title: How do cuticular hydrocarbons evolve? Physiological constraints and climatic and biotic selection pressures act on a complex functional trait.
abstract: Cuticular hydrocarbons (CHCs) cover the cuticles of virtually all insects, serving as a waterproofing agent and as a communication signal. The causes for the high CHC variation between species, and the factors influencing CHC profiles, are scarcely understood. Here, we compare CHC profiles of ant species from seven biogeographic regions, searching for physiological constraints and for climatic and biotic selection pressures. Molecule length constrained CHC composition: long-chain profiles contained fewer linear alkanes, but more hydrocarbons with disruptive features in the molecule. This is probably owing to selection on the physiology to build a semi-fluid cuticular layer, which is necessary for waterproofing and communication. CHC composition also depended on the precipitation in the ants' habitats. Species from wet climates had more alkenes and fewer dimethyl alkanes than those from drier habitats, which can be explained by different waterproofing capacities of these compounds. By contrast, temperature did not affect CHC composition. Mutualistically associated (parabiotic) species possessed profiles highly distinct from non-associated species. Our study is, to our knowledge, the first to show systematic impacts of physiological, climatic and biotic factors on quantitative CHC composition across a global, multi-species dataset. We demonstrate how they jointly shape CHC profiles, and advance our understanding of the evolution of this complex functional trait in insects.
authors.affiliation: Institute of Zoology, Faculty of Biology, University of Mainz, Johannes-von-Müller-Weg 6, 55099 Mainz, Germany menzelf@uni-mainz.de.
authors.forename: Florian
authors.identifier: http://orcid.org/0000-0002-9673-3668
authors.initials: F
authors.lastname: Menzel
authors.affiliation: Department of Entomology, National Museum of Natural History, Smithsonian Institution, Washington, DC 20560, USA.
authors.forename: Bonnie B
authors.initials: BB
authors.lastname: Blaimer
authors.affiliation: Department of Animal Ecology and Tropical Biology, Biocentre, University of Würzburg, Am Hubland, 97074 Würzburg, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Schmitt
mesh_terms: D000473:Alkanes; D000475:Alkenes; D060105:Animal Shells / Q000737:chemistry*; D000818:Animals; D001000:Ants; D005075:Biological Evolution; D017753:Ecosystem; D006838:Hydrocarbons / Q000737:chemistry*; D010641:Phenotype
chemical_list: D000473:Alkanes; D000475:Alkenes; D006838:Hydrocarbons
keywords: adaptation; climatic niche; cuticular hydrocarbons; selection pressure; viscosity; water loss rate