Department of Zoology and Biological Station, University of Oklahoma, Norman, OK 73019, USA.
Evolution. 2010 Sep;64(9):2535-46. doi: 10.1111/j.1558-5646.2010.00998.x.
The genic capture model offers a promising solution to the lek paradox. Heightened condition dependency of sexually selected traits is a prerequisite of this model. Condition dependency is empirically inferred by the sensitivity of traits to stressors. The magnitude of ecological stress (e.g., competition and predation) experienced by populations varies considerably. Thus, condition dependence should manifest more in populations experiencing higher levels of stress. We experimentally assessed the sensitivity of a sexually selected trait (posterior gnathopod) to food resource stress in an amphipod species. We found that gnathopod size variation was 59% higher under food stress, with no corresponding effect on nonsexually selected traits. In addition, we assessed levels of gnathopod variation and the allometry of gnathopods for males sampled from natural populations for two amphipod species that experience different levels of stress (driven by contrasting size-selective predation and associated life-history trade-offs). Populations that experience higher resource stress had both steeper allometries and greater gnathopod size variation. These results suggest that the magnitude of ecological stress experienced by natural populations strongly impacts condition dependency of sexually selected traits, and could play an important role in shaping trait variation and thus the opportunity for sexual selection.
基因捕获模型为雷克斯悖论提供了一个有前途的解决方案。性选择特征的条件依赖性增强是该模型的前提。条件依赖性是通过特征对胁迫的敏感性来经验推断的。种群所经历的生态胁迫（例如竞争和捕食）的程度差异很大。因此，条件依赖性应该在经历更高水平胁迫的种群中表现得更为明显。我们通过实验评估了一种两性选择特征（后颚足）对食物资源胁迫的敏感性，该特征在食物胁迫下的大小变化高达 59%，而对非性选择特征没有相应的影响。此外，我们评估了两种经历不同水平胁迫（由大小选择性捕食和相关生活史权衡驱动）的两种片脚类动物物种中从自然种群中采样的雄性的颚足变化程度和颚足的异速生长。经历更高资源胁迫的种群具有更陡峭的异速生长和更大的颚足大小变化。这些结果表明，自然种群所经历的生态胁迫的程度强烈影响性选择特征的条件依赖性，并可能在塑造特征变化从而为性选择提供机会方面发挥重要作用。
