and six ingroup taxa (Temnothorax dr02, T. mpala, T. rothneyi, T. smithi, T. cf. striatulus, and T. unifasciatus), the first exon of Wg missing for several outgroup taxa
I confirmed this by inspecting an argarose gel of the amplicon that usually contains intron; the fragment was shorter by approximately 100 bp in comparison to other taxa

Summary

Introduction

Temnothorax (Formicidae: Myrmicinae) is a diverse genus of ants found in a broad spectrum of ecosystems across the northern hemisphere These diminutive ants have long served as models for social insect behavior, leading to discoveries about social learning and inspiring hypotheses about the process of speciation and the evolution of social parasitism. While the biology of most species of Temnothorax is poorly known, several taxa are frequently used as model organisms for social insect behavior [5, 6] and ecology [7, 8] Studies on this genus have led investigators to discover new forms of social learning [9] and inspired hypotheses about speciation and the origins of parasitism [10].

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