Abstract

Reproductive isolation between geographically separated populations is generally considered the most common form of speciation. However, speciation may also occur in the absence of geographic barriers due phenotypic and genotypic factors such as chemical cue divergence, mating signal divergence and mitonuclear conflict. Here we performed an integrative study based on two genome-wide techniques, 3RAD and ultraconserved elements, coupled with cuticular hydrocarbon and mtDNA sequence data, to assess the species limits within the E. ruidum species-complex, a widespread and conspicuous group of Neotropical ants for which heteroplasmy has been recently discovered in some populations from southeast Mexico. Our analyses indicate the existence of at least five distinct species in this complex, two widely distributed along the Neotropics and three that are restricted to southeast Mexico and that apparently have high levels of heteroplasmy. We found that species boundaries in the complex did not coincide with geographic barriers. We therefore consider possible roles of alternative drivers that may have promoted the observed patterns of speciation, including mitonuclear incompatibility, cuticular hydrocarbon differentiation, and colony structure. Our study highlights the importance of simultaneously assessing different sources of evidence to disentangle the species limits of taxa with complicated evolutionary histories.