Folivory, herbivores, and environment in the understory of a tropical montane cloud forest

Foliar herbivory and abundance of folivorous insects were studied on shrub species (Miconia glaberrima, Moussonia deppeana, Ocotea psychotrioides, and Palicourea padifolia) in a tropical montane cloud forest, Veracruz, Mexico. Monthly, we determined folivore damage, insect abundance on leaves, and microenvironmental variables (air and soil temperatures, relative humidity, and soil water content). Folivory per month varied between 2.04 +/- 0.45 percent in April and 4.41 +/- 0.86 percent in September. The highest levels of folivory occurred during the end of the wet-warm season (Palicourea), the relatively dry-cool season (Miconia and Ocotea), or during both seasons (Moussonia). Eighty-eight percent of the herbivores were caterpillars (Lepidoptera). Insect abundance was lower in the dry-warm and the beginning of wet-warm seasons (April-July) and higher during the wet-warm and dry cool seasons. Leaf production was continuous throughout the year for Miconia, Moussonia, and Palicourea; Ocotea had a leafing peak during December-March (dry-cool). Folivory and insect abundance were negatively correlated with maximum temperature and positively correlated with soil water content. The correlations between folivory and leaf production were not significant for any of the studied species. Because leaves are produced throughout the year (except for Ocotea), insect abundance was not related to leaf flush. Also, folivory and insect abundance were not correlated (except for Palicourea). Thus, foliar phenology may not be an escape from herbivory, at least for the studied shrub species. Rather, environmental conditions may play an important role in insect abundance and indirectly affect foliar herbivory levels.