Pitcher Trevor E, Neff Bryan D, Rodd F Helen, Rowe Locke
Department of Zoology, University of Toronto, 25 Harbord Street, Toronto, Ontario M5S 3G5, Canada.
Proc Biol Sci. 2003 Aug 7;270(1524):1623-9. doi: 10.1098/rspb.2002.2280.
The trade-up hypothesis outlines a behavioural strategy that females could use to maximize the genetic benefits to their offspring. The hypothesis proposes that females should be more willing to accept a mate when the new male encountered is a superior genetic source to previous mates. We provide a direct test of the trade-up hypothesis using guppies (Poecilia reticulata), and evaluate both behavioural and paternity data. Virgin female guppies were presented sequentially with two males of varying attractiveness, and their responsiveness to each male was quantified. Male attractiveness (ornamentation) was scored as the amount of orange coloration on their body. Females were generally less responsive to second-encountered males, yet responsiveness to second males was an increasing function of male ornamentation. These attractive second males also sired a greater proportion of the offspring. There was an overall tendency for last-male advantage in paternity, and this advantage was most exaggerated when the second male was more ornamented than the first. Finally, we found that our estimate of relative sperm number did not account for any significant variation in paternity. Our results suggest that female guppies may use pre-copulatory mechanisms to maximize the genetic quality of their offspring.
升级假说概述了一种行为策略，雌性可利用该策略将其后代的遗传益处最大化。该假说提出，当遇到的新雄性比先前的配偶具有更优良的基因来源时，雌性应该更愿意接受该配偶。我们使用孔雀鱼（孔雀花鳉）对升级假说进行了直接测试，并评估了行为和亲子关系数据。将处于处女状态的雌性孔雀鱼依次与两名吸引力不同的雄性展示在一起，并对它们对每只雄性的反应进行量化。雄性的吸引力（装饰性）以其身体上橙色的数量来评分。雌性通常对第二次遇到的雄性反应较小，但对第二个雄性的反应是雄性装饰性的递增函数。这些有吸引力的第二个雄性也使更大比例的后代受精。在亲子关系上总体存在最后一个雄性占优势的趋势，当第二个雄性比第一个装饰性更强时，这种优势最为明显。最后，我们发现我们对相对精子数量的估计并不能解释亲子关系中的任何显著差异。我们的结果表明，雌性孔雀鱼可能利用交配前机制将其后代的遗传质量最大化。
