Community consequences of tri-trophic interactions

Links:

• Singer Home Page
   

• Evolutionary ecology of polyphagy
   

• Self-medication by polyphagous caterpillars
   

• Community ecology of the invasive gypsy moth caterpillar
   

• Evolutionary ecology of geographic variation in host use

Examples of Connecticut forest caterpillars that have been attacked by parasitoids: Orthosia rubescens (Noctuidae) with parasitic wasp larvae and tachinid fly eggs (left); Himella intractata (Noctuidae) with the cocoon of a parasitic wasp (middle); Phigalia titea (Geometridae) with tachinid fly eggs. On average, about 25% of these forest caterpillars die from parasitoids, but this mortality risk often depends on the host plant species. Photos by Michael S. Singer.

Tri-trophic interactions can cause trade-offs for insect herbivores in the fitness costs and benefits of using different host-plant species. Ecological trade-offs are theorized to play a central role in structuring ecological communities generally, particularly for species that share resources such as host plants. We hypothesize that patterns of herbivore-plant associations and possibly herbivore-herbivore associations arise from trade-offs between factors known to be consequential to herbivore fitness, such as food quality of host plants and refuge or defense from carnivores conferred by host plants. My lab is investigating this and related trade-off hypotheses in central Connecticut forests, focusing on polyphagous caterpillars, their host trees, and natural enemies (parasitoids, birds, and spiders). Current Master’s student, Tim Farkas, is investigating the interplay of top-down effects on the ecology and evolution of forest caterpillars. Some of this work has been done in collaboration with Dr. Kailen Mooney (Dept. Ecology and Evolutionary Biology, UC Irvine).

The basic observational data on caterpillar host-plant use and parasitism gathered for this project (begun in 2004) have been included in collaborative studies of geographic patterns in caterpillar parasitism (Stireman et al. 2005) and host specificity (Dyer et al. 2007) in temperate and tropical forests. I am continuing to work collaboratively with other scientists to further explore temperate to tropical gradients in the ecology and evolution of plant-caterpillar-parasitoid interactions.