Dataset for: Evolution and plasticity: Divergence of song discrimination is faster in birds with innate song than in song learners in Neotropical passerine birds

Plasticity is often thought to speed 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 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.

表型可塑性（Plasticity）常被认为可加速性状演化与物种形成进程。例如，鸟类鸣唱的可塑性或可部分解释，为何鸣唱学习类群的演化支多样性高于鸣唱由先天决定的近缘演化支。这一“鸣唱学习”假说预测：其一，鸣唱学习类群的鸣唱性状差异演化速率更快；其二，鸣唱学习类群对异域鸣唱的行为识别（前交配生殖隔离的替代指标）的演化速率更快。我们通过分析声学性状并开展回放实验，对上述预测展开验证：实验对象为中美洲的异域姊妹类群对，包含42个鸣唱学习型鸣禽亚目（Oscines）类群与27个非学习型亚鸣禽亚目（Suboscines）类群。研究结果却出人意料：非学习型类群的平均声学差异演化速率高于鸣唱学习型类群，且鸣唱识别的平均演化速率在非学习型类群中是鸣唱学习型类群的4.3倍。这一意外结果或源于鸣唱学习类群的鸣唱性状变异程度显著更高（高出54%-79%）——这意味着，鸣禽亚目鸣唱学习类群要达到与亚鸣禽亚目非学习型类群同等的鸣唱行为识别水平，需演化出更大的鸣唱绝对差异。该研究揭示了物种识别演化中的“学习劣势”，同时也是可塑性通过增加性状变异降低演化与多样化速率的重要例证。