Abstract
BackgroundFungus gardens of fungus-growing (attine) ants harbor complex microbiomes in addition to the mutualistic fungus they cultivate for food. Fungi in the genus Escovopsioides were recently described as members of this microbiome but their role in the ant-fungus symbiosis is poorly known. In this study, we assessed the phylogenetic diversity of 21 Escovopsioides isolates obtained from fungus gardens of leafcutter ants (genera Atta and Acromyrmex) and non-leafcutter ants (genera Trachymyrmex and Apterostigma) sampled from several regions in Brazil.ResultsRegardless of the sample locality or ant genera, phylogenetic analysis showed low genetic diversity among the 20 Escovopsisoides isolates examined, which prompted the identification as Escovopsioides nivea (the only described species in the genus). In contrast, one Escovopsioides isolate obtained from a fungus garden of Apterostigma megacephala was considered a new phylogenetic species. Dual-culture plate assays showed that Escovopsioides isolates inhibited the mycelium growth of Leucoagaricus gongylophorus, the mutualistic fungus cultivated by somes species of leafcutter ants. In addition, Escovopsioides growth experiments in fungus gardens with and without ant workers showed this fungus is detrimental to the ant-fungus symbiosis.ConclusionsHere, we provide clues for the antagonism of Escovopsioides towards the mutualistic fungus of leafcutter ants.
Highlights
Fungus gardens of fungus-growing ants harbor complex microbiomes in addition to the mutualistic fungus they cultivate for food
We obtained several Escovopsioides isolates from fungus gardens of different associated attine ant genera (Atta, Acromyrmex, Trachymyrmex and Apterostigma) and posed the following questions: (i) given that Escovopsioides was described from fungus gardens of Acromyrmex spp., do isolates of this fungus found on colonies of other genera of attine ants form a monophyletic clade?, (ii) are Escovopsioides from different associated attine ant species antagonists of the L. gongylophorus and the fungus gardens?, and (iii) is Escovopsioides capable to overcome the protective roles of the ant workers? We show that Escovopsioides associated with a wide range of ant species from various geographical areas belong to the same species (E. nivea)
We observed low genetic diversity in the main clade, comprising isolates associated with the higher-attine ant genera Atta, Acromyrmex and Trachymyrmex along with the type species, E. nivea CBS 135749T
Summary
Fungus gardens of fungus-growing (attine) ants harbor complex microbiomes in addition to the mutualistic fungus they cultivate for food. Fungi in the genus Escovopsioides were recently described as members of this microbiome but their role in the ant-fungus symbiosis is poorly known. Fungus-growing ants in the tribe Attini are found only on the American continent [1]. These insects cultivate fungi as the main food source for the colony [2]. As a subgroup within the higher attines, leafcutter ants in the genera Atta and Acromyrmex use fresh leaves and flowers as substrate to nourish the fungus cultivar. Leafcutter ants cultivate two phylogenetic clades of fungi including Leucoagaricus gongylophorus (Basidiomycota: Agaricales) [3]. Due to the high amount of leaves that leafcutter ants collect, these insects are considered agricultural pests, causing serious damage to several crops [4]
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