Sinervo B, Svensson E, Comendant T
Department of Ecology and Evolutionary Biology, University of California, Santa Cruz 95064, USA.
Nature. 2000 Aug 31;406(6799):985-8. doi: 10.1038/35023149.
A long-standing hypothesis posits that natural selection can favour two female strategies when density cycles. At low density, females producing many smaller progeny are favoured when the intrinsic rate of increase, r, governs population growth. At peak density, females producing fewer, high-quality, progeny are favoured when the carrying capacity, K, is exceeded and the population crashes. Here we report on the first example of a genetic r versus K selection game that promotes stable population cycles in lizards. Decade-long fitness studies and game theory demonstrated that two throat-colour morphs were refined by selection in which the strength of natural selection varied with density. Orange-throated females, r strategists, produced many eggs and were favoured at low density. Conversely, yellow-throated females, K strategists, produced large eggs and were favoured at high density. Progeny size should also be under negative frequency-dependent selection in that large progeny will have a survival advantage when rare, but the advantage disappears when they become common. We confirmed this prediction by seeding field plots with rare and common giant hatchlings. Thus, intrinsic causes of frequency- and density-dependent selection promotes an evolutionary game with two-generation oscillations.
一个长期存在的假说认为，在种群数量周期性变化时，自然选择可能会青睐两种雌性策略。在低密度时，当种群增长受内禀增长率r控制时，产生许多较小后代的雌性更受青睐。在种群密度峰值时，当超过环境容纳量K且种群数量崩溃时，产生较少但高质量后代的雌性更受青睐。在此，我们报告了首个关于遗传r与K选择博弈的例子，该博弈在蜥蜴中促进了稳定的种群周期。长达十年的适合度研究和博弈论表明，两种喉部颜色形态通过选择得到了优化，其中自然选择的强度随密度而变化。橙色喉部的雌性，即r策略者，产很多卵，在低密度时更受青睐。相反，黄色喉部的雌性，即K策略者，产大卵，在高密度时更受青睐。后代大小也应处于负频率依赖选择之下，因为大后代在稀少时将具有生存优势，但当它们变得常见时优势就会消失。我们通过在田间地块播撒稀有的和常见的巨型幼体证实了这一预测。因此，频率和密度依赖选择的内在原因促进了一个具有两代振荡的进化博弈。
