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1.
克隆植物与其传粉者的相互作用是植物繁殖生态学的重要研究领域之一。植物克隆生长与有性繁殖通常相伴进行,往往产生较大的花展示与复杂的克隆空间结构,通过传粉过程对有性繁殖过程产生影响,共同决定植物的适合度。本文回顾了克隆生长对被子植物传粉过程影响的国内外研究进展,从植物克隆大小、花资源空间配置、克隆构型与种群遗传结构四个方面讨论了克隆生长对传粉过程的影响及其生态学与进化生物学意义。早期研究预期,随着克隆增大,同株异花授粉水平增加,因而通过增大自交率或花粉阻塞效应降低植物的适合度。但是,后来的一些模拟与野外实验研究发现,传粉者在同一克隆内访问的花数量并不会随克隆增大而一直增加,访花行为也主要发生在分株内;而且分子标记的自交率组分分析也表明自交主要发生在分株内。另一方面,人工模型模拟以及传粉者访问行为研究表明,当花朵数量相同时,与所有花集中生长在同一分株上相比,将花朵分散在多个分株上的克隆生长方式不会增加,反而降低了同株异花授粉的发生水平。如果花序内花雌雄同熟,花朵同时提供与接收花粉,克隆生长会使植物接收到更高比例的异交花粉,在提高后代质量的同时不增加同株异花授粉概率。这是从传粉生物学角度对植物克隆生长习性进化的一个全新的解释。今后,克隆植物传粉生物学研究需要针对传粉者与克隆生长之间的相互作用建立理论模型,探究克隆大小、克隆构型、花资源空间配置模式对传粉者访问频率和行为、花粉散布、交配格局的影响。同时,需要在自然种群中,尤其是克隆与非克隆的近缘类群、同一物种克隆与非克隆种群开展比较研究,利用更高效的分子标记来研究克隆生长的生态与进化意义。  相似文献   

2.
植物表型受自身基因型、所处环境及其亲体所经历环境的共同影响;其中,亲体环境对子代表型的影响被称为亲体效应。亲体效应不仅可通过有性繁殖产生的种子传递给后代(即有性亲体效应),也可以通过克隆生长等无性繁殖产生的分株传递给后代(即克隆亲体效应)。亲体效应对植物种群,特别是对有性繁殖受限、缺乏遗传变异的克隆植物种群的长期进化可能发挥着极其重要的作用,因此,对亲体效应研究进展的梳理非常必要。对克隆亲体效应和有性亲体效应的内涵进行了阐释,并论述了克隆和有性亲体效应对子代表型、适合度、种内/种间竞争能力以及种群/群落结构和功能的潜在影响;阐述了亲体效应的潜在调控机制,包括供给机制、代谢物质调控机制、表观遗传机制等;论述了克隆亲体效应在克隆植物适应进化中的作用。未来可以就克隆亲体效应的遗传稳定性及其对克隆生活史性状变异的贡献程度,以及克隆和有性亲体效应引起的表型多样性对种内/种间关系、种群/群落多样性及生态系统结构、功能和稳定性的影响开展深入研究。  相似文献   

3.
草地植物种群繁殖对策研究   总被引:10,自引:2,他引:8  
植物的繁殖包括有性繁殖和无性繁殖两大类型,克隆繁殖是一种较为特殊的营养繁殖方式。本文综述了草地种子植物的生殖分配及生殖投资,克隆生长以及放牧对草地植物种群繁殖的影响。植物种群生物量、能量和养分生殖分配是植物种群生殖分配的重要内容,不同植物在结实期营养元素及能量的配置上有着显著的区别,这可能是植物在长期进化过程中形成的生殖对策,是适应环境的结果。在种群水平上,中等强度以上的放牧干扰有利于植物的克隆生长,但有性生殖减弱。草原植物发达的营养繁殖或克隆生长方式是对放牧的适应性对策。  相似文献   

4.
不同生境中克隆植物的繁殖倾向   总被引:14,自引:0,他引:14  
对克隆植物在林下、草原、荒漠、冻原、农田和水域等6种不同类型生境中的繁殖对策及其生态适应意义进行了归纳和总结。对克隆植物有性繁殖与无性繁殖之间的权衡关系及相对重要性随水分、光照和温度的变化规律进行了阐述。分析表明,在环境条件严酷地区,克隆植物的无性繁殖在种群更新中的相对重要性有所增加。对两种繁殖方式的生态功能特性进行比较,综述了有关二者权衡关系的研究成果及影响二者权衡关系的部分因素。从研究手段上对克隆植物繁殖对策的研究进行了思考与展望。  相似文献   

