Spiller David A
Department of Zoology, University of California, 95616, Davis, CA, USA.
Oecologia. 1984 Nov;64(3):322-331. doi: 10.1007/BF00379129.
To test for inter- and intraspecific competition between two common orb-weaving spiders, Metepeira grinnelli and Cyclosa turbinata, I conducted separate field experiments in the spring and summer. During the spring experiment, the prey-consumption rate of Metepeira was reduced at higher inter- and intraspecific densities, but Cyclosa was only affected by intraspecific density. During the summer experiment, Metepeira prey-consumption was not affected by inter- or intraspecific densities, while Cyclosa was affected by both inter- and intraspecific densities. In addition to competition for food, during the spring experiment Cyclosa was observed displacing Metepeira but not vice versa, whereas during the summer experiment Metepeira displaced Cyclosa but not vice versa. The seasonal reversal in the competitive advantage between the species was linked to their asynchronous phenologies; in the spring most Cyclosa were larger than Metepeira, whereas in the summer most Metepeira were larger than Cyclosa. I suggest that in this system, temporal variability in the competitive abilities may promote species coexistence.
为了测试两种常见的圆蛛——格林内尔流星蛛（Metepeira grinnelli）和陀螺状球蛛（Cyclosa turbinata）之间的种间和种内竞争，我在春季和夏季分别进行了野外实验。在春季实验中，流星蛛在种间和种内密度较高时，其猎物消耗率降低，但球蛛仅受种内密度影响。在夏季实验中，流星蛛的猎物消耗不受种间或种内密度影响，而球蛛则受种间和种内密度两者的影响。除了对食物的竞争外，在春季实验中观察到球蛛取代了流星蛛，但反之则不然，而在夏季实验中流星蛛取代了球蛛，但反之则不然。物种间竞争优势的季节性逆转与它们不同步的物候有关；在春季，大多数球蛛比流星蛛大，而在夏季，大多数流星蛛比球蛛大。我认为在这个系统中，竞争能力的时间变异性可能促进物种共存。
