LEAF DAMAGE DIVERSITY AND FREQUENCY IN A SOUTH FLORIDA MANGROVE ECOSYSTEM

Leaf damage plays an integral role in understanding plant-herbivore interactions within ecosystems, and frequencies of leaf damage can be tracked to inform ecological changes through time. Leaf damage studies often suggest that high frequencies of leaf damage correlate with herbivore diversity, a temporal trend that lends itself to the hypothesis that herbivory has increased in geologic time. In fact, leaf damage frequencies in the fossil record are generally lower than those in modern tropical forests. Modern mangroves, conversely, display comparable diversities and frequencies of leaf damage to ancient assemblages. Preservation bias may contribute to lower frequencies and fewer types of leaf damage in ancient assemblages. Moreover, high rates of leaf litter turnover and leaf habit may explain lower values in modern mangroves. Here, we document diversities and frequencies of leaf damage within a mangrove basin site in Barnes Sound, Florida. Because damaged leaves are most likely to abscise from the tree, we assess the fidelity of leaf damage types in the mangrove canopy and leaf litter. We collected one hundred red mangrove leaves each from the canopy and litter layer and used microscopic and imaging techniques to categorize and tabulate damage types, calculate total percent leaf loss per damage type, and assign a taphonomic grade to each leaf. Nine damage type categories occur on mangrove leaves: 1) holes; 2) rasping, which includes scraping of the leaf epidermis by the mangrove tree crab; 3) necrosis; 4) fungal; 5) leaf-mining; 6) leaf-margin; 7) galling; 8) oviposition; and 9) undefined. We found that, in modern mangroves, the frequency and diversity of leaf damage types reflects both herbivory and detritivory. Canopy herbivory by micro-arthropods, insects, and the mangrove tree crab were prominent. Pestalotiopsis fungi were commonly observed on canopy leaves, likely leading to necrosis. Rasping by pulmonated snails commonly degraded detrital leaves to their skeletal remains, obscuring canopy damage. Thus, leaf damage incurred in the canopy appears to be overprinted by detritivory in the leaf litter. Our results contribute to understanding the interplay between folivores and detritivores in leaf taphonomy, nutrient cycling, and preservation dynamics in mangroves.