Department of Biological Sciences, Purdue University, 915 W. State Street, West Lafayette, IN 47907-2054, U.S.A.
Department of Forestry and Natural Resources, Purdue University, 715 W. State Street, West Lafayette, IN 47907-2054, U.S.A.
Conserv Biol. 2019 Apr;33(2):377-388. doi: 10.1111/cobi.13217. Epub 2018 Dec 2.
Because of continued habitat destruction and species extirpations, the need to use captive breeding for conservation purposes has been increasing steadily. However, the long-term demographic and genetic effects associated with releasing captive-born individuals with varied life histories into the wild remain largely unknown. To address this question, we developed forward-time, agent-based models for 4 species with long-running captive-breeding and release programs: coho salmon (Oncorhynchus kisutch), golden lion tamarin (Leontopithecus rosalia), western toad (Anaxyrus boreas), and Whooping Crane (Grus americana). We measured the effects of supplementation by comparing population size and neutral genetic diversity in supplemented populations to the same characteristics in unaltered populations 100 years after supplementation ended. Releasing even slightly less fit captive-born individuals to supplement wild populations typically resulted in reductions in population sizes and genetic diversity over the long term when the fitness reductions were heritable (i.e., due to genetic adaptation to captivity) and populations continued to be regulated by density-dependent mechanisms over time. Negative effects for species with longer life spans and lower rates of population replacement were smaller than for species with shorter life spans and higher rates of population replacement. Programs that released captive-born individuals over fewer years or that avoided breeding individuals with captive ancestry had smaller reductions in population size and genetic diversity over the long term. Relying on selection in the wild to remove individuals with reduced fitness mitigated some negative demographic effects, but at a substantial cost to neutral genetic diversity. Our results suggest that conservation-focused captive-breeding programs should take measures to prevent even small amounts of genetic adaptation to captivity, quantitatively determine the minimum number of captive-born individuals to release each year, and fully account for the interactions among genetic adaptation to captivity, population regulation, and life-history variation.
由于栖息地的持续破坏和物种灭绝，出于保护目的而使用圈养繁殖的需求一直在稳步增加。然而，将具有不同生活史的圈养出生个体释放到野外后，长期的人口和遗传效应在很大程度上仍未可知。为了解决这个问题，我们为具有长期圈养繁殖和释放计划的 4 个物种开发了基于代理的正向时间模型：银鲑（Oncorhynchus kisutch）、金狮狨（Leontopithecus rosalia）、西部蟾蜍（Anaxyrus boreas）和美洲鹤（Grus americana）。我们通过比较补充种群的种群大小和中性遗传多样性与未经改变的种群在补充结束 100 年后的相同特征，来衡量补充的影响。释放适应能力稍差的圈养出生个体来补充野生种群，通常会导致长期的种群数量和遗传多样性减少，当适应能力的降低是可遗传的（即由于对圈养的遗传适应），并且随着时间的推移，种群继续受到密度依赖机制的调节时。寿命较长和种群更替率较低的物种的负面影响小于寿命较短和种群更替率较高的物种。释放圈养出生个体的年限较少或避免繁殖具有圈养血统的个体的计划，长期来看，种群规模和遗传多样性的减少幅度较小。在野外依靠选择来去除适应能力降低的个体，在一定程度上减轻了一些负面的人口效应，但对中性遗传多样性造成了巨大的代价。我们的研究结果表明，以保护为重点的圈养繁殖计划应采取措施防止对圈养的微小遗传适应，定量确定每年释放的圈养出生个体的最小数量，并充分考虑对圈养的遗传适应、种群调节和生活史变化之间的相互作用。
