Okanoya Kazuo
Faculty of Letters, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522 Japan.
Ann N Y Acad Sci. 2004 Jun;1016:724-35. doi: 10.1196/annals.1298.026.
The Bengalese finch Lonchura striata var. domestica is a domesticated strain of a wild species, the white-rumped munia Lonchura striata of Southeast Asia. Bengalese finches have been domesticated in Japan for 240 years. Comparing their song syntax with that of their wild ancestors, we found that the domesticated strain has highly complex, conspicuous songs with finite-state syntax, while the wild ancestor sang very stereotyped linear songs. To examine the functional utility of the song complexity, we compared serum levels of estradiol and measured the amount of nesting materials carried into the nest by female birds that were stimulated with either the complex "domesticated" song or the simple wild-type song. In the females stimulated with complex songs the estradiol levels were significantly higher and the amount of nesting material carried was significantly greater. We then performed brain lesions in the song system to identify the neural substrates that are responsible for these differences in song behavior. In Bengalese finches lesions of NIf, a higher order song control nucleus, resulted in simplification of the complex song syntax. That is, the complex "domesticated" syntax changed into the simple wild-type syntax. Based on these data, we hypothesize that mutations in the song control nuclei have occurred that enabled complex song syntax and became fixed into the population of domesticated Bengalese finches through a process of indirect sexual selection.
白腰文鸟的家养变种孟加拉雀（Lonchura striata var. domestica）是一种野生鸟类的驯化品种，其野生祖先为东南亚的白腰文鸟（Lonchura striata）。孟加拉雀在日本已被驯化了240年。通过比较它们与野生祖先的歌声句法，我们发现驯化品种拥有高度复杂、引人注目的具有有限状态句法的歌声，而野生祖先则唱非常刻板的线性歌曲。为了检验歌声复杂性的功能效用，我们比较了雌鸟的雌二醇血清水平，并测量了用复杂的“驯化”歌声或简单的野生型歌声刺激后进入鸟巢的筑巢材料数量。在用复杂歌声刺激的雌鸟中，雌二醇水平显著更高，携带的筑巢材料数量也显著更多。然后，我们对歌声系统进行了脑损伤实验，以确定导致这些歌声行为差异的神经基质。在孟加拉雀中，高级歌声控制核团NIf的损伤导致复杂歌声句法的简化。也就是说，复杂的“驯化”句法变成了简单的野生型句法。基于这些数据，我们假设在歌声控制核团中发生了突变，使得复杂的歌声句法得以出现，并通过间接性选择过程在驯化的孟加拉雀种群中固定下来。
