Trapping beetles in boreal coniferous forest – how many species do we miss?

Abstract

The beetle fauna of the Oulanka National Park region has been shown to include about 850 species, 630 of these being true forest dwellers. A combination of two commonly used sampling methods, pitfall traps and flight intercept traps, will show the presence of 55% to 60% of these in one year. However, even if all trapping results of the region are combined, only about 90% of the species are included in the material. A rare species is missed more often than a random one - only about 55% of them have been trapped. Species classified as threatened are still harder to detect, only 25% of them were caught with trapping.

Many rare and most threatened insects have a specialised mode of life. Their population may be small and they are frequently patchily distributed. These species are very hard to catch with standard trapping schemes. The potential breeding sites of the threatened species should be emphasised as indicators of conservation value rather than the hard to show presence of these species.

The higher the number of difficult to catch species, the harder it is to obtain a representative sample of the fauna. This factor may have a considerable effect on the estimates of insect diversity in the tropical regions, as many tropical species are believed to be, at least anecdotally, highly specialised ecologically.