title: Decline in gypsy moth (Lymantria dispar) performance in an elevated CO2atmosphere depends upon host plant species.
abstract: Plant species differ broadly in their responses to an elevated CO2atmosphere, particularly in the extent of nitrogen dilution of leaf tissue. Insect herbivores are often limited by the availability of nutrients, such as nitrogen, in their host plant tissue and may therefore respond differentially on different plant species grown in CO2-enriched environments. We reared gyspy moth larvae (Lymantria dispar) in situ on seedlings of yellow birch (Betula allegheniensis) and gray birch (B. populifolia) grown in an ambient (350 ppm) or elevated (700 ppm) CO2atmosphere to test whether larval responses in the elevated CO2atmosphere were species-dependent. We report that female gypsy moths (Lymantria dispar) reared on gray birch (Betula populifolia) achieved similar pupal masses on plants grown at an ambient or an elevated CO2concentration. However, on yellow birch (B. allegheniensis), female pupal mass was 38% smaller on plants in the elevated-CO2atmosphere. Larval mortality was significantly higher on yellow birch than gray birch, but did not differ between the CO2treatments. Relative growth rate declined more in the elevated CO2atmosphere for larvae on yellow birch than for those on gray birch. In preference tests, larvae preferred ambient over elevated CO2-grown leaves of yellow birch, but showed no preference between gray birch leaves from the two CO2atmospheres. This differential response of gypsy moths to their host species corresponded to a greater decline in leaf nutritional quality in the elevated CO2atmosphere in yellow birch than in gray birch. Leaf nitrogen content of yellow birch dropped from 2.68% to 1.99% while that of gray birch leaves only declined from 3.23% to 2.63%. Meanwhile, leaf condensed tannin concentration increased from 8.92% to 11.45% in yellow birch leaves while gray birch leaves only increased from 10.72% to 12.34%. Thus the declines in larval performance in a future atmosphere may be substantial and host-species-specific.
authors.affiliation: Department of Organismic and Evolutionary Biology, Harvard University, 16 Divinity Ave., 02138, Cambridge, MA, USA. mbt5@cornell.edu.
authors.forename: M B
authors.initials: MB
authors.lastname: Traw
authors.affiliation: Department of Entomology, University of Wisconsin, 53706, Madison, WI, USA.
authors.forename: R L
authors.initials: RL
authors.lastname: Lindroth
authors.affiliation: Department of Organismic and Evolutionary Biology, Harvard University, 16 Divinity Ave., 02138, Cambridge, MA, USA.
authors.forename: F A
authors.initials: FA
authors.lastname: Bazzaz
keywords: Betulaceae; Elevation CO2; Lymantria dispar; Nitrogen; Tannin