CAREER: Testing the adaptive significance of thermally-mediated behavioral responses of tropical and temperate dung beetles in a changing world

Temperature impacts the development and survival of insects, and warmer temperatures are expected to result in insect population declines. Insects could potentially compensate for temperature increases by shifting their behavior to take advantage of cooler microclimates in their environment. However, species that have evolved in relatively constant thermal environments, like tropical regions, may have limited ability to shift their behavior in response to temperature changes compared to species that have evolved in thermally variable environments, like temperate regions.

To understand the potential for behavioral shifts to buffer organisms from warming, this project will expose tropical and temperate dung beetles, a beneficial insect group, to temperature increases using laboratory experiments and field manipulations. Specifically, researchers will examine reproductive behaviors of dung beetles in response to warmer and more variable temperatures and investigate how behavioral responses impact offspring survival and development.

The researchers will then build a model to predict impacts of temperature change on insect populations. Native American high school students and undergraduate interns will carry out key pieces of the research. The project will simultaneously support STEM literacy and interest in STEM fields while advancing our understanding of the sensitivity of species from different latitudes to environmental stress.

Additional broader impacts include training of graduate students in physiology and ecology in the USA and at international field sites, thus strengthening students’ global networks. This project will enhance infrastructure by adding insect specimens to collections in the USA and Ecuador for teaching and future research.

Tropical ectotherms, which represent the vast majority of biological diversity on Earth, are predicted to be particularly at risk from increases in temperature mean and variance. However, there is a great deal of uncertainty in these predictions because models often fail to consider behavioral plasticity, which could buffer organisms from temperature change.

Theory suggests the capacity for behavioral plasticity should vary with the evolutionary history of organisms; species from temperate zones that evolved with more diurnal and seasonal temperature variation may have greater behavioral plasticity than species from the more invariant tropical zones. This project will incorporate realistic temperature changes (i.e. increases in both mean and variance) and focus on plasticity of reproductive behaviors of tropical and temperate dung beetles.

Dung beetles—an ecologically and economically valuable insect group—have considerable control over the developmental environment of their offspring, which in turn impacts offspring phenotype, fitness, and population dynamics. Using an integrated series of lab and field experiments, the project will 1) compare plasticity of reproductive behaviors among tropical and temperate species in response to temperature change, and 2) examine how these responses shape offspring phenotype and fitness.

Life table data will then be used to 3) develop a model to assess population viability of tropical and temperate species. Research will be integrated with a Native American high school education program and undergraduate internships to simultaneously support STEM literacy and interest in STEM fields while advancing our understanding of the potential for behavioral plasticity to buffer species from temperature changes.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.