PS 5-71 - Hurricane disturbance alters the trait composition of moth communities in a tropical rainforest

Abstract: Insects have been widely used to evaluate the state of an ecosystem due to their ubiquity and high sensitivity to disturbance and environmental change. Decades of research have shown that the composition of insect communities often mirrors the biotic and abiotic factors that shape their environment. While changes in taxonomic diversity and species composition have been well documented, less is known about changes in ecosystem functionality following disturbance, especially after abrupt and large-scale climatic events such as hurricanes. In this study, we assessed the impacts of category 4 Hurricanes Irma and María on the species trait composition of moth communities in the Luquillo Mountains of Puerto Rico. We focused on evaluating changes in body size and coloration, two eco-morphological traits that are known to represent varied life history strategies and different sensitivity to disturbance. Specifically, body size is related to many demographic and ecological processes such as fecundity, dispersal, and resource needs, while coloration influences defense against visually hunting predators. Moths were sampled monthly in Tabonuco and Sierra Palm forests in the 5 months before and 6 months after the passage of the hurricanes in September 2017. After taking scaled photographs of the moth specimens, we used the ImageJ software to measure the forewing length of at least 3 specimens per species (prioritizing males and right wings when possible). We also classified species as cryptic (i.e., camouflage with natural surroundings), aposematic (i.e., showing bright red or yellow markings), mimics (i.e., resembling beetles or wasps), or flash coloration (i.e., hindwing with color and forewing cryptic), which represent different anti-predator defense mechanisms. With this morphological data, we calculated the community weighted means (CWM) of each trait and used two-way ANOVAs to evaluate whether trait composition differed between habitat (Tabonuco vs. Palm) and period (before vs. after the hurricanes). Our results show a significant decrease in the CWM of forewing length after the hurricanes, indicating a loss of larger-sized moth species. Hurricane disturbance also led to a lower incidence of warning coloration (aposematism/mimicry/flash). These changes were consistent in both forest types, but more pronounced in Palm forests. Altered trait composition might be explained by reduced food availability in the initial months after the hurricanes, when herbaceous vegetation becomes dominant in the understory due to increased light availability. Our findings demonstrate how the functional integrity of biological communities may be altered by hurricane disturbance, which could result in cascading effects at the ecosystem level.