爱思英语编者按:两性关系与传宗接代。

Sexual selection
性选择

Speed-dating birds
闪电约会的鸟儿

Choosing their own mates works best for zebra finches
自由选择伴侣,对斑胸草雀来说最合适

sex.jpg

Fancy flying back to my place?
想要再飞回我这里吗?

1 MOST research into how animals choose their mates looks at how partners show preference for certain physical traits, which may well indicate genetic fitness—usually measured as reproductive success. Yet in some species, mating preferences are more individualistic. Zebra finches are one. They are choosy about their mates and there is not a lot of agreement about who is the best catch. Once hitched, zebra finches tend to be monogamous and the fathers share in the child care.

大多数对动物择偶的研究都着眼于观察雌雄性如何显示对对方某种身体特征的偏好,通常以繁殖成功率来衡量,以充分表明基因的优劣。然而对于一些物种,择偶偏爱性会显得偏利己主义。斑胸草雀(Zebra finches)就是这样的一个物种。它们对于伴侣的选择很挑剔,而且对于最佳伴侣的特征并没有太多定论。一旦被异性选中,斑胸草雀会更愿意实行一夫一妻制,并且雄鸟会参与后代的抚育工作。

2 Malika Ihle and her colleagues at the Max Planck Institute for Ornithology, in Seewiesen, Germany, wondered what would happen if the finches were prevented from choosing their mates. So they constructed an experiment to discover if birds allowed to pursue life with a chosen mate fared any better than those forced into an arranged union. To do this they studied 160 bachelor zebra finches, putting together groups of 20 males and 20 females in an aviary to get to know each other.

假如不让斑胸草雀自由选择配偶将会怎样,来自德国威森马普鸟类学院的玛丽卡•伊勒(Malika Ihle)和她的同事们对此很好奇。因此他们组织了一场试验,以观察被允许自由选择配偶的斑胸草雀是否会比配偶由人工搭配的斑胸草雀生活的好些。为使试验顺利开展,他们细查了160只尚未交配的斑胸草雀幼鸟,并将其中的20只雄鸟和20只雌鸟放在同一个大鸟舍里,让它们逐渐互相认识。

3 Pairs that started grooming each other—a sign of courtship—were deemed couples. Half of those couples got to stay together, but the other half were forced to pair off with someone else’s chosen mate. The reason for this was that the researchers wanted to make sure all the individuals had been found desirable by another finch, even if not by the one they ended up with. This meant that whatever happened next wasn’t because some of the birds were simply losers.

那些互相给彼此清理羽毛的鸟儿——这是求偶的信号——被视为一对。但是只有一半这样的一对可以在一起交配,而另一半的雌雄斑胸草雀却只能和被其他的斑胸草雀看中的对象交配。这样做的目的是为了确保所有的斑胸草雀都会有异性斑胸草雀青睐于它,即使最终未能成为配偶。也就是说,不管之后出现什么情况,都排除了斑胸草雀自身的原因。

4 All the couples were given their own cages for a few months, to help the forced pairs develop bonds. Then they were released into a group aviary where they started their families. Over the next five months—enough time for the finches to raise three separate broods—the researchers continued to observe them, both directly and with video. The experiment was then repeated with the same birds, this time forcing two-thirds of the couples into arranged matches and allowing only one-third to stay with their chosen mate.

所有的情侣都被放在只属于两者的的鸟笼内数月,这样做的目的是帮助那些由人工搭配的情侣缔结情感纽带,然后将它们放入大型团体鸟舍内繁衍后代。在接下来的五个月里——足够一对成年雌雄斑胸草雀孵出三窝雏鸟——研究者们通过直接或录像的方式继续观察它们。后来研究人员又以同一批的其他斑胸草雀进行了相同的试验,只是这次有三分之二的雌雄斑胸草雀情侣是由人工搭配,只有三分之一的雌雄斑胸草雀是和自己中意的对象待在一起。

5 The results, published this week in PLoS Biology, showed a clear advantage for birds who had chosen each other over those who had not: they had 37% more surviving young. Those strong-armed into a relationship yielded more eggs that went unfertilised or got lost, and more deaths of hatched chicks. Females in forced couplings were not as interested in sex, and males were less keen to look after the chicks. The males who had their partners chosen for them also did more philandering.

本周的《公共科学图书馆•生物学》杂志上刊登了这次试验,结果显示,那些可以自由选择配偶的斑胸草雀情侣具有一个明显的优势:其后代的存活率要比由人工搭配的情侣的后代多出37%。被强制分在一起的斑胸草雀情侣往往会下出更多发育不良的蛋,甚至丢失,孵出的雏鸟也会有更多夭折的。人工搭配的斑胸草雀情侣中,雌性对交配并不感兴趣,雄性一方也不太热衷于照顾雏鸟,而且还到处拈花惹草。

6 Dr Ihle and her colleagues say the evidence supports the idea that zebra finches select their mates based on how well they get along, putting behaviour ahead of seeking genetic compatibility. The researchers argue that if the finches were choosing mates for genetic reasons, they would expect to see more embryos die because of genetic defects caused by a degree of interbreeding between a more limited selection of partners. But they did not see that at all. Instead, the difference in the survival of chicks appeared to depend on the youngsters being looked after well by their parents, whatever they looked like.

伊勒博士和她的同事们表示,试验前,他们提出了一个观点:斑胸草雀选择配偶是基于两者相处的融洽度,相对于寻求基因的互补性,它们更看中对方的品行习性,而这次试验证明了这个观点。他们解释称,假如斑胸草雀选择配偶是出于基因的考虑,那么在一个相当有限的配偶可选范围内进行一定程度的种族内交配,则会产生遗传缺陷,这将导致很多胚胎死亡。但是这种情况并没有出现。相反,那些存活的斑胸草雀幼鸟所存在的差异似乎取决于它们被父母照顾得好坏程度,不管它们看起来像什么。

【译者注】
PLoS,美国科学公共图书馆(the Public Library of Science)的简称,该机构由生物医学科学家哈罗德·瓦尔缪斯、帕克·布朗和迈克尔·艾森创立于2000年10月,是一家由众多诺贝尔奖得主和慈善机构支持的非赢利性学术组织,为科技人员和医学人员服务并致力于使全球范围科技和医学领域文献成为可以免费获取的公共资源。PLoS已出版了8种生命科学与医学领域的期刊,可以免费获取全文,如PLoS Biology、PLoS Medicine、PLoS Computational Biology、PLoS Genetics、PLoS Pathogens、PLoS ONE、PLoS Neglected Tropical Diseases,这8种期刊已成为国际上顶级水平的科学期刊(来自百度百科)。