Hybridization of an invasive shrub affects tolerance and resistance to defoliation by a biological control agent

Authors: WILLIAMS, WYATT - Oregon Department Of Fish & Wildlife; FRIEDMAN, JONATHAN - Us Geological Survey (USGS); Gaskin, John; NORTON, ANDREW - Colorado State University

Submitted to: Evolutionary Applications
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/15/2013
Publication Date: 3/1/2014
Publication URL: http://handle.nal.usda.gov/10113/58596
Citation: Williams, W., Friedman, J., Gaskin, J.F., Norton, A. 2014. Hybridization of an invasive shrub affects tolerance and resistance to defoliation by a biological control agent. Evolutionary Applications. 7(3):381-393.

Interpretive Summary: Classical biological control, a common strategy involving the importation of highly specific insect that eat certain invasive plants only, may be negatively affected by plant hybridization. We investigated hybridization between two parent species of the invasive shrub tamarisk (Tamarix spp.) in the western U.S., and how differences in plant traits affect attack by a biological control agent. Although there was a strong correlation between plant species and latitude of plant origin, hybridization explained more variation in several plant traits than latitude alone. Elevated levels of T. ramosissima hybridization resulted in both higher investment in roots and tolerance to defoliation and less resistance to insect attack. Because tamarisk hybridization occurs predictably on the western U.S. landscape, managers may be able to exploit this information to maximize control efforts.

Technical Abstract: Evolution has contributed to the successful invasion of exotic plant species in their introduced ranges, but how evolution affects particular control strategies is still under evaluation. For instance, classical biological control, a common strategy involving the importation of highly specific insect herbivores, may be negatively affected by host hybridization because of shifts in plant traits, such as root allocation or chemical constituents. We investigated introgression between two parent species of the invasive shrub tamarisk (Tamarix spp.) in the western U.S., and how differences in plant traits affect interactions with a biological control agent. Although there was a strong correlation between T. ramosissima introgression and latitude of plant origin, introgression explained more variation in several plant traits than latitude (i.e. local adaptation) alone. Elevated levels of T. ramosissima introgression resulted in both higher investment in roots and tolerance to defoliation and less resistance to insect attack. Because tamarisk hybridization occurs predictably on the western U.S. landscape, managers may be able to exploit this information to maximize control efforts. Genetic differentiation in plant traits in this system underpin the importance of plant hybridization and may explain why some biological control releases are more successful than others.