My research aims to understand the ecology of plant communities, with a particular interest in plant-pollinator interactions and the development of novel quantitative methods.
Biodiversity-ecosystem function relationships in natural systems
Ecosystem services (e.g. carbon storage, pollination) are derived from Earth’s incredible diversity and are essential for human life. It is unclear how these services will be affected by exceptional rates of extinction and frequent losses of species in response to human activities. Thus far, our perception of how biodiversity – including species identity, variation within and among species, and community-level metrics such as richness and evenness – drives ecosystem services relies on highly-controlled, unrealistic experiments, the results of which cannot be extended to the real world.
Resolving this knowledge gap is difficult, because ecologists lack analytical approaches suitable for the correlative structure of real world data, in which abundance is highly variable, community composition changes non-randomly, and richness is confounded with both. A new and promising approach for overcoming these impediments is an adaptation of evolutionary biology’s Price equation for use in ecology. The “ecological” Price equation partitions any spatial or temporal changes in ecosystem services into three different components of biodiversity: species richness; community composition; and the “context dependence effect”, which includes any factor that changes species’ abundances and/or per-capita contributions to ecosystem services.
Plant-pollinator interactions and pollination efficiency
Pollination ecology has often viewed plant-pollinator interactions in terms of abundance – how many flowers, and how many pollinators. However, we would never simply count the number of trees in a forest to estimate carbon storage, so pollination ecologists need to do better in this area. So far, little work has examined whether variation in pollinator behavior (nectar vs. pollen foraging, order or plant visits, etc.) or traits (body size, tongue length, hairiness, etc.) affects the actual benefit that plants receive per pollinator visit. For the past two years I have led field work on a NSF project during which I have carried out >1,000 such assessments while refining the field and laboratory methods (chemical staining and identification of pollen grains).
Clarifying definitions of ecological concepts
A well-known bit of Confucian wisdom is the importance of “calling things by their right name”. Less-known is the clarification that follows: “If language is not in accordance with the truth of things, affairs cannot be conducted successfully”. Ecologists have often run afoul of this advice, by developing terminology with no clear definition, or by applying existing terminology incorrectly. There is a need for quantitative ecologists to not only propose new theory, but actively clarify existing theory through reviews, examples, and easily-understood writing.
I want to identify ecological concepts that are missing or poorly defined, develop mathematical definitions, and communicate the properties of these concepts to other ecologists. One example of this research is my recent collaboration with Rutgers graduate student Molly MacLeod, in which we developed null models to provide the first quantitative definition of “rewiring”, or temporal changes in species interactions within bipartite networks (MacLeod and Genung et al. Ecology, 2016). In another example, focused on evolutionary ecology, I defined various concepts in “community and ecosystem genetics” (a field advocating that evolution acts on heritable traits in dominant species to predictably affect community structure and ecosystem function) by adding a third “community” level to Lewontin’s (1974) framework of “genotype” and “phenotype” space (Genung et al. Functional Ecology, 2011).
Effects of within-species variation in plants on associated communities and ecosystem processes
Not all individuals of a species are exactly the same; this is an obvious statement, but for many years, within-species variation was under-appreciated. Spurred on by the now-established field of community genetics, within-species genetic variation is recognized as a driver of community structure and ecosystem processes (Genung et al. Functional Ecology 2011). My PhD focused on indirect genetic effects (IGEs), which occur when the expression of genes in one individual affects the phenotype of an interacting individual. To my knowledge, my co-authors and I were the first to apply IGEs, which were well-established in behavioral ecology, to plant-plant interactions. We showed that IGEs between interacting plants could impact above- and below-ground biomass (Ecology Letters 2012, Ecology and Evolution 2013), herbivory (Oecologia 2012), pollinator visitation (Ecology Letters 2012, PLoS ONE 2010), decomposition rates (PLoS ONE 2013), and nutrient cycling (PLoS ONE 2013). Following the publication of this research, I was invited to write an article for The Scientist describing the many ways IGEs can manifest themselves in a range of biological disciplines (The Scientist 2014).
Effects of plant genotypic diversity on plant-pollinator interactions
Plant genotypic diversity (the number of unique genotypes in an area) can affect the number of pollinator visits received by a focal plant. This may be due to the overall increased productivity of plants growing in genotype mixtures, as plant in mixtures can produce more floral biomass and thus attract more visitors (PLoS ONE 2010). However, pollinator visitation is sometimes increased due to interactions between particular plant genotypes even in the absence of increases in floral biomass (Ecology Letters 2012). This may be due to synchrony in flowering time between neighboring plants, as plants with prolific floral displays may attract visitors when benefit neighboring plants. These genotype interactions have the potential to alter the coevolutionary dynamics of the interacting plants (Functional Ecology 2011), if the differences in pollinator visitation have consequences for plant fitness.
Do genetic and species-level differences affect plant range shifts caused by climate change?
Predicting the responses to species and communities to climate change is critically important. Along with Joe Bailey, I helped organize a special feature for Functional Ecology that included papers on the genetic mechanisms and evolutionary consequences of plant range shifts that are induced by climate change. In our contribution (Bailey et al. 2014, Functional Ecology), we suggested that indirect genetic effects (effects of the phenotype of one individual due to the expression of genes in a different individual), which can drive plant-soil feedbacks, local adaptation and genotypic diversity effects, just to name a few, will be important to understanding the consequences of climate change.