PDF(Pubmed)
Abstract：
Competition affects mixed-mating strategies by limiting available abiotic or biotic resources such as nutrients, water, space, or pollinators. Cleistogamous species produce closed (cleistogamous, CL), obligately selfed, simultaneously with open (chasmogamous, CH), potentially outcrossed flowers. The effects of intraspecific competition on fitness and cleistogamy variation can range from limiting the production of costly CH flowers because of resource limitation, to favouring CH production because of fitness advantages of outcrossed, CH offspring. Moreover, the effects of competition can be altered when it co-occurs with other environmental variations. We grew plants from seven populations of the ruderal Lamium amplexicaule, originating from different climates and habitats, in a common garden experiment combining drought, interspecific competition, and seasonal variation. All these parameters have been shown to influence the degree of cleistogamy in the species on their own. In spring, competition and drought negatively impacted fitness, but the CL proportion only increased when plants were exposed to both treatments combined. We did not observe the same results in autumn, which can be due to non-adaptive phenotypic variation, or to differences in soil compactness between seasons. The observed responses are largely due to phenotypic plasticity, but we also observed phenotypic differentiation between populations for morphological, phenological, and cleistogamy traits, pointing to the existence of different ecotypes. Our data do not support the hypothesis that CL proportion should decrease when resources are scarce, as plants with reduced growth had relatively low CL proportions. We propose that variation in cleistogamy could be an adaptation to pollinator abundance, or to environment-dependent fitness differences between offspring of selfed and outcrossed seeds, two hypotheses worth further investigation. This opens exciting new possibilities for the study of the maintenance of mixed-mating systems using cleistogamous species as models that combine the effects of inbreeding and reproductive costs.
摘要：
竞争通过限制可用的非生物或生物资源，如营养素，影响混合交配策略。水,空间,或传粉者。cleistogamous物种产生封闭(cleistogamous，CL),强制自食，同时开放(chasmogamous，CH),潜在的花朵。种内竞争对适应性和cleistogamy变异的影响可能由于资源限制而限制昂贵的CH花的生产，为了有利于CH生产，因为它具有优势，CH后代。此外，当竞争与其他环境变化共同发生时，竞争的影响可以改变。我们从7个红豆杉种群中种植植物，来自不同的气候和栖息地，在一个结合干旱的普通花园实验中，种间竞争，和季节性变化。所有这些参数都已被证明会影响该物种中的cleistogamy的程度。在春天,竞争和干旱对健身产生了负面影响，但是CL比例仅在植物暴露于两种处理组合时才增加。我们在秋天没有观察到同样的结果，这可能是由于非适应性表型变异，或季节之间土壤密实度的差异。观察到的反应主要是由于表型可塑性，但我们也观察到种群之间的表型分化，物候,和cleistogamy特征，指向不同生态型的存在。我们的数据不支持以下假设：当资源稀缺时，CL比例应该降低，由于生长减少的植物具有相对较低的CL比例。我们认为cleistogamy的变异可能是对传粉者丰度的适应，或自交和异交种子的后代之间依赖于环境的适应性差异，两个假设值得进一步研究。这为使用cleistogamily物种作为结合近亲繁殖和生殖成本影响的模型来研究混合交配系统的维护开辟了令人兴奋的新可能性。
