Can interactions between native and non-native trees in urban landscapes influence herbivore abundance and diversity?

As urban and suburban regions radically expand throughout the United States, a large variety of non-native plant species both invasive and non-invasive are becoming increasingly prevalent. While invasive plants have proven to be detrimental to native ecosystems, few studies have assessed the impacts of non-native, non-invasive ornamental species. Most non-native plant species produce a smaller abundance and fewer species of herbivores, especially caterpillars, and suburban landscapes are often planted with a mixture of natives and non-natives. This begs the question: can the association between native and non-native plants influence the abundance of herbivorous insects in suburban landscapes? Associational Resistance (AR) and Associational Susceptibility (AS) are widely cited concepts in ecology and are used to better understand the relationship between an herbivore and its host plant in various plant community contexts. This study investigates the roles that AR and AS play in mediating caterpillar abundance and species richness on native red maples (Acer rubrum), when either native or non-native neighbor trees are present. In a two year field experiment, we are assessing caterpillar abundance and feeding on native plants when provided neighboring plants that vary in origin (native vs. non-native) and relatedness (congener vs. non-congener). In addition, we are also monitoring natural enemy abundance and diversity on these plots. Results from year 1 of this study will be presented and discussed.