Three ways to distinguish species: Using behavioural, ecological, and molecular data to tell apart two closely related ants, Camponotus renggeri and Camponotus rufipes (Hymenoptera: Formicidae)

Abstract

The closely related Camponotus renggeri and Camponotus rufipes (subgenus Myrmothrix) often live in sympatry in the Brazilian 'cerrado' savannah, and are distinguished by nuances in their blackish body colour and by the colour of the legs. Variation in morphological characters, however, makes species separation difficult and it has been suggested that the two species should be merged into one. As appropriate species identification is essential for studies in ecology and evolutionary biology, here we examine how natural history data (habitat preference, nesting biology) and molecular tools (nuclear and mitochondrial markers) perform in distinguishing sympatric populations of C.renggeri and C.rufipes. In our study area, C.rufipes was only seen in cerrado sensu stricto (scrub of shrubs and trees), whereas C.renggeri occurred in cerrado sensu stricto and cerradão (closed woodland). Camponotus renggeri nested underground or in fallen/erect dead trunks, whereas C.rufipes constructed distinctive nests of dry straw. Nest persistence through time was higher in C.rufipes, especially in the hot/rainy season. Nest distribution was random in C.renggeri and aggregated in C.rufipes. Molecular data consistently showed that, regardless of the source of genetic variation, the uppermost hierarchical level of divergence is observed between species, unambiguously differentiating the individuals identified as C.renggeri and C.rufipes as two independent evolutionary lineages. Mitochondrial data throughout the species' geographical ranges further confirmed a consistent genetic divergence between C.renggeri and C.rufipes along their distribution in Brazil. Our integrated approach combining morphological traits with natural history and molecular data confirms that C.renggeri and C.rufipes are valid species that can be separated in our study area relatively well.