Effects of trembling aspen (Populus tremuloides) stand density and diversity on the abundance and survival of Lithocolletis salicifoliella in northern Michigan.

Abstract

Biotic factors such as host plant density and diversity can effect the abundance of its herbivores. Predation and parasitism can further effect the fate of these organisms. The purpose of this investigation was to observe the herbivory interaction between Lithocolletis salicifoliella and trembling aspen (Populus tremuloides). We compared blotch miner activity in two stands of differing aspen density, total tree density, and diversity. Our hypotheses stated that the mean number of mines per leaf, and the fate of the organisms would be similar in each stand. Trees were counted and species diversity noted within the two stands, resulting in the classification of one as an aspen monoculture and the other as a polyculture. The number of mines per leaf was recorded for 20 leaves from 50 trembling aspen branches in each stand, and 80 leaves were haphazardly collected. All mines on collected leaves were opened and the fate of each miner was noted as either alive, preyed upon, parasitized, or dead due to other causes. The mean number of mines per leaf was greater in the monoculture than in the polyculture. The survivorship of L. salicifoliella was unrelated to its location between the two stands; however, the cause of death was dependent on whether the miner was in the monoculture or polyculture. It can be concluded that with an increased density of trembling aspen, there is a higher number of mines per leaf, and the larvae are more susceptible to parasitism than any other cause of death. In a polyculture, which has a lower density of trembling aspen, there are fewer mines per leaf, and larvae are more likely to be preyed upon than killed by any other means.