5.
入侵植物剑叶金鸡菊(Coreopsis lanceolata)既可进行有性繁殖,又能进行克隆繁殖,其繁殖特征可能对其入侵性具有重要影响,然而目前相关研究较少。通过观测剑叶金鸡菊的花序开花动态、交配系统、种子萌发特性等有性繁殖特征及克隆繁殖特征,研究了上述繁殖特性及其与入侵性之间的关系。结果表明,剑叶金鸡菊每年4月下旬开始现蕾,5–11月为花果期。单个花序的花期为5–6天,至果实成熟开裂约18天。单个花序自交及同株异花授粉不亲和,为异株异花授粉的异交型,其花粉-胚珠比(P/O比)为103549.40±7162.44。花序高花粉活力及本地蜂传粉行为保障了花粉资源,因而结实率高达12000粒.株–1。自然条件下其种子的萌发率高达50%以上,且2–3天即可萌发。剑叶金鸡菊克隆繁殖能力非常强,整个生长季节均可见从根蘖长出的密集型克隆分株,8月下旬开始出现游击型克隆生长,通过密集型和游击型克隆生长,剑叶金鸡菊排斥其他物种形成单优种群。上述研究结果说明,剑叶金鸡菊的入侵性与其繁殖特征密切相关。  相似文献   

6.
群落中克隆植物的重要性   总被引:26,自引:5,他引:21  
宋明华  董鸣 《生态学报》2002,22(11):1960-1967
综述了群落水平上克隆植物的重要性,克隆植物的生态习性,克隆植物的竞争关系等方面的研究进展,并试图在克隆植物竞争关系的背景下,结合其生境状况,探讨植物克隆性与植物物种多样性的关系。克隆植物的等级系统(基株—分株系统—分株)使其具有克隆性所赋予的多样的生活史、资源利用以及空间占据方式。列举了克隆植物的特性及其在群落中的作用。这些例子表明,克隆性强烈地影响和制约着植物群落的空间格局与竞争关系。然而克隆性也能通过权衡活动性与局部持久性来缓解对物种共存的抑制。克隆植物具有在时空尺度上分株间相互调节的机制,直接体现在群落中小尺度(个体与个体间)与大尺度(种群与种群间)间的相互作用上。丰富了传统的竞争和生态位划分理论,为群落中物种共存提供了合理解释。因此克隆植物在群落中的出现拓宽了群落系统潜在机制的范围。  相似文献   

7.
克隆植物的表型可塑性与等级选择   总被引:15,自引:0,他引:15       下载免费PDF全文
 表型可塑性是指生物个体生长发育过程中遭受不同环境条件作用时产生不同表型的能力。进化的发生有赖于自然选择对种群遗传可变性产生的 效力以及各基因型的表型可塑性。有足够的证据说明表型可塑性的可遗传性,它实际上是进化改变的一个成分。一般通过优化模型、数量遗传 模型和配子模型来研究表型可塑性的进化。植物的构型是相对固定的,并未完全抑制表型可塑性。克隆植物因其双构件性而具有更广泛的、具 有重要生态适应意义的表型可塑性。构件性使克隆植物具有以分株为基本单位的等级结构,从而使克隆植物的表型选择也具有等级性。构件等 级一般包含基株、克隆片段或分株系统以及分株3个典型水平。目前认为克隆植物的自然选择有两种模式,分别以等级选择模型和基因型选择模 型表征。等级选择模型认为:不同的等级水平同时也是表型选择水平,环境对各水平具有作用,各水平之间也有相互作用,多重表型选择水平 的净效应最终通过繁殖水平——分株传递到随后的世代中。基因型选择模型指出:克隆生长引起分株的遗传变异,并通过基株内分株间以及基 株间的非随机交配引起种子库等位基因频率的改变,产生微进化。这两种选择模式均突出强调了分株水平在自然选择过程中的变异性以及在进 化中的重要性,强调了克隆生长和种子繁殖对基株适合度的贡献。基因型选择模型包含等级选择模型的观点,是对等级选择模型的重要补充。 克隆植物的表型可塑性表现在3个典型等级层次上,由于各层次对自然选择压力具有不同的反应,其表型变异程度一般表现出“分株层次>分株 片段层次>基株层次”的等级性反 应模式。很多证据表明,在构件有机体中构件具有最大的表型可塑性,植物的表型可塑性实际上是构件而非 整个遗传个体的反应。这说明克隆植物的等级反应模式可能具有普适性。如果该反应模式同时还是构件等级中不同“个体”适应性可塑性反应 的模式,那么可以预测: 1)在克隆植物中,分株层次受到的自然选择强度也最大,并首先发生适应性可塑性变化, 最终引起克隆植物微进化 ;2)由于较弱的有性繁殖能力,克隆植物在进化过程中的保守性可能大于非克隆植物。克隆植物等级反应模式的普适性亟待验证。  相似文献   

