Yet More “Weeds” in the Garden: Fungal Novelties from Nests of Leaf-Cutting Ants

<div><p>Background</p><p>Symbiotic relationships modulate the evolution of living organisms in all levels of biological organization. A notable example of symbiosis is that of attine ants (<i>Attini</i>; <i>Formicidae</i>: <i>Hymenoptera</i>) and their fungal cultivars (<i>Lepiotaceae</i> and <i>Pterulaceae</i>; <i>Agaricales</i>: <i>Basidiomycota</i>). In recent years, this mutualism has emerged as a model system for studying coevolution, speciation, and multitrophic interactions. Ubiquitous in this ant-fungal symbiosis is the “weedy” fungus <i>Escovopsis</i> (<i>Hypocreales</i>: <i>Ascomycota</i>), known only as a mycoparasite of attine fungal gardens. Despite interest in its biology, ecology and molecular phylogeny—noting, especially, the high genetic diversity encountered—which has led to a steady flow of publications over the past decade, only two species of <i>Escovopsis</i> have formally been described.</p><p>Methods and Results</p><p>We sampled from fungal gardens and garden waste (middens) of nests of the leaf-cutting ant genus <i>Acromyrmex</i> in a remnant of subtropical Atlantic rainforest in Minas Gerais, Brazil. In culture, distinct morphotypes of <i>Escovopsis</i> sensu lato were recognized. Using both morphological and molecular analyses, three new species of <i>Escovopsis</i> were identified. These are described and illustrated herein—<i>E. lentecrescens</i>, <i>E. microspora</i>, and <i>E. moelleri</i>—together with a re-description of the genus and the type species, <i>E. weberi</i>. The new genus <i>Escovopsioides</i> is erected for a fourth morphotype. We identify, for the first time, a mechanism for horizontal transmission via middens.</p><p>Conclusions</p><p>The present study makes a start at assigning names and formal descriptions to these specific fungal parasites of attine nests. Based on the results of this exploratory and geographically-restricted survey, we expect there to be many more species of the genus <i>Escovopsis</i> and its relatives associated with nests of both the lower and higher <i>Attini</i> throughout their neotropical range, as suggested in previous studies.</p>