Karlson Ronald H, Levitan Don R
Ecology Program (SLHS), University of Delaware, 19716, Newark, DE, USA.
Oecologia. 1990 Jan;82(1):40-44. doi: 10.1007/BF00318531.
Empirical evidence from studies of the sea urchin Diadema antillarum suggests that this organism widely disperses its offspring, that both recruitment and mortality rates are independent of local densities, and that local food availability does not regulate local population sizes. These attributes would indicate that local populations are generally open and recruitment-limited. Given that current populations have been devastated by a 1983-1984 mass mortality event which spread throughout the range of this species, we examine current population trends and evaluate the prospects for population recovery under the assumptions of recruitment-limitation and density-independent rates of recruitment and mortality. Specifically, we evaluate the dynamics of five, local populations at Lameshur Bay, St. John, U.S.V.I. in order to 1) determine current rates of recruitment and mortality, 2) predict population densities based on the above assumptions, 3) compare predicted densities against observed 1984-1988 densities, and 4) predict future population densities based on current trends. We estimate current recruitment rates at 0.02-0.11 individuals/m/yr and per capita mortality rates at 0.27-0.47 deaths/yr. Over the period 1985-1988, predicted densities based on these annual rates did not differ significantly from actual observed densities. Therefore, the assumptions that recruitment and mortality rates are density-independent and that local populations are recruitment-limited are sufficient, at present, to adequately predict current population trends. These trends indicate no recovery towards pre-mass mortality densities. The above description of the dynamics of open, recruitment-limited populations may be appropriate for a wide variety of organisms. We note the prevalence of animals with extensive larval dispersal capabilities. Populations located near the limits of their distribution, in freshwater streams and ponds, mountain tops, or other similarly isolated populations may also be subject to recruitment-limitation. Remote, recruitment-limited populations are likely to be more susceptible to local extinction than less remote populations. Dispersal distances and the scale of the processes controlling recruitment and mortality are important determinants of the degree of openness of local populations.
对海胆白棘三列海胆的研究得出的经验证据表明，这种生物会广泛散播其后代，补充率和死亡率都与当地密度无关，而且当地食物供应量也不会调节当地种群规模。这些特性表明，当地种群通常是开放的且受补充限制。鉴于当前种群已因1983 - 1984年的大规模死亡事件而遭到重创，该事件波及了此物种的整个分布范围，我们研究了当前的种群趋势，并在补充限制以及补充和死亡率与密度无关的假设下，评估了种群恢复的前景。具体而言，我们评估了美属维尔京群岛圣约翰岛拉梅舒尔湾五个当地种群的动态，以便：1）确定当前的补充率和死亡率；2）基于上述假设预测种群密度；3）将预测密度与1984 - 1988年观察到的密度进行比较；4）根据当前趋势预测未来种群密度。我们估计当前的补充率为每年每平方米0.02 - 0.11个个体，人均死亡率为每年0.27 - 0.47例死亡。在1985 - 1988年期间，基于这些年率预测的密度与实际观察到的密度没有显著差异。因此，目前，补充率和死亡率与密度无关以及当地种群受补充限制的假设足以充分预测当前的种群趋势。这些趋势表明，种群并未恢复到大规模死亡前的密度。上述对开放的、受补充限制的种群动态的描述可能适用于多种生物。我们注意到具有广泛幼体扩散能力的动物很常见。位于分布范围边缘的种群，如淡水溪流和池塘、山顶或其他类似孤立的种群，也可能受到补充限制。与距离较近的种群相比，偏远的、受补充限制的种群可能更容易局部灭绝。扩散距离以及控制补充和死亡率的过程的尺度是当地种群开放程度的重要决定因素。
