Cornell Lab of Ornithology, 159 Sapsucker Woods Road, Ithaca, New York 14850, USA.
Ecology. 2013 Jan;94(1):83-93. doi: 10.1890/12-0940.1.
Seed production that varies greatly from year to year, known as "masting" or "mast-fruiting" behavior, is a population-level phenomenon known to exhibit geographic synchrony extending, at least in some cases, hundreds of kilometers. The two main nonexclusive hypotheses for the driver of such geographically extensive synchrony are (1) environmental factors (the Moran effect), and (2) the mutual dependence of trees on outcrossed pollen (pollen coupling). We tested 10 predictions relevant to these two hypotheses using 18 years of acorn production data on two species of California oaks. Data were obtained across the entire ranges of the two species at 12 sites (10 for each species) separated by up to 745 km. In general, our results provided strong support for the importance of the Moran effect as a driver of spatial synchrony in and between these two species. Particularly compelling was evidence of close concordance between spatial synchrony in acorn production and key environmental factors extending over the range of both species and significant spatial cross-synchrony between the two species, despite considerable differences in their geographical ecology. Because oaks are monoecious, female flowers are not necessarily related to pollen production, and thus, our tests do not address the role of pollen coupling in bisexual species where pollen and flower production are necessarily correlated. For the oak species considered here, however, the Moran effect is a key driver of large-scale spatial synchrony in acorn production.
种子产量在不同年份波动较大，被称为“结实高峰期”或“结实高峰期”行为，是一种表现出地理同步性的种群水平现象，至少在某些情况下，这种地理同步性可以延伸数百公里。导致这种广泛地理同步的两个主要非排他性假设是：(1)环境因素（莫兰效应），(2)树木对外来花粉的相互依赖（花粉耦合）。我们使用两种加利福尼亚栎树的 18 年橡果产量数据来检验这两个假设的 10 个预测。数据是在两个物种的整个范围内，在 12 个地点（每个物种 10 个）收集的，这些地点之间的距离最远可达 745 公里。总的来说，我们的结果强烈支持了莫兰效应作为驱动这两个物种及其之间空间同步性的重要因素。特别引人注目的是，在两个物种的范围内，橡果产量的空间同步与关键环境因素之间存在密切的一致性，尽管它们的地理生态存在很大差异，而且这两个物种之间存在显著的空间同步性，这为莫兰效应作为驱动这两个物种及其之间空间同步性的重要因素提供了强有力的证据。由于栎树是雌雄同体的，雌花不一定与花粉产量有关，因此，我们的测试并没有解决在雌雄同花的物种中花粉耦合在其中的作用，在雌雄同花的物种中，花粉和花的产量必然是相关的。然而，对于这里考虑的栎树物种来说，莫兰效应是橡果产量大规模空间同步的关键驱动因素。
