Ant-gardens: a specialized ant-epiphyte mutualism capable of facing the effects of climate change

It is suggested that specialized mutualisms are more vulnerable to climate change. Ant-gardens (AGs) are a complex and specialized mutualistic system represented by epiphytic plants that specifically inhabit the arboreal nest built by canopy ants in tropical forests. Different ant-epiphyte ensembles constitute the AGs throughout the Neotropics. However, neither the environmental factors that determine their geographical distribution nor the effects of climate change on this canopy biological system are known. Here, we estimated the ecological niche and elevational distribution of the Neotropical AGs as an entity (regardless of species composition), and individually for six AG ant and 16 AG epiphyte species in order to determine and compare their current and future distributions (vulnerability), using two unrelated Global Circulation Models for the year 2070 under two Representative Concentration Pathways (RCP4.5: optimistic and RCP8.5: pessimistic). The current potential distribution of the AGs is discontinuous from Tamaulipas, Mexico, to Rio Grande do Sul, Brazil, in low elevation areas with high mean annual temperatures (> 25 °C) and precipitation (> 2400 mm). In contrast, the individual distributions of the AG ants and epiphytes tended not to follow to this climatic profile and were segregated by both latitude and elevation. The geographic distribution of most AG ant and epiphyte species diminished under climate change, while that of the AGs increased, even under the pessimistic scenario. This suggests that AGs allow the species that comprise them to broaden their ecological niche and be more resistant to climate change than they would be outside of this system.