A central theme of our research is that the social environment – that is, the density and genetic composition of groups of interacting conspecifics – can significantly influence the life histories, productivity, and functioning of individuals and populations. Characterizing the distribution of genetic diversity at spatial and temporal scales relevant to these interactions thus enables a deeper understanding of the processes of trait evolution and diversification. Importantly, determining what aspects of intraspecific diversity most closely predict population success offers practical guidance to management and restoration efforts, in the face of contemporary anthropogenic change to marine coastal habitats.
Families: A genetic battleground
In many organisms conflicts among family members are inevitable, emerging from the relatedness asymmetries that are an inherent consequence of sexual reproduction. Fathers and mothers, sons and daughters, and brothers and sisters may sometimes die for each other, but given the right circumstances, they will also kill each other. The intensity of these conflicts depends upon (1) the opportunities for parents and offspring to interact and (2) the mating system. Marine organisms have diverse reproductive modes as well as high incidences of multiple mating and so provide unmatched opportunities for testing the role of conflict on the expression and evolution of many traits.
- The influence of mating systems on reproductive strategies, offspring size, and fitness in a clade of marine snails. All organisms face two allocation trade-offs: (a) many small vs. a few large offspring, and (b) present vs. future reproduction. Nowhere are these allocation trade-offs more apparent than in the variation in egg, offspring, and clutch size exhibited among marine invertebrates. This work focuses on a rarely considered, but pervasive, source of variation in egg and offspring size: the inevitable conflicts of interest that arise in families of sexually reproducing organisms over the optimal distribution of parental resources among siblings. This project characterizes how variation in the mating system of a marine snail (Nucella), through its effects on family conflict, accounts for variation in maternal provisioning and offspring size.
Neighbors: relatedness and ecosystem function
The scope for the social environment to influence ecological interactions extends far beyond the immediate family. A growing body of research demonstrates that genetic diversity within key species can play a critical role in determining community and ecosystem function. However, these studies consider only the number of genotypes in an assemblage, implicitly treating all genotypes as equally distinct from one another. But the degree of genetic differentiation between genotypes can be a key determinant of whether interactions among individuals are competitive or cooperative.
- Multiscale genetic diversity in the Eastern oyster, Crassostrea virginica. The genetic diversity of groups of interacting individuals, especially for ecological dominants or habitat-forming species, can have profound effects at the population, community, and ecosystem levels, influencing total biomass, resilience from disturbance, invasion success, and the abundance and diversity of other species. However, our understanding of the spatial scales at which genetic diversity is partitioned in natural populations is limited. More importantly, how this diversity is distributed at scales where it has been shown to affect these ecological processes remains largely unexplored. This work will examine the distribution and consequences of genetic diversity at multiple spatial scales in C. virginica, an economically and ecologically important species.
- Genetic diversity and kin structure of Zostera marina. We are quantifying the genetic and kin structures of two North Carolina seagrass populations expressing different life history strategies and to relate these structures to localized variations in resilience. This research will provide information essential to quantify population level variations in seagrass resilience to disturbance and will provide a new approach for managers to assess areas for restoration or preservation of Z. marina.
Intraspecific trait variation
Sea turtles and snail personalities