The leaf-cutting ant nest samples in this study were found
to host at least seven species of fungi ranging from generalist,
opportunistic Aspergillus spp. to Escovopsis , which specializes
in parasitizing the fungal crop of leaf-cutting ants (Currie
2001). Workers with functioning glands reduced both the
number and diversity of fungi found compared to treatments
with blocked glands. Only Escovopsis and the hyperabundant
A. fumigatus (Latgé 1999) were found in treatments where the
attending workers had functioning antimicrobial-producing
glands. Other fungi only occurred when the fungal crop was
not tended by workers with functional glands. Escovopsis has
evolved to be highly successful in natural leaf-cutting ant nest
environments (Currie 2001; Currie and Stuart 2001) and, as
our results show, is able to grow on the fungal crop even when
workers are producing antimicrobial compounds from their
metapleural glands. In this antimicrobial-rich setting,
Escovopsis is then able to exclude most of the opportunistic
fungi found in this study. Interestingly, however, our results
suggest that the specialist Escovopsis may be less dominant if
the antimicrobial secretions of the ants are reduced, through
blocking of themetapleural gland, in which setting other fungi
are far more competitive against Escovopsis. Consequently,
antimicrobial secretions may be more important for protection
against more opportunistic fungal pathogens than previously
thought.