阿利效应对陕西宁陕朱鹮（Nipponia nippon）再引入种群的影响

Allee effects, the reduction of vital rates at low population densities, can occur through several mechanisms, all of which potentially apply to reintroduced populations. According to the Re-introduction Specialist Group of the IUCN, a reintroduction is any attempt to establish a species in an area that was once part of its historical range, but from which it has been extirpated or become extinct. Since the number of organisms released in reintroductions is usually much lower than the site-specific carrying capacity, and the reintroduced populations are initially at low densities, hence Allee effects can potentially lead to reintroduction failure. Therefore, we would focus on the reintroduced population of the Crested Ibis (Nipponia nippon) in Ningshan County by investigating demographic parameters such as annual variation of population number, female breeding probability, female productivity, adult or juvenile survival and per capita population growth rate. We aim to determine the relationship between the fitness parameter and per capita population growth rate to ibis population size or density which could demonstrate the causing mechanisms, types and strengths of Allee effects in the ibis population. As reintroductions are almost invariably characterized by small propagule sizes, the importance of the Allee effect must be considered in order to assess its potential impact on the probability of success in reintroductions, and we must consider this potential impediment to the survival, increase, and spread of small groups of reintroduced individuals in order to propose strategies for minimizing Allee effects.

阿利效应—低种群密度下存活力（个体平均存活率和繁殖力）的下降—可通过若干机制潜在地作用于再引入种群。按照国际自然保护联盟（IUCN）再引入专家组的定义，再引入就是在物种的历史分布区建立再引入种群的尝试。由于再引入行动中释放个体的数量常远远低于释放地的环境容纳量，而且最初阶段均处于低密度状态，因而阿利效应有可能导致再引入计划的失败。本研究试图以陕西宁陕朱鹮（Nipponia nippon）再引入种群为研究对象，调查种群参数如种群数量及年度变化、雌性繁殖概率、雌性生产力、成体、幼体存活率以及单位个体平均增长率。分析个体适合度和个体平均增长率与种群数量或密度之间的相关关系，确定影响朱鹮再引入种群的阿利效应的产生机制、作用类型和强度。再引入种群几乎永远具有小的繁殖群体，因此我们必须考虑阿利效应对再引入种群存活、增长和扩散的潜在阻碍作用以及对再引入成功率的影响，提出阿利效应的最小化策略。

阿利效应（Allee effect AE）是指低种群密度下存活力（个体平均存活率和繁殖力）的降低，可通过若干机制潜在地作用于再引入种群。再引入（reintroduction）就是在物种的历史分布区建立再引入种群的尝试。在大多数的再引入计划中，由于释放个体的数量远低于释放地的环境容纳量且最初阶段均处于低密度状态，所以衡量阿利效应对再引入小种群的影响是十分必要的。本研究以陕西宁陕朱鹮（Nipponia nippon）再引入种群为研究对象，通过环志标识和无线电跟踪的方法进行野外监测，记录调查了雌性繁殖概率、雌性生产力、成体及幼鸟存活率、雌性配对率、性比、年龄结构、配对数量及集群数量等种群参数。分析研究个体适合度和个体平均增长率与种群数量的相关关系，确定影响种群存活、增长和扩散的阿利效应的类型和强度，进而探讨再引入种群阿利效应的产生机制，并提出阿利效应的最小化策略。结果表明，2007-2016年间宁陕朱鹮再引入种群的雌性繁殖概率、雌性生产力、成体存活率均与该种群的种群数量呈显著的正相关关系（Pearson r=0.319，P=0.03；Pearson r=0.814，P=0.008；Pearson r=0.905，P=0.001）。由此说明该种群中可能存在种群阿利效应（Demographic AE）。通过对2007-2017年间秋冬季节朱鹮夜宿集群的动态变化、集群大小、性别组成和年龄结构的研究表明，偏雄性的性比结构造成雄性个体择偶困难，雄性个体间竞争加剧。个体适合度降低引发了配对限制的阿利效应—成分阿利效应（Component AE）。2011-2017年，朱鹮种群年平均增长率随种群数量的逐渐增加而呈缓慢降低的趋势，但并未出现种群年均增长率为负值的临界点，种群数量也尚未出现下降趋势。因此该种群中可能存在的阿利效应为微弱的种群阿利效应。上述研究结果为朱鹮及其他濒危物种小种群的保护管理提供了理论依据和野外实践参考。