Testing the Role of Reproductive Assurance Selfing in the Maintenance of Mixed Mating

Kalisz 9726980植物的交配系统(它的异交而不是自花授粉的程度)是种群水平上遗传变异的重要决定因素。虽然理论研究已经证明，完全异交或完全自交都是稳定的进化状态，但混合交配(即后代由自交和异交花粉混合而成)并不那么容易解释。然而，在所研究的近一半的动物授粉植物中，观察到了中等异交率(在20%-80%之间)。目前的研究利用冬季一年生草本植物Collinsia Verna作为模式生物，研究传粉者活动在花季变化的后果及其对作为后备策略的自花授粉进化的影响(即生殖保证自交)。通过一系列综合田间试验和控制环境试验，利用单株的克隆复制，可以量化导致延迟自交、自花授粉结果成功的特定花卉属性与这些个体表现出的近交抑制程度之间的相关性。这些测量将根据一种新的田间生物测定进行解释，该测定允许我们从经历共同资源条件的成对花的角度来量化传粉者失败的频率。田间对传粉者失败和自交能力的估计将与三个群体在整个花季和两年内得出的自然异交率的估计进行比较。这项拟议的研究解决了通过传粉者介导的花粉限制对延迟自交的选择压力、混合交配的表达以及自然种群中表达的近亲繁殖抑制之间的联系。繁殖保证自交的实际物理过程在很少的物种中得到了表征。量化花内自花授粉的时间和相关的形态特征将解决进化生态学中的一个重要问题：发育过程(如花药和雌蕊伸长的时间)如何影响自交率以及它们如何进化。此外，这项研究将首次检验Schoen和Brown(1991)的混合交配模型，该模型表明，当传粉者可获得性存在环境变化时，生殖保证在推动混合交配系统进化方面比近亲繁殖衰退更重要。因此，植物遗传学家、作物育种者和自然资源保护者将对这项工作感兴趣，他们研究的物种可能会因为不寻常的天气模式或关键传粉者的区域性流行病(例如最近蜜蜂种群发生的情况)而变得限制花粉。

Kalisz 9726980 A plant's mating system (the degree to which it outcrosses rather than self pollinates) is a vital determinant of genetic variability at the population level. While theoretical studies have demonstrated that either complete outcrossing or complete selfing are stable evolutionary states, mixed mating (whereby progeny are sired by a mixture of self and outcross pollen) is not as easily explained. Yet in nearly half of the animal pollinated plants studied, intermediate outcrossing rates (those between 20-80%) are observed. The current study utilizes the winter annual, Collinsia verna, the Blue-eyed Mary, as a model organism to examine the consequences of variability of pollinator activity over the flowering season and its influence on the evolution of self pollination as a back-up strategy (i.e., reproductive assurance selfing). Using clonal replicates of individual plants in a series of integrated field and controlled environment experiments, the correlations between specific floral attributes conferring delayed selfing, fruiting success via self pollination, and the degree of inbreeding depression expressed by those individuals will be quantified. These measurements will be interpreted in the light of a novel field bioassay which allows us to quantify the frequency of pollinator failure from the perspective of paired flowers which are experiencing common resource conditions. Field estimates of pollinator failure and selfing ability will be compared with estimates of the natural outcrossing rates derived for three populations across the flowering season and across two years. The proposed research addresses the links between selective pressures on delayed selfing via pollinator mediated pollen limitation, the expression of mixed mating, and inbreeding depression expressed in natural populations of Collinsia verna. The actual, physical process of reproductive assurance selfing has been characterized for very few species. Q uantifying the timing of self-pollination within a flower, and the associated morphological traits will address an important issue in evolutionary ecology: how developmental processes (like the timing of anther and pistil elongation) contribute to selfing rates and how they evolve. Moreover, this research will be the first to test the mixed mating model of Schoen and Brown (1991) which indicates that when environmental variation in pollinator availability exists, reproductive assurance is more important in driving the evolution of a mixed mating system than is inbreeding depression. As a result, this work will be of interest to plant geneticists, crop breeders and conservationists who work with species which may become pollen-limited due to unusual weather patterns or regional epidemics in key pollinators (e.g. as has happened recently to honeybee populations).