Crown architecture and leaf anatomic traits influencing herbivory on Clethra scabra Pers. : comparing adaptation to wetlands and drained habitats.

Abstract

We tested the hypothesis that tree species adapted to ecotones between forest-swamps have leaf structures varying in response to land water saturation (drained and wetland), which could further influence their resistance against insect herbivory. The hypothesis was tested at the crown and leaf scale. We assessed differences in the plant architecture (height, circumference at breast height, trunk height, and crown) and leaf traits (sclerophylly and anatomy) of tree species inhabiting wetland and drained soils and investigated which variables explained variance in leaf herbivory rates. The study was conducted in Montane and wetland Forests in the Itacolomi State Park, in Southern Brazil, focusing on the Clethra scabra Pers., which inhabits both habitats, and also Myrcia amazonica DC. and Myrcia laruotteana Cambess (congeneric) which inhabit Montane forest and wetland forest, respectively. It was found that C. scabra individuals in wetland areas had simpler crown structure and higher leaf sclerophylly rates than those individuals of this species in the drained habitat. However, the two C. scabra populations did not differ regarding overall foliage thickness and damage by herbivory between drained and wetland habitats. Variables that were related to herbivory in this species were adaxial epidermis thickness and circumference at breast height. Myrcia individuals from wetland areas had less damaged leaves but thinner epidermis than in drained soils, but no variable correlated to herbivory at the leaf scale. Our hypothesis was partially corroborated and suggests that C. scabra is more influenced by soil saturation than Myrcia, and its herbivory is related with structural and anatomic parameters.