The Interplay between Incipient Species and Social Polymorphism in the Desert Ant Cataglyphis.

In social insects, due to considerable polyphenism as well as high level of hybridization, the delimitation of species can be challenging. The genus Cataglyphis presents a high level of diversification, making it an excellent model with which to study evolutionary paths. Israel appears to be a "hot spot" for recent speciation in this genus. Although previous studies have described multiple species of Cataglyphis in Israel, a recent genetic study has questioned the existence of some of these historically described species. The present study focuses on an apparent species complex, the C. niger species complex which includes C. niger, C. savigyi, and C. drusus that are distinguishable by their mitochondrial DNA (and therefore named mitotypes) but not by their nuclear DNA. Using a multi-method approach (genetics, chemistry and behavior), we show that these mitotypes also differ in their social structures and are readily distinguishable by their cuticular hydrocarbons profiles. While most populations of the different mitotypes are allopatric, at our study site they are sympatric, but nonetheless maintain the observed differences between them. This raises the evolutionary question: Are these incipient species that have diverged with gene flow, or is this a case of social and chemical polymorphism that is maintained within a single species? Unveiling the interplay between social polyphenism and species segregation is at the core of evolutionary biology.