Assessment of Arthropod Communities of Rare and Declining Plant Taxa
Insect communities are an important part of ecological interactions, especially involving relationships with plants. Because of this importance, there are especially interesting interactions when species are rare or in decline. To get at some of these interactions, this project examines pollination biology of a threatened plant and the arthropod community of a common, but declining tree. The pollination biology component focuses on the federally threatened Pitcher’s thistle (Cirsium pitcheri), a rare plant found only on the dunes of three of the Great Lakes. This species is declining over much of its range and is subject to a host of threats, including several non-native weevils that cause plant and seed mortality. Pollination data is critical to the recovery of the species for a few reasons. One of these is that it provides baseline insect/arthropod community data that can be used after weevil treatments have been applied to assess any negative effects on the pollinator community. A second reason is that it can help understand the dynamics of pollinators in the system and how they might interact with other plants in the area as part of a pollination network. This aspect of the project will take place mostly in field sites that are located in the lakeshore dunes of Door County, WI. During this first portion, there is potential to conduct some field work with Kay Havens and Pati Vitt. The second component of the project focuses on the arthropod community of black walnut (Juglans nigra), a common tree. While this species occurs over much of the eastern United States, the recent spread of Thousand Canker Disease is predicted to wipe out black walnuts throughout their range. The loss of such a common species can have widespread effects, particularly for arthropods that depend on the walnut for all stages of their lifecycle. This portion of the project would include the capture and cataloging of arthropods present on different parts of the trees. This will provide important baseline data to understand the changes that will occur to the arthropod community after the decline of the walnut. Massive declines of dominant tree species in the past have led to extirpation or extinction of associated arthropods and can cause an extinction cascade. For example, ash trees (Fraxinus spp.) have at least 43 arthropod species that depend fully on them, as well as dozens more that utilize only a handful of species, including ash. The loss of ash trees due to emerald ash borer is likely to result in the extinction of these species. Because these arthropods interact with a much larger community of organisms, disruption of those interactions is likely to have widespread negative cascading affects within the community. Considering the importance of a common tree species with a wide geographic distribution, it is important to catalog these arthropod species before their extinction occurs. A random sampling of walnut trees will be made at the Chicago Botanic Garden and adjacent areas.