摘要
Aims Plant populations in managed grasslands are subject to strong selection exerted by grazing,mowing and fertilization.Many previous studies showed that this can cause evolutionary changes in mean trait values,but little is known about the evolution of phenotypic plasticity in response to land use.In this study,we aimed to elucidate the relationships between phenotypic plasticity—specifically,regrowth ability after biomass removal—and the intensity of grassland management and levels of temporal variation therein.Methods We conducted an outdoor common garden experiment to test if plants from more intensively mown and grazed sites showed an increased ability to regrow after biomass removal.We used three common plant species from temperate European grasslands,with seed material from 58 to 68 populations along gradients of land-use intensity,ranging from extensive(only light grazing)to very intensive management(up to four cuts per year).Important Findings In two out of three species,we found significant population differentiation in regrowth ability after clipping.While variation in regrowth ability was unrelated to the mean land-use intensity of populations of origin,we found a relationship with its temporal variation in Plantago lanceolata,where plants experiencing less variable environmental conditions over the last 11 years showed stronger regrowth in reproductive biomass after clipping.Therefore,while mean grazing and mowing intensity may not select for regrowth ability,the temporal stability of the environmental heterogeneity created by land use may have caused its evolution in some species.
在人工管理的草原上,植物种群受到放牧、刈割和施肥的强烈选择。以往的许多研究表明,这可能会导致性状平均值的进化性变化,但是人们对响应土地利用的表型可塑性的进化了解甚少。在本研究中,我们旨在阐明表型可塑性(特别是在生物量去除后的再生能力)与草原管理强度本身及其时间变化水平之间的关系。我们通过野外同质园实验,检测了来自高强度刈割和放牧地点的植物是否在生物量去除后有更强的再生能力。我们选用了源自欧洲温带草原的3种常见的植物物种,其种子材料来自沿土地利用强度梯度的58-68个种群,对应的土地利用方式由粗放式管理(仅有轻度的放牧)过渡到非常集约式管理(多达每年4次收割)。研究结果表明,3个物种当中的两种在刈割后的再生能力存在显著的种群差异。虽然再生能力的变异与种群原生地的平均土地利用强度无关,但是我们发现长叶车前(Plantago lanceolata)的再生能力与土地利用强度的时间变化相关。在过去11年中,经历了较小环境条件变化的植物在刈割之后有较强的生殖生物量再生能力。因此,尽管平均的放牧和刈割强度可能不会对再生能力造成选择,但是土地利用所导致的环境异质性的时间稳定性可能会造成某些物种再生能力的进化。
基金
The work was supported by the Deutsche Forschungsgemeinschaft Priority Program 1374'Infrastructure-Biodiversity-Exploratories’through project SCHE 1899/1-1 to J.F.S.
