Luijckx Pepijn, Ho Eddie Ka Ho, Gasim Majid, Chen Suyang, Stanic Andrijana, Yanchus Connor, Kim Yun Seong, Agrawal Aneil F
Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, Canada M5S 3B2
Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, Canada M5S 3B2.
Proc Natl Acad Sci U S A. 2017 Jan 17;114(3):534-539. doi: 10.1073/pnas.1604072114. Epub 2017 Jan 4.
A leading hypothesis for the evolutionary maintenance of sexual reproduction proposes that sex is advantageous because it facilitates adaptation. Changes in the environment stimulate adaptation but not all changes are equivalent; a change may occur along one or multiple environmental dimensions. In two evolution experiments with the facultatively sexual rotifer Brachionus calyciflorus, we test how environmental complexity affects the evolution of sex by adapting replicate populations to various environments that differ from the original along one, two, or three environmental dimensions. Three different estimates of fitness (growth, lifetime reproduction, and population density) confirmed that populations adapted to their new environment. Growth measures revealed an intriguing cost of complex adaptations: populations that adapted to more complex environments lost greater amounts of fitness in the original environment. Furthermore, both experiments showed that B. calyciflorus became more sexual when adapting to a greater number of environmental dimensions. Common garden experiments confirmed that observed changes in sex were heritable. As environments in nature are inherently complex these findings help explain why sex is maintained in natural populations.
关于有性生殖进化维持的一个主要假说提出，有性生殖具有优势是因为它促进了适应性。环境变化会刺激适应性，但并非所有变化都是等同的；变化可能沿着一个或多个环境维度发生。在两项针对兼性有性轮虫萼花臂尾轮虫的进化实验中，我们通过使重复种群适应在一个、两个或三个环境维度上与原始环境不同的各种环境，来测试环境复杂性如何影响有性生殖的进化。三种不同的适合度估计（生长、终生繁殖和种群密度）证实种群适应了它们的新环境。生长测量揭示了复杂适应性的一个有趣代价：适应更复杂环境的种群在原始环境中损失了更多的适合度。此外，两项实验均表明，萼花臂尾轮虫在适应更多环境维度时变得更倾向于有性生殖。共同培养实验证实观察到的有性生殖变化是可遗传的。由于自然界中的环境本质上是复杂的，这些发现有助于解释为什么有性生殖在自然种群中得以维持。
