入侵植物光梗蒺藜草表型可塑性和遗传分化在适应异质生境中的作用

Invasive species experience a variety of novel environments and establishment in a novel range is likely to be facilitated by some combination of genetic variation within a population and plasticity. Our research focuses on understanding the relative importance of genetic variation and plasticity in determining the relative success of populations of an invasive annual plant, Cenchrus calyculatus Cav., undergoing a recent range expansion in Inner Mongolia of China. We used the relative advanced methods whole-range studies to investigate function of the genetic variation and plasticity among different populations (heterogenetic environments) in the successful invasion. Micro environmental variation experienced by dispersing offspring can generate heterogeneity in the strength and direction of selection across generations. Fine-grained heterogeneity within the spatial scale of seed dispersal should select for adaptive phenotypic plasticity. Addressing this question requires using a two-pronged experimental approach: first, characterizing fine-scaled patterns of heterogeneity and how they affect plant phenotype and fitness under field conditions; second, using greenhouse studies to measure levels of genetic variation for phenotypic plasticity. Therefore, using the whole range analysis method, comparatively analyze on the plant plasticity in variable farmland, grassland and desert regions (morphological, physiological and genetic variation) and rapid adaptation under different habitats, in order to reveal the strong invasive (adaptation) of the basic biological characteristics, to provide theoretical guidance for the scientific basis and practical control methods, and provide the basic information for further study on the mechanism of plant invasion.

光梗蒺藜草（Cenchrus calyculatus Cav.）为内蒙古自治区一种危害日益严重的外来入侵植物，给当地的农林牧业、人民生产、经济发展和生态系统等均造成严重危害。根据申请者多年的调查研究，发现该植物目前正由农田和草原生态区侵入半固定和固定沙漠地区，且呈快速蔓延趋势。到目前为止，对光梗蒺藜草次级入侵发生原因及过程的研究非常少。为此本项目以光梗蒺藜草为研究对象，通过全境分析法，比较研究农田、草原和沙漠地区该植物的可塑性（形态、生理）和遗传变异在不同生境下快速适应的作用，以期揭示其强入侵性（适应性）的基本生物学特性，为其科学防除方法提供理论基础与实践指导，同时为其入侵机制的深入研究提供基础资料。

以光梗蒺藜草为研究对象，采用同质园实验法，发现光梗蒺藜草入侵后在形态特征和生理特征上均表现出可塑性适应变化,即不同分布区光梗蒺藜草苗期、抽穗期、成熟期的植株高度、叶片长、叶片宽、叶片长宽比均存在显著差异或极显著差异，表现出明显的变异性。其中植株高度在苗期的变异系数最大，达14.97%-18.61%；不同分布区光梗蒺藜草种子长、宽、长宽比差异显著，长宽比的变异幅度最大，为35.71%-68.75%；扫描电镜下发现种子超微结构也出现明显的可塑性变化；不同分布区光梗蒺藜草叶绿素含量、净光合速率、光补偿点、光饱和点、暗呼吸速率同样存在极显著差异。且通辽市科左后旗的光梗蒺藜草表现出较强的可塑性，能更好地适应入侵地生境。.采用AFLP技术分析14个光梗蒺藜草种群的遗传多样性，发现其Nei's基因多样性指数为0.3450，Shannon's信息多样性指数为0.5177，说明光梗蒺藜草在物种水平上具有较高的遗传多样性。Popgene得到遗传分化系数Gst为0.3600，表明36％遗传变异分布于种群间，种群间基因流Nm为0.8889。cpDNA序列AMOVA分析结果显示光梗蒺藜草种群内的变异大于种群间，其中来源于种群内的变异为81.89％。结合遗传多样性特点和TCS单倍型网状图揭示出光梗蒺藜草种群是由少数个体或种群扩张后形成，在扩张过程中保留了原始单倍型，可能的入侵地点为通辽市科左后旗哈仑胡顿，而后随牛羊反复向周边旗县扩散和入侵。为下一步的科学防控提供了科学依据。