STAGGERED FLOWERING IN THE DIPTEROCARPACEAE - NEW INSIGHTS INTO FLORAL INDUCTION AND THE EVOLUTION OF MAST FRUITING IN THE ASEASONAL TROPICS
STAGGERED FLOWERING IN THE DIPTEROCARPACEAE - NEW INSIGHTS INTO FLORAL INDUCTION AND THE EVOLUTION OF MAST FRUITING IN THE ASEASONAL TROPICS
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DOI：
10.1086/284837
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发表时间：
1988-07-01
影响因子：
2.9
通讯作者：
APPANAH, S
中科院分区：
文献类型：
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作者：
ASHTON, PS;GIVNISH, TJ;APPANAH, S
远东低地雨林的优势树种龙脑香属植物的超年度肥大结实被认为是一种通过饱食减少种子捕食的适应。然而，这一解释提出了四个重要问题。(1)什么授粉的物种花的间隔超过一年？(2)大量开花的物种如何避免对传粉者的竞争？(3)在季节性气候中，诱导几个科中的许多物种以超过一年的不规则间隔开花的成花诱导的环境线索是什么？(4)而且，最重要的是，什么因素会导致物种的结果时间的初始物候聚集？一旦存在这样一个物种的物候核心，对捕食者饱足的选择就可以将其他物种带入相同的结果时间表，并完善种子释放的同步性。关键的问题是，在季节性气候中不规则地开花的物种的物候核心最初是如何出现的。这里提出的观测和分析表明，这些问题的答案是错综复杂的相互关系和厄尔尼诺南方涛动现象。(1)一些大量开花的龙脑香果由蓟马授粉，蓟马在大量开花之间保持在低水平，并在龙脑香果开花时密度爆炸。(2)大量开花的dipterocarp物种在Shorea节Mutica显着减少重叠的开花时间错开其开花期，从而减少竞争传粉者和/或堵塞的柱头与外来花粉。新技术用于分析一种特定的资源利用模式是否显著减少了重叠，克服了以前技术中固有的错误，只要总开花季节或资源范围不是由外部条件决定的，而是由开花时间或所讨论的物种所使用的资源范围决定的，就应该使用它。(3)利用各物种花期持续时间与平均开花日期的线性关系，推导出Shorea组Mutica的成花诱导时间。对气象记录的分析表明，诱导是由三个或更多夜晚的最低夜间温度下降约2摄氏度或更多引起的。这个非同寻常的触发器可能是与干燥气团入侵季节性热带有关的最可靠的信号。(4)这样的触发器似乎并不直接适应在季节性热带地区，但在季节性热带地区，它会导致在旱季开始时开花，在雨季开始时成熟的果实。这表明龙脑香科最初可能出现在季节性热带地区，尽管它们的物种多样性中心现在在季节性热带地区。具有这种适应季节性热带的开花触发器的树木入侵季节性热带，可以帮助解释物种开花和结果或多或少同步的物候核心的起源。在某些情况下，造成这些大规模流动的干旱可能是西太平洋厄尔尼诺-南方涛动现象的气候影响所造成的，这一点可以从厄尔尼诺年与干旱和热带马尔代夫迎风坡上的桅杆结果的时间关系中得到证明。
The supra-annual mast fruiting of dipterocarps, dominant trees of Far Eastern lowland rain forests, has been considered an adaptation to reduce seed predation through satiation. However, this explanation raises four important questions. (1) What pollinates species that flower at intervals of more than one year? (2) How do mass-flowering species avoid competition for pollinators? (3) What is the environmental cue for floral induction that induces scores of species in several families to flower at irregular intervals of more than one year in an aseasonal climate? (4) And, most important, what factors could cause an initial phenological aggregation of species' fruiting times? Once such a phenological core of species exists, selection for predator satiation could entrain other species into the same fruiting schedule and perfect the synchrony of seed release. The essential question is how such a phenological core of species, flowering at irregular intervals in an aseasonal climate, could initially arise. The observations and analyses presented here indicate that the answers to these questions are intricately related to each other and to the El Nino-Southern Oscillation phenomenon. (1) Several mass-flowering dipterocarps are pollinated by thrips, which persist at low levels between mass flowerings and can explode in density as the dipterocarps come into flower. (2) Mass-flowering dipterocarp species in Shorea section Mutica significantly reduce the overlap in flowering times by staggering their flowering periods, thereby reducing competition for pollinators and/or the clogging of stigmas with foreign pollen. The new technique used to analyze whether a particular pattern of resource use significantly reduces overlap overcomes an error inherent in previous techniques, and it should be used whenever the total flowering season or range of resources is determined not by external conditions, but by the range of flowering times or resources used by the species in question. (3) The time of floral induction in Shorea section Mutica is derived using the linear relationship between the duration of each species' flowering period and mean flowering date. An analysis of meteorological records suggests that induction is caused by a drop of roughly 2C or more in minimum nighttime temperature for three or more nights. This extraordinary trigger is probably the most reliable signal associated with an invasion of the aseasonal tropics by a dry air mass. (4) Such a trigger does not appear to be directly adaptive in the aseasonal tropics, but in the seasonal tropics it would result in flowering at the onset of dry season and ripening fruits at the beginning of rainy season. This suggests that the Dipterocarpaceae may have arisen initially in the seasonal tropics, even though their center of species diversity is now in the aseasonal tropics. Invasion of the aseasonal tropics by trees having such a floral trigger, adapted to the seasonal tropics, could help explain the origin of a phenological core of species flowering and fruiting more or less synchronously at intervals of several years. The droughts causing these mass flowerings may, in some cases, be driven by the climatic effects of the El Nino-Southern Oscillation phenomenon in the western Pacific, as evidenced by the temporal association of El Nino years with drought and mast fruiting on windward slopes of tropical Malesia.