Diversity of producers (e.g. plants) usually increases the diversity of associated organisms, but the scale (i.e. the spatial area of plant diversity considered) at which plant diversity acts on other taxa has rarely been studied. Most evidence for cross‐taxon diversity relations come from above‐ground consumers that directly interact with plants. Experimental tests of plant diversity effects on elusive organisms inhabiting the leaf litter layer, which are important for nutrient cycling and decomposition, are rare. Using a large tree diversity experiment, we tested whether tree diversity at the larger plot (i.e. community) or the smaller neighbourhood scale relates to the abundance, species richness, functional and phylogenetic diversity of leaf litter ants, which are dominant organisms in brown food webs. Contrary to our expectations of scale‐independent positive tree diversity effects, ant diversity increased only with plot but not neighbourhood tree diversity. While the exact causal mechanisms are unclear, nest relocation or small‐scale competition among ants may explain the stronger tree diversity effects at the plot scale. Our results indicate that even for small and less mobile organisms in the leaf litter, effects of tree diversity are stronger at relatively larger scales. The finding emphasizes the importance of diverse forest stands, in which mixing of tree species is not restricted to small patches, for supporting arthropod diversity in the leaf litter.

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The outcome of seed fate (probability of predation or dispersal) depends on the interplay between granivores and seed traits. Furthermore, changing environmental conditions affecting granivore behavior might additionally alter seed dispersal patterns.Based on microcosm experiments and time-lapse videos, we tested in a structural equation model how dry or wet conditions in a slug-legume seed system affect slug movement behavior, thus influencing seed encounter, ingestion and dispersal locations. We additionally analyzed how interactions between slug weight, chemical and morphological seed traits determine the fate of ingested seeds and used point pattern analysis of seed locations to detect potential dispersal patterns.While dry or wet conditions had no direct effect on the time slugs spent moving, dry conditions significantly increased the slug's homing behavior. Higher slug movement increased the chance of seed encounter, smaller seeds with low seed coat permeability were preferably ingested and the proportion of ingested seeds increased with increasing seed oil content. A high proportion of ingested seeds was dispersed via endozoochory, but none of the tested seed traits could explain seed fate.Endozoochory led to clumped dispersal patterns around the slug's shelter with clustering significantly more pronounced for seeds in dry conditions due to increased homing behavior in slugs. These dispersal patterns indicate potential directed dispersal to moist microsites but whether this leads to higher recruitment and hence successful directed dispersal remains to be tested.

Within the Natura 2000 network, there is a legal imperative to protect endangered species. A lack of knowledge about habitat requirements for these species undermines the ability to make informed decisions about appropriate conservation measures, especially for isolated populations that may have developed habitat preferences specific to their region. Carabus menetriesi is an endangered ground beetle found in Europe and warrants protection under EU law. We collected occupancy data of C. menetriesi using live pitfall traps over two seasons in 2016 and 2018 at a protected nature reserve in southern Bavaria, Germany. Here, we present the results of a patch-occupancy modeling approach to determine habitat preferences for C. menetriesi at this site. Our model shows that increasing Sphagnum cover and habitat diversity led to higher occupancy levels for C. menetriesi at this site, while tree cover was negatively correlated with occupancy, but increased the detectability of the species. Implications for insect conservation Measures for protecting the C. menetriesi population at the study site were taken in accordance with our results. Areas with high tree cover were thinned at several sites, although the success of this measure has yet to be determined. Our findings about habitat diversity suggest that expansion of low intensity grazing in the area, a measure that was suggested as a result of our survey and is currently in process of implementation, might benefit the species. Whether our results can be transferred to C. menetriesi populations in different habitats remains to be investigated, however, our methodological approach with regard to both the data collection and analysis can be used to assess other populations and provide important information about relevant habitat parameters for that population. This will allow conservation managers to make well-informed decisions about conserving C. menetriesi, or indeed other similar carabid species with isolated populations.

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