Choosy Females Spur New Spider Species（雌性的挑剔 促使蜘蛛新种的产生（图））_生物论文

达尔文认为：雌性动物优先选择那些富有魅力的雄性配偶可以最终导致新物种的产生，但是现在的各种证据越来越不支持这种观点。新的研究发现了一种极为罕见的性选择的例子：研究人员发现雌性跳蛛是根据花纹和舞姿来选择配偶，从而促使新种的进化。

10,000多年前，亚利桑那州东南地区的气候变得非常干燥，在这个时期，为了适应被干旱的沙漠隔离的几座山地环境，这里的一种跳蛛(Habronattuspugillis)分成了几个种群。现在，每种山地环境下的雄性的跳蛛都是不同的，如前腿的花纹、前眼上的白色条纹的图案、甚至头的形状都具有自己的特征。此外，求爱舞姿的节奏和舞姿也不同。但是整个地区的雌性跳蛛却是一样的。雄性蜘蛛的这种差异表明：自然选择对于雌性和雄性两种性别的作用是不同的。

研究人员在亚利桑那州采集了很多的雌雄性的跳蛛。通过比较雄性跳蛛的外观和行为，他们发现在10,000后的今天，已经有三个种群发生了变化。他们认为：蜘蛛线粒体DNA随机突变率比较快，这表明：性别选择是一个促进因素。

Galiuro山脉的雄性跳蛛需要三次、甚至更长的时间来引诱santa Tita山脉的雌蛛，即使他们成功交配，后代也很少能够孵化。这个结果表明：这些山脉中的蜘蛛已经进入了分成两个不同新种的进程。

Cornell大学的进化生物学家kelly Zemudio说：这项研究提供了一个非常有力的证据，性别选择可以促使新种的产生。很少有人研究遗传学、形态学和行为学交叉领域，这是一件非常有意义的事情。

原文：

Darwin suggested that females‘ preference（优先选择） for attractive matesspeeds up the formation of new species. But empirical evidence to back up thisclaim has remained elusive. A new study reveals a rare example of sexualselection at work: Its authors find that female jumping spiders’ choosiness forornamented and dancing mates drives the evolution of new spider species.

Handsome. FemaleHabronattus spiders love ornaments on theforelegs of dancing males, and different preferences are separating thespecies.
CREDIT: SUSAN E. MASTA

The dancing spiders strut theirstuff on different stages: A climate change that dried out Southeastern Arizona about 10,000 years ago split thepopulation of jumping spiders (Habronattus pugillis) into several populations that now inhabitseveral mountain ranges separated by inhospitable desert. Today, male jumpingspiders look strikingly different in each mountain range: The ornamentation oftheir frontmost pair of legs, the white stripepatterns of the front eyes, and even the shape of the head is characteristicfor each region. Moreover, the rhythm and the pattern of steps during thecourtship dance distinguish each population of males. Female spiders areuniform across the region, suggesting that the differences in the males aren‘tdue to natural selection acting on both sexes.

To investigate whether females’ mating preferences couldbe behind these differences, evolutionary biologists Susan Mastaand Wayne Maddison of the University of Arizona in Tucson collected male and female jumping spidersin the Arizona mountains. By comparing the male spiders‘appearance and behavior, they could get a handle on how much three populationshad changed in the last 10,000 years. Then they figured out that this changewas faster than the rate of random mutations in the spider’s mitochondrial DNA,suggesting that sexual selection had given them a push, the team reports in the2 April issue of the Proceedings of the National Academy of Sciences.

An indication that sexual selection is driving thejumping spider populations into distinct species is their change in matingbehavior. Male spiders from the Galiuro mountainrange needed three times longer to seduce virgin females from the Santa Ritamountains. Even when they succeeded in mating, fewer offspring hatched. Theseresults indicate that spiders from those mountain ranges are in the process ofdiverging into two separate species.

The study provides compelling evidence that sexualselection can drive the formation of new species, says Kelly Zamudio, an evolutionary biologist at Cornell University. Very few studies have looked at thecombination of genetics, appearance, and behavior, Zamudiosays: "That‘s the coolest thing."

--CHRISTIAN HEUSS

摘自：http://sciencenow.sciencemag.org/cgi/content/full/2002/408/3