“本地入侵种”对河源溪流土著鱼类多样性的影响研究——以青弋江流域为例

Anthropogenic disturbances have been recognized as a driver that facilitates "native-invaders" successfully inhabiting headwater streams. However, how the native-invaders affect the diversity of indigenous fishes in these ecosystems are still unclear. Our proposal will select the headwater streams within the Qingyi basin, Anhui Province, as our study area. We will use three main methods (i.e., field survey, diet examination and control experiment) to identify the influences of these native-invading fishes on the indigenous fish diversity within headwater streams. First, by careful site-setting and substantial field-sampling, we will reveal the spatial and temporal patterns of the diversity and organizations of indigenous fish assemblages within this study area. And then, the sole and combined effects of three categories of independent variables (i.e., native-invading fish, local habitat and dam size) on indigenous fish assemblages will be examined. Second, after the qualitative and quantitative examinations on fish stomach contents, we will identify the feeding habits of both native-invading and indigenous fishes, by which the potential interspecific interactions (i.e., competition and/or predation) between them will be discovered. Third, using the control experiments in bypass-stream systems, we will reveal the effect of native-invading fishes on the survival, somatic growth and reproduction of indigenous fishes, and will then explain the mechanisms of how these invaders affect the sustainment and multiplication of indigenous fish populations. As a result, our proposal will bring forward a base for the conservation, restoration and management of the headwater-stream ecosystems and the stream fish diversity within this study area and even our country.

基于人为干扰可促进“本地入侵种”扩散至河源溪流这一重要生态现象，针对本地入侵种如何影响河源溪流土著鱼类这一关键科学问题，本项目以青弋江流域的河源溪流为研究区域，分别运用野外调查、食性分析与控制试验3种研究方法，系统地研究本地入侵鱼类对河源溪流土著鱼类多样性的影响：（1）通过周密的样点设置与大量的野外取样，研究土著鱼类群落结构及其多样性的时空格局，解析入侵鱼类、局域栖息地和水坝大小3类变量对土著鱼类群落的独立和联合影响；（2）通过胃含物的定性和定量分析，研究入侵鱼类和土著鱼类的食性特点及其种间关系，解析入侵鱼类对土著鱼类的潜在竞争和捕食风险；（3）通过溪流旁路系统的控制性试验，研究入侵鱼类对土著鱼类的存活、生长和繁殖等重要生活史过程的影响，解析入侵鱼类影响和危害土著鱼类的种群维持与繁衍的生态学机制。为研究区域内、乃至全国的河源溪流生态系统及其鱼类多样性的保护、恢复和管理提供科学依据。

针对本地入侵种如何影响河源溪流土著鱼类这一科学问题，本项目以皖南山区的溪流系统为研究区域，运用野外调查、胃含物分析、控制试验等研究方法，系统的研究了本地入侵鱼类对河源溪流鱼类多样性的影响及其机制。（1）通过野外调查研究发现，低头坝坝上蓄水区的鱼类群落受局域栖息地、支流空间位置和水坝变量的联合影响，其中物种数主要受水坝变量影响，而物种组成主要取决于局域栖息地特征和支流空间位置变量。低头坝影响鱼类群落的作用大小，依赖于水坝的蓄水功能，而水坝大小的相对重要性较低；由于物种间的生态习性差异，本地入侵种和土著种对低头坝的响应不同，前者受益而后者受损。本地入侵鱼类对土著鱼类的取代过程，不仅改变了局域群落的α多样性，还引起群落相似性的变化，尽管土著鱼类的物种组成呈异质化趋势，但入侵种却呈同质化趋势；此外，群落相似性的变化趋势在一定程度上随组成数据和多度数据而变化。（2）通过鱼类胃含物分析研究发现，尽管不同物种间的食物多样性和食性宽度存在差异，但物种间的食物重叠度较高，尤其是麦穗鱼、高体鳑鲏等入侵种与光唇鱼、原缨口鳅等土著种的食物度极高。（3）通过控制试验研究发现，入侵种麦穗鱼显著降低了土著种宽鳍鱲幼鱼的存活率和生长，但对宽鳍鱲成鱼的繁殖特征无显著影响。