Lineage-specific trait variations and plasticity of obligate parthenogenetic animals following the expansion of distribution range to a continental archipelago.

Two asexual lineages, JPN1 and JPN2, of panarctic Daphnia pulex expanded the distribution range to Japan from North America, independent of each other. According to the mutation rates within these lineages, JPN1 lineage colonized Japan earlier than JPN2 lineage. Moreover, the ratio of nonsynonymous to synonymous mutation rates (dN/dS) was lower in JPN1 than in JPN2 lineage. Accordingly, it is hypothesized that variations of phenotypic traits differ between these two lineages. In addition, since they are obligate parthenogenetic animals, the lineage occupying a larger distribution range should have a larger phenotypic plasticity. To test these hypotheses, we experimentally examined the phenotypic variations of fitness-related traits, including digestive, life history and morphological traits, among several genotypes of these lineages. We found that within-lineage variations of most traits were smaller in JPN1 than in JPN2. In addition, the overall phenotypic variations were also smaller ...泛北极蚤状溞（panarctic Daphnia pulex）的两个无性谱系JPN1与JPN2彼此独立地从北美扩张至日本，拓展了其分布范围。基于这些谱系内部的突变率分析可知，JPN1谱系定殖日本的时间早于JPN2谱系。此外，JPN1谱系的非同义替换与同义替换突变率之比（dN/dS）低于JPN2谱系。 据此，研究提出假说：这两个谱系的表型性状变异存在差异。此外，由于二者均为专性孤雌生殖动物，分布范围更广的谱系应当具备更强的表型可塑性。为验证上述假说，本研究针对这两个谱系的多个基因型开展实验，检测了其与适合度相关的表型性状变异，涵盖消化性状、生活史性状与形态性状。 研究发现，相较于JPN2谱系，JPN1谱系内多数性状的谱系内变异更小。此外，整体表型变异同样更小……