Wise David H, Wagner James D
Department of Biological Sciences, University of Maryland, Baltimore County Campus, 21228-5398, Baltimore, MD, USA.
Oecologia. 1992 Aug;91(1):7-13. doi: 10.1007/BF00317234.
Previous research by many investigators has demonstrated food limitation in both web-building and wandering spiders. Field experiments have tested for exploitative competition for prey in web-building, but not wandering species. As a first step to examining the question of whether spiders without webs exhibit exploitative competition, we manipulated densities of young stages of a common wolf spider, Schizocos ocreata, and measured (1) spider growth rate and (2) numbers of Collembola, a potential prey organism. Replicate populations of recently hatched S. ocreata were established in 1-m fenced plots at four levels: 0×, 0.25×, 1× and 4× natural density. Increasing spider density had a negative effect on spider growth rate, defined as increase in weight or cephalothorax width. Early in the experiment spider density had a weak negative effect on Collembola numbers [p(F)=0.08]. Taken together, this probable response by Collembola and the clear effect of spider density on growth rate constitute the first experimental evidence of intraspecific exploitative competition for prey in a species of wandering spider. We discuss (1) the strength of this evidence given the constraints of the experiment's design, and (2) the implications of the strong convergence in spider densities that had occurred after 2.5 months.
此前许多研究人员的研究已证明结网蜘蛛和游走蜘蛛都存在食物限制。野外实验已对结网蜘蛛捕食方面的剥削性竞争进行了测试，但未涉及游走性蜘蛛。作为研究无网蜘蛛是否存在剥削性竞争这一问题的第一步，我们对一种常见狼蛛——食蟹瘤腹蛛幼体的密度进行了控制，并测量了（1）蜘蛛的生长速率以及（2）弹尾虫（一种潜在猎物）的数量。在1米见方的围栏区域内，以四个密度水平建立了近期孵化的食蟹瘤腹蛛的重复种群：0倍、0.25倍、1倍和4倍自然密度。蜘蛛密度的增加对蜘蛛生长速率产生了负面影响，生长速率定义为体重或头胸部宽度的增加。在实验早期，蜘蛛密度对弹尾虫数量有微弱的负面影响[p(F)=0.08]。综合来看，弹尾虫的这种可能反应以及蜘蛛密度对生长速率的明显影响，构成了游走性蜘蛛物种内捕食方面种内剥削性竞争的首个实验证据。我们讨论了（1）鉴于实验设计的局限性，该证据的力度，以及（2）2.5个月后蜘蛛密度出现的强烈趋同现象的影响。
