Escovopsis (Ascomycota: Hypocreales), a parasite of Attini ant fungus gardens: new species, virulence and a critical review

• Ano de defesa: 2020
• Autor(a) principal: Caixeta, Marcela Cristina Silva
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Universidade Federal de Viçosa
• Palavras-chave em Português: Escovopsis; Escovopsioides; Micoparasitismo; Formicidae; Simbiose; Virulencia; Entomologia Agrícola
• Link de acesso: https://locus.ufv.br//handle/123456789/28976

Several other microorganisms are found in the colonies of attine ants, among them, other filamentous fungi, bacteria and yeasts. Some of these have well-defined ecological roles within the interaction, but it is likely that most of these relationships are still poorly understood. This is the case of Escovopsioides (Ascomycota: Hypocreales). It is known that this fungus is phylogenetically close to Escovopsis and that it has the ability to inhibit the growth of the ants’ mutualistic fungus, but less intensely than Escovopsis. In addition, from the recent standardization of methods for describing new species, two species previously considered within Escovopsis are being relocated into two new genera: Luteomyces and Sympodiorosea. These findings highlight the importance of investigating the diversity of Escovopsis and the other fungi associated with it. Taxonomic and phylogenetic studies contribute accuracy and help define ecological investigations of interactions within the complex systems that attine ant colonies represent. Escovopsis has long been considered a threat to these ants mainly because of its ability to damage the fungus consumed by ants, being classified as a mycoparasite (a fungus that parasitizes another fungus). However, this type of relationship has been described in experiments using sub-colonies (usually small colonies without a queen), fungus gardens fragments without the presence of the queen and workers, or even in co- cultivation experiments, where fungi are tested in isolation from other organisms that comprise the system. In the light of these considerations, the general objectives of this thesis were: (i) to contribute to knowledge of the diversity of Escovopsis found in association with leaf-cutting ants (a clade derived from the Attini tribe); (ii) to test the virulence of Escovopsis and Escovopsioides in colonies and (iii) to offer a critical review of the above considerations of Escovopsis and its relatives. In the first chapter, we sampled the fungus gardens of two species of leaf-cutting ants Acromyrmex subterraneus subterraneus and Acromyrmex balzani. From morphological and phylogenetic analyses, we propose three new species: Escovopsis R6, Escovopsis R12(associated with A. subterraneus subterraneus) and Escovopsis IT4-1 (associated with A. balzani). These results demonstrate how complex the network symbiotic found in attine ants can be, with the presence of different fungi species; in addition, they contribute to our understanding of the diversity and evolutionary history of Escovopsis. In chapter 2, we tested the hypothesis that Escovopsis and Escovopsioides have low virulence. For this, we divided colonies of A. subterraneus subterraneus in three different conditions: (i) queenright colonies – with queen, workers and fungus garden; (ii) queenless colonies – colonies without a queen and (iii) only fungus garden, without the queen and any workers. Our results showed that queenless colonies and fungus garden are fated to death regardless of exposure to fungi. Escovopsis and Escovopsioides were not able to cause the death of queenright colonies although Escovopsis shows some harmful effects on the colonies mainly in the first days after inoculation. Finally, in the third chapter we review the information contained in the literature on the mycoparasite of the attines’ fungus garden and present our ideas based on recent results. Contrary to previous studies, we propose that Escovopsis has low virulence in healthy colonies of attine ants, requiring a fundamental change in the current view of this fungus and its relatives. Keywords: Escovopsis. Escovopsioides. Mycoparasitism. Attine ants. Symbiosis. Virulence. Host-parasite interactions.