Aquatic Heteroptera as indicators for terrestrialisation of floodplain habitats

The distribution of aquatic Heteroptera (Corixidae and Gerromorpha) in three backwater systems of the Austrian Alluvial Forest National Park differing in connectivity to the Danube River was examined at 44 locations between 1999 and 2003. The most common species were Aquarius paludum and Gerris lacustris (Gerridae).Various statistical analyses were used to define the relationship between species occurrence and 15 environmental variables and to test their influences on species distribution. Canonical correspondence analysis suggested that the main environmental gradients were the transitions from water surface richly covered with branches and Lemna and vegetated shoreline, which most species preferred, to open habitats with little shoreline vegetation, which only a few species preferred.This study shows the potential significance of heteropterans as indicator groups for paleopotamic conditions and aquatic habitats with strong terrestrialisation processes.