School of Biological Sciences, University of East Anglia, Norwich, UK.
Institute of Zoology and Biomedical Research, Jagiellonian University, Kraków, Poland.
Glob Chang Biol. 2020 Aug;26(8):4226-4239. doi: 10.1111/gcb.15186. Epub 2020 Jun 19.
Earth's biodiversity is undergoing mass extinction due to anthropogenic compounding of environmental, demographic and genetic stresses. These different stresses can trap populations within a reinforcing feedback loop known as the extinction vortex, in which synergistic pressures build upon one another through time, driving down population viability. Sexual selection, the widespread evolutionary force arising from competition, choice and reproductive variance within animal mating patterns could have vital consequences for population viability and the extinction vortex: (a) if sexual selection reinforces natural selection to fix 'good genes' and purge 'bad genes', then mating patterns encouraging competition and choice may help protect populations from extinction; (b) by contrast, if mating patterns create load through evolutionary or ecological conflict, then population viability could be further reduced by sexual selection. We test between these opposing theories using replicate populations of the model insect Tribolium castaneum exposed to over 10 years of experimental evolution under monogamous versus polyandrous mating patterns. After a 95-generation history of divergence in sexual selection, we compared fitness and extinction of monogamous versus polyandrous populations through an experimental extinction vortex comprising 15 generations of cycling environmental and genetic stresses. Results showed that lineages from monogamous evolutionary backgrounds, with limited opportunities for sexual selection, showed rapid declines in fitness and complete extinction through the vortex. By contrast, fitness of populations from the history of polyandry, with stronger opportunities for sexual selection, declined slowly, with 60% of populations surviving by the study end. The three vortex stresses of (a) nutritional deprivation, (b) thermal stress and (c) genetic bottlenecking had similar impacts on fitness declines and extinction risk, with an overall sigmoid decline in survival through time. We therefore reveal sexual selection as an important force behind lineages facing extinction threats, identifying the relevance of natural mating patterns for conservation management.
由于人为因素导致的环境、人口和遗传压力的综合作用，地球的生物多样性正在经历大规模灭绝。这些不同的压力会使种群陷入一个称为灭绝旋涡的强化反馈循环中，在这个循环中，随着时间的推移，协同压力相互叠加，降低了种群的生存能力。性选择是一种广泛存在的进化力量，它源于动物交配模式中的竞争、选择和生殖变异，可以对种群的生存能力和灭绝旋涡产生重要影响：(a) 如果性选择加强了自然选择，以固定“好基因”并清除“坏基因”，那么鼓励竞争和选择的交配模式可能有助于保护种群免受灭绝；(b) 相比之下，如果交配模式通过进化或生态冲突产生负荷，那么性选择可能会进一步降低种群的生存能力。我们通过对经过 10 多年的单配和多配交配模式下的实验进化的模式昆虫赤拟谷盗的重复种群进行测试，验证了这两种对立的理论。在性选择分化了 95 代之后，我们通过一个由 15 代环境和遗传压力循环组成的实验灭绝旋涡，比较了单配和多配种群的适应性和灭绝情况。结果表明，来自单配进化背景、性选择机会有限的品系，在灭绝旋涡中适应性迅速下降，最终完全灭绝。相比之下，来自多配进化历史的种群，性选择机会更强，适应性下降缓慢，到研究结束时，有 60%的种群存活下来。营养剥夺、热应激和遗传瓶颈这三个旋涡压力对适应性下降和灭绝风险的影响相似，随着时间的推移，整体呈指数下降。因此，我们揭示了性选择是面临灭绝威胁的谱系的一个重要力量，确定了自然交配模式对保护管理的相关性。
