Abstract
The abundance and taxonomic composition of the aquatic insect fauna were
investigated, with focus on adult water bugs, water beetles and water
scavenger beetles (Heteroptera: Nepomorpha and Gerromorpha, and
Coleoptera: Hydradephaga and Hydrophilidae) in two different freshwater
habitats: (1) a periodically flooded area of the Special Zoological
Reserve in Kopački rit Nature Park, Croatia; and (2) melioration canals
in the wider area of the Nature Park during 2005. Aquatic insects are
generally abundant in various water systems, including floodplains that
are exposed to water level fluctuations. Our aims were (1) to determine
abundance and species richness in relation to habitat type; (2) to
determine the influence of high flood peaks and oscillations during high
water levels on the diversity of aquatic Coleoptera and Heteroptera in
the flooded area; and (3) to identify characteristic species associated
with each habitat type. We collected 71 species; 41 were captured at
canals and 64 at the flooded area. Diversity of the two habitat types
varied depending on the months but there were remarkable differences in
species pool and their abundance. Both high and low water levels as well
as oscillations during high water levels had major influence on species
assemblages at the flooded area. Diversity of aquatic Coleoptera and
Heteroptera was higher when the water level decreased after high water
level peaks. A total of 11 species fulfilled the criteria for
specificity and were sufficiently abundant to be suitable species
characteristic for these two habitats. A higher proportion of
significant characteristic species was present in the flooded area than
in the canals. The presence of two Red List species of water beetles (Graphoderus bilineatus De Geer, 1774 and Berosus geminus
Reiche et Saulcy, 1856) and nine significant characteristic species at
the flooded area clearly indicates that the contribution of floodplains
in maintaining freshwater biodiversity is not only important regionally
but also at the international level. Also, our results suggest that the
power of high water levels is an important factor that can be used in
analyses on aquatic Coleoptera and Heteroptera assemblages, showing the
uniqueness of large floodplain areas.
Keywords
canal habitat, flooded habitat, water levels, flood intensity, significant species, Kopački rit Nature Park
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