Choat J H, Andrew N L
Department of Zoology and Leigh Marine Laboratory, University of Auckland, Auckland, New Zealand.
Oecologia. 1986 Sep;68(3):387-394. doi: 10.1007/BF01036744.
The subtidal coralline flats of northeastern New Zealand support a characteristic guild of grazing herbivores. The most important members of this guild are an echinometrid echinoid, patellid, turbinid and trochid gastropods. Densities of these herbivores fluctuate through time. Interactions within and among the different species of echinoids and gastropods were investigated experimentally. Different combinations of species were caged at densities up to 5 times that of ambient for a 24 week period in an experiment designed to differentiate between intra- and interspecific competition.The echinoidEvechinus chloroticus and the turbinid gastropodCookia sulcata exhibited reduced mean dry weight with increasing intraspecific densities. There was little evidence of density-related mortality in these species. The limpetCellana stellifera showed comparatively large losses of weight and enhanced mortalities in intraspecific experimental treatments but this was not related to density.Investigation of interspecific interactions amongstEvechinus andCookia revealed no evidence of a negative influence of one species on the other. In terms of dry weight,Cookia was indifferent to the presence ofEvechinus, andEvechinus benefited in the reciprocal interaction.Cookia also enjoyed an enhanced mean dry weight when in the presence ofCellana compared to the equivalent intraspecific treatments. There were no coherent trends in proportional mortality in any treatments with enhanced interspecific densities. Cellana, in the presence ofCookia, exhibited a dramatic decrease in mortality rate and increase in mean dry weight. The presence of the turbinid gastropod was clearly beneficial to the limpet when compared to the intraspecific treatments with enhanced intraspecific densities and the control cages containingCellana at ambient density. We suggest that subtidal areas constitute poor habitats for limpets in the absence of agents such asCookia which may provide or maintain suitable sites for attachment and grazing.For the combinations of densities and species investigated there was a consistent trend towards positive interspecific interactions. It seems unlikely that at the sites investigated interspecific competition could act to restrict distributions, or limit abundances of species.
新西兰东北部潮下带的珊瑚藻滩上生活着一群具有特色的食草性动物。这个群体中最重要的成员是一种棘皮动物海胆、笠贝、钟螺和马蹄螺。这些食草动物的密度随时间波动。研究人员通过实验研究了不同种类海胆和腹足类动物内部以及它们之间的相互作用。在一项旨在区分种内竞争和种间竞争的实验中，将不同物种的组合以高达环境密度5倍的密度关在笼子里24周。棘皮动物绿海胆和钟螺腹足类动物库克螺随着种内密度的增加，平均干重降低。在这些物种中，几乎没有证据表明密度与死亡率有关。星状笠贝在种内实验处理中体重损失相对较大，死亡率增加，但这与密度无关。对绿海胆和库克螺之间种间相互作用的研究表明，没有证据表明一个物种对另一个物种有负面影响。就干重而言，库克螺对绿海胆的存在无动于衷，而绿海胆在相互作用中受益。与同等种内处理相比，库克螺在有笠贝存在时平均干重也有所增加。在种间密度增加的任何处理中，比例死亡率都没有一致的趋势。在有库克螺存在的情况下，笠贝的死亡率显著降低，平均干重增加。与种内密度增加的种内处理以及含有环境密度笠贝的对照笼子相比，钟螺腹足类动物的存在显然对笠贝有益。我们认为，在没有像库克螺这样的生物的情况下，潮下带区域对笠贝来说是较差的栖息地，库克螺可能会提供或维持适合附着和觅食的场所。对于所研究的密度和物种组合，种间相互作用呈现出一致的积极趋势。在所研究的地点，种间竞争似乎不太可能限制物种的分布或数量。
