Landscape and community ecology of dung beetles
Dung beetles contribute important ecosystem services in agricultural and natural settings by burying and eating manure. While they have been used as model systems in several areas of biology, there are some large gaps in our understanding of their landscape and community ecology. We are working through a range of questions about these organisms including (1) How are dung beetle communities shaped by landscape structure? (2) How do landscape context and diet mediate pesticide exposure for this group? (3) Can we use dung beetles as a soil restoration tool on reclaimed coal mine sites? This is a new project we began in 2023, stay tuned for more.
Impacts of imported fire ant on insect communities and ecosystem services
Oh dear! Imported fire ants have been one of the worst invasive species in the southern US for a long time. Now, due to a combination of factors they're advancing further north than expected. We're launching projects to understand (1) how and why their range is expanding northward, (2) what happens to insect communities as fire ants invade, and (3) how this impacts a variety of ecosystem services and disservices.
Biodiversity and ecosystem services in bioenergy crops
As we cope with climate change, agricultural landscapes are likely to transform as growers adopt bioenergy crops. This will have strong impacts on biodiversity, but their direction and magnitude will depend on which crops are adopted, how they are managed, and where they are grown. There are a wide range of crop types which range from annuals like corn to perennial grass monocultures or diverse native plant communities. Using a long-term experimental array at Michigan State University's Kellogg Biological Station, in 2021 we conducted broad biodiversity censuses (including plants, arthropods, vertebrates, and microbes) to see who lives in each crop and what they do.
Publications on this topic:
Haan, N.L., Helms, J., & Landis, D.A. In press. Bioenergy crops shape ant communities and functional roles. Frontiers in Conservation Science
Landscape ecology of natural enemies and pest suppression
How does landscape structure influence insect communities and the ecosystem services they provide? The amounts of various habitat types and their spatial configuration play a part in controlling flows of insects in and out of agricultural systems, with important implications for pest suppression.
Monarch butterfly conservation
The eastern migratory monarch population has declined since the 1990s, and scientists are trying to understand causes of the decline and what can be done about it. We've found that when common milkweed stems regrow after being cut back by disturbances (mowing, burning, etc.) they can receive several times more monarch eggs, contain fewer arthropod predators, and can have enhanced survival of early-stage monarch caterpillars.
Haan, N.L., and Landis, D.A. 2020. Grassland disturbance effects on first-instar monarch butterfly survival, floral resources, and flower-visiting insects. Biological Conservation. Open access
Myers, A.T., N.L. Haan, and D.A. Landis. 2020. Video surveillance reveals a diverse and largely nocturnal community of monarch butterfly egg predators. Journal of Insect Conservation. Open acces
Hermann, S.L., Blackledge, C., Haan, N.L., Myers, A.T., and Landis, D.A. 2019. Predators of monarch butterfly eggs and neonate larvae are more diverse than previously recognized. Scientific Reports. Open access
Haan, N.L. and Landis, D.A. 2019. Grassland disturbance increases monarch butterfly oviposition and decreases arthropod predator abundance. Biological Conservation. Link
Haan, N.L. and Landis, D.A. 2019. The importance of shifting disturbance regimes in monarch butterfly decline and recovery. Frontiers in Ecology and Evolution. Open access
Endangered butterfly recovery, parasitic plants, and grassland management in the Pacific Northwest
Grasslands in the Pacific Northwest are home to several rare species with complex and sometimes conflicting management objectives. Taylor's checkerspot (Euphydryas editha taylori) is an endangered grassland butterfly. Managers needed information on its interactions with host plants, which include the common native species Castilleja hispida, the threatened native species Castilleja levisecta, and the weedy exotic Plantago lanceolata. As a PhD student I examined several aspects of its relationship to these hosts.
Haan, N.L., Bowers, M.D., and Bakker, J.D. 2021. Preference, performance, and chemical defense in an endangered butterfly using novel and ancestral host plants. Scientific Reports 11. doi: 10.1038/s41598-020-80413-y. Open access
Haan, N.L., Bakker, J.D., and M.D. Linders. 2018. Instar-specific effects of host plants on survival of endangered butterfly larvae. Ecological Entomology 43,742-753. Link
Haan, N.L., J.D. Bakker, and M.D. Bowers. 2017. Hemiparasites can transmit indirect effects from their host plants to herbivores. Ecology 99,399-410. Link
Dunwiddie, P.W., N.L. Haan, M.J. Linders, J.D. Bakker, C. Fimbel, T.B. Thomas. 2016. Intertwined fates: opportunities and challenges in the linked recovery of two rare species. Natural Areas Journal 36,207-215. Open access
Taylor's checkerspot on one of its host plants, Castilleja levisecta
Castilleja hispida, a hemiparasitic plant and checkerspot host