Search

Abstract eDNA metabarcoding has become a standard method for assessing wood‐inhabiting fungi and bacteria, yet determination of dead‐wood‐inhabiting beetles still relies on time‐consuming collection of beetle specimens. We thus tested whether beetle species can be identified by eDNA sequencing of wood in a mesocosm experiment that manipulated species assemblages. Dead wood samples were taken at exit holes of beetles and DNA was extracted and analyzed using two comparative methods: (i) metabarcoding with standard arthropod primers (421 bp) and (ii) using short species‐specific primers (120–264 bp) with Sanger sequencing. Results showed that beetle DNA was amplified by each of the two approaches, however, with (i) we detected only one non‐target saproxylic beetle species. In addition, we identified 80 different OTUs with four non‐targeted species of arthropods. For (ii) we detected the targeted species in two fresh beetle exit holes out of 20 samples. We suggest that, in contrast to fungi and bacteria, this eDNA metabarcoding approach is not able to reliably detect saproxylic beetles from wood samples, likely due to rapid degradation of their target DNA. Adapting such an approach for large‐scale analyses thus requires a better knowledge of degradation processes affecting DNA quality and quantity in wood.

Woodland ecosystems of Europe have undergone major transitions in the last centuries. Changes in land use and the loss of natural forest dynamics have often led to structurally poor, uniform and dense stands. Not surprisingly, open forest species relying on a heterogeneous stand structure have suffered dramatic population declines. The European Nightjar Caprimulgus europaeus, a nocturnal insectivorous bird, has undergone such a decline in its main Swiss stronghold in Valais. Despite the species’ potential to colonize new sites and habitat restoration measures implemented since 2001, recolonisation of restored sites has not taken place, suggesting problems with the current habitat restoration strategy. In order to refine management recommendations, we compared habitat structure and moth abundance, a key Nightjar food source, at sites that are still occupied and at sites that had been abandoned but have recently been restored. Vegetation structure was more heterogeneous and moth abundance greater at occupied than at abandoned sites. More specifically, occupied sites harboured a greater coverage of bare ground, while abandoned sites exhibited a higher amount of regeneration and intermediate shrub layer. The occurrence of natural perches was also higher in occupied sites. Abandoned sites are thus characterised by lower prey abundance and denser vegetation cover, the combination of which is likely to lead to lower prey availability for hunting Nightjars. Restoration action would benefit from maintaining snags and dead branches and by targeting unproductive habitats characterised by mineral soils, thereby slowing down regeneration and shrub regrowth. For future successful management of Nightjar habitats, it seems thereby essential trying to find the balance between actions that allow opening the lower and mid-strata of the forest while sustaining high moth populations.