Species richness and abundance of native leaf miners are affected by the presence of the invasive horse-chestnut leaf miner

The effect of the alien horse-chestnut leaf miner, <i>Cameraria ohridella</i>, on native fauna was studied by comparing the species richness of native leaf miner communities and the abundance of selected native leaf miner species in the presence and absence of horse-chestnut trees infested by <i>C. ohridella</i>, in various environments in Europe. The species richness of native leaf miner communities in Switzerland was lower at sites where <i>C. ohridella</i> was present than at control sites. In Switzerland, France and Bulgaria, several native leaf miner species were significantly less abundant in the vicinity of infested horse-chestnuts. The native species most affected by the presence of the invasive alien species were those occurring early in the year and sharing their parasitoid complex with <i>C. ohridella</i>. These results suggest apparent competition mediated by shared natural enemies because these are the only link between <i>C. ohridella</i> and native leaf miners using other food resources.