Plant phenotype and interspecific competition between insects determine sawfly performance and density

Tested the effects of pinyon pine Pinus edulis phenotype and competitive interactions on the colonization success, mortality fecundity, and sex ratios of a foliage-feeding sawfly, Neodiprion edulicolis. Sawfly survival was significantly higher on susceptible trees than on resistant trees, but fecundity was significantly lower on susceptible trees. Interactions with a stem moth, Dioryctria albovitella, caused significantly reduced sawfly fecundity on susceptible trees. Sawfly mortality, rather than sawfly fecundity, was the dominant factor influencing population growth rates. -from Authors