Evidence of concurrent local adaptation and high phenotypic plasticity in a polar microeukaryote

Here we investigated whether there is evidence of local adaptation in strains of an ancestrally marine dinoflagellate to the lacustrine environment they now inhabit (optimal genotypes) and/or if they have evolved phenotypic plasticity (a range of phenotypes). Eleven strains of Polarella glacialis were isolated and cultured from three different environments: the polar seas, a hyposaline and a hypersaline Antarctic lake. Local adaptation was tested by comparing growth rates of lacustrine and marine strains at their own and reciprocal site conditions. To determine phenotypic plasticity, we measured the reaction norm for salinity. We found evidence of both, limited local adaptation and higher phenotypic plasticity in lacustrine strains when compared with marine ancestors. At extreme high salinities, local lake strains outperformed other strains, and at extreme low salinities, strains from the hyposaline lake outperformed all other strains. The data suggest that lake populations may have evo...

本研究旨在探究祖先为海洋的甲藻（dinoflagellate）菌株是否存在对其当前栖息的湖泊环境的局部适应（local adaptation）证据（即最优基因型），以及是否演化出表型可塑性（phenotypic plasticity）（即一系列表型）。从三种不同环境中分离并培养了11株极地泼莱拉藻（Polarella glacialis）：极地海域、一个低盐度南极湖泊与一个高盐度南极湖泊。通过比较湖泊菌株与海洋菌株在自身及互置生境条件下的生长速率，验证了局部适应性。为测定表型可塑性，我们对盐度的反应规范（reaction norm）进行了测量。研究发现，与海洋祖先菌株相比，湖泊菌株同时存在有限的局部适应和更高的表型可塑性。在极高盐度条件下，本地湖泊菌株表现优于其他菌株；而在极低盐度条件下，来自低盐度湖泊的菌株表现优于所有其他菌株。数据表明，湖泊种群可能已演化出...