The diversity and abundance of nocturnal insects in the agricultural landscape with a focus on moths
Melanie Hahn, Diploma thesis
Study Description
The protection and preservation of the diversity of species is an important aim of the Convention on Biological Diversity. The intensification of agriculture is seen as a crucial threat concerning the conservation of biodiversity. Since agriculture is the major land use in Germany, the focus of this diploma thesis was to study the community composition of nocturnal insects – especially moths (Lepidoptera) – in the agricultural landscape. Moths (and other nocturnal insects) can play a considerable role in pollination and they are a major food source for bats and – mainly as caterpillars – for birds. In Germany more than 40 % (601 species) of the Macrolepidoptera, containing butterflies and moths, are classified as threatened or near threatened at the national Red List. Insects were sampled by the use of light-traps from Mai to September 2008 at different agricultural sites and forests in Southern Palatinate. I concentrated on the insect communities trapped in vineyards, vegetable fields and forests. Vegetation surveys were accomplished for the agricultural sites and their margins to get more information about the availability of (potential) host plants for caterpillars.
Altogether, nearly 67.000 insects which can be attributed to 14 orders with an estimated biomass of 3.940 g could be trapped at 14 vineyards, 13 vegetable fields and 6 forests. There occurred statistically significant differences in terms of total individual number and total biomass per site and night between the three site categories. Especially the orders Lepidoptera, Diptera and Coleoptera were of great concern.
Noctuidae which form the greatest part of the trapped Macrolepidoptera at the agricultural sites were further analyzed and therefore taxonomically determined to the species level. Clusteranalyses and non-metric multidimensional scaling showed a distinct separation of the detected Noctuidae communities between the three site categories. In vegetable fields significantly less Noctuidae could be detected than in vineyards. A reason for this can be seen in the different availability of host plants with less plants occurring in the vegetable fields and their margins. Furthermore, in the analyzed vineyards no insecticides are used since the two pest species European Grapevine Moth (Lobesia botrana) and the Vine Moth (Eupoecilia ambiguella) were targeted with pheromones in the study area.
The differences in the insect communities could have an impact on the food availability for other species like, for example, bats. The potential prey of the Common Pipistrelle (Pipistrellus pipistrellus) and the Serotine bat (Eptesicus serotinus) occurred with less biomass in the vegetable field in comparison to the vineyards. Since in the vegetable fields only a small number of Noctuidae (and other Lepidoptera) could be trapped, plants which depend on these moth species for pollination could be negatively affected due to the lack of their pollinators.
To enhance the diversity and abundance of moths, plant species rich field margins could be of great importance if they contain the host plants of caterpillars and nectar sources for adult Lepidoptera.
Some results were presented in the following poster:
Hahn, M., Stahlschmidt, P., Brühl, C. A. (2009): Biomass, abundance and diversity of nocturnal insects – with a focus on moths (Lepidoptera) – in organic and conventionally managed vineyards. Poster Presentation, Young Environmental Scientist Meeting (YES-Meeting), Landau (more Info)