外来入侵植物大狼耙草 (Bidens frondosa L.) 表型可塑性及其在不同入侵种群的变异研究

Owing to the increasing influence of humans, many alien species have invaded and continue to invade new regions at an unprecedented rate, exerting strong impacts on ecosystems, economics and human welfare. Understanding the factors that contribute to the success of invasive species may facilitate the prediction of future invasions, determine the best ways to control invasive species, and eliminate the impact of invasive species on native communities. Hence, reasons of invasvieness of alien plant species are an important research topic in ecology and invasion biology, and of considerable applied relevance..Bidens frondosa, an annual weed (Asteraceae) native to North America, has rapidly spread and invaded many provinces in China in recent years. Seriously, it has invaded from cropland to natural reserves. The species has already become an emerging alien invasive weed. Unfortunately, no knowledge except that report about its distribution are available. This alien invasive species is continuing to spread in China.Up to now, the invasion mechanism of B. frondosa is still unkown to us..Phenotypic plasticity is often cited as one of the mechanisms of most plant invasion. However, few studies have evaluated the plasticity of a diverse set of traits between invasive species and their congeners, as well as variation for plasticity among invasive populaitons by both common garden experiment and field investigation..In order to understand the effects of phenotypic plasticity and variation for plasticity among invasive populaitons on invasiveness of B. frondosa, the phenotypic plasticity of morphology, growth, physiology and reproduction between B. frondosa and its congener invasive speices B. pilosa, native species B. tripartita, as well as variation for plasticity among invasive populaitons will be carried out by both common garden experiment and field investigation. This study will lead to the understanding of invasion mechanisms of this weed and provide a basis for invasiveness, invasiablity and prediction invasion of B. frondosa. Meanwhile, the study will provide fundamental data for the theory about relationship of phenotypic plasticity with invasiveness.

为什么有些物种能够成功入侵而有些物种却入侵失败？一直以来是入侵生态学的热点问题。大狼耙草Bidens frondosa是菊科鬼针草属外来种，原产北美，近年在我国多省区爆发，给农田和自然生态系统造成严重威胁。目前除有分布的调查报告外，有关入侵机制的研究鲜有报道。表型可塑性和多数外来入侵植物的入侵性相关，是多数外来入侵植物入侵机制之一。但很少有人把同质种植园实验和野外调查结合起来详细研究各性状的表型可塑性。本项目拟通过同质种植园和野外研究相结合，对大狼耙草和近缘的入侵种三叶鬼针草 B. pilosa、本地种狼耙草B. tripartita以及大狼耙草在我国不同入侵种群的形态和生长、生理和繁殖及其表型可塑性进行比较，探讨大狼耙草的表型可塑性及可塑性在不同入侵种群的变异对入侵性的影响，揭示其入侵机制，为大狼耙草的入侵性、生境的可入侵性及预测等提供依据，并为表型可塑性与植物入侵性相关的理论提供资料。

大狼耙草(Bidens frondosa)隶属菊科鬼针草属，原产北美，是我国爆发性很强的外来入侵种，入侵机制鲜有报道。表型可塑性是外来入侵植物的入侵机制之一。本项目通过同质种植园实验和野外研究，在种间(与近缘种比较)和种内(入侵种群比较)两个生态学水平上研究了大狼耙草形态、生长、生理和繁殖等性状及其表型可塑性，揭示大狼耙草入侵的若干机制，为管理提供依据。主要研究内容和结果如下：.1. 野外研究表明：大狼耙草株高、生物量显著低于入侵种三叶鬼针草(B. pilosa)，与金盏银盘(B. biternata)相似，但显著高于本地种狼耙草(B. tripartita)；繁殖分配、种子产量、比叶面积等显著高于三个近缘种；各性状的表型可塑性指数平均值与三叶鬼针草相似，高于两个近缘本地种。大狼耙草不同入侵种群株高和生物量随纬度增加降低；辽宁和广西种群各性状差异显著；北方两个种群繁殖分配最大，达50%。所有种群形态和生物量及其分配都具较高的可塑性。2. 同质种植园研究表明：大狼耙草和近缘入侵种和本地种的形态和生长性状对资源的响应量有差异，可塑性不同。大狼耙草和三叶鬼针草对光照的可塑性大于本地种狼耙草和金盏银盘。氮养分增加时，大狼耙草、金盏银盘和狼耙草生物量增加分别为119%、121%、77%。可塑性在大狼耙草不同入侵种群间有变异。例如，氮养分增加时，河北、河南、湖北、广西种群的生物量增加分别为124%、147%、116%和119%；比叶面积在广西种群中显著增加，在河南种群中减少，在河北和湖北种群中无明显变化；各性状的表型可塑性指数平均值分别为0.33、0.43、0.34和0.33。本研究未发现大狼耙草高于近缘本地种的生理性状如最大光净光合速率、叶绿素含量等。大狼耙草的萌发具有可塑性，低温 (15℃) 时，种子不萌发， 20℃~ 35℃时，萌发率随温度升高增加；PEG浓度增加时，萌发率降低；PEG浓度20%时，萌发率低于近缘本地种狼耙草。各种群在萌发率、萌发势、萌发指数和萌发速率方面均有差异。.本研究揭示了高的表型可塑性和性状值提高大狼耙草对资源的捕获和竞争能力；高的繁殖分配、种子产量和萌发率保证其产生大量后代，定居和入侵新生境。且可塑性在不同入侵种群间有变异，可能进化出更大的可塑性，提高在新生境中的入侵。在管理上，应控制已定居种群的扩散，防止新的入侵，减少生境中可利用的资源。