Frequency dependence of pollinator visitation rates suggests that pollination niches can allow plant species coexistence
Frequency dependence of pollinator visitation rates suggests that pollination niches can allow plant species coexistence
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DOI：
10.1111/1365-2745.13025
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发表时间：
2018-09-01
影响因子：
5.5
通讯作者：
Pauw, Anton
中科院分区：
文献类型：
--
作者：
Benadi, Gita;Pauw, Anton
1.在一个营养级中，多种物种是如何共存的？资源生态位是经典的答案，但在植物中，共享一小部分非生物资源，资源分配的可能性是有限的。一个可能的解释是，植物物种有不同的授粉生态位，每个物种专门针对一个子集的可用动物物种。如果这种传粉者分配导致负频率依赖，使得每种植物的繁殖在其变得丰富时减少，那么传粉生态位可以维持植物的多样性，只要负频率依赖的强度足以克服物种间的适合度不平等.我们通过在南非Fynbos植被的7，000 m2地块中量化物种相对丰度对传粉者访问率的影响来验证这一想法。此外，我们在较小的空间尺度（9 m（2）样地）上量化了种内丰度变化的影响，记录了物种的授粉生态位，并测试了传粉者对植物物种子集中种子集的重要性。我们发现，访问率确实急剧下降，在33种植物的丰富度增加，但访问率也有些沮丧，在非常罕见的物种，访问率和相对丰富度之间的关系是驼峰形的。植物物种之间的传粉者生态位分区是明显的，但不太明显，比许多其他研究。更广义的物种的访问率略高，这表明他们有机会获得更大的授粉资源。在种内水平和较小的空间尺度，结果不太清楚，物种之间的变化。传粉者促进大多数物种的结实。合成.结果表明，在一定的丰度阈值以上，种内传粉竞争可以限制常见物种的繁殖，从而促进植物种间共存。然而，最稀有的植物物种可能由于花粉限制而灭绝，即Allee效应。此外，与传粉者的相互作用可能会引入植物物种之间的频率无关的健身差异，从而增加稳定共存所需的负频率依赖的强度。这些发现揭示了传粉生态位在植物共存中的作用。
1. How do many species coexist within a trophic level? Resource niches are the classical answer, but in plants which share a small set of abiotic resources, the possibilities for resource partitioning are limited. One possible explanation is that plant species have different pollination niches, with each species specialized to a subset of the available animal species. If this pollinator partitioning results in negative frequency dependence such that each plant species' reproduction is reduced when it becomes abundant, pollination niches could maintain plant diversity, provided that the strength of negative frequency dependence is sufficient to overcome fitness inequalities between species.2. We tested this idea by quantifying the effect of species relative abundance on pollinator visitation rate in a 7,000 m(2) plot of South African Fynbos vegetation. In addition, we quantified the effect of intraspecific abundance variation at a smaller spatial scale (9 m(2) plots), documented species' pollination niches, and tested the importance of pollinators for seed set in a subset of the plant species.3. We found that visitation rate indeed declined sharply across the 33 plant species with increasing abundance, but visitation rate was also somewhat depressed in very rare species such that the resulting relationship between visitation rate and relative abundance was hump-shaped. Pollinator niche partitioning among plant species was evident, but less pronounced than in many other studies. Visitation rate was slightly higher in more generalized species, suggesting that they have access to a larger pollination resource. At the intraspecific level and smaller spatial scale, results were less clear and varied among species. Pollinators enhanced seed set in most species.4. Synthesis. The results imply that, above an abundance threshold, intraspecific competition for pollination could limit the reproduction of common species, thus promoting plant species coexistence. However, the rarest plant species could become extinct due to pollen limitation, that is, an Allee effect. In addition, interactions with pollinators may introduce frequency-independent fitness differences between plant species, thereby increasing the strength of negative frequency dependence required for stable coexistence. These findings shed new light on the role of the pollination niche in plant coexistence.