外来种入侵对乡土生物多样性的影响机制

外来种入侵是全球性变化研究的重要组成部分，已经成为各国生物多样性保 护和管理的核心问题。近年来，大多数人给予了外来种对生态系统的负面作用充分的论述和研究，而忽视了它们的积极效应。如何客观辨证地评价外来种的作用和可能的影响是规避和管理外来种所带来的风险的前提和保障。在综述外来种、乡土种和外来种入侵的基本概念及其危害情况的基础上，系统阐述了外来种侵入和种群扩大对生物多样性所带来的正负两方面的影响。外来种入侵可能的影响途径及其机制主要包括：（1）竞争与排斥；(2）杂交；（3）打断或改变食物链关系；（4）带入病毒等。外来种入侵对乡土物种多样性的影响途径和机制实际上是上述众多因素综合作用的结果。外来种之所以给生态系统和人 类带来危害和损失，根本原因在于人们缺乏外来种入侵的相关知识以及预防手段和意识，更缺乏对外来种的有效管理。规避外来种所带来的风险，最关键是要尽可能地避免人为的、有意的协助外来种的入侵，并在做好各种安全措施后，有计划、有步骤地慎重引入，科学管理，规划发展。目前对外来种入侵的生态学知识还是零碎的、局部的、表象的，深入研究外来种的生物学生态学特性及其入侵的生态学机制是当前最为急迫的工作。建议我国近期加强外来种的本底调查与现状评估、外来种入侵的通道与入侵过程及其影响因素、外来种入侵的生态过程及其效应以及外来种入侵的进化后果等方面的工作。

INFLUENCE OF ALIEN SPECIES INVASION ON NATIVE BIODIVERSITY

Alien Species Invasion, the important part of research on Global Change, has become the focus of protection and administration of biodiversity throughout the world. Recently adequate discussion and research have been given on the negative influence of alien species on ecosystem,with the ignorance of their positive parts. How to objectively access the action and possible influence is the precondition and indemnification of sidestepping the risk brought from alien species. Based on the concept of alien species, native species, alien species invasion and its harm, the positive and negative influence of alien species and population amplification on diversity of species are expatiated systematically. The possible influence path and its mechanism are summarized objectively, including: (1) competition and exclusion, (2) hybridization, (3) interrupting or changing the relationship between food chain, (4) bringing virus, and so on. It is drawn that the influence path and mechanism arise from synthesis of numerous factors. The reason that alien species bring harm and loss to human lies in that man lack correlative knowledge, preventative means and consciousness, and effective management. To sidestep the risk arisen from alien species, we should avoid introducing alien species intentionally and plan it deliberately and systematically after taking sufficient safe measures. At present the knowledge on alien species invasion is factionary, partial and superficial. The urgent work at present is to study biological and ecological characteristics of alien species and the ecological mechanism of invasion. It is suggested that we should strengthen such work as background of investigation, present assessment, the invasion path, factors affecting invasion, the ecological process and effect of alien species invasion and evolutionary consequence, and so on.