Data_Sheet_1_The Disconnect Between Short- and Long-Term Population Projections for Plant Reintroductions.docx

The reintroduction of rare species in natural preserves is a commonly used restoration strategy to prevent species extinction. An essential first step in planning successful reintroductions is identifying which life stages (e.g., seeds or large adults) should be used to establish these new populations. Following this initial establishment phase, it is necessary to determine the level of survival, growth, and recruitment needed to maintain population persistence over time and identify management actions that will achieve these goals. In this 5-year study, we projected the short- and long-term population growth rates of a critically endangered long-lived shrub, Delissea waianaeensis. Using this model system, we show that reintroductions established with mature individuals have the lowest probability of quasi-population extinction (10 individuals) and the highest increase in population abundance. However, our results also demonstrate that short-term increases in population abundances are overly optimistic of long-term outcomes. Using long-term stochastic model simulations, we identified the level of natural seedling regeneration needed to maintain a positive population growth rate over time. These findings are relevant for planning future reintroduction efforts for long-lived species and illustrate the need to forecast short- and long-term population responses when evaluating restoration success.

在自然保护地实施珍稀物种再引入，是防范物种灭绝的常用生态修复策略。规划成功的物种再引入项目，首要核心步骤是确定应选用何种生活史阶段（如种子或成熟个体）来建立新生种群。完成这一初始建群阶段后，还需明确维持种群长期存续所需的存活率、生长率和补充率水平，并确定可达成上述目标的管理措施。在这项为期5年的研究中，我们对极危长寿命灌木Delissea waianaeensis的短期与长期种群增长率进行了预测。基于该模型系统，我们发现以成熟个体为建群来源的再引入项目，其准种群灭绝（种群规模降至10个个体时的灭绝风险）概率最低，且种群丰度增幅最高。但研究结果同时表明，仅依据种群丰度的短期增长来预判长期结果，未免过于乐观。通过长期随机模型模拟，我们明确了维持种群长期正向增长率所需的天然幼苗更新水平。本研究结果可为长寿命物种的未来再引入规划提供科学参考，同时也揭示：在评估修复成效时，需对种群的短期与长期响应进行预测。