Entomopathogenic fungi associated to leaf-cutting ants from Argentina

We investigated the entomopathogenic fungi associated with different species of leaf-cutting ants at several sites of Argentina.  Sites were located at two very different Phytogeographical Provinces.  We collected 45-50 ants/nest, and 9 to 13 nests/site.  From 2654 ants, we recorded 34.9% of ants infected with entompathogenic fungi (those which appeared from inside the ants at intersegmental membranes and/or joints of legs and antennae).  F. oxysporum, F. solani and Purpureocillium lilacinum were the most widely distributed, followed by Beauveria bassiana and Metarhizium sp.   Furthermore, F. oxysporum and F. solani had infected more ants at very site (5.4-19.8% and 3.7-29.6%, respectively).  We found from few to several rare species exclusively at particular sites.  C. equinulata var verticillata could be considered an endemic and/or indicator species of the Rey National Park, in the Yungas Phytogeographical Province, as it was found in several nests only at this site.   Rey National Park also exhibited the greatest richness but with very low abundances in comparison to the others sites, and intermediate richness per nest.  We also found that the proportion of infected ants varied substantially (0-58 %; 8.5-46 %; 16-52 %; 2-100 % and 2-68 %) among nests of the same site, as well as among sites (averages from 17.7 to 53.9 %), suggesting a different immunological status and/or different behavioral sanitary response and/or associations with symbiotic mutualists.  We conclude that the composition of entomopathogenic micoflora is mainly dependent on the microhabitat and Phytogeographical Province, and probably on ant defenses rather than on the species of ant.