8.
植物有性繁殖与资源分配的关系研究对于揭示植物生活史特征及繁育系统进化具有重要意义。新疆郁金香(Tulipa sinkiangensis)是新疆天山北坡荒漠带特有的一种多年生早春短命植物。在自然生境中,该物种仅以有性繁殖产生后代,每株能产生1-8朵花,且不同植株上的花数及果实数以及花序不同位置上的花与果实大小明显不同。本文通过对新疆郁金香有性繁殖与营养生长及植株大小的关系以及花序中不同位置花及果实间的资源分配研究,旨在揭示营养生长、个体大小及开花次序对其繁殖分配的影响。结果表明:在开花和果实成熟阶段,新疆郁金香植株分配给营养器官(鳞茎和地上营养器官)与繁殖器官的资源间均存在极显著的负相关关系(P<0.01),说明其植株的营养生长与生殖生长间存在权衡关系。多花是新疆郁金香的一个稳定性状,其植株上花数目、花生物量、果实生物量和种子数量与植株生物量间均呈极显著的正相关关系(P<0.01),说明新疆郁金香植株的繁殖分配存在大小依赖性。在具2-5朵花的新疆郁金香植株中,花序内各花的生物量、花粉数和胚珠数、结实率、果实生物量、结籽数、结籽率及种子百粒重按其开花顺序依次递减,说明花序内各花和果实的资源分配符合资源竞争假说。植株通过减少晚发育的花或果实获得的资源来保障早发育的花或果实获得较多的资源,从而达到繁殖成功。  相似文献   

9.
很多入侵植物具有克隆性,克隆整合对入侵克隆植物生长和繁殖具有重要的贡献。自然界中,植物生长和繁殖所需的各种资源如光照、水分和矿质养分等在空间上分布通常是异质的,但关于异质环境下克隆整合对入侵植物和本土同属植物种间关系影响的研究相对缺乏。通过温室控制实验,将入侵植物南美蟛蜞菊(Wedelia trilobata)和同属本土植物蟛蜞菊(W.chinensis)的分株对单独种植或者混合种植在异质性光照条件下,同时通过保持或者切断分株之间的连接来控制克隆整合效应的有无,研究异质光照环境下克隆整合对南美蟛蜞菊和蟛蜞菊种间关系的影响。克隆整合对南美蟛蜞菊和蟛蜞菊的生长和繁殖都有促进作用,且南美蟛蜞菊比蟛蜞菊从克隆整合中获益更多。与单独种植相比,两者混种对南美蟛蜞菊的叶生物量有显著影响,而对本地种蟛蜞菊的根生物量有显著影响。克隆整合和种间关系对南美蟛蜞菊的总生物量和叶生物量产生了显著的交互作用,而对蟛蜞菊各指标无显著影响。克隆整合状态显著影响了南美蟛蜞菊和蟛蜞菊的种间关系。这些结果表明,异质环境下克隆整合可以改变入侵植物南美蟛蜞菊和本土植物蟛蜞菊的生长性状及种间关系。  相似文献   

10.
不同生境下珠芽蓼(蓼科)的繁殖策略比较   总被引:3,自引:0,他引:3  
在青藏高原横断山区以海拔相同的高山流石滩和高寒草甸中的珠芽蓼(Polygonum viviparum)居群为研究对象,探讨该物种在不同生境条件下的繁殖策略以及无性繁殖和有性繁殖间的关系。结果发现,流石滩居群的珠芽蓼植株高度和珠芽数量显著低于高寒草甸居群,而珠芽和花总数量、花数量和每个花序上的花比例却显著高于高寒草甸居群。研究结果表明珠芽蓼在环境更为恶劣的高山流石滩生境中增加了对繁殖器官和花资源的投资,说明在高山植物中繁殖优先于营养生长,且有性繁殖比无性繁殖具有更为重要的作用。而对每个植株上花数量和珠芽数量的统计结果表明,两者呈显著的负相关关系,进一步证明了同一植株内无性繁殖和有性繁殖的权衡关系。  相似文献   

