Data from: Distinct effects of pollinator dependence and self-incompatibility on pollen limitation in South African biodiversity hotspots

Global synthesis indicates that limitation of plant fecundity by pollen receipt (pollen limitation) is positively related to regional plant diversity and is higher for self-incompatible than self-compatible species. While self-incompatible species are always dependent on pollinating agents, self-compatible species may be pollinator-dependent or autofertile. This should cause variation in pollen limitation among self-compatible species, with lower pollen limitation in autofertile species because they do not depend on pollinators. We hypothesized that the intensity of pollen limitation in self-incompatible compared with pollinator-dependent self-compatible species should depend on whether pollen limitation is determined more by quantity than quality of pollen received. We compared pollen limitation between these three groups using a dataset of 70 biotically pollinated species from biodiverse regions of South Africa. Comparison with a global dataset indicated that pollen limitation in the South African biodiversity hotspots was generally comparable to other regions, despite expectations of higher pollen limitation based on the global plant diversity–pollen limitation relationship. Pollen limitation was lowest for autofertile species, as expected. It was also higher for pollinator-dependent self-compatible species than self-incompatible species, consistent with increased pollen-quality limitation in the former group due to negative consequences of pollinator-mediated self-pollination. However, there was a higher frequency of plants with zygomorphic flowers, which were also more pollen-limited, among pollinator-dependent self-compatible species. Thus, we could not attribute this difference in pollen limitation exclusively to a difference in pollen quality. Nevertheless, our results indicate that comparative studies should control for both pollinator dependence and self-incompatiblity when evaluating effects of other factors on pollen limitation.

全球性综合研究表明，通过花粉接收限制植物繁殖力的现象（即花粉限制，pollen limitation）与区域植物多样性呈正相关，且自交不亲和（self-incompatible）物种的花粉限制程度高于自交亲和（self-compatible）物种。尽管自交不亲和物种始终依赖传粉媒介（pollinating agents），但自交亲和物种既可依赖传粉者，也可具备自发可育（autofertile）特性。这会导致自交亲和物种间的花粉限制程度存在差异：自发可育物种无需依赖传粉媒介，因此花粉限制程度更低。我们提出假说：相较于依赖传粉的自交亲和物种，自交不亲和物种的花粉限制强度，取决于花粉限制更多由接收花粉的数量还是质量所决定。我们利用来自南非生物多样性丰富区域的70种生物传粉（biotically pollinated）物种的数据集，对这三类物种的花粉限制水平开展了比较分析。与全球数据集对比后发现，尽管基于全球植物多样性-花粉限制关系的预期，南非生物多样性热点（biodiversity hotspots）区域的花粉限制程度本应更高，但实际整体上与其他区域并无显著差异。正如预期，自发可育物种的花粉限制程度最低。依赖传粉的自交亲和物种的花粉限制程度也高于自交不亲和物种，这与前者因传粉媒介介导的自交授粉（pollinator-mediated self-pollination）产生负面影响而导致花粉质量限制加剧的结果相一致。但在依赖传粉的自交亲和物种中，两侧对称花（zygomorphic flowers）植物的占比更高，且这类植物的花粉限制程度也更强。因此，我们无法将这类花粉限制的差异完全归因于花粉质量的差异。尽管如此，我们的研究结果表明，在评估其他因素对花粉限制的影响时，比较研究应同时控制传粉依赖程度与自交不亲和性这两个变量。