Plant Hybrid Zones as Sinks for Pests

An 8-year study of how aphids are distributed and survive on hybrid and pure host populations showed that the more susceptible hybrid trees acted as pest sinks supporting most of the aphid population. At least 85 to 100 percent of the aphid population was concentrated on less than 3 percent of the host population, with the center of a pest's distribution being the hybrid zone of its host. The concentration of aphids on such a small segment of the host population suggested that susceptible plants not only acted as sinks in ecological time, but may also have prevented aphids from adapting to the more numerous resistant hosts in evolutionary time. This has important implications for the potential management of pest evolution in agriculture and in understanding natural pest distributions.