Hydrophyte community structure affects the presence and abundance of the water beetle family Dytiscidae in water bodies along the Drava River

Here, we examine the relationships between the macrophyte community structure and the presence and abundance of the water beetle family Dytiscidae in 35 water bodies along the Drava River (Slovenia). In addition, selected water quality parameters were examined. The surveyed water bodies differed in altitude, type, size and distance from the Drava River. With the exception of a weak size effect on the water beetles, these parameters did not significantly affect the community structure. For hydrophyte plants, the community structure was significantly related to water quality parameters, which explained 38% (p ≤ 0.05) of the variability of species presence and abundance. For the water beetles, the oxygen concentration, and the sodium, potassium and chlorine ion concentrations were significant, together explaining 24% (p ≤ 0.05) of the species variability. Redundancy analysis revealed the importance of the presence and abundance of the low-growth plant species Potamogeton trychoides for the occurrence of Cybister lateralimarginalis, Dytiscus marginalis, Graphoderus cinereus, Graphoderus austriacus, Hydaticus seminiger and Acilius canaliculatus, while other water beetle species were more related to floating leaf plant species. Altogether, the presence and abundance of hydrophytes explained 35% of the variability of the Dytiscidae water beetle species presence and abundance. This study demonstrates the importance of selected natant plant species and submerged plant species, with low-growth forms for the occurrence of large and medium sized Dytiscidae water beetle species. Therefore, correct management of the macrophyte vegetation can positively affect the richness of these Dytiscidae species.