Hamner W M
Australian Institute of Marine Science, 4810, Townsville, Queensland, Australia.
Oecologia. 1978 Jan;34(3):267-281. doi: 10.1007/BF00344906.
Intraspecific competition for space and light occurred when Tridacna crocea burrowed into coralline substratum of boulders on leeward coral reefs in the central Great Barrier Reef near Townsville, Australia. Intensity of competition was linearly related to clam density. Above about 200 clams/m, all clams physically contacted one another and all shells sustained damage. Mortality in isolated populations due to intraspecific competition was estimated at 40%. Principles of intraspecific competition in plants were tested for applicability to T. crocea populations. Juvenile mortality due to competitive stress was density dependent. Aggregated distributions of one year old clams changed to random or regular distribution of adults. Normal size-frequency distribution for juveniles became skewed for older groups. A bimodal size-frequency distribution of the population was related to selective mortality in 1-3 year old clams. Adult mortality due to crowding was less severe but significant. Growth rates were inhibited by competition. Deformations in morphology resulted from crowding. Intraspecific competition for space and light by adults inhibited recruitment of young. Animal adaptations to reduce mortality under crowded conditions were also important. Larvae aggregated on settling and oriented with posterior ends pointed away from nearest neighbors. Positional alignment within the substratum was selectively advantageous. Burrowing posteriorly was preferential, but anterior and sideways burrowing as well as twisting within the burrow were also observed. Movement within substratum served to reduce local damage to the shell. Proteinaceous deposits secreted through perforations in the shell reduced subsequent damage. T. crocea populations exhibited many animal adaptations that reduced mortality during the first years of life, but as cohorts matured, plant-like patterns of competitive interaction became more significant.
当大堡礁中部汤斯维尔附近澳大利亚海域背风珊瑚礁上的波纹唇鱼钻入巨石的珊瑚质基质时，就会发生对空间和光照的种内竞争。竞争强度与蛤的密度呈线性关系。在每平方米约200只蛤以上时，所有蛤都会相互物理接触，所有贝壳都会受到损伤。据估计，孤立种群中因种内竞争导致的死亡率为40%。对植物种内竞争的原理进行了测试，以检验其对波纹唇鱼种群的适用性。因竞争压力导致的幼体死亡率取决于密度。一岁蛤的聚集分布变为成体的随机或规则分布。幼体的正常大小频率分布在年龄较大的群体中变得偏斜。种群的双峰大小频率分布与1至3岁蛤的选择性死亡有关。因拥挤导致的成体死亡率虽不那么严重但很显著。竞争抑制了生长速度。拥挤导致形态变形。成体对空间和光照的种内竞争抑制了幼体的补充。动物在拥挤条件下减少死亡率的适应方式也很重要。幼虫在定居时聚集，并将后端指向远离最近邻居的方向。在基质内的位置排列具有选择性优势。优先向后挖掘，但也观察到向前和向侧面挖掘以及在洞穴内扭转。在基质内移动有助于减少对贝壳的局部损伤。通过贝壳上的穿孔分泌的蛋白质沉积物减少了后续损伤。波纹唇鱼种群表现出许多动物适应方式，这些方式在生命的最初几年降低了死亡率，但随着群体成熟，类似植物的竞争相互作用模式变得更加显著。
