Cáceres C E
Section of Ecology and Systematics, Corson Hall, Cornell University, Ithaca, NY 14853, USA.
Proc Natl Acad Sci U S A. 1997 Aug 19;94(17):9171-5. doi: 10.1073/pnas.94.17.9171.
Theoretical models suggest that overlapping generations, in combination with a temporally fluctuating environment, may allow the persistence of competitors that otherwise would not coexist. Despite extensive theoretical development, this "storage effect" hypothesis has received little empirical attention. Herein I present the first explicit mathematical analysis of the contribution of the storage effect to the dynamics of competing natural populations. In Oneida Lake, NY, data collected over the past 30 years show a striking negative correlation between the water-column densities of two species of suspension-feeding zooplankton, Daphnia galeata mendotae and Daphnia pulicaria. I have demonstrated competition between these two species and have shown that both possess long-lived eggs that establish overlapping generations. Moreover, recruitment to this long-lived stage varies annually, so that both daphnids have years in which they are favored (for recruitment) relative to their competitor. When the long-term population growth rates are calculated both with and without the effects of a variable environment, I show that D. galeata mendotae clearly cannot persist without the environmental variation and prolonged dormancy (i.e., storage effect) whereas D. pulicaria persists through consistently high per capita recruitment to the long-lived stage.
理论模型表明，重叠世代与随时间波动的环境相结合，可能会使原本无法共存的竞争者得以持续存在。尽管有广泛的理论发展，但这种“储存效应”假说几乎没有得到实证关注。在此，我首次对储存效应在竞争自然种群动态中的作用进行了明确的数学分析。在纽约州的奥奈达湖，过去30年收集的数据显示，两种悬浮取食性浮游动物——门多塔盔形溞和蚤状溞的水柱密度之间存在显著的负相关。我已经证明了这两个物种之间存在竞争，并且表明它们都拥有能形成重叠世代的长寿卵。此外，进入这个长寿阶段的补充数量每年都有所不同，因此两种水蚤都有相对于其竞争者更受青睐（补充数量更多）的年份。当计算有无可变环境影响时的长期种群增长率时，我发现如果没有环境变化和延长的休眠期（即储存效应），门多塔盔形溞显然无法持续存在，而蚤状溞则通过持续较高的人均补充数量进入长寿阶段而得以持续存在。
