Effects of pollen shortage and self-pollination on seed production of an endangered tree, Magnolia stellata
Effects of pollen shortage and self-pollination on seed production of an endangered tree, Magnolia stellata
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DOI：
10.1093/aob/mci107
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发表时间：
2005-05-01
期刊：
影响因子：
4.2
通讯作者：
Tomaru, N
中科院分区：
文献类型：
--
作者：
Hirayama, K;Ishida, K;Tomaru, N
背景和目的花粉限制是种子生产的重要决定因素，并且可以由花粉数量不足（花粉短缺）和质量不足（主要与自花授粉有关）引起。对于具有大花展示的动物授粉树种，花粉限制可以通过由于传粉者的吸引力增加而增加的花粉量之间的平衡来确定，由于geitonogamy增加而增加自花授粉。花粉短缺和自花授粉对种子生产的贡献进行了定量研究，在自然授粉的昆虫授粉，雌雄异熟，濒危树木，木兰stellata，这有一个大的，艳丽的花shower.Methods手动自花授粉和异花授粉进行，以确定出售种子生产的影响。通过对自由授粉种子的微卫星分析，测定了异交率，并间接估计了自花授粉引起的胚死亡率。人工异花授粉的平均坐果率、每果结实率和每株胚珠存活率分别是人工自花授粉的1.37、3.15和3.34倍，而人工授粉的平均坐果率、每果结实率和每株胚珠存活率分别是人工自花授粉的1.37、3.15和3.34倍。表明自花授粉导致果实和结实的近交衰退。多株异交率（t（m））居中，为0.632，初级自交率为0.657。这表明频繁的geitonogamous销售发生。花粉缺乏引起的胚珠死亡率为80.8%，自花授粉引起的胚死亡率为45.9%。stellata受到花粉短缺和自花授粉的强烈限制。低效率的甲虫授粉和自花授粉系统通过异步开花可能是负责高度的花粉短缺和频繁的geitonogram。这是尽管一个大的，艳丽的花卉展示和物种的雌雄异株系统。
Background and Aims Pollen limitation is a significant determinant of seed production, and can result from both insufficient pollen quantity (pollen shortage) and quality (mainly relating to self-pollination). For animal-pollinated tree species with large floral displays, pollen limitation may be determined by a balance between increased pollen quantity due to increased attractiveness for pollinators, countered by increased self-pollination due to increased geitonogamy. The contributions of pollen shortage and self-pollination on seed production were quantitatively examined in the natural pollination of an insect-pollinated, dichogamous, endangered tree, Magnolia stellata, which has a large, showy floral display.Methods Manual self- and cross-pollinations were conducted to determine the effects of selling on seed production. The outcrossing rate was measured using microsatellite analyses of open-pollinated seeds, and the embryo mortality rate caused by self-pollination was indirectly estimated. The frequency of ovule mortality due to pollen shortage was also inferred using the embryo mortality and ovule survival rates from natural pollination.Key Results The average fruit set, seed set per fruit, and Ovule survival rate per tree from hand cross-pollination were 1.37, 3.15, and 3.34 times higher than those from hand self-pollination, respectively, indicating that self-pollination causes inbreeding depression for fruit and seed set. The multilocus-outcrossing rate (t(m)) was intermediate, 0.632, and the primary selfing rate was 0.657. This indicates that frequent geitonogamous selling occurs. The ovule mortality rate due to pollen shortage and the embryo mortality rate due to self-pollination were estimated to be 80.8 % and 45.9 %, respectively.Conclusions It is concluded that seed production of M. stellata is strongly limited by both pollen shortage and self-pollination. Inefficient beetle-pollination and the automimicry system via asynchronous flowering might be responsible for the high level of pollen shortage and frequent geitonogamy. This is despite a large, showy floral display and the dichogamous system of the species.