The overarching goal of my dissertation research has been to examine how trait variation within key species scales up to determine the organization of multi-trophic interactions (i.e. food webs). To do this, I’m using field-based common garden experiments with a dominant, host-plant species (Salix hookeriana) to identify the importance of genetic (G) and environmental (E) variation, and their interaction (G x E), in determining the phenotypes of host-plants, and the cascading effects of these phenotypes on their associated trophic interactions with arthropods.
Key findings so far:
(1) Provide further empirical support for the hypothesis that genetic variation in host-plant traits determines the assembly of insect-herbivore communities. There are 3 other important points though: (1) in contrast to the often-assumed importance of leaf secondary chemistry, we found that plant size was often a better predictor of herbivore community composition; (2) plant traits varied substantially in their degree of heritability (e.g. plant size was weakly heritable whereas leaf chemistry was highly heritable), which has important implications for predicting herbivore community assembly in different environments; (3) herbivore responses to host-plant genotype were weakly correlated at most, likely because different herbivore species were associated with different suites of plant traits (e.g. plant size and leaf secondary chemistry), which also exhibited weak correlations.
(2) Provide empirical support for the theoretical prediction that intraspecific genetic variation leads to increased food-web complexity. This occurred because heritable variation in host-plant size and leaf chemistry had direct and indirect effects on the assembly of its associated insect food web, resulting in different host-plant genotypes supporting unique compositions of trophic interactions (ms in review, link to presentations). More broadly, these results suggest that preserving genetic variation within key species may be critical for maintaining complex and robust food webs under future environmental change.
(3) Stay tuned for results from GxE experiments! Check out my blog-posts on “Ant-altered” and “Wind-swept” food webs for more details on my environmental manipulations.