Journal of Systematics and Evolution
Xiaofei Tian1,2*, Maki Toyota2, Hajime Ohtsuki2, and Jotaro Urabe2,3
Abstract: Evolutionary theory suggests the hypothesis that among genetically isolated populations, phenotypic variation should be smaller in populations with smaller ratios of nonsynonymous to synonymous substitutions (dN/dS) because smaller dN/dS ratios occur under greater purification selections. Two distinct lineages (JPN1 and JPN2) of panarctic Daphnia pulex, invaded independently into Japan from North America, provide an excellent opportunity to test this hypothesis because the earlier invader JPN1 has a lower dN/dS ratio than JPN2. Therefore, we examined phenotypic variations in fitness-related traits, including digestive, life-history and morphological traits, among several genotypes within these two lineages. We found that phenotypic variations were smaller within the JPN1 lineage than within the JPN2 lineage. Furthermore, within-lineage variation of the phenotypic plasticity to changing food levels was smaller in the JPN1 lineage than in the JPN2 lineage. These results support the hypothesis that the JPN1 lineage has been more efficiently subjected to negative selection. However, the magnitude of the phenotypic plasticity of these traits was, on average, at the same level between the JPN1 and JPN2 lineages and its direction differed among genotypes of these lineages, suggesting that the JPN2 genotypes may have exploited niches that were different from those of the JPN1 genotypes.
. [J]. Journal of Systematics and Evolution.
Xiaofei Tian, Maki Toyota, Hajime Ohtsuki, and Jotaro Urabe. Lineage-specific trait variations and plasticity of obligate parthenogenetic animals following the expansion of distribution range to a continental archipelago[J]. J Syst Evol.
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