11.
Most plants can reproduce both sexually and asexually (or vegetatively),and the balance between the two reproductive modes may vary widely between and within species.Extensive clonal growth may affect the evolution of life history traits in many ways.First,in some clonal species,sexual reproduction and sex ratio vary largely among populations.Variation in sexual reproduction may strongly affect plant's adaptation to local environments and the evolution of the geographic range.Second,clonal growth can increase floral display,and thus pollinator attraction,while it may impose serious constraints and evolutionary challenges on plants through geitonogamy that may strongly influence pollen dispersal.Geitonogamous pollination can bring a cost to plant fitness through both female and male functions.Some co-evolutionary interactions,therefore,may exist between the spatial structure and the mating behavior of clonal plants.Finally,a trade-off may exist between sexual reproduction and clonal growth.Resource allocation to the two reproductive modes may depend on environmental conditions,competitive dominance,life span,and genetic factors.If different reproductive modes represent adaptive strategies for plants in different environments,we expect that most of the resources should be allocated to sexual reproduction in habitats with fluctuating environmental conditions and strong competition,while clonal growth should be dominant in stable habitats.Yet we know little about the consequence of natural selection on the two reproductive modes and factors which control the balance of the two reproductive modes.Future studies should investigate the reproductive strategies of clonal plants simultaneously from both sexual and asexual perspectives.  相似文献   

12.
Asexual and sexual reproductive strategies in clonal plants   总被引:1,自引:0,他引:1  
Most plants can reproduce both sexually and asexually (or vegetatively), and the balance between the two reproductive modes may vary widely between and within species. Extensive clonal growth may affect the evolution of life history traits in many ways. First, in some clonal species, sexual reproduction and sex ratio vary largely among populations. Variation in sexual reproduction may strongly affect plant’s adaptation to local environments and the evolution of the geographic range. Second, clonal growth can increase floral display, and thus pollinator attraction, while it may impose serious constraints and evolutionary challenges on plants through geitonogamy that may strongly influence pollen dispersal. Geitonogamous pollination can bring a cost to plant fitness through both female and male functions. Some co-evolutionary interactions, therefore, may exist between the spatial structure and the mating behavior of clonal plants. Finally, a trade-off may exist between sexual reproduction and clonal growth. Resource allocation to the two reproductive modes may depend on environmental conditions, competitive dominance, life span, and genetic factors. If different reproductive modes represent adaptive strategies for plants in different environments, we expect that most of the resources should be allocated to sexual reproduction in habitats with fluctuating environmental conditions and strong competition, while clonal growth should be dominant in stable habitats. Yet we know little about the consequence of natural selection on the two reproductive modes and factors which control the balance of the two reproductive modes. Future studies should investigate the reproductive strategies of clonal plants simultaneously from both sexual and asexual perspectives. Translated from Acta Phytoecologica Sinica, 2006, 20(1): 174–183 [译自: 植物生态学报]  相似文献   

13.
The relative importance of sexual and clonal reproduction for population growth in clonal plants is highly variable. Clonal reproduction is often more important than sexual reproduction but there is considerable interspecific variation and the importance of the two reproductive modes can change with environmental conditions. We carried out a demographic study on the woodland strawberry (Fragaria vesca), a widespread clonal herb, at 12 sites in Switzerland during 2 years. Study sites were selected in two different habitats, i.e., forest and forest edge. We used periodic matrix models to estimate annual population growth rates and carried out prospective analyses to identify life cycle components that influence population growth rates most. Retrospective analyses were applied to study how the two different habitats affected population dynamics. Furthermore, we tested whether trade-offs between sexual and clonal reproduction occurred. There were large differences in annual population growth rates between sites and large within-site differences between years. Results of the prospective analyses clearly indicate that clonal reproduction is the dominant reproductive pathway whereas sexual reproduction is rather insignificant for population growth. Compared to forest habitats, forest edge habitats had higher population growth rates in the first year but smaller growth rates in the second year. We attribute these differing habitat effects to different water availabilities during consecutive years. No trade-offs between sexual and clonal reproduction were found. In conclusion, population growth of F. vesca relies heavily on clonal reproduction. Furthermore, reproduction and survival rates of F. vesca depend highly on spatio-temporal variation of environmental conditions.  相似文献   

