Dengler et al. (2014) Agriculture, Ecosystems & Environment

Jürgen Dengler, Monika Janišová, Péter Török, Camilla Wellstein (2014): Biodiversity of Palaearctic grasslands: a synthesis. Agriculture, Ecosystems & Environment, in press, DOI: dx.doi.org/10.1016/j.agee.2013.12.015

Abstract
This article introduces a Special Issue on biodiversity of Palaearctic grasslands and provides a synthesis of the current knowledge on this topic. Four major categories of grasslands can be distinguished in the Palaearctic biogeographic realm: (a) zonal steppes (in areas too dry for forests), (b) arctic-alpine grasslands (in areas too cold for forests), (c) azonal and extrazonal grasslands (where hydrology, soil conditions, relief or natural disturbances within the forest biomes prevent tree growth locally) and (d) secondary grasslands (which replace natural forests in consequence of human land use). We summarize the present knowledge about species richness patterns (mainly of vascular plants) along abiotic and land use gradients. Further, we highlight the usefulness of diversity measures not based on species richness, namely functional diversity, phylogenetic diversity and within-species diversity. The strong differences observed for diversity patterns according to analyzed biodiversity parameter, spatial scale or taxonomic group call for comparative studies and caution when generalizing results. A particular challenge are the extreme plot-scale species richness values found in grasslands of a few European regions. We propose a conceptual model that explains the findings by an interplay of various factors acting at different levels: (i) The largest species pool is expected for habitats under conditions that prevailed over the last few million years, with a slight shift towards intermediate positions, i.e. for the Palaearctic in open, semi-dry, base-rich situations. (ii) The landscape-level species pool is increased by continuity of a grassland patch in space and time and heterogeneity of the surrounding landscape. (iii) The coexistence of regionally available species at a plot scale is due to reduced competitive exclusion according to Intermediate Disturbance Hypothesis, mowing once a year without fertilization being particularly effective. Ecosystem functions and services of Palaearctic grasslands are often positively connected to their biodiversity. At the same time, these communities and their biota are nowadays highly endangered. The semi-natural (High Nature Value) grasslands of Europe are mainly threatened by agricultural intensification or abandonment on low-productive sites in remote areas, while the natural steppes of the Palaearctic have largely been destroyed by conversion into arable land. Finally, we present some promising conservation and management approaches and call for a strong and comprehensive Convention on Grassland Conservation.

Highlights
•The paper deals with natural, semi-natural and improved Palaearctic grasslands.
•High species richness at plot-scale occurs in semi-dry basiphilous grasslands.
•Palaearctic grasslands have a big species pool including many threatened biota.
•Semi-natural grasslands are threatened by intensification and abandonment.
•Natural steppes have largely been converted to arable land.

Keywords
Conservation, Disturbance, Land use, Semi-natural, Species richness, Steppe

László & Tóthmérész (2012) Insect Conservation & Diversity

László, Z., Tóthmérész, B. (2012), Landscape and local effects on multiparasitoid coexistence. Insect Conservation and Diversity. doi: 10.1111/j.1752-4598.2012.00225.x



Abstract

1. When resources are spatially fragmented, strength of competition between species is diminished by alternative patterns of resource use and parasitoids of the same host species become potential competitors. The coexistence of competing species in spatially fragmented habitats may be achieved, however, due to niche partitioning and alternative responses to patch characteristics. To evaluate responses to resource patterns facilitating coexistence, we examined the resource use patterns of four parasitoid species (Orthopelma mediator, Pteromalus bedeguaris, Torymus bedeguaris and Glyphomerus stigma) of the gall inducer Diplolepis rosaeat both landscape and local scales.
2. Parasitoid species of rose gall communities behave differently at landscape and local scales. Parasitism rates and parasitoid incidence showed correlations with local characteristics in some cases, with landscape characteristics in others and, in some other cases with both.
3. Species responses to the examined characteristics depend rather on life history traits of parasitoids than on their frequency within the community. The examined parasitoids responded differently to landscape and local characteristics, while their phenology corresponded with their responses. Species emerging earlier in spring (O. mediator and P. bedeguaris) responded only to local variations, while later emerging species (T. bedeguaris and G. stigma) were sensitive to landscape characteristics as well.
4. Differences between species-specific and overall responses highlight the importance of species characteristics when considering multiparasitoid communities, and support both fine and coarse partitioning between different species coexisting in the community.

Keywords
Coexistence, land use, landscape fragmentation, parasitism rate, parasitoid incidence, tritrophic system