Expanded view of the ecological genomics of ant responses to climate change

Abstract

Ecological genomics provides a window into potential responses of organisms to environmental change. Given the abundance, broad distribution and diversity of roles that ants play in many ecosystems, they are an ideal group to serve as ecosystem indicators of climatic change. At present, only a few whole-genome sequences of ants are available (19 of > 16,000 species), mostly from tropical and sub-tropical regions. To address this, we sequenced the genomes of seven whole colonies of six species from the genus Aphaenogaster: A. ashmeadi, A. floridana, A. fulva, A. miamiana, A. picea, and A. rudis. The geographic ranges of these species collectively span eastern North America from southern Florida to southern Canada, which comprises a latitudinal gradient in which many climatic variables are changing rapidly. For the six genomes, we assembled an average of 271,039 contigs into 47,337 scaffolds. The mean genome size was 270 Mb, which was comparable to that of other sequenced ant genomes (212.83 to 396.03 Mb). Looking across all currently sequenced ant genomes, we found support for a relationship between biogeographic variables and genome similarity and size. The strongest correlations were between genomic similarity and two main groups of climate variables relating to cold temperatures and precipitation. These results point to climate as a mechanism leading to genomic differences in ants and provide a point of departure for future work that explores the responses of ants to climatic change at the interface of ecology and evolution.