Rapid life‐history changes caused by size‐selective harvesting are often interpreted as a response to direct harvest selection against a large body size. However, similar trait changes may result from a harvest‐induced relaxation of natural selection for a large body size via density‐dependent selection. Here, we show evidence of such density‐dependent selection favouring large‐bodied individuals at high population densities, in replicated pond populations of medaka fish. Harvesting, in contrast, selected medaka directly against a large body size and, in parallel, decreased medaka population densities. Five years of harvesting were enough for harvested and unharvested medaka populations to inherit the classically predicted trait differences, whereby harvested medaka grew slower and matured earlier than unharvested medaka. We show that this life‐history divergence was not driven by direct harvest selection for a smaller body size in harvested populations, but by density‐dependent natural selection for a larger body size in unharvested populations.

中文翻译：

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依赖密度的自然选择介导收获诱导的性状变化

因体型选择性收获而导致的生活史快速变化通常被解释为针对大体型直接选择收获的反应。但是，相似的性状变化可能是由于收获导致的通过密度依赖选择对大体型自然选择的放松而导致的。在这里，我们证明了这种密度依赖的选择有利于青鱼复制池塘中高密度种群的大个体。相比之下，收获时直接选择了具有较高体型的青aka，与此同时，减少了青decreased的种群密度。五年的收获足以使已收获和未收获的med高种群继承经典预测的性状差异，从而收获的aka高得比未收获的med高慢并且成熟得早。