Dissertation Research: Diversity, Specificity, and Dynamics of Rhizobia-legumes Associations in Canyons of the Sonoran Desert

项目总结最近，人们对豆类-根瘤菌联合作为研究互惠关系的模式系统的兴趣越来越大，但一个主要的障碍是对土著群落的遗传结构知之甚少。我们知道关联可以是特定的，也可以是混杂的，但很少有研究描述原生豆科根瘤菌群落的空间或时间变化。我们打算研究自然环境中根瘤菌和豆科植物群落的空间和时间变化水平。我们将比较不同地理尺度的关联，从结核内部到峡谷之间。我们将考虑月份、季节和年份之间的变化，来衡量关联性如何随着时间的变化而变化。通过考虑协会的特殊性和土著社区的遗传结构，我们的目标是更好地理解共同进化塑造这种互惠关系的潜力。这项工作利用来自15个植物物种的1329个菌株的序列来表征植物分类群、微生境差异和季节差异对根瘤菌遗传变异和联合的专一性的影响。我们将通过详细描述自然系统，描述根瘤菌的遗传多样性，并测量在自然进化的种群中实现专门化和通用化的程度，来帮助理解这种重要的互惠关系。

PROJECT SUMMARYRecently, there has been growing interest in legume-rhizobia associations asmodel systems for studying mutualisms, but a central obstacle is that little is known aboutthe genetic structure of native communities. We know that associations can be specificor promiscuous, but very few studies have described spatial or temporal variation innative rhizobia-legume communities. We intent to examine levels of spatial andtemporal variation in communities of rhizobia and legumes in natural environments. Wewill compare associations at various geographic scales, from within nodules to betweencanyons. We will measure how associations change over time, considering variationbetween months, seasons, and years. By considering specificity of associations and thegenetic structure of a native community, our goal is to better understand the potential forcoevolution to shape this mutualism. The proposed work uses sequences from 1329strains from 15 plant species to characterize the effect of plant taxa, microhabitatdifferences, and seasonal differences on rhizobial genetic variation and specificity ofassociations. We will contribute to the understanding of this imporant mutualism byseeking to describe natural systems in detail, characterizing rhizobial genetic diversity,and measuring the extent that specialization and generalization is achieved in naturallyevolving populations.