Pollination in Verbascum thapsus (Scrophulariaceae):: The advantage of being tall
Pollination in Verbascum thapsus (Scrophulariaceae):: The advantage of being tall
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DOI：
10.2307/2446490
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发表时间：
1998-11-01
影响因子：
3
通讯作者：
Aarssen, LW
中科院分区：
文献类型：
--
作者：
Donnelly, SE;Lortie, CJ;Aarssen, LW
根据“有效授粉”假说，高大的身材从强大的顶端优势吸引更大的传粉者访问，从而允许更大的花粉负荷和/或更大的异交率，这反过来又产生更有力的后代与更大的基因型变异和/或更少的近交衰退。这一假设的组成部分进行了测试毛蕊花thapsus，通常生长不分枝超过2米高，强大的顶端优势抑制所有腋生分生组织。一项自然种群调查表明，有访花传粉者的植物比没有访花传粉者的最近邻个体显著高。排除传粉者的自然种群中的植物通过延迟自交机制产生种子。然而，延迟自交下授粉排除导致只有75%的种子集获得与自然授粉。在自然授粉，去雄花经历了50%的花粉沉积减少花关闭的时间，但只有5%的减少，相对于完整的花种子集。因此，较高的植物吸引更多的传粉者和最大的种子集不能实现没有传粉者。在温室和自然群体中人工自交和人工杂交的植物中的结实和种子质量的比较表明，植物是完全自交亲和的，没有早期作用的近交衰退的证据。然而，这并不排除近亲繁殖抑郁症在以后的生活阶段表现出来的可能性。结果表明，V. thapsus具有混合交配系统，具有生殖保证的潜力和不同水平的异交，这取决于影响传粉者可用性的变量（例如，人口规模）。
According to the "effective pollination" hypothesis, tall stature resulting from strong apical dominance attracts greater pollinator visitation, thus allowing larger pollen loads and/or greater outcrossing rates, which in turn produces more vigorous offspring with greater genotypic variability and/or less inbreeding depression. Components of this hypothesis were tested in Verbascum thapsus, which commonly grows unbranched to over 2 m tall with strong apical dominance suppressing all axillary meristems. A natural population survey indicated that plants with visiting pollinators were significantly taller than their nearest neighboring individuals not possessing a visiting pollinator. Plants in natural populations with excluded pollinators produced seeds via a delayed selfing mechanism. However, delayed selfing under pollinator exclusion resulted in only 75% of the seed set obtained with natural pollinators. Under natural pollination, emasculated flowers experienced a 50% reduction in pollen deposition by the time of flower closure but only a 5% reduction in seed set relative to intact flowers. Hence, taller plants attracted more pollinators and maximum seed set could not be achieved without pollinators. Comparison of seed set and seed mass in plants that were artificially selfed and artificially crossed tin both the greenhouse and in natural populations) indicated that plants were fully self-compatible with no evidence of early-acting inbreeding depression. However, this does not exclude the possibility that inbreeding depression is manifested in later life stages. The results suggest that V. thapsus has a mixed mating system with potential for reproductive assurance and various levels of outcrossing depending on variables affecting pollinator availability (e.g., population size).