 By Lasair ní Chochlain and Eva Perry Urban trees provide important habitats for insects and other arthropods. Dr. Paola Olaya-Arenas, an adjunct professor at Universidad Icesi, presented the results of her research on Bogotá’s urban trees and associated insect communities to the University of Maryland’s Department of Entomology this April. Dr. Olaya-Arenas and collaborators sampled insects associated with Ficus americana Aubl. located in parks and on sidewalks in three urban areas in Bogotá, Colombia. A diverse and abundant community of herbivores, predators, and parasitoids was sampled, and information about their feeding habits, other host trees, and damage to plant tissue is described in Dr. Olaya-Arenas et al., 2022 bilingual publication “Insects associated with urban trees in Bogotá (Colombia): exploring their diversity and function.” This publication can be downloaded from the following link (Electronic book link), and it is a good guide for citizens and visitors of the city. In her research, Dr. Olaya-Arenas found that the location of F. americana trees in urban environments influences the diversity of herbivores, predators, and parasitoids. Insect communities were more diverse in park trees than in sidewalk trees, with herbivores predominating and driving this pattern. The diversity of predators and parasitoids did not differ between park and street trees (see Figure 1).  Figure 1. Insect functional group diversity in park and sidewalk trees. Species richness (q0) panels show the number of species in park or sidewalk samples. Shannon index (q1) panels account for both species number and individual counts. Simpson index (q2) panels indicate the probability that two randomly selected individuals from a sample are different species (Roswell et al., 2021). Mealybugs and scale insects are notable tree pests, and parasitoids play a role in controlling these insects in urban environments (see Figure 2). Dr. Olaya-Arenas found that scale insects on park trees were more often parasitized compared to scale insects on sidewalk trees. This suggests that reproductive fitness for parasitoids may decrease when parasitizing insects on sidewalk trees. An additional driver of this may be the reduction in scale diversity on sidewalk trees. Parasitoids that specialize may be unable (or less likely) to parasitize the scales present on sidewalk trees.  Figure 2. Parasitism of scale insects and mealybugs. Photo credits to: Paola Olaya-Arenas. Overall, Dr. Olaya-Arenas found that the planting location of urban F. americana trees significantly influences herbivore and predator abundance, herbivore diversity, and parasitism rates for some scales. This research highlights the need for a deeper understanding of insects, their interactions, and their associations with host trees in the landscape when planning tree plantings in urban areas to mitigate pest damage and safeguard ecosystem services.
When the students had the opportunity to personally connect with Dr. Olaya-Arenas, she spoke of the value of taking time off between degrees to work and gain experience, as well as enjoying a mental and physical break from the pace that comes with graduate school life. After traveling abroad for most of her graduate school and postdoctoral training, she said that one of the things she most enjoys about being back in Colombia is being near her family and friends from home. We look forward to following Dr. Olaya-Arenas’ continued work on this and other research projects, as well as the positive impact that she is making in her community. Citations:
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