MELANIZED FUNGI ON THE INTEGUMENTS OF HIGHER ATTINE ANTS

Seen as superorganisms, attine ants’ colonies host interactions between these insects and microorganisms, as well as among microorganisms. Fungi in the order Chaetothyreales, also known as black yeasts and their relatives, seem to be associated to these insects. For example, the genus Phialophora is found on the integument of Apterostigma ants and seems to inhibit actinobacteria species present in the same location. Also, Phialophora species have been found in low abundance in drones and gynes of Atta, a genus of higher attine. Nevertheless, little is known about the diversity and function of melanized fungi in two other genera of higher attines, Acromyrmex and Trachymyrmex. The present work aims to expand the knowledge on the presence of melanized fungi found on the integument of these insects. Through the utilization of two culture dependent methods, we assessed the diversity of black fungi on the integument of two higher attines’ species Acromyrmex coronatus (leafcutter) and Trachymyrmex tucumanus (non-leafcutter). After isolation, axenic cultures were obtained and identified based on either ITS region or partial tef1 gene sequencing, as well as morphological identification. Overall, 106 melanized fungi were recovered from both ant species, including: the ubiquous genus Cladosporium (44.3% of the isolates), fungi in the order Chaetothyriales (11.3%), the entomopathogen genus Acrodontium (8.5%), and fungi commonly found in leaf-litters, such as Oidiodendron (11.3%). Although the Chaetothyriales isolates have been identified to the genus level, we noticed that only one of the 11 isolates obtained does not belong to Herpotrichiellaceae, the same family Phialophora belongs to. Despite the highest number of isolates recovered from the integuments of A. coronatus ants (n= 72), no significant differences were observed between the diversity of both communities of melanized fungi. The observed abundance of Cladosporium and the fact that it was found on the integument of other higher attines suggest this fungus might be a symbiont of these ants. However, the characteristic saprotrophic lifestyle of the genus and the absence of any species or isolate that seem to be specific of the attine system so far, suggests that this fungus might be a transient in this system. On the other hand, the Chaetothyriales isolates formed distinct clades on the ITS filogram, grouping according to its original ant species, which might indicate specificity. However, more studies are needed to evaluate if there are Chaetothyriales species that coevolved with the attines and how they interact with the ants and their associated microorganisms.