Tuesday, August 13, 2019
Exhibit Hall, Kentucky International Convention Center
Joshua P. Scholl, Dpt. of Ecology and Evolutionary Biology University of Arizona, University of Arizona, Tucson,, AZ, Bethany Farah, University of Arizona, Tucson, AZ, Kayla Cuestas, Ecology and Evolutionary Biology, University of Arizona and Judith Bronstein, Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ
Background/Question/Methods: Mutualistic relationships between different species are some of the most important drivers of ecological diversity, but it is not fully understood how city landscapes alter these relationships. Many species of plants engage in a mutualistic relationship with ants where they exude sugary nectar from extrafloral nectaries; the nectaries attract and feed ants that then protect the plant by killing and eating other insects on the plants, including potential herbivores. In the Sonoran Desert the barrel cactus
Ferocactus wislizeni can potentially form such a mutualistic relationship with many different ant species, including non-native species. In this study, the ant species composition and quality of protection services towards cacti was compared between cacti found in urban Tucson, AZ and cacti found on Tumamoc Hill, a rural research station near Tucson, AZ. The response rate of ants to simulated herbivores (ten, first-instar
Manduca sexta larva) was measured as the speed of recruitment (maximum number of ants found on plant after all caterpillars were killed) and aggressiveness (the number of ants it took to remove 50% of the larva). Habitat factors (irrigation, patch size, patch connectivity, and substrate) and cactus characteristics (height, diameter, fruit number, and proximity to other cacti) were also recorded and investigated.
Results/Conclusions: In those ant species that were found in both rural and urban landscapes, aggressiveness and recruitment were similar, but more ants overall were recruited in the urban landscape. It is important to note however that we did not find any invasive species in our samples, despite sampling in areas of high irrigation where these species are known be present. Fire ants (Solenopsis xyloni) were the most prevalent species and strongly correlated with highly disturbed habitats as measured by little to no patch connectivity, small patch size and surrounding anthropogenic structures. Although fire ants were the most aggressive species and thus the best defenders of herbivores, they also did not show any floral tissue avoidance and thus are likely to drive off pollinators as well as herbivores. Other habitat features did not show significant correlation with ant behavior or cactus features as expected from rural studies and highlight the complicated nature of urban environments.
