No abstract

Flatfishes bury themselves for camouflage and protection. Whereas species-specific preferences for certain sediments were previously shown, the role of scales in interaction with sediment has not been investigated. Here, scale morphology and sediment friction were examined in four European pleuronectiforms: Limanda limanda, Platichthys flesus, Pleuronectes platessa, and Solea solea. All species had different scale types ranging from cycloid to ctenoid scales. On the blind side, the number of scales is higher and scales have less ctenial spines than on the eye side. The critical angle of sediment sliding (static friction) significantly depended on the grain size and was considerably higher on the eye side. The effect of mucus was excluded by repeated measurements on resin replicas of the skin. Our results demonstrate the impact of scale morphology on sediment interaction and give an insight about the ability of scales to keep sand. Exposed scales and a higher number of ctenial spines on the eye side lead to an increase of friction forces, especially for sediments with a smaller grain size. Our results suggest that the evolution of scales was at least partly driven by their interactions with sediment which confirms the relevance of sediment for the distribution and radiation of Pleuronectiformes.

The consequences of different management strategies following natural disturbances are a matter of global concern. In former production forests around the Northern Hemisphere, the abandonment of intervention, such as removal of dead wood, after outbreaks of bark beetles has been increasingly promoted to regain more natural conditions. However, many focal species of conservation, such as the barbastelle bat Barbastella barbastellus, do not primarily depend on dead wood but might respond indirectly to disturbance-induced changes of forest structural attributes. We investigated the response of B. barbastellus foraging activity and roost selection by combining acoustic surveys, radio telemetry, and airborne light detection and ranging (LiDAR) to characterize B. barbastellus habitat use on different scales. B. barbastellus foraging activity increased with increasing canopy opening. Maternity colonies were recorded exclusively in trees killed by bark beetles. Bats preferred roost trees with a higher volume (m 3 ha À1 ) of live trees in the surrounding, and trees with on average larger diameters than nearby control trees. Our results revealed that outbreaks of bark beetles result in forest structural attributes that are suitable habitat for B. barbastellus. Salvage logging, i.e., the removal of beetleaffected trees, generally deteriorates the positive effects of bark-beetle outbreaks on the foraging and roosting habitat of B. barbastellus. We recommend maintaining snags of large diameter if salvage logging is mandatory.

No abstract

Natural disturbances are increasing around the globe, also impacting protected areas. Although previous studies have indicated that natural disturbances result in mainly positive effects on biodiversity, these analyses mostly focused on a few well established taxonomic groups, and thus uncertainty remains regarding the comprehensive impact of natural disturbances on biodiversity. Using Malaise traps and meta‐barcoding, we studied a broad range of arthropod taxa, including dark and cryptic taxa, along a gradient of bark beetle disturbance severities in five European national parks. We identified order‐level community thresholds of disturbance severity and classified barcode index numbers (BINs; a cluster system for DNA sequences, where each cluster corresponds to a species) as negative or positive disturbance indicators. Negative indicator BINs decreased above thresholds of low to medium disturbance severity (20%–30% of trees killed), whereas positive indicator BINs benefited from high disturbance severity (76%–98%). BINs allocated to a species name contained nearly as many positive as negative disturbance indicators, but dark and cryptic taxa, particularly Diptera and Hymenoptera in our data, contained higher numbers of negative disturbance indicator BINs. Analyses of changes in the richness of BINs showed variable responses of arthropods to disturbance severity at lower taxonomic levels, whereas no significant signal was detected at the order level due to the compensatory responses of the underlying taxa. We conclude that the analyses of dark taxa can offer new insights into biodiversity responses to disturbances. Our results suggest considerable potential for forest management to foster arthropod diversity, for example by maintaining both closed‐canopy forests (>70% cover) and open forests (<30% cover) on the landscape.