Leaf traits and herbivory on deciduous and evergreen trees in a tropical dry forest

Abstract

Deciduous and evergreen trees coexist in tropical dry forests, but exhibit distinct leaf syndromes for resource-use efficiency and defenses against herbivores. Moreover, these functional groups may have contrasting patterns of temporal variation in leaf traits and herbivory along leaf ontogeny. We tested these predictions by comparing a set of leaf traits related to water stress and defense, and herbivory levels between young and mature leaves from evergreen leaf-exchanger and deciduous species. We evaluated deciduous and evergreen trees within the same habitat type: a tropical dry forest with 90–100% of leaf deciduousness during the dry season. We sampled 10 individuals of three deciduous and three evergreen species. Evergreen plants had greater leaf thickness and concentration of phenolics and tannins. On the other hand, deciduous plants had higher leaf nitrogen content and specific leaf area. Deciduous plants lost twice as much leaf area by herbivory as evergreen plants (6.48% versus 3.20%), and leaf damage was positively related to both phenolic compounds and nitrogen content. Mature leaves from both phenological groups had higher levels of tannins and phenolic compounds, and lower levels of nitrogen and herbivory increment than young leaves. Our results suggest an adaptive convergence on leaf traits primarily related to water stress for different species within each phenological group. Some of these traits also play a role in leaf palatability, although the fitness consequences of the absolute difference in leaf damage (approximately 3%) between evergreen and deciduous species remain unclear.