Insects, Urbanization, and Climate Change
Cities are warmer than the surrounding landscape, causing some insects to grow, reproduce, or develop faster than they do outside the city. Elsa’s current work in the lab of Steve Frank looks at how urban warming alters the abundance and ecology of insects that live on and around street trees. For example, gloomy scale insects (the little bumps covering the branch in the photo) are most abundant in the hottest urban sites around Raleigh, NC. Understanding how plant-insect interactions work in cities today may give a preview of how the surrounding forests will also change with global warming.
Throughout the Amazon, a few species of ants build their nests in trees and embed seeds of specific plants in the nest walls. The plants grow, forming conspicuous hanging gardens. The plants don’t grow anywhere else, and if the ants don’t have the plants, their nests fall apart during the rainy season. (Click here to go to video of the ants picking up the seeds.)
What keeps these particular ants and seeds together? At least some of the ant-garden seeds attract only gardening ants, while other ants seem to dislike the seeds. The seeds have a strong smell, some components of which attract the gardening ants from a distance and help them find the seeds. Then additional chemical cues on the seeds prompt the ants to pick up the seeds and carry them to their nests.
At the University of Wisconsin-Milwaukee, Elsa studied North America’s only predatory butterfly caterpillar, Feniseca tarquinius. This caterpillar eats aphids, small immobile insects that excrete a sweet syrup that ants like to eat. The ants usually defend the aphids in exchange for this honeydew. But they leave Feniseca caterpillars alone.
It turns out the ants ignore the caterpillars because the aphid chemistry rubs off on the caterpillars, fooling the ants into thinking that the predators are just extra-large aphids.
Youngsteadt, E., Ernst, A. F., Dunn, R. R., and Frank, S. D. In press. Responses of arthropod populations to warming depend on latitude: evidence from urban heat islands. Global Change Biology.
Dale, A. G., Youngsteadt, E., and Frank, S. D. 2016. Forecasting the effects of heat and pests on urban trees: impervious surface thresholds and the ‘Pace to Plant’ technique. Arboriculture and Urban Forestry 42(3):181-191. link pdf
Reese, A., Savage, A. M., Youngsteadt, E., McGuire, K., Koling, A., Watkins, O., Frank, S. D., and Dunn, R. R. 2016. Urban stress is associated with variation in microbial species composition—but not richness—in Manhattan. The ISME Journal 10:751-760. link pdf
Youngsteadt, E., Appler, R.H., López-Uribe, M. M., Tarpy, D. R., and Frank, S. D.. 2015. Urbanization increases pathogen pressure on feral and managed honey bees. PLoS ONE 10: e0142031. link
Youngsteadt, E., Henderson, R. C., Savage, A. M., Ernst, A. F., Dunn, R. R., and Frank, S. D. 2015. Habitat and species identity, not diversity, predict the extent of refuse consumption by urban arthropods. Global Change Biology. link pdf
Savage, A. M., Hackett, B., Guénard, B., Youngsteadt, E., and Dunn, R. R. 2015. Fine-scale heterogeneity across Manhattan’s urban habitat mosaic is associated with variation in ant composition and richness. Insect Conservation and Diversity 8:216–228. link pdf
Youngsteadt, E., Dale, A. G., Terando, A. J., Dunn, R. R., and Frank, S. D. 2015. Do cities simulate climate change? A comparison of herbivore response to urban and global warming. Global Change Biology 21:97-105. link pdf
Youngsteadt, E., Guerra, P. and Schal, C. 2010. Divergent chemical cues elicit seed collecting by ants in an obligate multi-species mutualism in lowland Amazonia. PLoS ONE, 5:e15822. link
Booth, W., Youngsteadt, E., Schal, C. and Vargo, E. 2009. Characterization of 8 polymorphic microsatellite loci in the neotropical ant-garden ant, Camponotus femoratus. Conservation Genetics, 10:1401-1403. pdf link
Youngsteadt, E., Nojima, S., Häberlein, C.,Schulz, S. and Schal, C. 2008. Seed odor mediates an obligate ant-plant mutualism in Amazonian rainforest. Proceedings of the National Academy of Sciences, 105: 4571-4575. link
Youngsteadt, E., Fan, Y., Stay, B., and Schal, C., 2005. Cuticular hydrocarbon synthesis and its maternal provisioning to embryos in the viviparous cockroach Diploptera punctata. Journal of Insect Physiology, 51: 803-809. pdf
Youngsteadt, E., and DeVries, P. J., 2005. The effects of ants on the entomophagous butterfly caterpillar Feniseca tarquinius and the putative role of chemical camouflage in the Feniseca-ant interaction. Journal of Chemical Ecology, 31: 2091-2109. pdf
Neotropical Ant-Gardens: Behavioral and Chemical Ecology of an Obligate Ant-Plant Mutualism. link
In the News
CBC Quirks and Quarks “Ants perform street cleaner role on Broadway” December 6, 2014
Miller McCune “Curiouser and Curiouser” podcast February 2011
BioScience March 2008
NCSU News January 2008
ScienceNOW (“Smelly seeds”) January 2008