Cryptic species divergence and the evolution of cuticular hydrocarbon profiles in parabiotic ants

The success of social insects is largely entwined with their elaborate communication system. Long-chained hydrocarbon molecules on the surface of insects make up specific profiles that function in species and nest-mate recognition, task allocation and mate-choice. Cuticular hydrocarbons (CHCs) thus facilitate the functioning of the sophisticated lifestyle of social insects, but aside from that also provide a barrier to pathogens and water loss. Due to this dual role in communication and ecological adaptation, CHCs are a strongly selected trait and are postulated to be drivers of rapid species divergence. This makes CHCs a particularly interesting trait to study, yet because of their dual role elucidating their genomic basis proved difficult in the past. Here, I examine the genomic basis of cuticular hydrocarbon diversity and evolution in mutualistic ants and investigate the interplay between CHC profiles and local environmental parameters. I focus on the two species Crematogaster levior and Camponotus femoratus that inhabit a shared nest, a so-called ant-garden, in large parts of the Amazonian rainforest. Both species were found to show striking diversity in their cuticular hydrocarbon profiles that were postulated to be a sign for cryptic species. This species complex thus provides an ideal model to study the evolution of CHC profiles either within highly diverse species or sister species. In the first chapter of this thesis, I elucidate species status of both Cr. levior and Ca. femoratus and show that both species split into morphologically nearly indistinguishable cryptic sister species (Cr. levior A and B, and Ca. femoratus PAT and PS) with exceptionally distinct CHC profiles. For this, morphometric measurements, DNA barcoding and the analysis of CHC profiles were combined in an integrative approach and provide three lines of conclusive evidence for the existence of cryptic species. I furthermore examine the distribution of the single species across the sampling range in French Guiana and find that in both ...