Browsing by Subject "urban adaptation"

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    The spatial scale of adaptation in common ragweed (Ambrosia artemisiifolia)
    (2019-09) Gorton, Amanda
    Environmental variation at both large and small spatial scales can influence the ecological and evolutionary trajectory of plant populations. Decades of common garden and reciprocal transplant experiments have demonstrated that local adaptation is widespread. However, most experiments examining local adaptation compare populations at a single spatial scale. For my dissertation, I combined field experiments and population genetics to examine how environmental variation at three spatial scales—small (i.e., among populations), regional (i.e., urban vs. rural), and continental (i.e., across latitudes)—shapes local adaptation in common ragweed (Ambrosia artemisiifolia L.). I found evidence for adaptation to urban environments and latitudinal gradients in climate. More specifically, I found evidence that phenotypic divergence at small spatial scales (e.g. within a city) can be greater than divergence found at larger spatial scales. Across latitudes, I found that photoperiod influences the fitness of common ragweed populations, and the relevant spatial scale for adaptation varies across life history stages. In addition, for northern populations of ragweed, I found that climate change is already causing maladaptation. Lastly, my population genomic work with RNA-seq identified new traits of interest that may be involved in local adaptation, including stomatal opening and closing and seed dormancy. I discuss these results with regard to how they can help us understand local adaptation more broadly and in turn predict how plants may respond to climate change.
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    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 Lab
    Urbanization 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.