Fungal symbionts in arboreal plant-ants
Veronika E. Mayer, Veronika Elisabeth Mayer , Maximilian Nepel , Rumsais Blatrix , Hermann Voglmayr
Department of Botany and Biodiversity Research, University of Vienna, Vienna, Austria; Department of Botany and Biodiversity Research, University of Vienna, Vienna, Austria ; Department of Microbiology and Ecosystem Science, University of Vienna, Vienna, Austria ; Centre d’Ecologie Fonctionnelle et Evolutive, CNRS UMR, Montpellier , France ; Department of Botany and Biodiversity Research, University of Vienna, Vienna, Austria
Fungus cultivation is astonishingly abundant in tropical ant–plant symbioses. In these symbioses, the plants host ants in specialized hollow structures called domatia, and often provide extrafloral nectar and food bodies for the ants’ nutrition. In return, ant-plants get protection against herbivores and pathogens, reduced competition through pruning of the surrounding vegetation, and nitrogen and possibly other nutrients from ant activity. Such symbioses have evolved many times independently and are widespread throughout the tropics. In recent years fungal symbionts of the ascomycete order chaetothyriales have been frequently found to be another partner. They occur in the domatia of ant occupied ant-plants in dark patches which are manured and used as a food source by the ants, reminding somehow to the fungus cultivation of Attine ants. Apart from fungi the patches also contain nematodes, bacteria and spores of opportunistic fungi. To investigate transmission mode and genetic variability of the fungal symbiont we investigated the fungiculture in the Azteca/Cecropia ant-plant association. We infer from our data, that in the latter system the transmission of the fungal symbiont for fungiculture is vertical. Compared to the chaetothyriales found in the environment, the genetic variability of the fungi from fungal patches is limited indicating a selection of strains beneficial to the ant partner. Young queens starting a new colony establish a fungal inoculum before egg laying. This and the fact that larvae are nourished with patch material points to a fundamental importance of fungus cultivation for successful ant colony founding in this ant-plant system.