Halaj J, Ross D W, Moldenke A R
Department of Entomology, Cordley Hall 2046, Oregon State University, Corvallis, OR 97331, USA fax: (541) 737-3643; e-mail:
Department of Forest Science, Oregon State University, Corvallis, OR 97331, USA, , , , , , US.
Oecologia. 1997 Jan;109(2):313-322. doi: 10.1007/s004420050089.
Spiders and ants are potential competitors and mutual predators. Indirect evidence from previous research has suggested that ant foraging may significantly lower the abundance of arboreal spiders in young Douglas-fir plantations in western Oregon. This study tested the effect of foraging by ants, dominated by Camponotus spp., on spider assemblages in Douglas-fir canopies in a 5-month ant-exclusion experiment. The biomass of potential prey organisms on foliage, dominated by Psocoptera, increased significantly by 1.9- to 2.4-fold following ant exclusion. The removal of ants did not affect the abundance of flying arthropods in the vicinity of tree canopies as indicated by sticky trap catches. The abundance of hunting spiders, the majority being Salticidae, increased significantly by 1.5- to 1.8-fold in trees without ants in the late summer; neither the abundance of web-building spiders nor the average body size of hunting and web-building spiders were significantly affected by ant removal. Spider diversity and community structure did not differ significantly between control and ant-removal trees. The majority of prey captured by ants were Aphidoidea (48.1%) and Psocoptera (12.5%); spiders represented only 1.4% of the ants' diet. About 40% of observed ants were tending Cinara spp. aphids. Our observations suggest that the lower abundance of hunting spiders in control canopies with ants may be due to interference competition with ants resulting from ant foraging and aphid-tending activities. Direct predation of spiders by ants appeared to be of minor importance in this study system. This study did not provide sufficient evidence for exploitative competition for prey between ants and spiders.
蜘蛛和蚂蚁是潜在的竞争者和相互捕食者。先前研究的间接证据表明，蚂蚁觅食可能会显著降低俄勒冈州西部年轻花旗松种植园中树栖蜘蛛的数量。本研究在一项为期5个月的蚂蚁排除实验中，测试了以弓背蚁属为主的蚂蚁觅食对花旗松树冠层蜘蛛群落的影响。排除蚂蚁后，以啮目为主的树叶上潜在猎物生物的生物量显著增加了1.9至2.4倍。如粘性诱捕器捕获情况所示，去除蚂蚁并未影响树冠层附近飞行节肢动物的数量。夏末时，没有蚂蚁的树木中，游猎蜘蛛（大多数为跳蛛科）的数量显著增加了1.5至1.8倍；去除蚂蚁对结网蜘蛛的数量以及游猎蜘蛛和结网蜘蛛的平均体型均无显著影响。对照树和去除蚂蚁的树之间的蜘蛛多样性和群落结构没有显著差异。蚂蚁捕获的猎物中，大多数是蚜总科（48.1%）和啮目（12.5%）；蜘蛛仅占蚂蚁食物的1.4%。观察到的蚂蚁中约40%在照料松大蚜属蚜虫。我们的观察表明，对照树冠层中有蚂蚁时游猎蜘蛛数量较低，可能是由于蚂蚁觅食和照料蚜虫活动导致与蚂蚁的干扰竞争。在本研究系统中，蚂蚁对蜘蛛的直接捕食似乎不太重要。本研究没有提供足够的证据证明蚂蚁和蜘蛛之间存在对猎物的剥削性竞争。
