Deer herbivory reduces web-building spider abundance by simplifying forest vegetation structure

PeerJ

article

Elizabeth J. Roberson¹  Michael J. Chips²  Walter P. Carson²  Thomas P. Rooney¹ 

[1] Department of Biological Sciences, Wright State University;Department of Biological Sciences, University of Pittsburgh;Pittsburgh Sewer and Water Authority

关键词: White-tailed deer;    Exclosure;    Disturbance;    Trophic ricochet;    Non-metric multidimensional scaling;    Effect size;    Indirect effects;    Northern hardwoods;    Forest ecology;   

DOI  :  10.7717/peerj.2538

学科分类：社会科学、人文和艺术（综合）

来源: Inra

【 摘 要 】

Indirect ecological effects are a common feature of ecological systems, arising when one species affects interactions among two or more other species. We examined how browsing by white-tailed deer (Odocoileus virginianus) indirectly affected the abundance and composition of a web-building spider guild through their effects on the structure of the ground and shrub layers of northern hardwood forests. We examined paired plots consisting of deer-free and control plots in the Allegheny Plateau region Pennsylvania and Northern Highlands region of Wisconsin. We recorded the abundance of seven types of webs, each corresponding to a family of web-building spiders. We quantified vegetation structure and habitat suitability for the spiders by computing a web scaffold availability index (WSAI) at 0.5 m and 1.0 m above the ground. At Northern Highlands sites, we recorded prey availability. Spider webs were twice as abundant in deer-free plots compared to control plots, while WSAI was 7–12 times greater in deerfree plots. Prey availability was lower in deer-free plots. With the exception of funnel web-builders, all spider web types were significantly more abundant in deer-free plots. Both deer exclusion and the geographic region of plots were significant predictors of spider community structure. In closed canopy forests with high browsing pressure, the low density of tree saplings and shrubs provides few locations for web-building spiders to anchor webs. Recruitment of these spiders may become coupled with forest disturbance events that increase tree and shrub recruitment. By modifying habitat structure, deer appear to indirectly modify arthropod food web interactions. As deer populations have increased in eastern North America over the past several decades, the effects of deer on web-building spiders may be widespread.

【 授权许可】

CC BY