The Consequences of Plant Species Diversity and Genetic Diversity for Populations, Communities, and Ecosystems
Crawford, Kerri Margaret
Rudgers, Jennifer A.
Doctor of Philosophy
Plant species diversity plays an important role in structuring communities and mediating ecosystem processes. Experiments have shown increasing plant species richness increases primary productivity, arthropod species richness, nutrient cycling, and community stability. Because effects of diversity are driven by variation among individuals, it is expected that genetic diversity within a species may mimic the effects of species diversity. Indeed, recent experimental evidence has confirmed this prediction. However, few studies have simultaneously investigated the effects of plant species diversity and genetic diversity in the same system. Therefore, the relative importance of species diversity and genetic diversity for community structure and ecosystem processes remains unresolved, and, importantly, potential interactions between levels of diversity have rarely been investigated. Interactive effects between genetic diversity and species diversity are particularly important to investigate, as natural systems are composed of several genotypes of many different species. Here, I investigated how plant species diversity and genetic diversity influenced populations, communities, and ecosystems. First, I tested whether genetic diversity within populations of a weedy annual plant, Arabidopsis thaliana, influenced population success. Increasing genetic diversity increased several measures of population viability, including seedling emergence, biomass production, flowering duration, and seed set. This result suggests that highly genetically diverse populations, such as populations created from multiple introductions, may be more able to colonize novel environments than less genetically diverse populations. Next, I simultaneously manipulated plant species diversity and genetic diversity within a dominant plant species in a common garden. This experiment addressed how both levels of diversity influenced a key ecosystem process, primary productivity. Plant species diversity and genetic diversity interactively influenced biomass production, with productivity increasing the most with genetic diversity when high levels of species diversity were present. Finally, I explored how plant diversity in the common garden influenced arthropod community composition, and found that genetic diversity influenced arthropods more strongly than plant species diversity. Altogether, my work underscores the importance of understanding how plant species diversity and genetic diversity interactively influence ecological communities in order to gain a more holistic view of how communities are structured and what factors control ecosystem functioning.
Ecology; Evolution & development