Association patterns and habitat selection of dragonflies (Insecta: Odonata) at different types of Danubian backwaters at Vienna, Austria
Chwala, E.; Waringer, J.
Adult dragonflies, exuviae and larvae were recorded over one year (April 1988-May 1989) at different types of perennial and temporary standing water bodies at the Lobau, a rural part of the Danubian floodplain in southeast Vienna, Austria. At ten sites, records were made at weekly or bi-weekly intervals. From a total of 4472 adults, exuviae and larvae, six species comprised 75.4% of the catch: Platycnemis pennipes (Pallas) (Platycnemididae), the coenagrionids Ischnura elegans (van der Linden), Erythromma najas (Hansemann) and Coenagrion puella (L.), the lestid Sympecma fusca (van der Linden) and the libellulid Sympetrum vulgatum (L.), which was the most abundant anisopteran species. The total catch included twenty-nine of the seventy-nine Austrian species from six families (Lödl 1976a, b). Diversity (based on the indices of Shannon (H) and Simpson (D), as well as equitability (E) were highest at sunny, permanent water bodies with well-developed riparian and aquatic vegetation and ranged from 0.69 to 2.60, 1.56 to 11.05, and 0.30 to 0.85, respectively. Species richness (and abundance) was lowest at a temporary water which lacked aquatic vegetation and was heavily shaded by trees. In addition, the significance of differences in diversity at various water bodies was tested by using the jackknife procedure (Krebs 1989, Potvin & Roff 1993). A recurrent group analysis revealed two distinct species groups: group 1 with Lestes viridis (van der Linden), Coenagrion puella, Brachytron pratense (Müller), Aeshna mixta Latreille Sympetrum sanguineum (Müller), Sympetrum striolatum (Charpentier) and Sympetrum vulgatum and group 2 with Ischnura elegans, Erythromma najas and Anax imperator (Leach). Libellula quadrimaculata L. and Sympecma fusca were associated with one or both groups. Similarities of Odonata communities assessed by a cluster analysis of the Wainstein index corresponded well with similarities of habitat structure. For example, the similarity of association patterns of Odonata species was highest at sites 5 and 6, both sunny and with narrow reed belts, but with aquatic vegetation almost lacking. On the other hand, dissimilarities in species composition between sites were clearly reflected by marked differences in insolation, vegetation patterns, water flow characteristics or intensity of human disturbance.