AFLPs and mitochondrial haplotypes reveal local adaptation to extreme thermal environments in a freshwater gastropod

The way environmental variation shapes neutral and adaptive genetic variation in natural populations is a key issue in evolutionary biology. Genome scans allow the identification of the genetic basis of local adaptation without previous knowledge of genetic variation or traits under selection. Candidate loci for divergent adaptation are expected to show higher FST than neutral loci influenced solely by random genetic drift, migration and mutation. The comparison of spatial patterns of neutral markers and loci under selection may help disentangle the effects of gene flow, genetic drift and selection among populations living in contrasting environments. Using the gastropod Radix balthica as a system, we analyzed 376 AFLP markers and 25 mtDNA COI haplotypes for candidate loci and associations with local adaptation among contrasting thermal environments in Lake Mývatn, a volcanic lake in northern Iceland. We found that 2% of the analysed AFLP markers were under directional selection and 12%...环境变异如何塑造自然种群中的中性与适应性遗传变异，是进化生物学领域的核心议题之一。基因组扫描（Genome scans）无需预先知晓受选择的遗传变异或相关性状，即可鉴定本地适应的遗传基础。预期分化适应的候选位点所呈现的遗传分化系数（FST），将高于仅受随机遗传漂变、迁移与突变影响的中性位点。对比中性标记与受选择位点的空间分布格局，有助于厘清生活在迥异环境中的种群间基因流、遗传漂变与选择的作用效应。本研究以腹足类动物耳萝卜螺（Radix balthica）为研究系统，针对冰岛北部火山湖米湖（Lake Mývatn）内迥异的热环境条件，对376个扩增片段长度多态性（Amplified Fragment Length Polymorphism, AFLP）标记以及25个线粒体DNA细胞色素氧化酶亚基I（mtDNA COI）单倍型展开分析，以鉴定候选位点并探究其与本地适应的关联。本研究发现，所分析的AFLP标记中有2%处于定向选择之下，另有12%……