Data from: Coevolutionary patterns and diversification of ant-fungus associations in the asexual fungus-farming ant Mycocepurus smithii in Panama

Partner fidelity through vertical symbiont transmission is thought to be the primary mechanism stabilizing cooperation in the mutualism between fungus-farming (attine) ants and their cultivated fungal symbionts. An alternate or additional mechanism could be adaptive partner or symbiont choice mediating horizontal cultivar transmission or de novo domestication of free-living fungi. Using microsatellite-genotyping for the attine ant Mycocepurus smithii and ITS rDNA-sequencing for fungal cultivars, we provide the first detailed population-genetic analysis of local ant-fungus associations to test for the relative importance of vertical versus horizontal transmission in a single attine species. M. smithii is the only known asexual attine ant, and it is furthermore exceptional because it cultivates a far greater cultivar diversity than any other attine ant. Cultivar switching could permit the ants to re-acquire cultivars after garden loss, to purge inferior cultivars that are locally mal-adapted or that accumulated deleterious mutations under long-term asexuality. Compared to other attine ants, symbiont choice and local adaptation of ant-fungus combinations may play a more important role than partner fidelity feedback in the co-evolutionary process of M. smithii and its fungal symbionts.人们普遍认为，共生体垂直传播（vertical symbiont transmission）带来的伙伴保真度（partner fidelity）是维持培菌蚁（fungus-farming/attine ants）与其栽培真菌共生体之间互利共生关系稳定的核心机制。另一种或作为补充的机制，可能是通过适应性伙伴选择或共生体选择，介导栽培菌株的水平传播，或是对自由生活真菌开展从头驯化（de novo domestication）。我们针对培菌蚁Mycocepurus smithii开展微卫星基因分型（microsatellite-genotyping），并对其栽培真菌进行ITS核糖体DNA测序（ITS rDNA-sequencing），首次针对单一培菌蚁物种开展本地蚁-真菌关联的详细种群遗传分析，以验证垂直传播与水平传播的相对重要性。Mycocepurus smithii是目前已知唯一的无性生殖培菌蚁，其独特之处还在于其所栽培的菌株多样性远超其他所有培菌蚁。菌株转换可帮助蚁群在菌园损失后重新获取栽培菌株，或是清除本地适应性不佳、或在长期无性生殖过程中累积有害突变（deleterious mutations）的劣质菌株。相较于其他培菌蚁，在M. smithii与其真菌共生体的协同进化过程中，共生体选择以及蚁-真菌组合的本地适应，可能比伙伴保真度反馈发挥更为关键的作用。