Heritability and adaptive significance of the number of egg-dummies in the cichlid fish Astatotilapia burtoni
Heritability and adaptive significance of the number of egg-dummies in the cichlid fish Astatotilapia burtoni
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DOI：
10.1098/rspb.2010.2483
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发表时间：
2011-08-07
影响因子：
4.7
通讯作者：
Meyer, Axel
中科院分区：
文献类型：
--
作者：
Lehtonen, Topi K.;Meyer, Axel
慈鲷科鱼类是快速物种形成和丰富多样性的教科书例子，这尤其适用于haplochromines，一个大约有1800个物种的谱系。单色鱼雄性的独特之处在于它们的臀鳍上有椭圆形的亮点，称为“蛋斑”或“蛋假”。这些被认为是一个进化的关键创新，有助于部落的进化成功。卵斑被认为是模仿相应物种口孵雌性的卵，有助于受精成功，甚至有助于物种识别。有趣的是，卵斑数量不仅在物种之间变化很大，而且在某些种群内也是如此。这种高度的种内变异似乎是违反直觉的，因为选择可能会起到稳定与适应性措施相关的性状的作用。我们通过实验解决了这一“悖论”，发现在单染丽鱼Astatotilapia burtoni中，卵斑的数量与雄性的年龄、身体状况和优势地位有关。有趣的是，卵斑数也有很高的遗传成分（狭义遗传力为0.5）。这些结果表明，卵斑的功能可能与受精成功或物种识别关系不大，而是与配偶选择和/或雄性-雄性竞争有关，有助于解释这一重要性状的高变异性。
Cichlid fishes are a textbook example of rapid speciation and exuberant diversity-this applies especially to haplochromines, a lineage with approximately 1800 species. Haplochromine males uniquely possess oval, bright spots on their anal fin, called 'egg-spots' or 'egg-dummies'. These are presumed to be an evolutionary key innovation that contributed to the tribe's evolutionary success. Egg-spots have been proposed to mimic the ova of the mouthbrooding females of the corresponding species, contribute to fertilization success and even facilitate species recognition. Interestingly, egg-spot number varies extensively not only between species, but also within some populations. This high degree of intraspecific variation may appear to be counterintuitive since selection might be expected to act to stabilize traits that are correlated with fitness measures. We addressed this 'paradox' experimentally, and found that in the haplochromine cichlid Astatotilapia burtoni, the number of egg-spots was related to male age, body condition and dominance status. Intriguingly, the egg-spot number also had a high heritable component ( narrow sense heritability of 0.5). These results suggest that the function of egg-spots might have less to do with fertilization success or species recognition, but rather relate to mate choice and/or male-male competition, helping to explain the high variability in this important trait.