Independent Evolution of Linear and Branched Cuticular Hydrocarbons in the Desert Ant Cataglyphis niger

The epicuticle of Cataglyphis niger is endowed with hydrocarbons comprising both linear and branched alkanes. The linear alkanes create an impermeable layer that protects the ants from desiccation, whereas the branched alkanes have communicative roles. Studies of the biosynthesis of both classes of hydrocarbons revealed disparate pathways, which suggests an independent evolution. It is hypothesized that the driving force for the evolution of alkanes was acquiring means for attaining impermeability. Being more abundant in foragers linear alkanes have been secondarily coopted for signaling colony foraging intensity and accordingly adjusting task allocation. The evolution of branched alkanes is less clear and seems more complex. They are biosynthetically derived from branched fatty acid that may have been the roots of their evolution. Due to their bactericide activity branched fatty acids evolved as protective means. Secondarily, the biosynthesis of these acids was coopted for producing branched alkanes for communicative roles. Using branched alkanes as signals is adaptive due to their numerous isomers that convey large informational content. Moreover, being hydrophobic they blend within the linear alkane layer that covers the ants’ body surface. However, branched alkanes decrease the cuticular impermeability, so hypothetically their proportions are the result of a tradeoff steady state.