The role of pollen limitation on the coexistence of two dioecious, wind-pollinated, closely related shrubs in a fluctuating environment
The role of pollen limitation on the coexistence of two dioecious, wind-pollinated, closely related shrubs in a fluctuating environment
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DOI：
10.1007/s00442-010-1696-z
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发表时间：
2010-11-01
期刊：
影响因子：
2.7
通讯作者：
Franco, Miguel
中科院分区：
文献类型：
--
作者：
Cazares-Martinez, Juana;Montana, Carlos;Franco, Miguel
阐明物种共存的机制是生态学的一个重要目标。理论表明，当资源丰度波动时，如果竞争对中的每个物种都能更好地利用波动资源范围的相反极端的资源，则可以实现共存。尽管如此，允许共存的近端机制在很大程度上仍未被探索。在之前的一篇论文中，我们表明，两种滨藜物种的共存是由于它们对水资源波动的不同人口反应（生存、生长和补充）而促进的。在这里，我们探讨空间分布、花粉和资源限制对相同两个物种的繁殖成功（生产有活力的种子）的影响。对它们空间分布的分析表明，Atriplex acanthocarpa 具有丛集分布，这被认为可以提高风授粉植物授粉的有效性，而 Atriplex canescens 具有随机分布，这种模式预计会限制风授粉的成功。通过重复测量设计实施的花粉和资源（水和养分）添加实验表明，白花蒿的种子活力受到花粉和资源的限制，但这些影响在棘果花中可以忽略不计。在自然条件下，花粉限制将白蜡菊的种子数量限制为人工授粉时记录的种子数量的三分之一。当限制性资源（水）充足且幼苗补充发生时，花粉限制会降低其繁殖力（以及随之而来的潜在幼苗补充），从而逆转了 A. canescens 相对 A. acanthocarpa 的竞争优势。据我们所知，我们对奇瓦瓦沙漠中这一同属对的研究首次记录了花粉限制与物种共存之间的联系。
Elucidating the mechanisms of species coexistence is a crucial goal in ecology. Theory suggests that, when resource abundance fluctuates, coexistence can be achieved if each species in a competing pair is better at exploiting resources at opposite extremes of a fluctuating resource spectrum. Nonetheless, the proximal mechanisms allowing coexistence remain largely unexplored. In a previous paper, we showed that the coexistence of two Atriplex species was facilitated by their varying demographic response (in survival, growth and recruitment) to fluctuation in water availability. Here we explore the effect of spatial distribution, and pollen and resource limitation on the reproductive success (production of viable seeds) of the same two species. An analysis of their spatial distribution showed that Atriplex acanthocarpa had a clumped distribution, which is thought to increase the effectiveness of pollination in wind-pollinated plants, while Atriplex canescens had a random distribution, a pattern expected to restrict wind-pollination success. A pollen and resource (water and nutrients) addition experiment implemented through a repeated-measures design demonstrated that seed viability of A. canescens was both pollen and resource limited, but that these effects were negligible in A. acanthocarpa. Under natural conditions, pollen limitation restricted seed number in A. canescens to only one-third of that recorded when manual pollination was performed. By decreasing its fecundity (and consequent potential seedling recruitment), pollen limitation reverses the competitive advantage of A. canescens over A. acanthocarpa when the limiting resource (water) is abundant and seedling recruitment takes place. To our knowledge, our study of this congeneric pair in the Chihuahuan Desert is the first to document a link between pollen limitation and species coexistence.