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The influence of habitat structure on aquatic beetles in southern Bohemia
KOLÁŘ, Vojtěch
I studied the influence of fishpond management and environmental characteristics on diving beetles (Coleoptera: Dytiscidae), which are important predators in aquatic systems. In 2014 I used live traps to study diving beetle communities in 117 ponds in South Bohemia. The ponds were divided in three categories: intensively managed, extensively managed, and without fish. In total 26 species of diving beetles were found (N=1346). Overall, the beetles prefered shallow litoral zones with cattail (Typha), manna grass (Glyceria) and reed (Phragmites). The number of species declined with increasing alttitude and depth near the trap, while their abundance increased with pond area and amount of detritus near the trap. Beetles occured more in ponds with lower pH, lower conductivity and higher oxygen content. More beetles were found in fishless ponds. On the other hand, some ponds with high density of fishes but well preserved littoral zone had similar communities of diving beetles to the fishless ponds. This shows that high density of fish in ponds decreases the diversity and abundance of diving beetles, most likely because it decreases the vegetation in littoral zone. During the survey, four new localities of Graphoderus bilineatus were found; the species is protected by NATURA 2000 and has been known from very few recent localities in the Třeboň area.
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The influence of biotic and abiotic factors on the communities of predatory diving beetles
KOLÁŘ, Vojtěch
Diving beetles (Dytiscidae) are important inhabitants of water bodies, where their adults and larvae often represent top predators in the absence of fish. I carried out a literature review of biotic and abiotic factors that may affect the occurrence of aquatic insects with emphasis on the impact of aquaculture practises. In 2011 and 2012 I also carried out a field survey at two pond systems near Jindřichův Hradec. I used five baited traps in both the littoral zone and at the edge of the littoral zone and open water. Ponds with fish usually had very low diving beetle abundances, although one pond with fish but well-developed littoral zone had a relatively high number of species, similar to ponds without fish. My survey therefore confirmed high importance of littoral vegetation for diving beetles. This implies that intensive aquaculture practises are detrimental for the diversity of aquatic insects at a given locality. I have also found one individual of the rare diving beetle Colymbetes striatus, previously known from only a few localities in the Czech Republic.
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Diversity of diving beatles in cultural landscape
EBERMANNOVÁ, Petra
Diving beetles (Dytiscidae) are the most speciose family of predatory aquatic beetles. This work consisted of a literature review of factors influencing the diversity of diving beetles in time and space and a field survey of diving beetles in various parts of vegetated littoral habitats of human-altered water bodies during the season. The survey took place at nine ponds near the villages of Třebín and Dubné and on the edge of the town of České Budějovice in spring, summer and autumn 2011. The results showed a preference of diving beetles for ponds with smaller amounts of fish, less nutrient supply and larger vegetation coverage. All these factors influence the abundance of diving beatles. One rare species, Hydrovatus cuspidatus, was found during the survey.
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