Are Ants and Trees in a Relationship? Urban Ecology Gossip on Grinnell's Campus

Matias Bambi

As human urbanization increases, and wildlife habitat destruction along with it, the spaces that urban landscapes create are critical to understand for species conservation. Fragmentation and loss of native vegetation are two factors associated with habitat destruction that are known to reduce arthropod species richness and increase replacement of native arthropod species with exotic/ invasive ones (Hashimoto et al., 1994; Gibb and Hochuli, 2002; McKinney, 2006). However, isolated trees in urban landscapes can serve as habitat refuges for ant species and other arthropods; examining population dynamics between ants and trees in urban settings may provide insight to how urban planners can best incorporate species conservation into their designs.

Yasuda and Koike investigated how trees contributed to ant and other arthropod abundance and diversity in the urban landscape of Matsudo City, Japan. More specifically, they examined how host tree arrangement, size, and species, as well as surrounding land abundances, influenced arthropod abundance and variety. When in the field, these entomologists searched for arthropods primarily on the trunks of the trees as tree bark plays an important role as egg-laying sites and pathways to canopy resting sites for some arthropod species (Moeed and Meads, 1983; Nicolai, 1986; Hanula and Franzreb, 1998; Majer et al., 2003). Yasuda and Koike found that tree species had the greatest influence on arthropod abundance, with tree size also having a significant effect and arrangement (cluster, linear, or isolated) having little effect (Yasuda & Koike, 2009). The authors note, however, that this differs from other studies, which have found that tree arrangement was an important factor in arthropod richness and abundance (Majer and Delabie, 1999; Ozanne et al., 2000; Reyes-López et al., 2003; Gove and Majer, 2006). Yasuda and Koike assert that to increase arthropod diversity and abundance, it is important to include tree species that attract arthropods in urban landscapes. Their research highlights the importance of investigating arthropod-tree population dynamics in order to better understand ecological community structures in urban planning.

A map of Matsudo City from Yasuda & Koike 2009 (left) and a map of Grinnell's Campus (right). https://bit.ly/2YTgnai

In their paper, Yasuda and Koike discuss the importance of tree selection when considering arthropod abundance and diversity. This is a concept that we can apply to our urban landscaping here in Grinnell. The derecho in 2020 devasted many trees on campus, and its aftermath provides us with an opportunity to think about how trees we select to plant might affect other species on campus. With this in mind, my lab partners, Tianyu and Will, and I seek to determine how ant abundance and ant species abundance is affected by host tree species and tree arrangement on the Grinnell College campus. To do this, we have travelled around North campus to observe what species of ants (and their abundance) are found on given tree species’ lower trunks, and how tree arrangement (clumped, linear, or isolated) might affect ant community structure (see pictures below). Through our study, we hope to provide better insight into the population dynamics between ant and tree species on campus. By examining this relationship, our findings could provide insight about important community structures, which could be incorporated into future tree-planting projects here in Grinnell.

        Two entomologists from our lab group observing ants and distance between trees in Grinnell's North campus.        

 

Works Cited:

Gibb, H., Hochuli, D.F., 2002. Habitat fragmentation in an urban environment: large and small fragments support different arthropod assemblages. Biological Conservation 106, 91–100

Gove, A.D., Majer, J.D., 2006. Do isolated trees encourage arboreal ant foraging at ground-level? Quantification of ant activity and the influences of season, in Veracruz, Mexico. Agriculture, Ecosystems and Environment 113, 272–276.

Hanula, J.L., Franzreb, K., 1998. Source, distribution and abundance of macroarthropods on the bark of longleaf pine: potential prey of the red-cockaded woodpecker. Forest Ecology and Management 102, 89–102.

Hashimoto, Y., Kamihogi, A., Hattori, T., 1994. A study on the conservation of fragmented forest as inhabitant arthropods in the newtown, using ant-biodiversity for indicator as arthropods-biodiversity. Journal of the Japanese Institute of Landscape Architects 57, 223–228 (in Japanese).

Majer, J.D., Delabie, J.H.C., 1999. Impact of tree isolation on arboreal and ground ant communities in cleared pasture in the Atlantic rain forest region of Bahia, Brazil. Insectes sociaux 46, 281–290.

Majer, J.D., Recher, H.F., Graham, R., Gupta, R., 2003. Trunk invertebrate faunas of Western Australian forests and woodlands: influence of tree species and season. Austral Ecology 28, 629–641.

McKinney, M.L., 2006. Urbanization as a major cause of biotic homogenization. Biological Conservation 127, 247–260

Moeed, A., Meads, M.J., 1983. Invertebrate fauna of four tree species in Orongorongo Valley, New Zealand, as revealed by trunk traps. New Zealand Journal of Ecology 6, 39–53

Nicolai, V., 1986. The bark of trees: thermal properties, microclimate and fauna. Oecologia 69, 148–160

Ozanne, C.M.P., Speight, M.R., Hambler, C., Evans, H.F., 2000. Isolated trees and forest patches: patterns in canopy arthropod abundance and diversity in Pinus sylvestris (Scots Pine). Forest Ecology and Management 137, 53–63.

Reyes-López, J., Ruiz, N., Fernández-Haeger, J., 2003. Community structure of groundants: the role of single trees in a Mediterranean pastureland. Acta Oecologica 24, 195–202.

Yasuda, Mika, and Fumito Koike, 2009. The Contribution of the Bark of Isolated Trees as Habitat for Ants in an Urban Landscape. Landscape and Urban Planning, 276-281.