Edeline Eric, Carlson Stephanie M, Stige Leif C, Winfield Ian J, Fletcher Janice M, James J Ben, Haugen Thrond O, Vøllestad L Asbjørn, Stenseth Nils C
Centre for Ecological and Evolutionary Synthesis, Department of Biology, University of Oslo, P.O. Box 1066 Blindern, 0316 Oslo, Norway.
Proc Natl Acad Sci U S A. 2007 Oct 2;104(40):15799-804. doi: 10.1073/pnas.0705908104. Epub 2007 Sep 26.
Selective harvest of large individuals should alter natural adaptive landscapes and drive evolution toward reduced somatic growth and increased reproductive investment. However, few studies have simultaneously considered the relative importance of artificial and natural selection in driving trait changes in wild populations. Using 50 years of individual-based data on Windermere pike (Esox lucius), we show that trait changes tracked the adaptive peak, which moved in the direction imposed by the dominating selective force. Individual lifetime somatic growth decreased at the start of the time series because harvest selection was strong and natural selection was too weak to override the strength of harvest selection. However, natural selection favoring fast somatic growth strengthened across the time series in parallel with the increase in pike abundance and, presumably, cannibalism. Harvest selection was overridden by natural selection when the fishing effort dwindled, triggering a rapid increase in pike somatic growth. The two selective forces appear to have acted in concert during only one short period of prey collapse that favored slow-growing pike. Moreover, increased somatic growth occurred concurrently with a reduction in reproductive investment in young and small female pike, indicating a tradeoff between growth and reproduction. The age-specific amplitude of this change paralleled the age-specific strength of harvest pressure, suggesting that reduced investment was also a response to increased life expectancy. This is the first study to demonstrate that a consideration of both natural selection and artificial selection is needed to fully explain time-varying trait dynamics in harvested populations.
对大型个体进行选择性捕捞应该会改变自然适应景观，并推动进化朝着体细胞生长减少和生殖投资增加的方向发展。然而，很少有研究同时考虑人工选择和自然选择在推动野生种群性状变化方面的相对重要性。利用50年基于个体的温德米尔梭子鱼（Esox lucius）数据，我们表明性状变化跟踪了适应峰，该适应峰朝着主导选择力施加的方向移动。在时间序列开始时，个体一生的体细胞生长下降，因为捕捞选择很强，而自然选择太弱，无法超越捕捞选择的强度。然而，随着梭子鱼数量的增加以及可能的同类相食现象的增加，在整个时间序列中，有利于快速体细胞生长的自然选择也在增强。当捕捞努力减少时，自然选择超越了捕捞选择，引发了梭子鱼体细胞生长的迅速增加。这两种选择力似乎仅在一段有利于生长缓慢的梭子鱼的猎物崩溃的短时期内共同起作用。此外，体细胞生长的增加与年轻和小型雌梭子鱼生殖投资的减少同时发生，这表明生长和繁殖之间存在权衡。这种变化的年龄特异性幅度与年龄特异性捕捞压力强度平行，表明投资减少也是对预期寿命增加的一种反应。这是第一项证明需要同时考虑自然选择和人工选择才能充分解释捕捞种群中随时间变化的性状动态的研究。
