Effect of variation in herkogamy on outcrossing within a population of Gilia achilleifolia
Effect of variation in herkogamy on outcrossing within a population of Gilia achilleifolia
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DOI：
10.1038/sj.hdy.6800780
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发表时间：
2006-02-01
期刊：
影响因子：
3.8
通讯作者：
Delph, LF
中科院分区：
文献类型：
--
作者：
Takebayashi, N;Wolf, DE;Delph, LF
花形态的多样化特征通常被认为是操纵植物交配系统的精心设计的机制。我们评估了一种这样的机制，花药-柱头分离（雌雄异体交配），在控制植物间异交水平变化的有效性。种群内异交率的变化有可能影响近亲繁殖抑制和交配制度之间的共同进化。利用四种多态性同工酶，比较了两组个体在自然条件下的异交率估计值：一组为低异交，另一组为高异交。高偶配组异交率（0.572）高于低偶配组（0.335）。这表明种群内异交率的变化可能会导致先前观察到的异族通婚和近交抑制之间的关联（Takebayashi和Delph， 2000）。以往的研究未能发现雌雄异体交配与异交率之间的关系，这表明在种群研究中，性状的功能可能由于不受控制的环境变化而被模糊。此外，雌雄异体杂交对延迟自交者异交率的影响在传粉者可用性较低时可能特别突出。我们对异交率的种群水平估计值（0.444）略低于15年前对同一种群的估计值（0.75），这表明传粉者的可用性可能在不同的年份之间波动。异交率的年内和年内变化都可能对交配系统的进化产生重大影响。
The diverse features of floral morphology are often thought to be well-designed mechanisms to manipulate plant mating systems. We evaluated the effectiveness of one such mechanism, anther - stigma separation (herkogamy), in controlling variation in the level of outcrossing among plants in a population of Gilia achilleifolia. Variation in outcrossing rates within populations has the potential to influence the coevolution between inbreeding depression and mating system. Using four polymorphic allozymes, we compared the outcrossing-rate estimates of two groups of individuals under natural conditions: one group with low herkogamy and another with high herkogamy. The high herkogamy group had a higher outcrossing rate (0.572) than the low herkogamy group (0.335). This suggests that the within-population variation in outcrossing rate could potentially cause the previously observed association between herkogamy and inbreeding depression (Takebayashi and Delph, 2000). A previous study of floral traits among G. achilleifolia populations failed to detect a relationship between herkogamy and outcrossing rate, demonstrating that the functionality of traits may be obscured in among-population studies as a consequence of uncontrolled environmental variation. Additionally, the effect of herkogamy on outcrossing rate in delayed selfers such as G. achilleifolia may be particularly prominent when pollinator availability is low. Our population-level estimate of outcrossing rate (0.444) was somewhat lower than an estimate from the same population, 15 years prior to our study (0.75), suggesting that pollinator availability may fluctuate among years. Both within-year and among-year variation in the outcrossing rate may have a strong influence on mating-system evolution.