Dimensions: The Microbial Basis of Animal Speciation

生物多样性研究的一个核心问题是生命是如何从一个物种发展到现在的180万个物种的？对大多数动物来说，物种被归类为相互交配的个体群体。因此，新的动物物种可以通过基因突变产生，最终阻止两个群体产生杂交后代。然而，动物物种也可能通过获得数百万细菌的差异而发生变化，这些细菌通常生活在它们体内的共生关系中。这项研究解决了我们关于生物多样性如何产生的知识中的一个主要空白：宿主物种内的细菌共生群落是否会导致物种之间的杂交致死。为此，调查将利用几种不同杂交致死水平的模式昆虫纳索尼亚来解决三个目标：（一）检验关于细菌多样性是物种特异性的，在死亡的杂交种中异常减少的预测；（二）检验关于免疫基因在杂交种中优先错误表达的预测，并将特定基因表达差异与杂交种细菌群落的改变联系起来；（三）检验杂交种的死亡率是由于有益细菌减少还是由于致病菌增加。该研究将整合动物-微生物共生的遗传、分类和功能维度，以全面确定细菌共生体对模型系统中物种形成的影响。在分类学上，研究人员将描述新的细菌物种和现有的细菌物种的新功能。初步研究表明，纳索尼亚的细菌种类中有25%是科学上的新物种。遗传方面的研究将包括杂交对动物基因表达和它们的细菌共生体的遗传多样性的影响。从功能上讲，这项工作将揭示宿主在整个发育过程中对细菌共生体的依赖，并测试细菌共生体在新动物物种的产生中是否与基因一样重要。该项目的更广泛影响包括(i)在范德比尔特大学开设一门新的本科课程，让学生参与研究；（ii）创建一个在线存储库，用于收集本研究中发现的共生体的分类信息；（iii）通过可公开访问的数据库传播数据；（iv）以新的方式扩展对包括人类在内的所有动物的物种形成和共生关系的理解。最后，拟议的研究将为一名研究生、一名研究助理和几名参与志愿服务、实习和研究的本科生提供培训。

One of the central questions in biodiversity research is how did Life go from one to currently 1.8 million described species? For most animals, species are categorized as groups of individuals that interbreed with each other. Therefore, new animal species can arise by genetic mutations that ultimately prevent two groups from producing hybrid offspring. However, animal species may also change by acquiring differences in the millions of bacteria that typically live in symbiotic relationships inside them. This research addresses a major gap in our knowledge about how biodiversity arises: whether or not the symbiotic community of bacteria within a host species can contribute to hybrid lethality between species. To that end, the investigation will address three aims using several species of the model insect Nasonia that vary in their level of hybrid lethality: (i) Test the prediction that bacterial diversity is species-specific and abnormally reduced in hybrids that die (ii) Test the prediction that immunity genes are preferentially misexpressed in hybrids, and associate specific gene expression differences to the alterations in the hybrids' bacterial community (iii) Test if hybrid mortality is due to either a reduction in beneficial bacteria or an increase in pathogenic bacteria. The studies will integrate genetic, taxonomic, and functional dimensions of animal-microbe symbioses to comprehensively determine the consequences of bacterial symbionts on speciation in a model system. Taxonomically, the investigators will characterize new species of bacteria and existing species of bacteria in novel functions. Preliminary studies suggest 25% of the bacterial species in Nasonia are new to science. Genetic aspects of the studies will include the effects that hybridization can have on animal gene expression and the genetic diversity of their bacterial symbionts. Functionally, this work will unravel the host's dependence on bacterial symbionts throughout development, and test whether bacterial symbionts are as important as genes in the generation of new, animal species. Broader impacts of this project include (i) the development of a new undergraduate course at Vanderbilt University that will involve students in the research, (ii) the creation of an online repository for taxonomic information on the symbionts discovered in this research, (iii) dissemination of data through publically accessible databases, and (iv) extensions to understanding speciation and symbiosis in new ways across all animals, including humans. Finally, the proposed research will provide training to one graduate student, one research assistant, and several undergraduates involved in volunteerships, internships, and research for credit.