Does leaf flushing in the dry season affect leaf traits and herbivory in a tropical dry forest?

Abstract

In tropical dry forests (TDFs), stem-succulent deciduous species produce leaves during the dry season which coincides with the period of lower herbivore abundance. In this study, we evaluated the effects of abiotic factors (precipitation and day length) on the vegetative phenology of three stem-succulent deciduous species (Cochlospermum vitifolium, Commiphora leptophloeos, and Manihot anomala) during 2 years. In addition, we compared leaf damage by herbivores and leaf defensive traits (specific leaf area, thickness, and content of phenolic compounds) on leaf cohorts produced before and during the rainy season by these stem-succulent deciduous species. We also evaluated herbivory and defensive traits on leaves produced during the rainy season by 14 non-succulent deciduous species. There was a positive effect of precipitation and day length on the amount of green leaves exhibited by the three stem-succulent species. The leaf cohort produced during the dry season by stem-succulent species showed lower leaf damage and content of phenolic compounds than the cohort produced during the rainy season by the same species and by non-succulent deciduous species. Leaf damage was only affected (positively) by the content of phenolic compounds, suggesting the production of induced defenses during leaf expansion. In general, herbivory levels were low in this study (0.57–6.37%) when compared with other TDFs, suggesting that a scape from herbivores due to anticipated leaf production is a weak selective force affecting plant fitness. These variations in leaf traits are mostly related to contrasting water conservation strategies among phenological groups. Further studies should evaluate other defensive and nutritional traits, as well as their variations along the leaf lifespan, to unravel herbivory patterns in TDFs.