Davis Andrew R, Campbell D James
Australian Flora and Fauna Research Centre, Department of Biological Sciences, University of Wollongong, 2522, Wollongong, New South Wales, Australia.
Oecologia. 1996 Dec;108(4):701-707. doi: 10.1007/BF00329045.
Among sessile marine invertebrates, the dispersion patterns of settling larvae are likely to strongly affect the nature and strength of subsequent intraspecific interactions. We use a recently developed graphical analysis technique to examine in situ spacing among settled larvae of the colonial ascidian Clavelina moluccensis. Larvae were mapped at settlement each day for 1 month at the time of their release from adults. Experimental plots measuring 90×90 mm were located on naturally occurring bare patches of wood on pier pilings which were extensively encrusted with sponges and ascidians. An inclusive one-tailed nearest-neighbour analysis applied at the time of the maximum number of individuals per plot revealed consistent fine-scale regular spacing between settled larvae. Furthermore, a two-tailed goodness-of-fit analysis indicated two modes of spacing: one at about 4.5 mm and the other at around 9 mm. No contact between larvae was observed at settlement and the spatial regularity is interpreted as a response of settling larvae to water-borne cues released from settled individuals. The two modes of spacing indicate the possibility of kin recognition as has been demonstrated for bryozoans. Water-borne cues may also limit local population density, as those plots with a high density of settlers showed a much greater decrease in settlement rate over time than low-density plots. Our findings are consistent with the hypothesis that intraspecific competitive interactions shape the patterns of dispersion of these invertebrates on hard substrata in the field.
在固着生活的海洋无脊椎动物中，附着幼体的扩散模式可能会强烈影响后续种内相互作用的性质和强度。我们使用一种最近开发的图形分析技术，来研究群体海鞘莫氏住囊虫附着幼体在自然环境中的间距情况。在幼体从成体释放后的1个月时间里，每天对附着时的幼体进行定位绘图。在码头桩柱上天然存在的光秃木块上设置了90×90毫米的实验样方，这些桩柱上大量附着着海绵和海鞘。在每个样方中个体数量达到最大值时进行的包含性单尾最近邻分析表明，附着幼体之间存在一致的小尺度规则间距。此外，双尾拟合优度分析显示出两种间距模式：一种约为4.5毫米，另一种约为9毫米。在附着时未观察到幼体之间有接触，这种空间规则性被解释为附着幼体对已附着个体释放的水体线索的一种反应。这两种间距模式表明存在亲属识别的可能性，苔藓虫类已证明有这种现象。水体线索也可能会限制局部种群密度，因为定居者密度高的样方随着时间推移，附着率的下降幅度比低密度样方大得多。我们的研究结果与以下假设一致，即种内竞争相互作用塑造了这些无脊椎动物在野外硬基质上的扩散模式。
