Oviposition and larval mycelia preference of the saproxylic European stag beetle

Abstract In the light of evidence‐based conservation, we analysed the relation between the European stag beetle ( Lucanus cervus ) and a selection of ten common wood‐decomposing fungi. We studied log preference and number of offspring for logs inoculated with different fungi during oviposition in a cafeteria experiment. A second experiment assessed survival and relative growth rates of larvae placed in substrates colonised by the different fungal species. The selected fungi used in both experiments are phylogenetically diverse and represent different rot types. Females laid no eggs in logs with brown‐rot fungi and all larvae died in brown‐rot mycelia within 33 days due to black spot. All white‐rot fungi were accepted for oviposition, with no species‐specific preferences. The larval survival rate in white‐rot species was at least 57% and the relative growth rate of larvae was positive (except for the toxic Omphalotus illudens ). At rot type level, we can confirm the optimal oviposition hypothesis, a match between oviposition and larval habitat. Our findings contradict the association of brown‐rot fungal species with stag beetles, as reported in some literature, which is probably based on the presence of fruiting bodies. We conclude that the European stag beetle is a white–rot‐dependent species and accepts numerous species of white‐rot fungi without a clear preference. This is relevant for evidence‐based conservation when restoring its habitat or building artificial habitats (such as log piles) as well as for ex situ breeding campaigns.