Alien pests and their influence on native biota in leaf litter of non-native trees

Non-native trees have been introduced into Europe for hundreds of years. Some have become an important part of the human diet, and many have aesthetic value. Nevertheless, some of them became aliens and host other alien species that might have undesirable effects on native organisms. We studied the possible effects of an alien-alien relationship (formed by the Horse-chestnut tree, Aesculus hippocastanum, and the Horse-chestnut leaf miner, Cameraria ohridella) on litter-dwelling invertebrates in the Czech Republic. We studied 42 sites widely distributed throughout the country. Leaf litter samples were collected under A. hippocastanum trees. Macro-arthropods were reared and collected using metallic extractors. Beetles, true bugs and terrestrial isopods were analyzed in detail as the most diversified taxa. Environmental predictors were abundance of Horse-chestnut leaf miner in litter, day of start of rearing, weight and volume of the sample and distance to the forest. We found that beetles, true bugs, and terrestrial isopods were the most abundant and species-rich taxa. The most important independent variables that influenced native biota were the total abundance of emerged Horse-chestnut leaf miner adults and the distance to large forests. The total number of individuals of all invertebrates and the abundance of terrestrial isopods were positively associated with abundance of the Horse-chestnut leaf miner, and the species richness of true bugs was higher in areas far from forests. This study describes how an alien-alien relationship can influence a leaf litter community of native biota. The results illustrate that the leaf litter of the non-indigenous tree could support a diverse arthropod community. Non-native leaf miner has the potential to accelerate decomposition of leaf litter of non-native tree for native biota.