Graphoderus bilineatus

Abstract: Summary Lowland riverine floodplains are among the most dynamic and heterogeneous of ecosystems, but many have been extensively modified. Their provision of important habitats provides a key motivation for restoring natural flow regimes (in terms of magnitude, frequency, duration, timing and rate of change of hydrological conditions). Despite general recognition that aquatic insects respond to changes in water availability, there is little agreement about the influence of flow regime components on community structure in floodplains. We analysed a 6-year (2005 and 2007–2011) data set of aquatic insects (Heteroptera and Coleoptera) in a large Danubian floodplain characterised by pronounced hydrological variability. We hypothesised that abundance and assemblage structure would depend on flow regime components. In particular, we predicted that high-flow events in the mainstream and concurrent high-magnitude floods of prolonged duration would have a positive effect on diversity and abundance and that insect assemblages would differ between phases of hydrological connectivity. In addition, we assessed whether the survival of two threatened aquatic insects, Graphoderus bilineatus and Berosus geminus, depends on hydrological connectivity. Abundance and species richness of Heteroptera and Coleoptera increased during years with frequent extremely high flood pulses and prolonged flooding. Multivariate ordination showed subtle relationships between hydrological conditions, hydrological connectivity and insect assemblages with number of days in flood providing the best fit. Spring floods had a more pronounced effect on the assemblages than autumn floods. The time lag between flood occurrence and its apparent effect on aquatic insects was 17–31 days, reflecting insect life cycles. The abundance of G. bilineatus (Coleoptera: Dytiscidae) was affected by mean water level during the month preceding sampling, whereas the abundance of B. geminus (Coleoptera: Hydrophilidae) was related to the occurrence of prolonged high-magnitude floods. The current water regime of the Danube River favours generalist species with high dispersal capacities and broad niches and food resources. Changes in flow management practices could remove the positive influence of floods on aquatic insect communities and lead to losses of threatened species that depend on these river–floodplain habitats. Our results contribute to the understanding necessary for appropriate evaluation and prioritisation of international floodplain conservation efforts.

Abstract: Populations of the endangered diving beetle Graphoderus bilineatus are decreasing across Europe. Evidence‐based conservation of its local populations requires good knowledge of its habitat requirements, but data from different countries are often incomplete or contradictory. Graphoderus bilineatus was common until 1950s but then almost disappeared in the Czech Republic. Using data from a recent field survey in its core distributional area in the Czech Republic, we evaluate its habitat preferences at the habitat and microhabitat scale. We found that extensively managed fishponds can provide similarly suitable habitats for G. bilineatus as do more natural habitats including floodplain and sandpit pools, while the species is typically absent in intensively managed fishponds. All else being equal, the species is more likely found in larger water bodies surrounded by other wetlands and is more often absent at sites in agricultural landscape. We detected only weak preferences on the microhabitat scale. They suggested that G. bilineatus tends to occur in deeper water but closer to the shore and in microhabitats dominated by Glyceria or Typha. These microhabitat associations partly differ from those reported from other countries. Moreover, G. bilineatus was found at localities with higher species richness of large‐bodied aquatic beetles, both common and threatened, supporting the species status as an umbrella species for other aquatic macroinvertebrates. Our findings provide guidelines for conservation management of currently known localities and other potentially suitable sites, including the creation of new ones. Finally, our study reinforces the Annex II species status of G. bilineatus in the Habitats and Species Directive.

Abstract: Verspreiding en biotopen van Graphoderus bilineatus (Coleoptera: Dytiscidae) De verspreiding en biotopen van de gestreepte waterroofkever Graphoderus bilineatus zijn in 2004 en 2005 onderzocht in opdracht van de provincie Zuid-Holland en het Ministerie van lnv. Deze waterroofkever is wettelijk beschermd middels de Flora- en Faunawet en de Habitatrichtlijn. Graphoderus bilineatus kwam vroeger in grote delen van Nederland voor, maar is tegenwoordig vrijwel beperkt tot de grote laagveengebieden in de provincies Friesland, Overijssel, Utrecht en Noord- en Zuid-Holland. De belangrijkste biotopen in Nederland zijn sloten en kanalen met een breedte tussen 1,5 en 20 meter, een diepte tussen 50 en 150 centimeter met helder water, en meestal een vrij spaarzame vegetatie van drijvende en submerse waterplanten. Uit het buitenland is G. bilineatus vooral bekend uit grotere wateren. Op basis van een verspreidingsmodel wordt voor de laagveengebieden van ons land het potentiele voorkomen van G. bilineatus voorspeld. In 141 kilometerhokken voorspelt het model de aanwezigheid van deze soort met een waarschijnlijkheid van meer dan 70%.

Abstract: Protected beetles in the Netherlands (Coleoptera) The status of all by law protected beetles of the Netherlands is discussed. Several specimens of Cerambyx cerdo are known from the Netherlands, but all of these are considered to have been imported with oak-wood. Taking the European distribution into account it is supposed that Cerambyx cerdo once inhabited the Netherlands, but became extinct centuries ago as a result of the disappearance of suitable oak-trees. Both Osmoderma eremita and Dytiscus latissimus were very rare during the last two centuries. Only few specimens from isolated localities were collected in the 20th century, hence they are now considered extinct in the Netherlands. Graphoderus bilineatus was not uncommon in the beginning of the 20th century. Although it still occurs in a number of locations, especially in peat marshes, it has declined considerably. Lucanus cervus has been recorded for centuries from a few isolated localities. It is believed that Lucanus cervus has survived in the Netherlands in coppiced oak, in the absence of oak-trees dying naturally.