Rapid Leaf-Miner Colonization of Introduced Trees and Shifts in Sources of Herbivore Mortality

Abstract

We measured diversity and abundance of leaf-mining insects on two introduced members of the Fagaceae, an oak, Quercus acutissima, and a chestnut, Castanea crenata, in north Florida. In less than 20 yr populations of both trees have recruited leaf-miner faunas as diverse as those found on native oaks, but some species recorded on Q. acutissima and C. crenata never completed larval development. Discounting unsuccessful colonists, the introduced host with more local native congeners, Q. acutissima, has a greater diversity of associated miners than does C. crenata. Abundance of miners differs greatly among C. crenata, Q. acutissima, and Q. nigra, a native host for most species. Castanea crenata consistently has higher density of miners than does Q. acutissima, although most of this difference is attributable to two species. Larval survivorship and sources of mortality of all miners, and of numerically dominant species analyzed separately, also vary among host species. So does foliar nitrogen content. Survivorship of all miners is highest on C. crenata, intermediate on Q. acutissima, and lowest on Q. nigra, resulting in part from significantly lower parasitism rates on C. crenata than on Q. nigra. The greater foliar nitrogen content of C. crenata compared with Q. nigra also appears responsible for enhanced survivorship of at least one dominant miner on the introduced host.