Jürgen Schmidl

Association of extinction risk of saproxylic beetles with ecological degradation of forests in Europe.

To reduce future loss of biodiversity and to allocate conservation funds effectively, the major drivers behind large-scale extinction processes must be identified. A promising approach is to link the red-list status of species and specific traits that connect species of functionally important taxa or guilds to resources they rely on. Such traits can be used to detect the influence of anthropogenic ecosystem changes and conservation efforts on species, which allows for practical recommendations for conservation. We modeled the German Red List categories as an ordinal index of extinction risk of 1025 saproxylic beetles with a proportional-odds linear mixed-effects model for ordered categorical responses. In this model, we estimated fixed effects for intrinsic traits characterizing species biology, required resources, and distribution with phylogenetically correlated random intercepts. The model also allowed predictions of extinction risk for species with no red-list category. Our model revealed a higher extinction risk for lowland and large species as well as for species that rely on wood of large diameter, broad-leaved trees, or open canopy. These results mirror well the ecological degradation of European forests over the last centuries caused by modern forestry, that is the conversion of natural broad-leaved forests to dense conifer-dominated forests and the loss of old growth and dead wood. Therefore, conservation activities aimed at saproxylic beetles in all types of forests in Central and Western Europe should focus on lowlands, and habitat management of forest stands should aim at increasing the amount of dead wood of large diameter, dead wood of broad-leaved trees, and dead wood in sunny areas.

The insect assemblage in water filled tree-holes in a European temperate deciduous forest: community composition reflects structural, trophic and physicochemical factors

Abstract(1) A study of the metazoan community occurring in water-filled tree-holes in southern Germany has been performed to determine the relationships among the key species of arthropods found within the community and a range of structural, physical and chemical factors, using multivariate techniques. (2) Four animal species were sufficiently common to allow identification of the preferred environments for their larvae. The aedine mosquito, Aedes geniculatus, prefers shallow open tree-holes with relatively little leaf litter even though these may represent less permanent water-bodies. The scirtid beetle, Prionocyhon serricornis, occurs in larger, deeper holes with greater amounts of leaf litter and a more predictable aquatic environment, although open water is not a requisite. Larvae of the orthocladiine chironomid, Metriocnemus cavicola, favours shallow more open tree-holes with higher litter content but with sufficient open water to ensure an adequate oxygen supply. The eristaline syrphid, Myatropa florea, favours shallow, open tree-holes with low litter content. (3) There is no evidence that interspecific interactions affect the distribution or abundance of any of these species. (4) The autecological results are discussed in light of those available for phytotelm dwellers elsewhere. The food-web overall may be interpreted as so simple that it is driven by ‘bottom-up’ environmental factors with no part played by those community-level ‘top-down’ processes that may be adduced for more complex, multi-trophic level webs occurring elsewhere. No “processing chain commensalism” could be found in the arthropod community of the temperate German deciduous tree-hole dwellers.

Ants on oaks: effects of forest structure on species composition

The ant fauna of oak forest canopies in Northern Bavaria was studied by canopy fogging on 45 trees in August 2000 and May 2001. The study focused on a comparison of several different forestry management practices resulting in several types of canopy cover. Forests surveyed were: (1) high forest (high canopy cover), (2) coppice with standards (low canopy cover), (3) forest pasture with mostly solitary trees (very low canopy cover) and (4) transitional forest from former coppice with standards to high forest (approaching high canopy cover). This comprised a full gradient of canopy coverage. On the 45 oak trees sampled, a total of 17 ant species were found. Species composition was dependent on the different forestry management practices. The total number of species and the number of species listed in the Red Data Books of both Germany and Bavaria were much higher in the forest pasture and the coppice with standards, as compared to the high forest. The transitional forest was at an intermediate level. The highest number of ant species was found in the forest pasture. This can be explained by the occurrence of species of open habitats and thermophilous species. In the coppice with standards, forest dwelling and arboricolous species dominated, whereas the high forest showed much lower frequencies of arboricolous species like Temnothorax corticalis, Dolichoderus quadripunctatus and Temnothorax affinis. A multivariate analysis revealed that canopy cover (measured as “shade”, in percentage intervals of canopy cover) was the best parameter for explaining species distribution and dataset variation, and to a lesser extent the amount of dead wood, canopy and trunk diameter. Thus ant fauna composition was mostly driven by structural differences associated to the different forestry management practices. Many ant species clearly preferred the more open and light forest stands of the coppice with standards as compared to the dense and shady high forest.

“Primeval forest relict beetles” of Central Europe: a set of 168 umbrella species for the protection of primeval forest remnants

Identification of forest stands with priority for the conservation of biodiversity is of particular importance in landscapes with a long cultural and agricultural history, such as Central Europe. A group of species with a high indicator value for the naturalness of forest ecosystems are saproxylic insects. Some of these species, especially within the order Coleoptera, have been described as primeval forests relicts. Here, we compiled a list of 168 “primeval forest relict species” of saproxylic beetles based on expert knowledge. These species can serve as focal and umbrella species for forest conservation in Central Europe. They were selected because of their dependence on the continuous presence of primeval forest habitat features, such as over-mature trees, high amounts of dead wood, and dead wood diversity, as well as their absence in managed Central European forests. These primeval forest relict species showed a moderately strong clumping pattern within the phylogeny of beetles, as indicated by phylogenetic signal testing using the D-statistic. When we controlled for phylogenetic relatedness, an ordinal linear model revealed that large body size and preference for dead wood and trees of large diameter are the main characteristics of these species. This list of species can be used to identify forest stands of conservation value throughout Central Europe, to prioritize conservation and to raise public awareness for conservation issues related to primeval forests.