Ecological traits of dragonfly (Odonata) assemblages along an oligotrophic Dinaric karst hydrosystem

Abstract

Ecological traits of dragonfly larvae in tufa-depositing habitats of the Dinaric karst were studied monthly over a one-year period (2007–2008). The study encompassed various lotic karst habitats (springs, mountainous rivers, streams, tufa barriers) and microhabitats (angiosperms, mosses, cobbles, sand, silt with leaf litter). The aims of the study were to identify dragonfly composition, abundance and spatial distribution, their habitat and microhabitat preferences, and to determine the most important environmental factors explaining dragonfly assemblages in the studied hydrosystem. The dragonfly fauna was composed of eight species, Onychogomphus forcipatus (Linnaeus, 1758) was the most widespread and the most numerous. Water temperature, ammonium and oxygen concentrations had the highest influence on dragonfly assemblages. The most favorable habitat type were tufa barriers, less favorable were lower lotic habitats, while dragonflies were almost completely absent from upper lotic habitats and their springs. Dragonfly larvae preferred microhabitats with inorganic substrates (i.e. cobbles and sand) and slower water velocity, while they mostly avoided mosses associated with the strongest current. This study provides an important contribution to the knowledge of dragonfly ecology in lotic habitats of the Dinaric karst.