Section of Integrative Biology, University of Texas at Austin, Austin, TX, 78712, USA.
Department of Biology, University of Texas at Tyler, Tyler, TX, 75799, USA.
Microb Ecol. 2018 Aug;76(2):530-543. doi: 10.1007/s00248-017-1124-6. Epub 2017 Dec 28.
Group-living can promote the evolution of adaptive strategies to prevent and control disease. Fungus-gardening ants must cope with two sets of pathogens, those that afflict the ants themselves and those of their symbiotic fungal gardens. While much research has demonstrated the impact of specialized fungal pathogens that infect ant fungus gardens, most of these studies focused on the so-called higher attine ants, which are thought to coevolve diffusely with two clades of leucocoprinaceous fungi. Relatively few studies have addressed disease ecology of lower Attini, which are thought to occasionally recruit (domesticate) novel leucocoprinaceous fungi from free-living populations; coevolution between lower-attine ants and their fungi is therefore likely weaker (or even absent) than in the higher Attini, which generally have many derived modifications. Toward understanding the disease ecology of lower-attine ants, this study (a) describes the diversity in the microfungal genus Escovopsis that naturally infect fungus gardens of the lower-attine ant Mycocepurus smithii and (b) experimentally determines the relative contributions of Escovopsis strain (a possible garden disease), M. smithii ant genotype, and fungal cultivar lineage to disease susceptibility and colony fitness. In controlled in-vivo infection laboratory experiments, we demonstrate that the susceptibility to Escovopsis infection was an outcome of ant-cultivar-Escovopsis interaction, rather than solely due to ant genotype or fungal cultivar lineage. The role of complex ant-cultivar-Escovopsis interactions suggests that switching M. smithii farmers onto novel fungus types might be a strategy to generate novel ant-fungus combinations resistant to most, but perhaps not all, Escovopsis strains circulating in a local population of this and other lower-attine ants.
群居可以促进预防和控制疾病的适应性策略的进化。菌圃蚁必须应对两组病原体，一组是影响蚂蚁自身的病原体，另一组是它们共生菌圃的病原体。虽然大量研究表明了专门感染蚁菌圃的真菌病原体的影响，但这些研究大多集中在所谓的高等织菌蚁上，这些蚁被认为与两个白绒柄菇真菌类群广泛协同进化。相对较少的研究涉及低级 Attini 的疾病生态学，它们被认为偶尔会从自由生活的种群中招募（驯化）新的白绒柄菇真菌；因此，低级 Attini 与其真菌之间的协同进化可能比高等 Attini 弱（甚至不存在），高等 Attini 通常具有许多衍生的修饰。为了了解低级 Attini 蚂蚁的疾病生态学，本研究（a）描述了天然感染低级 Attini 蚂蚁 Mycocepurus smithii 菌圃的微真菌属 Escovopsis 的多样性，（b）实验确定了 Escovopsis 菌株（一种可能的花园疾病）、M. smithii 蚂蚁基因型和真菌栽培系对疾病易感性和菌落适应性的相对贡献。在受控的体内感染实验室实验中，我们证明了对 Escovopsis 感染的敏感性是蚂蚁-栽培物-Escovopsis 相互作用的结果，而不仅仅是由于蚂蚁基因型或真菌栽培系。复杂的蚂蚁-栽培物-Escovopsis 相互作用的作用表明，将 M. smithii 的农民转移到新型真菌类型可能是一种策略，可以产生对大多数（但不是所有）在当地群体中循环的 Escovopsis 菌株具有抗性的新型蚂蚁-真菌组合，这种策略适用于这种和其他低级 Attini 蚂蚁。
