Data from: Evolution and plasticity: divergence of song discrimination is faster in birds with innate song than in song learners in Neotropical passerine birds

<b>Abstract</b><br/>Plasticity is often thought to accelerate trait evolution and speciation. For example, plasticity in birdsong may partially explain why clades of song learners are more diverse than related clades with innate song. This “song learning” hypothesis predicts that 1) differences in song traits evolve faster in song learners, and 2) behavioral discrimination against allopatric song (a proxy for premating reproductive isolation) evolves faster in song learners. We tested these predictions by analyzing acoustic traits and conducting playback experiments in allopatric Central American sister pairs of song learning oscines (N = 42) and non-learning suboscines (N = 27). We found that non-learners evolved mean acoustic differences slightly faster than did leaners, and that the mean evolutionary rate of song discrimination was 4.3 times faster in non-learners than in learners. This unexpected result may be a consequence of significantly greater variability in song traits in song learners (by 54–79%) that requires song-learning oscines to evolve greater absolute differences in song before achieving the same level of behavioral song discrimination as non-learning suboscines. This points to “a downside of learning” for the evolution of species discrimination, and represents an important example of plasticity reducing the rate of evolution and diversification by increasing variability.

<b>摘要</b><br/>可塑性通常被认为能加速性状进化与物种形成。例如，鸟类鸣唱的可塑性或许能部分解释为何鸣唱学习者分支比具有先天鸣唱能力的近缘分支更为多样。这一“鸣唱学习”假说预测：1) 鸣唱学习者的鸣唱性状差异进化速度更快；2) 鸣唱学习者对异域鸣唱的行为辨别（交配前生殖隔离的替代指标）进化速度更快。我们通过分析声学特征并对中美洲异域分布的鸣唱学习型鸣禽亚目鸟类（N=42）与非学习型亚鸣禽（N=27）的姐妹种对开展回放实验，对这些预测进行了验证。结果显示，非学习型鸟类的平均声学差异进化速度略快于学习者，且非学习型鸟类的鸣唱辨别平均进化速率是学习者的4.3倍。这一出乎意料的结果或许源于鸣唱学习者鸣唱性状的变异性显著更高（高出54–79%），使得鸣唱学习型鸣禽需在鸣唱上进化出更大的绝对差异，才能达到与非学习型亚鸣禽同等水平的鸣唱行为辨别能力。这揭示了“学习的弊端”在物种辨别进化中的存在，并为可塑性通过增加变异性降低进化与分化速率提供了重要例证。