The structure and dynamics of a water beetle community in a ...

Table 5 – Relative abundance of the three dominant groups and the most abundant species of water beetles in
the light trap samples in 2002–2006.
2002 (n=1,006) 2003 (n=7,578) 2004 (n=8,713) 2005 (n=3,283) 2006 (n=8,670)
Dytiscidae 53.42% 15.74% 8.52% 23.03% 6.58%
Ilybius fuliginosus 33.02% 5.52% 2.10% 1.81% 1.07%
Ilybius ater 8.74% 5.02% 0.47% 1.07% 1.37%
Rhantus suturalis 4.63% 3.77% 0.87% 0.27% 2.32%
Ilybius subtilis 3.18% 0.03% 1.50% 18.98% 0.34%
Hydrophiloidea 18.97% 76.56% 80.71% 62.94% 75.99%
Hydrobius fuscipes 10.61% 68.40% 66.08% 44.53% 62.16%
Enochrus coarctatus 6.37% 5.04% 7.78% 14.14% 6.81%
Anacaena lutescens 0.41% 2.35% 5.64% 3.51% 1.61%
Enochrus quadripunctatus 0.00% 0.13% 0.35% 0.30% 3.91%
Scirtidae 27.50% 7.70% 10.52% 13.76% 17.23%
Cyphon variabilis 12.36% 1.32% 5.06% 0.73% 4.42%
Cyphon coarctatus 7.85% 2.33% 0.47% 0.27% 0.49%
Cyphon ochraceus 2.89% 0.46% 0.46% 8.41% 9.95%
Cyphon padi 1.81% 3.42% 4.42% 2.89% 1.49%
Effects of weather and water depth on flight activity
The aggregated weekly flight activity (‘seasonal aspect’) is influenced by air
temperature and water depth in the wetland (Fig. 13 and Table 6). No significant effect of
other variables or seasonal patterns that cannot be explained by temperature and water depth
were detected (Table 6). A threshold temperature is apparent in all groups (Fig. 14). The
minimum temperatures required for flight, as found by threshold additive models, were
13.5°C (all families), 15.8°C (Dytiscidae), 17.7°C (Hydrophiloidea), and 12.1°C (Scirtidae).
Several individuals of all three groups were, however, caught even at temperatures below 10
°C.
Short-term fluctuations of the flight activity can be explained by fluctuations of air
temperature (Fig. 15 and Table 7). The effect of cloud coverage in the Hydrophiloidea and
Scirtidae was also significant but very weak.
Fig. 13 – The effects of environmental variables on the seasonal aspects of the flight activity of water beetles
(fitted values with 95% confidence interval).
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