Contrasting response of mountain birch to damage by Eriocrania leafminers in polluted and unpolluted habitats

The leafmining larvae of Eriocrania spp. (Lepidoptera, Eriocraniidae) develop in the expanding leaves of mountain birch, Betula pubescens subsp. czerepanovii (Orlova) Hämet-Ahti. The larva usually consumes over a half of the leaf, implying moderate foliar damage to an individual shoot. I demonstrated that in unpolluted forests, effects of damage are restricted to the mined leaf, which grows smaller and demonstrates higher fluctuating asymmetry than intact leaves. In contrast, in heavily polluted industrial barrens, mining of the single leaf adversely affects the entire shoot; timing and expression of responses depend on shoot type. In infested short shoots, intact leaves grow smaller and more asymmetrical than leaves in control shoots, whereas infested long shoots demonstrated no current-year response; this difference suggests that long shoots are more competitive than short shoots and can acquire additional resources to compensate for herbivore damage. In contrast, in the next year after damage, no consequences of mining were detected in short shoots, whereas infested long shoots produced lower numbers of axillary long shoots than controls. The detected interactive effects of pollution and leaf damage most probably result from resource limitation in birches growing on low-nutritive toxic soils.Key words: Betula pubescens subsp. czerepanovii, foliar damage, fluctuating asymmetry, Kola peninsula, leaf size, shoot growth.