竞争压力下轮虫的快速进化及其生态效应：生态进化动态实验研究

Brachionus calyciflorus and B. angularis (Rotifera) individuals will be collected from lakes and clonally cultured in laboratory. B. calyciflorus and B. angularis clones with different fitness (intrinsic rates of population increase) and genetic characteristics will be screened by means of experimental population ecology and used to constitute non-evolving populations and evolving populations. B. calyciflorus and B. angularis populations with similar generation times and evolutionary rates, and the herbivorous rotifers and cladoceran (Moina macrocopa) populations differing in generation time and evolutionary rate, will be respectively used to construct different competitive systems in chemostat culture systems. By means of experimental ecology and biological statistics, with microsatellites as molecular markers,and under different initial densities of non-evolving populations of the competitors, the rapid evolution of the rotifer populations will be tested in real time. Concurrent quantitative dynamics of the populations of the competitors will be documented, and their reciprocally interaction will be analyzed. A plausible mechanistic link between ecological and evolutionary dynamics will be put forward. Dynamics models of the population density of the competitors will be constructed. The contribution of evolutionary factors such as genetically based phenotypic change to population growth of one competitor, relative to ecological factors such as changes in the population density of another competitor will be analyzed. The results will illustrate the rapid evolution in rotifers driven by exploitation competition and its ecological consequence, and the process and the regularity of the interaction between the ecological dynamics and the evolutionary dynamics within the competitive systems, and help us further understand the mechanisms of population dynamics regulation, coexistence of competitive species in zooplankton community, and shaping and maintenance of biodiversity.

本项目拟通过野外采集、实验室克隆培养和比较研究筛选出具有不同适合度（种群内禀增长率）和遗传特征的轮虫克隆，人工构建轮虫非进化种群和进化种群；以世代时间和进化速率相似的萼花臂尾轮虫和角突臂尾轮虫等植食性轮虫与多刺裸腹溞等枝角类在恒化培养条件下分别组成竞争系统；应用实验生态学、生物统计学和数学建模等方法，以微卫星为分子标记，在不同的多刺裸腹溞种群起始密度等条件下，研究各竞争系统中竞争双方的种群数量动态、轮虫种群进化动态及其相互间的关系，以及进化因素和生态因素在影响竞争双方种群增长过程中的相对重要性；构建竞争双方的种群数量动态模型。研究结果将揭示不同的利用性竞争压力下轮虫种群的快速进化及其生态效应、进化动态和生态动态间相互作用的过程和规律，加深人们对种群动态调节、竞争压力下的物种共存、生物多样性形成和维持等机制的理解。

生态进化动态研究进一步促进了生态学和进化生物学等学科的整合，加深了人们对生物多样性形成和维持机制的理解。本项目通过野外采集、实验室克隆培养和比较研究筛选出具有不同适合度和遗传特征的轮虫克隆；应用实验生态学、生物统计学和数学建模等方法，以mtDNA COI基因为分子标记，研究了在不同起始密度的多刺裸腹溞（Moina macrocopa）和角突臂尾轮虫（Brachionus angularis）竞争压力下，萼花臂尾轮虫（B. calyciflorus）种群结构的快速变化和动态模型、竞争双方的种群数量动态及其相互间的关系，以及进化因素和生态因素在影响竞争双方种群增长过程中的相对重要性，取得了以下主要研究结果：.采自镜湖水体中的11个角突臂尾轮虫克隆中，克隆3、6和11可用于组成进化种群。采自西洋湖水体中的11个萼花臂尾轮虫克隆中，克隆3和8可用于组成进化种群。.筛选出具有较高多态性的11对角突臂尾轮虫和萼花臂尾轮虫微卫星引物。.角突臂尾轮虫竞争压力下，萼花臂尾轮虫种群结构随着培养时间的延长而发生快速的变化。当角突臂尾轮虫起始密度为2、4和8 ind./mL时，萼花臂尾轮虫克隆SA在种群中所占比例与培养时间之间的关系依次为：y= 2.61x+ 28.49（R2= 0.91, P< 0.05）、y= -0.21x2+ 4.46x+ 22.12（R2= 0.85, P< 0.05）和y= -0.56x2 +9.01x+ 12.58（R2= 0.91, P< 0.05）。各角突臂尾轮虫起始密度下萼花臂尾轮虫克隆SA在种群内所占比例总体上低于克隆SB的原因在于SB总体上表现出比SA较强的竞争能力。.多刺裸腹溞竞争压力下，萼花臂尾轮虫种群结构随着培养时间的延长而发生快速的变化。培养前5天萼花臂尾轮虫克隆SA在种群中所占的比例为76.7%~63.3%，明显的优势地位可归因于其较慢却较持久的种群增长，而培养后5天克隆SA优势地位（67.6%~50%）的消失可能与其较高浓度的代谢产物的自毒作用和较大的多刺裸腹溞竞争压力有关。当多刺裸腹溞密度为1、2和3 ind./5mL时，克隆SA所占比例与培养时间之间的关系依次为：y= -3.33x+ 88.33（R2= 0.57, P< 0.01）、y= -4.50x+ 86.17（R2= 0.82, P< 0.01）和y= -4.17x+ 84.17