Phenotypic plasticity and pollinator-mediated selection jointly influenced floral differentiation in an alpine primrose

Both pollinator-mediated selection and phenotypic plasticity play important roles in the flower diversification under different spatiotemporal environments. However, the effects of natural selection and phenotypic plasticity on the process of flower evolution have rarely been collectively studied. In this study, two populations of Primula sikkimensis (GLL and SJL populations) were hand-pollinated to evaluate selection for four floral traits. In addition, reciprocal transplant experiments were conducted to detect the degree of plasticity of these floral traits in both populations. We found significant differentiation of floral traits between populations, and some of them varied between years. Pollinator-mediated selection contributed to net selection on traits, which varied in space and time. Moreover, these four floral traits showed strong plasticity in individuals of the GLL population but weak plasticity in the SJL population. Finally, the degrees of phenotypic plasticity were positively correlated with the variability of net selection and pollinator-mediated selection. Our findings reveal that both phenotypic plasticity and pollinator-mediated selection concurrently influence flower differentiation, yet strong plasticity has the potential to weaken the effects of selection.传粉者介导的选择（pollinator-mediated selection）与表型可塑性（phenotypic plasticity）在不同时空环境下的花部多样化进程中均发挥着关键作用。然而，学界极少将自然选择（natural selection）与表型可塑性对花部演化进程的影响开展联合研究。本研究以两个锡金报春（Primula sikkimensis）种群（GLL种群与SJL种群）为研究对象，通过人工授粉的方式评估4种花部性状（floral traits）所受的选择效应；此外还开展了互易移植实验，以检测这两个种群中上述花部性状的可塑性程度。研究结果显示，不同种群间的花部性状存在显著分化，且部分性状在不同年份间亦存在变异。传粉者介导的选择对性状的净选择（net selection）具有贡献，且该效应在空间与时间维度上均存在波动。此外，这4种花部性状在GLL种群个体中表现出较强的表型可塑性，而在SJL种群个体中的可塑性则相对较弱。最后，表型可塑性程度与净选择及传粉者介导选择的变异程度呈显著正相关。本研究结果表明，表型可塑性与传粉者介导的选择共同作用于花部分化，但较强的表型可塑性有可能削弱自然选择的效应。