| 英文摘要: | Understanding the origin and maintenance of biological diversity via speciation is a priority in evolutionary biology. Allopatric speciation, the divergence of species resulting from geographical isolation, is universally accepted. In contrast, sympatric speciation, the divergence of species in the absence of geographical isolation, is controversial. The current debate focuses on the relative contribution of sympatric speciation to the origin of biodiversity in general and on the underlying genetic mechanisms. Sympatric speciation has been repeatedly suggested to play a role in the origin of social parasitism, but this has not been comprehensively tested. Fungal farming ants are an ideal model system to study this process. The ant social parasites to be studied lack a worker caste and do not contribute to colony maintenance tasks. Instead they are specialized on using the host colony's resources to maximize their own reproduction. Social parasitism appears to be a highly successful life-history strategy, given that social parasites have evolved more than 100 times independently and convergently in ants. Thus, these ants represent a unique series of natural experiments that allow for testing speciation patterns, for studying the genetic conditions underlying speciation processes in a comparative context, and for testing specific hypotheses regarding the evolution, ecology, and behavior of social parasitism. To take full advantage of this study system, the evolutionary history that shaped the rich mosaic of host-parasite interactions will be reconstructed and species boundaries in the leaf-cutting ants will be clearly delimited. On a practical level, this will enable the better identification of these commonly encountered and economically highly important ant species, which is important to agricultural researchers and pest management. Additionally, this project has real ramifications for the improvement of human agriculture and disease management through the study of an analogous natural system. This project will train high school students, undergraduates, graduate students and a post-doctoral researcher. In the course of the project a public outreach experience featuring this research on leaf-cutting ants and fungus-farming ants in general will be designed and implemented at the Smithsonian National Museum of Natural History for a national and international audience.
This project will employ an integrative phylogenomic, population genetic, behavioral, and taxonomic approach to achieve the following research goals: (i) Phylogenomic markers, so-called ultra-conserved elements (UCEs), will be employed to infer a comprehensive, fossil-calibrated molecular phylogeny for the fungus-farming ants. The phylogeny will be used to test whether the six social parasite species evolved independently, whether parasites are the closest relatives of their hosts, and whether so-called "incipient" parasites evolved more recently than morphologically derived parasites. (ii) In addition to the ants, we will reconstruct the phylogeny of the symbiotic fungi cultivated by the leaf-cutting ants and their close relatives that together comprise so-called "higher ant agriculture" utilizing UCE phylogenomic markers that the researchers have recently developed for the fungal order Agaricales. Rare shifts to new fungal cultivars can be associated with ant speciation, and therefore the possible role of fungal association in the ant speciation process will be tested. (iii) An integrative approach, incorporating phylogenomic, population genetic, and morphological data, will be utilized to taxonomically revise and reclassify the leaf-cutting ant genera Atta and Acromyrmex, including the satellite parasite genus Pseudoatta. A process of reciprocal illumination will be applied to clearly delineate species boundaries and recognize cryptic species. A clear understanding of species boundaries in leaf-cutting ants, some of which are serious agricultural pests in Latin America, will allow for unambiguous species identification and inform targeted pest management strategies. |