University of Potsdam, Evolutionary Biology/Systematic Zoology, Karl-Liebknecht-Strasse 24-25, 14476, Potsdam, Germany.
Plant Ecology and Nature Conservation, University of Potsdam, Am Mühlenberg 3, 14476, Potsdam, Germany.
BMC Evol Biol. 2019 Aug 28;19(1):175. doi: 10.1186/s12862-019-1494-0.
Organisms are expected to respond to changing environmental conditions through local adaptation, range shift or local extinction. The process of local adaptation can occur by genetic changes or phenotypic plasticity, and becomes especially relevant when dispersal abilities or possibilities are somehow constrained. For genetic changes to occur, mutations are the ultimate source of variation and the mutation rate in terms of a mutator locus can be subject to evolutionary change. Recent findings suggest that the evolution of the mutation rate in a sexual species can advance invasion speed and promote adaptation to novel environmental conditions. Following this idea, this work uses an individual-based model approach to investigate if the mutation rate can also evolve in a sexual species experiencing different conditions of directional climate change, under different scenarios of colored stochastic environmental noise, probability of recombination and of beneficial mutations. The color of the noise mimicked investigating the evolutionary dynamics of the mutation rate in different habitats.
The results suggest that the mutation rate in a sexual species experiencing directional climate change scenarios can evolve and reach relatively high values mainly under conditions of complete linkage of the mutator locus and the adaptation locus. In contrast, when they are unlinked, the mutation rate can slightly increase only under scenarios where at least 50% of arising mutations are beneficial and the rate of environmental change is relatively fast. This result is robust under different scenarios of stochastic environmental noise, which supports the observation of no systematic variation in the mutation rate among organisms experiencing different habitats.
Given that 50% beneficial mutations may be an unrealistic assumption, and that recombination is ubiquitous in sexual species, the evolution of an elevated mutation rate in a sexual species experiencing directional climate change might be rather unlikely. Furthermore, when the percentage of beneficial mutations and the population size are small, sexual species (especially multicellular ones) producing few offspring may be expected to react to changing environments not by adaptive genetic change, but mainly through plasticity. Without the ability for a plastic response, such species may become - at least locally - extinct.
生物预计将通过局部适应、范围转移或局部灭绝来应对环境变化。局部适应的过程可以通过遗传变化或表型可塑性发生，当扩散能力或可能性受到某种限制时，这种过程变得尤为重要。为了发生遗传变化，突变是变异的最终来源，并且突变体基因座的突变率可以受到进化变化的影响。最近的研究结果表明，有性物种中突变率的进化可以提高入侵速度，并促进对新环境条件的适应。基于这一观点，本研究使用个体基础模型方法来探讨在经历不同方向气候变化条件下，在不同的有色随机环境噪声、重组概率和有利突变概率的情景下，有性物种中的突变率是否也可以进化。噪声的颜色模拟了在不同栖息地中研究突变率进化动态的情况。
研究结果表明，在经历方向气候变化情景的有性物种中，突变率可以进化并达到相对较高的值，主要条件是突变体基因座和适应基因座完全连锁。相比之下，当它们不连锁时，只有在至少 50%的新突变是有利的，且环境变化速度相对较快的情况下，突变率才能略有增加。在不同的随机环境噪声情景下，这一结果是稳健的，这支持了在经历不同栖息地的生物中没有系统的突变率变化的观察结果。
鉴于 50%有利突变可能是不现实的假设，并且重组在有性物种中普遍存在，因此，在经历方向气候变化的有性物种中，突变率的进化可能不太可能。此外，当有利突变的百分比和种群规模较小时，产生较少后代的有性物种（特别是多细胞物种）可能不会通过适应性遗传变化来应对环境变化，而主要通过可塑性。如果没有可塑性反应的能力，这些物种可能会在至少局部灭绝。
