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Aim The aim of this study was to investigate the role of traits in beetle community assembly and test for consistency in these effects among several bioclimatic regions. We asked (1) whether traits predicted species’ responses to environmental gradients (i.e. their niches), (2) whether these same traits could predict co-occurrence patterns and (3) how consistent were niches and the role of traits among study regions. Location Boreal forests in Norway and Finland, temperate forests in Germany. Taxon Wood-living (saproxylic) beetles. Methods We compiled capture records of 468 wood-living beetle species from the three regions, along with nine morphological and ecological species traits. Eight climatic and forest covariates were also collected. We used Bayesian hierarchical joint species distribution models to estimate the influence of traits and phylogeny on species’ niches. We also tested for correlations between species associations and trait similarity. Finally, we compared species niches and the effects of traits among study regions. Results Traits explained some of the variability in species’ niches, but their effects differed among study regions. However, substantial phylogenetic signal in species niches implies that unmeasured but phylogenetically structured traits have a stronger effect. Degree of trait similarity was correlated with species associations but depended idiosyncratically on the trait and region. Species niches were much more consistent—widespread taxa often responded similarly to an environmental gradient in each region. Main conclusions The inconsistent effects of traits among regions limit their current use in understanding beetle community assembly. Phylogenetic signal in niches, however, implies that better predictive traits can eventually be identified. Consistency of species niches among regions means niches may remain relatively stable under future climate and land use changes; this lends credibility to predictive distribution models based on future climate projections but may imply that species’ scope for short-term adaptation is limited. ISSN:0305-0270 ISSN:1365-2699

Buxbaumia viridis is a well-known species of decaying deadwood, which is protected in Europe. All previous studies dealing with the ecology of B. viridis rely on the sporophyte generation because the gametophyte generation is allegedly undetectable. Recent advances have shown that the protonemal stage, including gemmae, is recognizable in the field, thereby considerably modifying our perception of the species&rsquo, range and habitat. In France, we demonstrate the existence of independent protonemal populations, with the implication that the range of B. viridis is widely underestimated. Sporophytes and sterile protonema do not share the same ecological requirements. The sporophyte stage was found in montane zones, almost exclusively in coniferous forests, and on well-decayed wood. The sterile protonemal stage extends to lower elevations, in broad-leaved forests, and on wood in a less advanced state of decay. Our results suggest that the humidity could be one of the most relevant explanatory variables for the occurrence of sporophytes. Opening of the canopy seems to promote sporophyte development. Previous anomalous observations of B. viridis growing on humus or bark might be explained by the presence of a protonemal population that is able to produce sporophytes under rarely occurring but favorable climatic events.

Intensive modern forestry is a threat to beetles depending on dead wood (saproxylic beetles). To mitigate these negative effects, forests are regularly set aside as woodland key habitats or retention patches, as supplements to nature reserves. However, there are considerable uncertainties regarding the relative effectiveness of woodland key habitats and retention patches. In addition, it is important to know if these types of conservation are effective for organisms with different ecology and biology. To explore these issues, the species richness, abundance and composition of spruce-associated saproxylic beetles was compared between 8 woodland key habitats, 9 retention patches and one nature reserve, in one production forest in Norway. Two types of flight intercept traps were used, which were placed on Norway spruce (Picea abies). Furthermore, I assessed if fungivores and cambium consumers of spruce-associated saproxylic beetles had similar responses to the management categories. Then I examined the relationship between the beetles and environmental variables. Lastly, it was tested for relationships between the species richness of saproxylic beetles and wood-decaying fungi found on the same logs as the traps. My results were that woodland key habitats, but not retention patches, had a significantly different species richness of saproxylic beetles from the nature reserve. No significant differences were found in species abundance. Furthermore, no significant differences were found in species richness or abundance of fungivores and cambium consumers between the management categories. Also, dead-wood parameters and sun-exposure could not explain the variation in species richness. However, species composition differences between management categories were significant for saproxylic beetles, but not for fungivores or cambium consumers. Lastly, the species richness of fungi did neither correlate with the species richness of saproxylic beetles, nor with the different functional groups. These results indicate that the conservation value of the woodland key habitats and the retention patches are useful supplements to the nature reserve, in terms of conserving spruce-associated saproxylic beetles in Selvik. Also, the correlation between spruce-associated saproxylic beetles and fungi appears to be weak on a relatively small temporal and spatial scale. However, it is unclear if the populations that were sampled in woodland key habitats and retention patches will be sustained over time, or if they will go extinct as a result of the relatively high degree of fragmentation in these management categories.