Invasive aphid species in the Hawaiian Islands:

Though none are native, at least 96 aphid species can be found on one or more of the Hawaiian Islands. As aphids cause both direct feeding damage and plant virus transmission, it is of great interest to identify the traits which have enabled these species, and not heterospecific congeners, to invade the archipelago. I am currently assimilating data on ecological and physiological traits believed to contribute to successful colonization of invasive species, for aphids. I am also currently investigating the extent to which intraspecific variation (i.e., both genotypic and phenotypic) has contributed to invasive success.

Population and community functioning in response to global climate change:

Although much has been learned in recent years about the effects of increased levels of CO2 and O3 on plants, exceedingly little is known about the effect of these gases on ecological interactions occurring across multi-trophic levels (e.g. plant/herbivore/natural enemy). My research at the Aspen FACE (Free-air CO2 and O3 enrichment) site in northern Wisconsin allows me to address how insect behavior, phenotypic plasticity, and the genetic structure of populations may be altered under atmospheric change. Preliminary data indicate that both behavior and phenotypic plasticity will change under increased levels of CO2 and O3. Furthermore, a changing climate may also result in changes in gene frequencies of insect populations, as parasitoids and predators exhibit different host preferences under different atmospheric conditions.

Insect alarm signaling:

Understanding how insects defend themselves from predators using alarm pheromones, allows insight not only into the evolution of intra-specific signaling, but also into how these compounds may be used to disrupt chemical communication among pest insects in IPM programs. As a model system, I conduct my research on pea aphids, Acyrthosiphon pisum, and multicolored Asian ladybird beetles, Harmonia axyridis. It is becoming clear that aphids use their cornicles (anatomical structures unique to aphids) to daub alarm pheromone droplets directly onto predators, so that clone-mates receive advance warning of a predator. By co-opting predator search behavior, information is relayed to clone-mates regarding predator location.

Phenotypic plasticity and mutualistic interactions:

I am also investigating aphid phenotypic plasticity in the presence and absence of ant mutualists, using facultative ant-tended cotton aphids, Aphis gossypii. Cotton aphids have high levels of plasticity, as a clone consists of any number of 4 alternate phenotypes, including winged and 'dwarf' individuals. Dwarf aphids have been viewed as a 'resistant phenotype' to declining host plant quality, however, cotton aphids also alter offspring phenotypes in response to chemical cues from searching predators. On plants previously searched by ladybird beetles, aphids produce primarily winged offspring. Subsequently, these winged aphids produce primarily dwarf offspring. Thus, chemical cues from searching predators generate transgenerational phenotypic changes in cotton aphids. The costs and benefits of producing dwarf offspring are a significant part of my ongoing research.