新外来种禾叶慈姑在异质生境中的繁殖策略及生态适应性研究

Biological invasion has been occurring frequently in the south of China and caused serious damages. Since invasive plants in the north are often ignored, it will be difficult to control the spread once invasion forms. Sagittaria graminea, exotic species, was found in wetland of Yalv River. For this exotic plant, its reproductive strategies and ecological adaptability has only been known a little. This project aims to study the following four aspects of Sagittaria graminea: 1) Testing the plasticity of reproductive strategies about Sagittaria graminea under different growthing conditions;2) Testing the ecological adaptability of Sagittaria graminea under different habitats; 3) studying of introgression between Sagittaria graminea and sympatric Sagittaria trifolia. Among the above studies, understanding the changes in reproductive strategies of Sagittaria graminea under different habitats could theoretically reveal the mechanism of certain exotic species improving ecological adaptability through their plasticity of reproductive strategies. Meanwhile, comparison between Sagittaria graminea (exotic species)and Sagittaria trifolia(native specoes) might ascertain the effect of the possible population spreading of Sagittaria graminea on the local biological diversity. Besides, testing the introgression etween Sagittaria graminea and sympatric Sagittaria trifolia could estimate the possibility of forming natural hybrids, which is significant for the evolution pattern and ecological risk prevention of invasive species.

外来种入侵引起的生态安全问题已经成为当今世界面临的重要环境问题之一。禾叶慈姑是近年来发现于鸭绿江口湿地的新记录外来种，目前，我们对其繁殖策略和生态适应性等方面的知识还知之甚少。本项目拟对该外来种在以下三方面加以重点研究：1）检验该外来种在异质生境下繁殖策略的可塑性；2）检验该外来种与土著种在伴生过程中竞争力的差异；3）检验该外来种与同域分布的野慈姑间的杂交亲和性及杂交后代的生态适应性。本项目的研究目的在于通过多种手段了解禾叶慈姑在不同生境中的繁殖策略变化，从理论上揭示一些外来种在新生境中通过调节繁殖策略的可塑性来提高其生态适应能力的机制，进而有助于了解入侵种的进化式样以及增强对其生态风险防范的能力。

项目以鸭绿江口沿岸湿地的外来种禾叶慈姑为研究对象，与伴生种和近缘本地种作对比，从繁殖生态学角度，探讨外来种禾叶慈姑在异质生境下的繁殖策略及生态适应性。特别是对其种群扩散机制做了深入探究并在此基础上对其可能的生态风险进行了评估。研究结果表明：1）禾叶慈姑目前有5个亚居群，每个亚居群有数目不等、大小不一的斑块组成，这些亚居群分布在鸭绿江沿岸及支流近江段的沿岸低位湿地，有些斑块已经形成单优种群；2）利用分子标记技术（RAPD）对现存的各亚居群采样分析表明，禾叶慈姑亚居群间以及个体间的遗传多样性非常低（0.14-0.17）；3）基质的营养成分影响禾叶慈姑花的雌雄性比并进而影响其对繁殖策略的选择 ；4）模拟实验表明，禾叶慈姑的分布受水分和养分的影响；5）在异质生境中禾叶慈姑的繁殖模式是通过影响有性繁殖和无性繁殖间的资源分配实现的；6）禾叶慈姑的繁殖力和竞争力都强于狭叶慈姑；7）禾叶慈姑与同域分布的狭叶慈姑间有基因流；8）禾叶慈姑的叶片浸提液具有较强的化感作用。因此外来种禾叶慈姑在异质生境中均表现出较高的繁殖力、竞争力及能量利用效率。本项目研究结果表明禾叶慈姑的生物学特性是其成功入侵的机制之一，具有重要的理论价值。