14.
The relationship between sexual reproduction and clonal growth in clonal plants often shows up at the ramet level. However, only a few studies focus on the relationship at the genet level, which could finally account for evolution. The sexual reproduction and clonal growth of Ligularia virgaurea, a perennial herb widely distributed in the alpine grasslands of the Qinghai‐Tibetan Plateau of China, were studied under different competition intensities and light conditions at the genet level through a potted experiment. The results showed that: (1) sexual reproduction did not depend on density or light, and increasing clonal growth with decreasing density and increasing light intensity indicated that intraspecific competition and light intensity may affect the clonal life history of L. virgaurea; (2) both sexual reproduction and clonal growth show a positive linear relationship with genet size under different densities and light conditions; (3) a threshold size is required for sexual reproduction and no evidence of a threshold size for clonal growth under different densities and light conditions; (4) light level affected the allocation of total biomass to clonal and sexual structures, with less allocation to clonal structures and more allocation to sexual structures in full sunlight than in shade; (5) light determined the onset of sexual reproduction, and the genets in the shade required a smaller threshold size for sexual reproduction to occur than the plants in full sunlight; and (6) no evidence was found of trade‐offs between clonal growth and sexual reproduction under different densities and light conditions at the genet level, and the positive correlation between two reproductive modes indicated that these are two integrated processes. Clonal growth in this species may be viewed as a growth strategy that tends to maximize genet fitness.  相似文献   

15.
Reproductive strategies can be associated with ecological specialization and generalization. Clonal plants produce lineages adapted to the maternal habitat that can lead to specialization. However, clonal plants frequently display high phenotypic plasticity (e.g. clonal foraging for resources), factors linked to ecological generalization. Alternately, sexual reproduction can be associated with generalization via increasing genetic variation or specialization through rapid adaptive evolution. Moreover, specializing to high or low quality habitats can determine how phenotypic plasticity is expressed in plants. The specialization hypothesis predicts that specialization to good environments results in high performance trait plasticity and specialization to bad environments results in low performance trait plasticity. The interplay between reproductive strategies, phenotypic plasticity, and ecological specialization is important for understanding how plants adapt to variable environments. However, we currently have a poor understanding of these relationships. In this study, we addressed following questions: 1) Is there a relationship between phenotypic plasticity, specialization, and reproductive strategies in plants? 2) Do good habitat specialists express greater performance trait plasticity than bad habitat specialists? We searched the literature for studies examining plasticity for performance traits and functional traits in clonal and non-clonal plant species from different habitat types. We found that non-clonal (obligate sexual) plants expressed greater performance trait plasticity and functional trait plasticity than clonal plants. That is, non-clonal plants exhibited a specialist strategy where they perform well only in a limited range of habitats. Clonal plants expressed less performance loss across habitats and a more generalist strategy. In addition, specialization to good habitats did not result in greater performance trait plasticity. This result was contrary to the predictions of the specialization hypothesis. Overall, reproductive strategies are associated with ecological specialization or generalization through phenotypic plasticity. While specialization is common in plant populations, the evolution of specialization does not control the nature of phenotypic plasticity as predicted under the specialization hypothesis.  相似文献   

16.
That trade-offs result from the allocation of limited resources is a central concept of life history evolution. We quantified trade-offs between sexual and clonal reproduction in the aquatic plant, Butomus umbellatus, by experimentally manipulating sexual investment in two distinct nutrient environments. Increasing seed production caused a significant but nonlinear trade-off. Pollinating half of all flowers strongly reduced clonal bulbil production, but pollinating the remaining flowers did not cause any further trade-off. Trade-offs were not stronger under low nutrient conditions that clearly limited plant growth. Experimentally induced trade-offs were not reflected in negative phenotypic correlations between sexual and clonal allocation among plants within eight populations grown in a uniform greenhouse environment. Diminishing effects of increased sexual allocation plus a lack of accord between experimental manipulations and phenotypic correlations suggest that trade-offs between sexual and clonal reproduction are unlikely to constrain the evolution of reproductive strategy in this species.  相似文献   

