Konijnendijk Nellie, Shikano Takahito, Daneels Dorien, Volckaert Filip A M, Raeymaekers Joost A M
Laboratory of Biodiversity and Evolutionary Genomics University of Leuven Ch. Deberiotstraat 32, B-3000 Leuven Belgium.
Ecological Genetics Research Unit Department of Biosciences University of Helsinki P.O. Box 65 FI-000 14 Helsinki Finland.
Ecol Evol. 2015 Sep 4;5(18):4174-86. doi: 10.1002/ece3.1671. eCollection 2015 Sep.
Local adaptation is often obvious when gene flow is impeded, such as observed at large spatial scales and across strong ecological contrasts. However, it becomes less certain at small scales such as between adjacent populations or across weak ecological contrasts, when gene flow is strong. While studies on genomic adaptation tend to focus on the former, less is known about the genomic targets of natural selection in the latter situation. In this study, we investigate genomic adaptation in populations of the three-spined stickleback Gasterosteus aculeatus L. across a small-scale ecological transition with salinities ranging from brackish to fresh. Adaptation to salinity has been repeatedly demonstrated in this species. A genome scan based on 87 microsatellite markers revealed only few signatures of selection, likely owing to the constraints that homogenizing gene flow puts on adaptive divergence. However, the detected loci appear repeatedly as targets of selection in similar studies of genomic adaptation in the three-spined stickleback. We conclude that the signature of genomic selection in the face of strong gene flow is weak, yet detectable. We argue that the range of studies of genomic divergence should be extended to include more systems characterized by limited geographical and ecological isolation, which is often a realistic setting in nature.
当基因流受到阻碍时，局部适应性往往很明显，比如在大空间尺度以及跨越强烈生态差异时所观察到的情况。然而，在小尺度上，比如相邻种群之间或跨越微弱生态差异时，由于基因流很强，局部适应性就变得不那么确定了。虽然关于基因组适应性的研究往往集中在前一种情况，但对于后一种情况下自然选择的基因组靶点却知之甚少。在本研究中，我们调查了三刺鱼（Gasterosteus aculeatus L.）种群在盐度从微咸水到淡水的小尺度生态过渡中的基因组适应性。该物种对盐度的适应性已得到反复证实。基于87个微卫星标记的基因组扫描仅揭示了少数选择特征，这可能是由于均一化基因流对适应性分化的限制。然而，在三刺鱼基因组适应性的类似研究中，检测到的位点反复出现成为选择靶点。我们得出结论，面对强大基因流时基因组选择的特征很微弱，但仍可检测到。我们认为，基因组分化的研究范围应扩大到包括更多以有限地理和生态隔离为特征的系统，这在自然界中往往是一种现实情况。
