Besiedlung künstlicher Kleingewässer durch Großlibellen (Odonata: Anisoptera) – eine 4-jährige Studie aus der Niederschlesischen Heide (SW Polen)

Dragonflies frequently colonize newly created pools. However, little is known about the longterm establishment of populations, especially of rare and endangered species. The aim of this study was to investigate the colonization process at small artificial waters by dragonflies with special focus on typical peat bog species. From 2015 to 2018, exuviae of dragonflies (Anisoptera) were collected quantitatively at six manmade pools, three new and three old ones, in the Lower Silesian Forest. The colonization success by damselflies (Zygoptera) was investigated qualitatively and served as an additional information on the biodiversity of these waters. In total, 26 Odonata species (9 Zygopterans and 17 Anisopterans) with successful reproduction were found. However, species diversity varied significantly both between the pools and the years of study. There were no significant differences between new and old pools. There were four peat bog species (Aeshna juncea, Leucorrhinia dubia, L. albifrons, L. pectoralis) among the autochthonous species. Longterm development could only be confirmed for A. juncea and L. dubia in particular pools. Leucorrhinia albifrons occurred only sporadically and was not found in the last study year (2018). By contrast, L. pectoralis did complete its development in the years 2017 and 2018. Generally, these species preferred waters with moderately or well developed vegetation. The results confirm that a wide range of species can reproduce in artificial pools. However, permanent reproduction could be recorded for just a few dragonfly species. Consequently, manmade pools in the Lower Silesian Forest should not be considered as longterm surrogate habitats but rather as temporary subpopulation patches of the regional dragonfly fauna.