Low host‐tree preferences among saproxylic beetles: a comparison of four deciduous species

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AbstractMany wood‐dwelling beetles rely on old hollow trees. In Europe, oaks are known to harbour a species‐rich saproxylic beetle fauna, while less is known regarding other broad‐leaved tree species. Furthermore, the extent to which saproxylic insect species have specialised on different tree species remains unknown.In this study, we sampled beetles through pitfall traps and window traps in four different tree species in a landscape with many old oaks.We recorded 242 saproxylic beetle species of which 27 were red‐listed. After eliminating the species recorded only on a single tree, few cases among the 171 remaining species in the data set were confined to a single tree species.Using odds ratios, we showed that 19 of the 171 beetle species showed significant associations withQuercus roburin at least one of the two trap types. ForAcer platanoides, Fraxinus excelsiorandTilia cordata, the corresponding numbers were 6, 2 and 5, respectively. One species showed a negative association withQ. robur.Using meta‐analysis, we quantified the degree of association between the beetle species and the tree species. The associations were most profound among species classified as obligate saproxylic rather than facultative in lifestyle. Overall, a significant association was only found withQ. robur.We conclude that the saproxylic fauna is dominated by non‐specialist species but includes a small proportion of truly host‐tree‐specific species. Furthermore, other broad‐leaved trees can be important as supporting habitats for many saproxylic organisms that have had presumed associations with oaks to date.