Herbivory Variability in Florida Plants: Rare Species Show Higher Mean but Less Skewed Distributions of Damage

Abstract

Herbivory is an important interaction between plants and insects that shapes plant populations, ecosystems, and evolutionary adaptations. Most studies of herbivory focus on mean levels of damage and how it might vary among populations that might differ in factors such as density or relative abundance. However, herbivory is often unequally distributed among individuals in a population and this variability in herbivore damage might complicate important ecological predictions. This study investigated patterns of herbivory by chewing insect herbivores on eight plant species in Florida: four rare and four common species. We hypothesized that the rare species would exhibit higher mean herbivory but have less skewed damage distributions compared to the common species. Field surveys at two Florida sites assessed herbivore damage metrics, including mean, variance, and skewness, across 480 plants within eight species mostly the Asteraceae family but also one in each of the Fabaceae, Polygonaceae, and Cactaceae families. Statistical analysis revealed that rare species experienced significantly higher mean herbivory and lower variance in damage distribution, supporting our hypothesis. The herbivory damage data collected fit better to log-normal distribution, which account for highly skewed data, compared to a normal distribution, which assumes values are symmetrically distributed around the mean. These findings suggest that rare species may be more susceptible to herbivores due to limited defenses, while the greater variability in herbivory observed in common species may be due to differences in resource availability or other interactions. This study highlights the ecological significance of herbivory variability and its implications for plant population dynamics. Expanding research to additional plant families and regions could further our understanding of these dynamics.

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