Browsing by Subject "environmental heterogeneity"
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Item Effect of variation in nitrogen environment and legume and rhizobia genetics on the outcome of the legume-rhizobium mutualism.(2017-09) Nedveck, DerekThe legume-rhizobium mutualism has been studied for its agricultural importance from the nitrogen that the rhizobia fix in exchange for carbon from the plant, and additionally used as a model to understand the evolution of mutualisms. The objective of this research was to further understand the variation present in natural populations of legumes and rhizobia, and to use a population perspective to build upon the work done with inbred plant lines and single strains of rhizobia. I applied a gradient of nitrogen (N) to a single cultivar of Lotus corniculatus inoculated with a population of rhizobia to develop expectations of how L. corniculatus responds to N addition. I then used a full-factorial greenhouse experiment with natural populations of L. corniculatus and their associated rhizobia to assess the amount of variation present in natural populations, and how they respond to N addition. From this, I found that plant populations did not show variation in nodule traits that could affect rhizobial fitness, whereas rhizobial populations showed variation in all traits measured. The effect of N addition on L. corniculatus in general causes a decrease in nodule size, although when tested in the context of natural populations, there was a plant population-dependent effect, as some populations increased, decreased, or did not alter the size of their nodules. This work underscores the importance to incorporate population scale information in how this mutualism responds to varying environmental conditions. Furthermore, considering the amount of variation found in rhizobial populations, future work should focus on sampling legumes and their associated rhizobia in order to have a more accurate measure of the amount of variation present in the mutualism.Item An urban-rural spotlight: evolution at small spatial scales among urban and rural populations of common ragweed(2021-01-12) Kostanecki, Adam; Gorton, Amanda J; Moeller, David A; kosta025@umn.edu; Kostanecki, Adam; University of Minnesota Moeller LabUrbanization produces similar environmental changes across cities relative to their neighboring rural environments. However, there may be high environmental heterogeneity across an urban-rural gradient. Previous research in Minneapolis, MN, USA, found mixed evidence that urban and rural plant populations of common ragweed have locally adapted, and that urban populations exhibit greater among-population divergence in ecologically-important traits. To investigate whether there are parallel patterns of urban-rural trait divergence across different urban areas, we examined trait variation across an urban-rural gradient in a second city, St. Louis, MO, USA. We used growth chamber and greenhouse common environments to investigate variation in six traits within and among 16 populations of common ragweed (eight from each urban and rural area). Urban and rural plants diverged significantly in three of five traits, with rural plants having lower percent germination, greater height and lower leaf dissection index. We also found greater variance in plant height among urban compared to rural populations, potentially driven by heterogeneity in human management practices on urban populations. Patterns of urban-rural trait divergence (e.g. in flowering time) differ substantially from those found previously in the reciprocal transplant experiment in Minneapolis, contradicting the hypothesis of parallel evolution across different metropolitan areas. The results of this study suggest that there is considerable population variation in ecologically-important traits, but that urban populations do not consistently differ from neighboring rural populations.