Rapid adaptation to a novel host in a seed beetle (Callosobruchus maculatus):: The role of sexual selection
Rapid adaptation to a novel host in a seed beetle (Callosobruchus maculatus):: The role of sexual selection
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DOI：
10.1111/j.1558-5646.2007.00038.x
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发表时间：
2007-02-01
期刊：
影响因子：
3.3
通讯作者：
Arnqvist, Goran
中科院分区：
文献类型：
--
作者：
Fricke, Claudia;Arnqvist, Goran
快速多样化在食草昆虫中很常见，通常是寄主转移的结果，导致开发新的食物来源。这反过来又与雌性产卵行为和幼虫喂养生物学的适应性进化有关。虽然自然选择是这种适应的典型驱动力，但性选择的作用尚不清楚。理论上，性选择可以加速或阻碍适应。为了评估自然选择和性选择对适应率的独立影响，我们对一种草食性野蹄甲（Callosobruchus macuriatus）进行了实验室自然选择实验。我们建立了复制选择系，在2 × 2正交设计中，我们改变了自然（食物类型）和性（交配系统）选择，并将我们的系繁殖了35代。在一半的品系中，我们诱导了宿主转移，而另一半则保持在祖先的宿主上。我们实验性地在一半的种群中实行一夫一妻制，而另一半种群则保持一夫多妻制。甲虫迅速适应了新的寄主，这主要涉及到雌性对寄主的接受度增加和幼虫发育速度加快。我们还发现，我们的交配系统处理影响了适应的速度，但这种影响取决于食物类型。当甲虫适应新的寄主时，性选择加强了自然选择，而居住在其适应高峰附近的种群（即使用其祖先寄主的种群）在没有性选择的情况下表现出更高的适应性。我们根据当前的性选择理论讨论了我们的发现，并提出生殖竞争的净进化效应可能主要取决于自然选择。在定向自然选择条件下，性选择通常会加速种群的适应，而在稳定自然选择条件下，性选择和性冲突带来的负荷往往会抑制种群的适合度。
Rapid diversification is common among herbivorous insects and is often the result of host shifts, leading to the exploitation of novel food sources. This, in turn, is associated with adaptive evolution of female oviposition behavior and larval feeding biology. Although natural selection is the typical driver of such adaptation, the role of sexual selection is less clear. In theory, sexual selection can either accelerate or impede adaptation. To assess the independent effects of natural and sexual selection on the rate of adaptation, we performed a laboratory natural selection experiment in a herbivorous bruchid beetle (Callosobruchus macuriatus). We established replicated selection lines where we varied natural (food type) and sexual (mating system) selection in a 2 x 2 orthogonal design, and propagated our lines for 35 generations. In half of the lines, we induced a host shift whereas the other half was kept on the ancestral host. We experimentally enforced monogamy in half of the lines, whereas the other half remained polygamous. The beetles rapidly adapted to the novel host, which primarily involved increased host acceptance by females and an accelerated rate of larval development. We also found that our mating system treatment affected the rate of adaptation, but that this effect was contingent upon food type. As beetles adapted to the novel host, sexual selection reinforced natural selection whereas populations residing close to their adaptive peak (i.e., those using their ancestral host) exhibited higher fitness in the absence of sexual selection. We discuss our findings in light of current sexual selection theory and suggest that the net evolutionary effect of reproductive competition may critically depend on natural selection. Sexual selection may commonly accelerate adaptation under directional natural selection whereas sexual selection, and the associated load brought by sexual conflict, may tend to depress population fitness under stabilizing natural selection.