Unraveling the evolutionary dynamics of high symbiont diversity in the fungus-farming ant genus Apterostigma: A phylogenomic approach

最著名的食用菌蚂蚁是Atta和Acromyrmex属的切叶蚂蚁，这两种蚂蚁是新大陆热带地区主要的植物收割动物。这些蚂蚁使用植物的叶子剪枝来培育一种最近进化的真菌物种，然后它们就会吃掉这些真菌物种。然而，一组更鲜为人知的无菌属真菌蚂蚁，培养的真菌物种的多样性比所有其他真菌蚂蚁的总和还要大。近缘种的无翅目昆虫培育出关系密切的真菌类群，但在蚂蚁和真菌4000万年的共同进化过程中，向远缘真菌类群的重大转变发生了多次。这项研究旨在更好地了解切叶蚂蚁及其培养的真菌的共同进化。这包括发展关于无翅目蚂蚁物种及其相关真菌的数量、多样性和分布的新知识，以及确定蚂蚁和真菌之间的进化关系。要解决的问题包括：为什么无翅果蚁属的切叶蚂蚁培养的真菌种类比所有其他真菌蚂蚁(切叶和不切叶)的总和更大？为什么一些无翅目蚂蚁物种只培养几种彼此关系密切的真菌，而另一些蚂蚁物种培养的却是只是远亲的多样真菌？这项研究的结果可能会使整个社会受益，因为种植真菌的蚂蚁为达尔文农业和达尔文医学的新兴领域提供了一种罕见的非人类模式系统，旨在通过研究类似的自然系统来改进人类农业和疾病管理。最近，从与切叶蚂蚁生活在一起的真菌和细菌物种中分离和描述了几种抗生素和抗疟疾喹诺酮，使它们的生物学与健康问题特别相关。此外，一些与切叶蚂蚁相关的真菌已经成为更有效生产生物燃料的模式。这项研究将通过对蚂蚁和真菌在自然界中分布范围内的蚂蚁和真菌进行全面的野外采集，并通过比较基于蚂蚁和真菌基因组数据的系统发育分析，记录无翅目蚂蚁和它们的真菌品种中是否存在共同物种模式。研究人员将使用有针对性的超保守遗传元件(UCES)浓缩来推断物种水平的系统发育。这些系统发育将被用来测试共同进化的假说，以及随着时间的推移宿主蚂蚁物种之间真菌物种的保真度和流动性。基因组UCE数据还将用于解决鲜为人知的无翅目蚂蚁物种复合体之间的物种边界(识别物种)。这对于重建特定物种的蚂蚁-真菌共同进化相互作用，以及修订蚂蚁分类和产生各种蚂蚁物种的图画识别检索表是必不可少的。

The best known fungus-farming ants are the leaf-cutting ants of the genera Atta and Acromyrmex, which are the dominant plant harvesting animals of the New World tropics. These ants use plant leaf cuttings in order to cultivate a single, recently evolved fungal species, which they then eat. However, a more poorly known group of fungus-farming ants in the genus Apterostigma, cultivate a greater diversity of fungal species than all other fungus-farming ants combined. Closely related species of Apterostigma cultivate closely related groups of fungi, but major shifts to distantly related fungal groups have occurred multiple times during 40 million years of co-evolution between Apterostigma ants and fungus. This research aims to better understand the co-evolution of leaf-cutting ants and the fungi they cultivate. This includes developing new knowledge about the numbers, diversity and distribution of Apterostigma ant species and their associated fungi, as well as determining the evolutionary relationships among both ants and fungi. Questions to be addressed include: Why do leaf-cutting ants in the genus Apterostigma cultivate a greater diversity of fungal species than all other fungus-farming ants (leaf-cutting and non-leaf-cutting) combined? Why do some Apterostigma ant species cultivate only a few fungi that are closely related to each other, while others cultivate diverse fungi that are only distant relatives? The results from this research may benefit society in general because fungus-farming ants provide a rare non-human model system for the emerging fields of Darwinian agriculture and Darwinian medicine, which aim to improve human agriculture and disease management through the study of analogous natural systems. Recently several antibiotics and antimalarial quinones have been isolated and described from fungi and bacterial species living in association with leaf-cutting ants, making their biology particularly relevant to issues of health. Further, some fungi associated with leaf-cutting ants have become models for more efficient biofuel production.This research will proceed by comprehensive field collecting of ants and fungi from nests throughout their distributions in nature, and documenting the presence or absence of co-speciation patterns in Apterostigma ants and their fungal cultivars, by comparing phylogenetic analyses based on genomic data for both ants and fungi. The researchers will employ targeted enrichment of Ultra-Conserved genetic Elements (UCEs) to infer the species-level phylogenies. These phylogenies will be used in testing hypotheses of co-evolution and fungal species fidelity and mobility among host ant species over time. The genomic UCE data will also be used to resolve species boundaries (identify species) among poorly known species-complexes of Apterostigma ants. This is essential for reconstructing species-specific ant-fungus co-evolutionary interactions as well as for revising ant taxonomy and producing pictorial identification keys to various ant species.