Rebecca Fies

Rebecca Fies

Rebecca Fies


Impact of flood control on communities of meadow butterflies in the Nationalpark Donau-Auen.

The impact of flooding regimes on temperate-zone butterfly communities has thus far received little attention. Along the river Danube in eastern Austria, a levee built in the late 19th century nowadays largely interrupts natural river dynamics. Only a fraction of the floodplain area still experiences annual inundations during summer after snow-melt in the Alps. Butterfly communities on meadows have to face another crucial and unpredictable event, viz. mowing. To study the influence of these two factors on butterfly communities we repeatedly counted butterflies over a vegetation period on 18 flooded and 20 non flooded meadows. Also a dataset from an earlier survey (2012) at the same region was used, to compare the influence of a strong summer inundation (my survey, 2013) to the influences of a softer inundation (2012). We also assessed the availability of nectar sources and the nutrient status of the meadows. The butterfly species list, containing species that were found in 2013, 2012, 2005 and in the Viennese part (listed by HÖTTINGER et al. 2013) contains 84 species, of which three species are listed as strongly endangered and 24 as endangered, on the Red list of Lower Austria. Species number per meadow was exclusively influenced by overall butterfly abundance; in turn, overall butterfly abundance, as expected, was lower on meadows affected by annual flooding. But nevertheless, species accumulation curves suggest that the species richness on the flooded, southern meadows was smaller than on the not flooded, northern meadows. Likewise, as expected, species composition differed significantly relative to flooding regime. Butterfly species which were more common on flooded meadows were not typical wetland species, but rather the most abundant ubiquitous species. Grass-feeders were more affected by flood regime than herb-feeders in general. In particular, Brassicaceae-feeding species of the family Pieridae were relatively more prevalent on nutrient-rich flood-prone meadows. The proportion of migratory and dispersive butterflies, but also butterflies showing a high fecundity and a long lifespan, was higher on flood-prone meadows. On flood-impacted meadows more butterflies were found which are characteristic for more humid habitats. Against expectations, disturbance effects of mowing were outweighed by flooding; mowing shaped species composition only if the annual inundation was less intense. Meadows with medium flooding impact by uprising groundwater (N_O) and annually flooded meadows are ruled by niche differentiation, whereas the butterfly assemblages on meadows without flooding impact are rather ruled by the limiting similarity theory.

Link to E-Thesis