MID-CANOPY HEIGHT AND LEAF THICKNESS ARE CORRELATED TO CATERPILLAR (LEPIDOPTERA) HABITAT CHOICE IN AN EASTERN USA, TEMPERATE, OAK-HICKORY FOREST

Abstract
Mechanical and chemical plant structures are important factors in determining herbivorous insect assemblages. During the summer of 2017, 2015 caterpillars (Lepidoptera), classified as either shelter builders or exposed feeders, were collected by hand from 40 felled trees in an oak-hickory temperate forest located in Toms Brook (Shenandoah County, Virginia, eastern USA). Preserved caterpillars were identified by morphological and molecular characteristics. I explored whether there are statistical relationships between caterpillar abundance and plant mechanical traits, such as leaf thickness, leaf toughness, and relative tree height. As a group, caterpillars were concentrated in the relative middle height of each trees’ canopy. Leaf thickness - but not leaf toughness - was correlated to overall caterpillar abundance. Specifically, shelter builders were more abundant on thicker leaves, and, in contrast, exposed feeding caterpillars were more abundant on thinner leaves. Whether caterpillars are shelter builders or exposed feeders, it appears that their presence within a tree varies substantially, and that this variation is related, in part, to relative canopy location and to leaf thickness. Also, these results support the hypothesis that leaves in the relative upper canopy, as defined by a relative tree height formula, experience reduced herbivory possibly due to abiotic factors, such as decreased water availability and increased exposure to UV radiation both of which reduce their nutritional content and palatability.
Description
Keywords
leaf toughness, leaf thickness, relative tree height, Lepidoptera
Citation