Evolution of asexual Daphnia pulex in Japan: variations and covariations of the digestive, morphological and life history traits

Background Several genetic lineages of obligate parthenogenetic Daphnia pulex, a common zooplankton species, have invaded Japan from North America. Among these, a lineage named JPN1 is thought to have started colonization from a single genotype several hundred to thousand years ago and subsequently produced many genotypes in Japan. To examine the phenotypic variations due to ecological drivers diverging the genotypes in new habitats, we measured heritability and variation in 17 traits, including life history, morphology and digestive traits, and the genetic distance among the D. pulex JPN1 genotypes in Japan. Results We found that most of the traits measured varied significantly among the genotypes and that heritability was highest in the morphological traits, followed by the digestive and life history traits. In addition, 93% of the variation in these traits was explained by the first three components in the principal component analysis, implying that variations of these heritable trai...背景 专性孤雌生殖的大型溞（Daphnia pulex）是一类常见浮游动物，其多个遗传谱系已从北美入侵日本。其中，命名为JPN1的谱系被认为于数百年至数千年前由单一基因型开始在日本定殖，随后演化出众多基因型。为探究新栖息地中驱动基因型分化的生态因子所引发的表型变异，本研究测定了17项性状（涵盖生活史、形态学与消化相关性状）的遗传力与变异水平，以及日本境内大型溞JPN1谱系各基因型间的遗传距离。结果 研究发现，绝大多数测定性状在不同基因型间存在显著差异；其中形态学性状的遗传力最高，其次为消化相关性状与生活史性状。此外，主成分分析（principal component analysis）结果表明，前三个主成分可解释这些性状93%的变异，提示这些可遗传性状的变异...