http://sciencenow.sciencemag.org/cgi/content/full/2006/420/2Despair Not, Frumpy Guys
By Julie Rehmeyer
ScienceNOW Daily News
20 April 2006
Always going after the attractive guy can have its downsides. Female birds gravitate toward flashy fellows, for example, but if they always picked mates with the same showy traits, the population would eventually become inbred. A new study of wild finches suggests a solution to the puzzle: All the males with showy feathers get paired in the spring. In the summer, still-single females fly far from home, where they settle for males with more subdued plumage and thereby contribute to the genetic diversity of the population.
Male finches know how to make an impression. They sport head and chest feathers that can range in color from brilliant yellow to red or purple. Not all males are so stylish, however: Some are as dull brown as the average female. In order to maintain a healthy genetic diversity in the finch population, it would make sense for females to occasionally seek out a color-challenged mate, but biologists were unsure what would motivate them to do this.
Evolutionary biologists Kevin Oh and Alexander Badyaev of the University of Arizona in Tucson tackled the problem by studying an isolated population of finches in Montana that Badyaev has followed for over 10 years. The researchers captured and marked more than 12,000 finches and then studied their mating habits over the spring and summer seasons.
Once female finches hatch, they instinctively leave their parents' neighborhood. But the team found that by the time the females got to their new digs, all the flashy males were already taken. That's because the older females in that location had had their pick of the male litter earlier in the season. Thus, the newcomers were forced to settle for the drab males that were left. This influx of females from another location keeps the population genetically healthy, even though all the girls still prefer the same bright coloration in a guy, says Badyaev, whose team reports its results online April 18 in Proceedings of the Royal Society B.
"It's a nice way of resolving the paradox," says ornithologist Peter Dunn of the University of Wisconsin in Milwaukee. "It's something that a lot of people have been scratching their heads about for five or ten years."
“我很丑，可是我很重要”
(2006-04-24 10:56:41)
群芳 译自
www.sciencenow.org，4月21日
一味追求漂亮迷人的伴侣可能导致整个种群质量下降。例如，雌鸟们往往容易被那些羽毛华丽的“小子”们所吸引，但是如果它们总是挑选那些外表漂亮的雄鸟进行交配，长此以往，将最终造成种群内的近亲繁殖现象。一项对野生雀类进行的研究为我们揭开这个谜底提供了答案：那些长满艳丽羽毛的雄雀在春季都找到了自己的伴侣。到了夏天，依然单飞的雌雀便会远离自己的家乡，寻找那些羽毛暗淡的雄雀，从而无形中保持了种群的遗传多样性。
雄雀通常知道如何给雌雀留下深刻的印象。它们炫耀着头部和胸脯的羽毛——其颜色从明黄到红或紫，五颜六色、应有尽有。然而并非所有的雄雀都这么“时髦” ——有的雄雀看着就像雌雀一样，生就一身土褐色。为了在雀种群中保持一种健康的遗传多样性，雌鸟有时选择相貌丑陋的雄鸟是有其积极意义的，但是生物学家却不能确定，到底是什么因素促使雌鸟作出“牺牲”。
为了搞清这一问题，美国图森市亚利桑那大学的进化生物学家Kevin Oh和Alexander Badyaev对生活在蒙大拿州的一个单独的雀种群进行了研究，在此之前，Badyaev曾对其进行了长达10年的追踪调查。研究人员先后捕捉了 12000多只雀鸟，并为它们做上标记，目的是研究这些鸟在春夏季节的交配行为。
雌雀在孵化后会本能地离开父母的生活区域。但是研究小组发现，这些雌鸟为自己寻找的新家几乎全是那些羽毛艳丽的雄鸟居住的地方。然而由于年纪大一些的雌鸟已经在早春时节选择了那些漂亮的“小伙”作为伴侣，因此，晚来的雌雀只好将剩下的灰头土脸的家伙作为自己的“老公”。Badyaev指出，尽管所有的“女孩儿”都钟情于那些外表英俊的“帅哥”，但这些从外地迁入的“姑娘”无疑保持了种群的遗传多样性。研究小组在4月18日的英国《皇家学会学报B卷》网络版上报告了这一研究成果。
密尔沃基市威斯康星大学的鸟类学者Peter Dunn表示：“这项研究结果是解释这一悖论的一条很好的途径。”Dunn指出：“有许多人在最近的5到10年里为此伤透了脑筋。”
