Flussjungfern am Niederrhein: Verbreitung und Habitatbindung (Odonata: Gomphidae)

Clubtails on the Lower Rhine, North Rhine-Westphalia, Germany: Distribution and habitat requirements (Odonata: Gomphidae) — This study aims to investigate the local distribution and to identify environmental factors that determine habitat selection of all species of Gomphidae on the Lower Rhine. Altogether exuviae of four gomphid species were recorded, however, their numbers differed widely. Compared to other large rivers, the total abundances of all species were low. Most abundant were Gomphus flavipes and G. vulgatissimus, with 4-5 exuviae on 200 m bank sections. Exuviae abundances of G. flavipes were positively correlated with the amount of fine sand, those of G. vulgatissimus with sand and total riparian vegetation cover. Both G. flavipes and G. vulgatissimus can be described as specialists for certain digging substrates and as opportunists in their emergence behaviour. We assume that low abundances of exuviae are caused by inappropriate and fragmented habitat structures, noticeably by the lack of fine substrate fractions. Additionally, hydro-morphology, drift, adjacent land use and shipping traffic may have a negative influence on gomphids.