TY - JOUR

T1 - Predator diversity and abundance provide little support for the enemies hypothesis in forests of high tree diversity

AU - Schuldt, Andreas

AU - Both, Sabine

AU - Bruelheide, Helge

AU - Härdtle, Werner

AU - Schmid, Bernhard

AU - Zhou, Hongzhang

AU - Aßmann, Thorsten

N1 - The funding by the German Science Foundation (DFG FOR 891/1) and by the National Science Foundation of China (NSFC 30710103907 and 30930005), as well as various travel grants to prepare the project financed by DFG, NSFC and the Sino-German Centre for Research Promotion in Beijing (GZ 524, 592, 698 and 699) are highly acknowledged. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

PY - 2011/7/28

Y1 - 2011/7/28

N2 - 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.

AB - 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.

KW - Ecosystems Research

KW - Biology

UR - http://www.scopus.com/inward/record.url?scp=79960859631&partnerID=8YFLogxK

UR - https://www.mendeley.com/catalogue/ea54d923-9611-3822-949f-d5d382ccf23c/

U2 - 10.1371/journal.pone.0022905

DO - 10.1371/journal.pone.0022905

M3 - Journal articles

C2 - 21829551

VL - 6

JO - PLoS ONE

JF - PLoS ONE

SN - 1932-6203

IS - 7

M1 - e22905

ER -