Evolution of increased Medicaco polymorpha size during invasion does not result in increased competitive ability

Species invading new habitats experience novel selection pressures that can lead to rapid evolution, which may contribute to invasion success and/or increased impact on native community members. Many studies have hypothesized that plants in the introduced range will be larger than those in the native range, leading to increases in competitive ability. There is mixed support for evolution of larger sizes in the introduced range, but few studies have explicitly tested whether evolutionary changes result in decreased competitive responses or increased competitive effects on other species in the community. Here we show that introduced Medicago polymorpha genotypes produced 14% more aboveground and 41% more belowground biomass than genotypes from the native range, suggesting evolutionary changes in size occurred after introduction. However, these size differences were only observed in the absence of competition. The competitive effects of introduced and native range genotypes on three specie...

入侵全新生境的物种会遭遇全新的选择压力（selection pressure），这可能推动其发生快速演化（rapid evolution），进而助力入侵成功（invasion success），或增强其对本地群落（native community）物种的负面影响。诸多研究曾提出假说：入侵分布区（introduced range）的植物个体尺寸会大于原生分布区（native range）的同类，进而提升其竞争能力（competitive ability）。针对入侵分布区植物体型演化更大的假说，现有研究的支持证据存在分歧；且鲜有研究明确检验演化改变是否会降低植物的竞争响应（competitive response），或是增强其对群落中其他物种的竞争效应（competitive effect）。本研究显示，入侵分布区的斑荚苜蓿（Medicago polymorpha）基因型（genotype）的地上生物量（aboveground biomass）较原生分布区基因型高出14%，地下生物量（belowground biomass）则高出41%，这表明入侵后该物种的体型发生了演化改变。不过，这类体型差异仅在无竞争的环境下被观测到。入侵分布区与原生分布区基因型对三种物种的竞争效应……