Role of stream morphology and predators as driving factors for the abundance of two common ephemeropteran genera in rural hilly areas

Lotic environments may play an important role for semi-aquatic species. Streams are among the most threatened breeding habitats for some macrobenthos taxa. Ephemeropterans are often considered good bioindicators. Two of the most common genera of mayflies are Ecdyonurus and Baetis. The species from the first genus are very sensitive toward organic pollution, while the second genus might be quite resistant. The aim of this study was to evaluate the relative importance of stream morphological features on the abundance of Ecdyonurus and Baetis genera at unpolluted sites upstream an urbanised area. Further, I assessed the relationships between the abundance of the studied mayflies and the common spring and stream predators, i.e. salamander larvae and fish. The substrate complexity, reflecting shelter availability, was the main feature affecting the abundance of both genera. The two genera showed distinct requirements only in terms of stream shading, with Baetis preferring sunny sites and Ecdyonurus shady sites. Baetis showed higher affinity for streams with trout occurrence and Ecdyonurus for streams with Salamandra salamandra larvae occurrence. This study underlines that when pollution is not a main factor, both sensitive and insensitive common Ephemeroptera genera show similar habitat requirements and that watercourse substrate heterogeneity should be attentively preserved.