There are three main questions that my research addresses:
(1) Is there a correlation between the genetic relatedness of eelgrass genotypes and how similar their traits are?
(2) What is the relative importance of functional vs. genetic differentiation for the outcome of interactions among eelgrass genotypes?
(3) What are the relative effects of relatedness, genotypic richness, and trait diversity on the performance of assemblages of eelgrass genotypes?
Correlation between genetic relatedness and trait differentiation
To test this relationship we collected 260 eelgrass plants from 5 sites and 3 tidal heights throughout Bodega Harbor. We identified each plant as a unique genotype and used this pool to calculate population allele frequencies and estimate the genetic relatedness of all possible pairs of genotypes. We selected a subset of 40 genotypes that covered a range of pairwise relatedness values and measured a suite of ecologically relevant traits including nutrient uptake rate, photosynthetic rate, phenolic content, rooting depth, leaf/rhizome growth rate, shoot propagation, and allocation to above vs. belowground biomass. We then used these traits measurements to calculate a multi-variate trait distance between all possible pairwise combinations of genotypes and looked for correlations with pairwise relatedness estimates. Surprisingly, we found no correlation between relatedness and trait distance in pairs of eelgrass genotypes.
Relative importance of functional vs. genetic differentiation
Functional trait differences and genetic distance are increasingly used as metrics to predict the outcome of species interactions and the maintenance of diversity. We apply these ideas to intraspecific diversity, with eelgrass genotypes, by explicitly testing the influence of trait distance and genetic relatedness on the outcome of pairwise interactions between eelgrass genotypes. We grew all possible combinations of 6 genotypes and monocultures of each in the field for a year. We found that increasing trait distance (but not relatedness) between eelgrass genotypes decreased the likelihood that both would persist over the course of the experiment, contrary to our expectations based on niche partitioning. In plots in which one genotype excluded another, the biomass and growth of the remaining genotype increased with the trait distance and genetic relatedness of the initial pair, presumably caused by some legacy of past interactions. Together these results suggest that sustained competition among functionally similar genotypes did not produce a clear winner, but rapid exclusion occurred among genotypes with distinct trait combinations. You can read more about the results here.
Relative influence of genotypic richness, relatedness, and trait diversity on assemblage performance
The patterns we observed in the pairwise experiment testing the effects of relatedness and trait distant on plant interactions may not hold true for assemblages of multiple genotypes because in mixtures individuals are interacting with several genotypes simultaneously with the potential for both positive and negative interactions and may disrupt patterns seen in pairwise interactions. To look for these effects, and to explicitly test the relative importance of the number vs. relatedness of genotypes in an assemblage for competition and performance, we conducted a field experiment crossing the genotypic richness and genetic relatedness of assemblages. We used the 40 genotypes that we measured traits on and examined the influence of trait diversity as well.