BREEDING SYSTEMS, POLLEN FLOW, AND CONTINUING EVOLUTION IN AVON GORGE SORBUS (WHITEBEAMS, ROWANS, AND SERVICE TREES)

雅芳峡谷花楸（白梁树、花楸树和服务树）的繁殖系统、花粉流和持续进化

• 批准号: NE/G011656/1
• 金额: $ 8.69万
• 依托单位: University of Bristol
• 依托单位国家: 英国
• 项目类别: Training Grant
• 财政年份: 2009
• 资助国家: 英国
• 起止时间: 2009 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FG011656%2F1
• 关键词: BREEDING; SYSTEMS; POLLEN; FLOW; CONTINUING

The Avon Gorge is one of the richest botanical sites in Britain, and is internationally important for its Sorbus diversity, with 3 endemic species and at least 3 endemic hybrids amongst the 19 taxa recorded (Rich et al. 2008). Four species are currently on the IUCN Red List of endangered species: S. bristoliensis, S. wilmottiana, S. anglica and S. eminens (IUCN, 2007). Recent research by Hiscock and CASE partner, Rich, has shown that Sorbus diversity in the gorge is generated primarily by hybridisation between sexual diploids S. aucuparia, S. torminalis, and (especially) S. aria, and the polyploid facultative apomict S. porrigentiformis and its derivatives, S. eminens and S. bristoliensis (Robertson et al. in preparation). The type of mating system employed by the various taxa is pivotal to this continuing evolutionary process. The 3 sexual taxa are obligate outcrossers whereas the hybrid polyploids are either obligate apomicts (producing asexual seed), or facultative apomicts (reproducing by a combination of apomixis and sexual reproduction). In the polyploids, apomixis is via pseudogamy with pollination being required to induce asexual seed development and produce a sexual endosperm. Importantly, however, our recent studies have shown that the rare apomictic polyploids, S. bristoliensis and S. wilmottiana, cannot utilize self-pollen or pollen from other con-specific individuals (clones) because of self-incompatibility. This necessitates that they receive pollen from other Sorbus species, in particular S. aria, in order to produce seeds via pseudogamy (Robertson et al. in preparation). Thus pollination is essential for all reproductive processes among the Sorbus taxa and consequently for their population dynamics and ongoing evolution. This research will aim to quantify pollen movement and pollen limitation among Sorbus taxa in the Avon Gorge and relate this to population dynamics and ongoing evolution of new Sorbus taxa. These data will then be used to inform our collaborators, Bristol City Council, Natural England, and The National Trust, on the most appropriate conservation strategies to preserve rare endemic Sorbus species and to maintain the process responsible for creating Sorbus diversity within the Avon Gorge. Our preliminary findings (Robertson et al. in preparation) indicate that S. aria is an essential source of pollen needed for seed production by the rare apomictic Sorbus species suggesting that S. aria will need to be considered in all Sorbus conservation strategies. The research proposed here has two main aims: 1) to characterize the mating system(s) of the 5 new Sorbus taxa and 2) to quantify flowering time, pollen movement and pollen limitation among the different Sorbus taxa in the Avon Gorge and relate this to reproductive output, population dynamics, and ongoing evolution of new Sorbus taxa. In particular, this work will confirm whether S.aria pollen is indeed driving reproduction and ongoing diversification of Sorbus in the Avon Gorge, and provide estimates of the number and density of S. aria needed to maintain these processes and guaratee successful reproduction of the rare endemic species. This will be accomplished through delivery of the following objectives: 1. Establish modes of reproduction (mating system) in newly described Sorbus taxa not already tested. 2. Determine annual and seasonal variation in flowering time for all Sorbus taxa. 3. Determine the primary pollinators of Sorbus pollinators. 4. Measure pollen limitation among sexual and apomictic Sorbus taxa. 5. Estimate distances of pollen flow from individual Sorbus trees (particularly S. aria) using fluorescent dust and polymorphic microsatellite markers. 6. Calculate pollen neighbourhoods and predict densities of S. aria required to effect seed production in rare pseudogamous apomicts.

埃文峡谷是英国植物资源最丰富的地区之一，其花梨多样性在国际上具有重要意义，在记录的 19 个类群中拥有 3 个特有物种和至少 3 个特有杂交品种（Rich 等，2008）。目前有四个物种被列入 IUCN 濒危物种红色名录：S. bristoliensis、S. wilmottiana、S. anglica 和 S. eminens（IUCN，2007）。 Hiscock 和 CASE 合作伙伴 Rich 最近的研究表明，峡谷中的花梨多样性主要是通过有性二倍体 S. aucuparia、S. torminalis 和（特别是）S. aria 与多倍体兼性无融合生殖 S. porrigentiformis 及其衍生物 S. eminens 和 S. bristoliensis（Robertson 等人正在准备）之间的杂交产生的。不同类群所采用的交配系统类型对于这种持续的进化过程至关重要。 3个有性分类群是专性异交体，而杂种多倍体是专性无性生殖（产生无性种子）或兼性无性生殖（通过无性生殖和有性生殖的组合进行繁殖）。在多倍体中，无融合生殖是通过假受精进行的，需要授粉来诱导无性种子发育并产生有性胚乳。然而，重要的是，我们最近的研究表明，罕见的无融合生殖多倍体，S. bristoliensis和S. wilmottiana，由于自交不亲和性而不能利用自体花粉或来自其他同种个体（克隆）的花粉。这就需要它们从其他花梨属物种（尤其是花梨属）获取花粉，以便通过假受精产生种子（Robertson 等人正在准备中）。因此，授粉对于花梨类群的所有繁殖过程至关重要，因此对于它们的种群动态和持续进化至关重要。这项研究旨在量化埃文峡谷山梨类群的花粉运动和花粉限制，并将其与新山梨类群的种群动态和持续进化联系起来。然后，这些数据将用于向我们的合作者、布里斯托尔市议会、自然英格兰和国家信托基金提供有关最适当的保护策略的信息，以保护稀有的特有花梨物种，并维持在埃文峡谷内创造花梨多样性的过程。我们的初步研究结果（Robertson 等人正在准备中）表明，S. aria 是稀有无融合生殖花梨物种种子生产所需花粉的重要来源，这表明 S. aria 需要在所有花梨保护策略中得到考虑。这里提出的研究有两个主要目的：1）表征 5 个新花梨类群的交配系统；2）量化埃文峡谷不同花梨类群之间的开花时间、花粉运动和花粉限制，并将其与新花梨类群的生殖产出、种群动态和持续进化联系起来。特别是，这项工作将确认 S.aria 花粉是否确实推动了埃文峡谷花梨的繁殖和持续多样化，并提供维持这些过程所需的 S.aria 数量和密度的估计，并确保稀有特有物种的成功繁殖。这将通过实现以下目标来实现： 1. 在尚未测试的新描述的花梨类群中建立繁殖模式（交配系统）。 2. 确定所有花梨类群开花时间的年度和季节变化。 3. 确定花梨授粉媒介的主要授粉媒介。 4. 测量有性生殖和无性生殖花梨类群中的花粉限制。 5. 使用荧光尘埃和多态性微卫星标记估计单个花梨树（特别是 S. aria）的花粉流距离。 6. 计算花粉邻域并预测影响稀有假受精无融合生殖种子生产所需的 S. aria 密度。