Premise of research. Breeding systems dictate the potential for self-fertilization in plants and may therefore have a strong influence on evolutionary and ecological processes. Previous investigations of breeding systems in Ericaceae indicate variation in self-sterility, but studies from the megadiverse genus Erica are almost entirely lacking. Here we quantify the degree of self-sterility and autofertility in Cape Erica species, quantify pollen-ovule ratios (P/Os), and test whether these are related to each other and vary across species with bird- versus insect-pollination syndromes.Methodology. We used controlled hand-pollinations, analyses of pollen tube development, and P/Os to investigate the breeding systems of 15 taxa (comprising 13 species) of Erica in the Cape Floristic Region of South Africa, spanning most main clades across the phylogeny.Pivotal results. In all but one species, seed set from autonomous selfing was almost absent and significantly lower than that from cross-pollination, and only one species had an autofertility index that was higher than 0.2. In 12 taxa, seed set following self-pollination was significantly reduced compared with that following cross-pollination, and the index of self-incompatibility (ISI) was higher than 0.8 for 10 taxa. Following self-pollination, pollen tubes reached the ovary in all species, and for two species with very low seed set in selfed flowers, fluorescence images revealed that self-pollen tubes entered into the ovules. P/Os ranged from 68 to 320 and are therefore low for obligate outcrossing species. These ratios did not correlate with the ISI and did not vary according to whether species conformed to insect- or bird-pollination syndromes.Conclusions. This study indicates that self-sterility is frequent in Cape Erica species and either involves a late-acting mechanism of self-incompatibility or is due to early inbreeding depression. P/Os in these species are consistently low and do not reflect variation in breeding systems and pollination syndromes.

中文翻译：

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开普植物区的Erica物种（Ericaceae）的繁殖系统和花粉胚珠比率

研究前提。育种系统决定了植物自我受精的潜力，因此可能对进化和生态过程产生重大影响。先前对埃里卡科（Ericaceae）育种系统的调查表明，自我不育存在差异，但几乎完全缺乏对巨型多样的埃里卡（Erica）属的研究。在这里，我们量化了埃里卡角物种的不育和自育程度，量化了花粉-胚珠比（P / O），并测试它们是否彼此相关，以及在鸟类与昆虫授粉综合症之间的差异。方法。我们使用受控的人工授粉，花粉管发育分析和P / O，调查了南非开普植物区的埃里卡的15个类群（包含13种）的繁殖系统，涵盖了整个系统发育的大部分主要进化枝。重要结果。除一个物种外，几乎所有物种都不存在自交自交的结实种子，并且显着低于异花授粉的结实种子，只有一个物种的自育指数高于0.2。在12个分类单元中，自花授粉后的结实种子与异花授粉后相比明显减少，并且10个分类单元的自交不亲和指数（ISI）高于0.8。自花授粉后，所有物种的花粉管都到达了子房，而对于自花中种子极少的两个物种，荧光图像显示自花粉管进入了胚珠。P / O范围从68到320，因此对于专性异交物种而言较低。这些比率与ISI不相关，并且不会根据物种是否符合昆虫或鸟类授粉综合征而变化。结论。这项研究表明，在埃里卡角种中，自我不育很常见，或者涉及自我不相容的后期作用机制，或者归因于近亲衰退。这些物种的P / O始终较低，不能反映出繁殖系统和授粉综合征的差异。