Relationships between plant and insect diversity
Positive relationships between plant and insect herbivore diversity could be driven by similar responses to environmental gradients or functional dependence of herbivores on plants. Working in Ozark glade grasslands with Jesse Miller and Ellen Damschen, we found support for a positive relationship between plant richness and grasshopper richness that became stronger after accounting for disturbance. Plant richness and time since disturbance had direct effects on grasshopper richness, whereas resources availability was mediated through plant richness (Miller et al. 2017). Overall, this work supports that plant and animal richness are functionally linked, rather than having similar responses to environmental gradients. Future work will investigate the functional traits (both plant and insect traits) that structure these communities.
Anthropogenic drivers of herbivore assemblages
Past agricultural land use generates persistent changes to soil conditions and plant communities in many ecosystems. In a study comparing grasshopper assemblages in post-agricultural sites to non-agricultural remnant longleaf pine woodlands, John Orrock and I (Hahn and Orrock 2015 J An Ecol) found a positive relationship between herbaceous plant cover and grasshopper abundance, but only in habitats without a history of agriculture. There were also taxa-specific effects of historic agriculture on grasshopper abundance, which resulted in shifting dominance from Schistocerca in sites with no history of agriculture to dominance of Melanoplus in sites with a history of agriculture. Collectively, these results suggest that the effect of historic agricultural land use extends beyond plants and soils to decouple plant-herbivore relationships, leading to a strong legacy of past agriculture on present-day insect herbivore assemblages.