17.
The loss of sex in clonal plants   总被引:6,自引:0,他引:6  
Most plants combine sexual and clonal reproduction, and the balance between the two may vary widely between and within species. There are many anecdotal reports of plants that appear to have abandoned sex for clonal reproduction, yet few studies have quantified the degree of sexual variation in clonal plants and fewer still have determined the underlying ecological and/or genetic factors. Recent empirical work has shown that some clonal plants exhibit very wide variation in sexual reproduction that translates into striking variation in genotypic diversity and differentiation of natural populations. Reduced sexual reproduction may be particularly common at the geographical margins of species' ranges. Although seed production and sexual recruitment may often be limited by biotic and abiotic aspects of the environment in marginal populations, genetic factors, including changes in ploidy and sterility mutations, may also play a significant role in causing reduced sexual fertility. Moreover, environmental suppression of sexual recruitment may facilitate the evolution of genetic sterility because natural selection no longer strongly maintains the many traits involved in sex. In addition to the accumulation of neutral sterility mutations in highly clonal populations, the evolution of genetic infertility may be facilitated if sterility is associated with enhanced vegetative growth, clonal propagation or survival through either resource reallocation or pleiotropy. However, there are almost no experimental data with which to distinguish among these possibilities. Ultimately, wide variation in genotypic diversity and gene flow associated with the loss of sex may constrain local adaptation and the evolution of the geographical range limit in clonal plants.  相似文献   

18.
Abstract.— Allocation to sexual reproduction is an important life-history trait in clonal plants. Different selection pressures between competitive and competition-free environments are likely to result in the evolution of specialized genotypes and to maintain genetic variation in reproductive allocation. Moreover, selection may also result in the evolution of plastic allocation strategies. The necessary prerequisite for evolution, heritable genetic variation, can best be studied with selection experiments. Starting from a base population of 102 replicated genotypes of the clonal herb Ranunculus reptans , we imposed selection on the proportion of flowering rosettes in the absence of competition (base population: mean = 0.391, broad-sense heritability = 0.307). We also selected on the plasticity in this trait in response to competition with a naturally coexisting grass in a parallel experiment (base population: 14% lower mean in the presence of competition, broad-sense heritability = 0.072). After two generations of bidirectional selection, the proportion of flowering rosettes was 26% higher in the high line than in the low line (realized heritability ± SE = 0.205 ± 0.017). Moreover, genotypes of the high line had 11% fewer carpels per flower, a 22% lower proportion of rooted rosettes, and a 39% smaller average distance between rosettes within a clone. In the second experiment, we found no significant responses to selection for high and low plasticity in the proportion of flowering rosettes (realized heritability ± SE =–0.002 ± 0.013). Our study indicates a high heritability and potential for further evolution of the proportion of flowering rosettes in R. reptans , but not for its plasticity, which may have been fixed by past evolution at its current level. Moreover, our results demonstrate strong genetic correlations between allocation to sexual reproduction and other clonal life-history characteristics.  相似文献   

19.
Clonality is a widespread life history trait in flowering plants that may be essential for population persistence, especially in environments where sexual reproduction is unpredictable. Frequent clonal reproduction, however, could hinder sexual reproduction by spatially aggregating ramets that compete with seedlings and reduce inter‐genet pollination. Nevertheless, the role of clonality in relation to variable sexual reproduction in population dynamics is often overlooked. We combined population matrix models and pollination experiments to compare the demographic contributions of clonal and sexual reproduction in three Dicentra canadensis populations, one in a well‐forested landscape and two in isolated forest remnants. We constructed stage‐based transition matrices from 3 years of census data to evaluate annual population growth rates, λ. We used loop analysis to evaluate the relative contribution of different reproductive pathways to λ. Despite strong temporal and spatial variation in seed set, populations generally showed stable growth rates. Although we detected some pollen limitation of seed set, manipulative pollination treatments did not affect population growth rates. Clonal reproduction contributed significantly more than sexual reproduction to population growth in the forest remnants. Only at the well‐forested site did sexual reproduction contribute as much as clonal reproduction to population growth. Flowering plants were more likely to transition to a smaller size class with reduced reproductive potential in the following year than similarly sized nonflowering plants, suggesting energy trade‐offs between sexual and clonal reproduction at the individual level. Seed production had negligible effects on growth and tuber production of individual plants. Our results demonstrate that clonal reproduction is vital for population persistence in a system where sexual reproduction is unpredictable. The bias toward clonality may be driven by low fitness returns for resource investment in sexual reproduction at the individual level. However, chronic failure in sexual reproduction may exacerbate the imbalance between sexual and clonal reproduction and eventually lead to irreversible loss of sex in the population.  相似文献   

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