Predator diversity and abundance provide little support for the enemies hypothesis in forests of high tree diversity

Peer reviewedPublisher PD

Predator Diversity and Abundance Provide Little Support for the Enemies Hypothesis in Forests of High Tree Diversity

Predatory arthropods can exert strong top-down control on ecosystem functions. However, despite extensive theory and experimental manipulations of predator diversity, our knowledge about relationships between plant and predator diversity - and thus information on the relevance of experimental findings - for species-rich, natural ecosystems is limited. We studied activity abundance and species richness of epigeic spiders in a highly diverse forest ecosystem in subtropical China across 27 forest stands which formed a gradient in tree diversity of 25-69 species per plot. The enemies hypothesis predicts higher predator abundance and diversity, and concomitantly more effective top-down control of food webs, with increasing plant diversity. However, in our study, activity abundance and observed species richness of spiders decreased with increasing tree species richness. There was only a weak, non-significant relationship with tree richness when spider richness was rarefied, i.e. corrected for different total abundances of spiders. Only foraging guild richness (i.e. the diversity of hunting modes) of spiders was positively related to tree species richness. Plant species richness in the herb layer had no significant effects on spiders. Our results thus provide little support for the enemies hypothesis - derived from studies in less diverse ecosystems - of a positive relationship between predator and plant diversity. Our findings for an important group of generalist predators question whether stronger top-down control of food webs can be expected in the more plant diverse stands of our forest ecosystem. Biotic interactions could play important roles in mediating the observed relationships between spider and plant diversity, but further testing is required for a more detailed mechanistic understanding. Our findings have implications for evaluating the way in which theoretical predictions and experimental findings of functional predator effects apply to species-rich forest ecosystems, in which trophic interactions are often considered to be of crucial importance for the maintenance of high plant diversity

Designing forest biodiversity experiments : general considerations illustrated by a new large experiment in subtropical China

Funded by German Research Foundation. Grant Number: DFG FOR 891/1 and 2 National Natural Science Foundation of China. Grant Numbers: NSFC 30710103907, 30930005, 31170457 , 31210103910 Swiss National Science Foundation (SNSF) Sino-German Centre for Research Promotion in BeijingPeer reviewedPublisher PD

Designing forest biodiversity experiments: general considerations illustrated by a new large experiment in subtropical China


 Biodiversity-ecosystem functioning (BEF) experiments address ecosystem-level consequences of species loss by comparing communities of high species richness with communities from which species have been gradually eliminated. BEF experiments originally started with microcosms in the laboratory and with grassland ecosystems. A new frontier in experimental BEF research is manipulating tree diversity in forest ecosystems, compelling researchers to think big and comprehensively.
 We present and discuss some of the major issues to be considered in the design of BEF experiments with trees and illustrate these with a new forest biodiversity experiment established in subtropical China (Xingangshan, Jiangxi Province) in 2009/2010. Using a pool of 40 tree species, extinction scenarios were simulated with tree richness levels of 1, 2, 4, 8 and 16 species on a total of 566 plots of 25.8 × 25.8 m each.
 The goal of this experiment is to estimate effects of tree and shrub species richness on carbon storage and soil erosion; therefore, the experiment was established on sloped terrain. The following important design choices were made: (i) establishing many small rather than fewer larger plots, (ii) using high planting density and random mixing of species rather than lower planting density and patchwise mixing of species, (iii) establishing a map of the initial 'ecoscape' to characterize site heterogeneity before the onset of biodiversity effects and (iv) manipulating tree species richness not only in random but also in trait-oriented extinction scenarios.
 Data management and analysis are particularly challenging in BEF experiments with their hierarchical designs nesting individuals within-species populations within plots within-species compositions. Statistical analysis best proceeds by partitioning these random terms into fixed-term contrasts, for example, species composition into contrasts for species richness and the presence of particular functional groups, which can then be tested against the remaining random variation among compositions.
 We conclude that forest BEF experiments provide exciting and timely research options. They especially require careful thinking to allow multiple disciplines to measure and analyse data jointly and effectively. Achieving specific research goals and synergy with previous experiments involves trade-offs between different designs and requires manifold design decisions.&#13

Revision of the Subgenus Burlinius Lopatin (Coleoptera, Chrysomelidae, Cryptocephalinae) from China and Description of Four New Species

This study revised the subgenus Burlinius Lopatin, 1965, of the genus Cryptocephalus Geoffroy, 1762 (Coleoptera, Chrysomelidae, Cryptocephalinae, Cryptocephalini), and describes four new species, namely, Cryptocephalus (Burlinius) longchiensis sp. nov., C. (Burlinius) baowenzhengi sp. nov., C. (Burlinius) tomurensis sp. nov., and C. (Burlinius) glabrelegantulus sp. nov. The species C. (Burlinius) turpis Chen, 1942, and C. (Burlinius) yangweii Chen, 1942, were revalidated and treated as distinct species. Another four species were transferred into this subgenus from the subgenus Cryptocephalus, namely, C. (Burlinius) flavolimbatus Pic, 1920 (stat. nov.), C. (Burlinius) pusus Schöller, 2009 (stat. nov.), C. (Burlinius) scutemaculatus Tan, 1992 (stat. nov.), and C. (Burlinius) shaowuanus Gressitt & Kimoto, 1961 (stat. nov.). Two species (including one more subspecies) were removed out of this subgenus, namely, C. (Burlinius) nigrolimbatus Jacoby, 1890, C. (Burlinius) pallidipes Pic, 1927, and C. (Burlinius) pallidipes nakatae Gressitt & Kimoto, 1961; they were transferred into the subgenus Cryptocephalus. Thus, the subgenus Burlinius Lopatin includes now a total of 26 species in China according to our revision. A key to all the Chinese species of this subgenus is provided as well as color illustrations and line drawings for the general habitus and genital structures

New species of the genus Pseudolathra Casey, 1905 (Coleoptera, Staphylinidae, Paederinae) from the Northwestern District of China

Two new species of the genus Pseudolathra Casey, 1905 from mainland China are reported in this paper, namely Pseudolathra gansuensis Li & Zhou, sp. nov. and P. assingi Li & Zhou, sp. nov. This genus is reported for the first time from Gansu Province, Northwest China. Both species are described in detail and supplemented with color plates of normal light photos of the habitus, sternites VII–IX and details of aedeagal structures in different views