Densities of endophytic fungi and performance of leafminers (Lepidoptera: Eriocraniidae) on birch along a pollution gradient

We examined densities of endophytic fungi and their associations with performance of Eriocrania leaf-mining moth larvae on white birch (Betula pubescens) and silver birch (B. pendula) around a large copper–nickel smelter in SW Finland. The analysis is based on 2-year data collected from sites distributed along the pollution gradient from 0 to 10.8 km from the smelter. Endophyte densities were low near the smelter in both years, and correlated negatively with foliar concentrations of heavy metals and aerial SO2 levels. Endophyte densities and species composition differed between years. Densities were over two times as high in 1994 compared to 1993. B. pubescens endophyte densities were higher compared to B. pendula throughout the gradient probably due to differences in leaf characteristics of the species. Site-specific correlations among Eriocrania parameters and endophyte densities revealed no consistent patterns, indicating that annual variation in their relationships may be related to other factors, such as environmental conditions and plant quality.