What makes you a potential partner? Insights from convergently evolved ant–ant symbioses

摘要

Mutualistic, commensalistic or parasitic interactions are unevenly distributed across the animals and plants: in certain taxa, such interspecific associations evolved more often than in others. Within the ants, associations between species of the genera Camponotus and Crematogaster evolved repeatedly and include trail-sharing associations, where two species share foraging trails, and parabioses, where two species share a nest without aggression. Camponotus and Crematogaster may possess life-history traits that favour the evolution of associations. To identify which traits are affected by the association, we investigated a neotropical parabiosis of Ca. femoratus and Cr. levior and compared it to a paleotropical parabiosis and a trail-sharing association. The two neotropical species showed altered cuticular hydrocarbon profiles compared to non-parabiotic species accompanied by low levels of interspecific aggression. Both species occurred in two chemically distinct types. Camponotus followed artificial trails of Crematogaster pheromones, but not vice versa. The above traits were also found in the paleotropical parabiosis, and the trail-following results match those of the trail-sharing association. In contrast to paleotropical parabioses, however, Camponotus was dominant, had a high foraging activity and often fought against Crematogaster over food resources. We suggest three potential preadaptations for parabiosis. First, Crematogaster uses molecules as trail pheromones, which can be perceived by Camponotus, too. Second, nests of Camponotus are an important benefit to Crematogaster and may create a selection pressure for the latter to tolerate Camponotus. Third, there are parallel, but unusual, shifts in cuticular hydrocarbon profiles between neotropics and paleotropics, and between Camponotus and Crematogaster.