Non-Additive Effects of Genotypic Diversity Increase Floral Abundance and Abundance of Floral Visitors

Background: In the emerging field of community and ecosystem genetics, genetic variation and diversity in dominant plant species have been shown to play fundamental roles in maintaining biodiversity and ecosystem function. However, the importance of intraspecific genetic variation and diversity to floral abundance and pollinator visitation has received little attention. Methodology/Principal Findings: Using an experimental common garden that manipulated genotypic diversity (the number of distinct genotypes per plot) of Solidago altissima, we document that genotypic diversity of a dominant plant can indirectly influence flower visitor abundance. Across two years, we found that 1) plant genotype explained 45 % and 92 % of the variation in flower visitor abundance in 2007 and 2008, respectively; and 2) plant genotypic diversity had a positive and non-additive effect on floral abundance and the abundance of flower visitors, as plots established with multiple genotypes produced 25 % more flowers and received 45 % more flower visits than would be expected under an additive model. Conclusions/Significance: These results provide evidence that declines in genotypic diversity may be an important but little considered factor for understanding plant-pollinator dynamics, with implications for the global decline in pollinators due t

Evolutionary Interactions in Invasive Species: the Importance of Plant-Soil Feedbacks to Local Adaptation and Rapid Evolution

Interactions between intraspecific plant variation and the environment can create evolutionary and ecosystem feedbacks, but the contribution of these feedbacks to the success of invasive plant species has rarely been explored or quantified. To test whether evolution occurs during the process of plant invasion I conducted three major experiments and a meta-analysis to test various aspects of this central question. First, I conducted a meta-analysis of studies that tested the Evolution of Increased Competitive Ability (EICA) hypothesis. The meta-analysis did not support EICA’s prediction that release from herbivores leads to reduced defenses and higher performance, but it showed that evolutionary change occurs in these traits across plant invasions. To test whether soils act as selective agents for invasive plants, I grew 13 populations of the invasive tree Ailanthus altissima in a common garden. Phenotypic variation showed that genetic differentiation correlated with climate and soil factors has occurred among populations, indicative of rapid evolution in response to local conditions. To test how soils act as selective agents, I conducted a study in which seeds from 3 populations were reciprocally transplanted in soils from those populations. Genetic variation and positive feedbacks to plant performance were expressed in soils with biotic communities, but not in sterilized soils. This indicates that soil biotic communities may select for plant performance and genetic variation in future generations. To test whether intraspecific variation associated with plant nutrient availability could create ecosystem feedbacks, I conducted a decomposition experiment of leaf litter from elevated carbon dioxide and nitrogen fertilization experiments. There were feedbacks that led to faster mass loss at control sites and in the nitrogen fertilized sites, but a negative feedback led to slower mass loss in elevated carbon dioxide sites. Environmental conditions, including anthropogenic alterations to environment, can create ecosystem feedbacks between intraspecific plant variation and processes that regulate soil nutrient availability. Overall, this dissertation indicates that evolution is broadly important in invasive plant species, that it occurs in response to climatic, abiotic soil properties, and soil biotic communities and that plant-soil feedbacks to ecosystem properties vary by environment, with theoretical and applied implications for all results

Appendix A. Population means, feedbacks, and soil properties.

Population means, feedbacks, and soil properties

Interactions between air pollution and terrestrial ecosystems: perspectives on challenges and future directions

Interactions between air pollution and terrestrial ecosystems play an important role in the Earth system. However, process-based knowledge of air pollution–terrestrial ecosystem interactions is limited, hindering accurate quantification of how changes in tropospheric chemistry, biogeochemical cycling, and climate affect air quality and its impact on humans and ecosystems. Here we summarize current challenges and future directions for advancing the understanding of air pollution–ecosystem interactions by synthesizing discussions from a multidisciplinary group of scientists at a recent Integrated Land Ecosystem–Atmosphere Processes Study (iLEAPS) early-career workshop. Specifically, we discuss the important elements of air pollution–terrestrial ecosystem interactions, including vegetation and soil uptake and emissions of air pollutants and precursors, in-canopy chemistry, and the roles of human activities, fires, and meteorology. We highlight the need for a coordinated network of measurements of long-term chemical fluxes and related meteorological and ecological quantities with expanded geographic and ecosystem representation, data standardization and curation to reduce uncertainty and enhance observational syntheses, integrated multiscale observational and modeling capabilities, collaboration across scientific disciplines and geographic regions, and active involvement by stakeholders and policymakers. Such an enhanced network will continue to facilitate the process-level understanding and thus predictive ability of interactions between air pollution and terrestrial ecosystems and impacts on local-to-global climate and human health