入侵种喜旱莲子草对土壤水分的表型可塑性反应

Phenotypic plasiticity in response to soil water content in the invasive species Alternanthera philoxeroides

研究了水生、湿生、中生和旱生生境条件下外来入侵种喜旱莲子草(Alternantheraphiloxe roides(Mart.)Griseb.)表型可塑性反应.结果表明:喜旱莲子草株长、茎节长度、总生物量积累在湿生和中生生境中最大;随土壤含水量减少,喜旱莲子草根冠比显著升高,分枝强度显著降低;土壤含水量与喜旱莲子草根系生物量投资呈显著负相关,茎、叶生物量投资随土壤含水量的减少而下降.研究结果表明,喜旱莲子草的最适宜水分生态位是湿生生境,在不同水分条件下,其不同表型结构有可能同时对环境选择作出反应,在种群生存与维持、生长、繁殖等功能方面实现种群个体各器官生物量投资的优化配置来适应多样化的环境.

The phenotypic plasticity of the invasive species Alternanthera philoxeroides were studied in four different soil water contents, which correspond to aquatic habitat, moist habitat, mesophytic habitat and xeric habitat respectively. The largest total length of genet, internode length and total biomass of Alternanthera philoxeroides were observed in the moist and mesophytic habitat. Branching intensity decreased significantly, while root/shoot ratios increased significantly with the decrement of soil water content. Allocation of root biomass showed negative correlation with soil water content significantly, while allocation of stems and leaves decreased significantly with the decrement of soil water content. The results indicated that Alternanthera philoxeroides had a high plasticity response to the environments with different soil water contents. Moist habitat might be the optimum, however, Alternanthera philoxeroides could respond to selection from environments on several different phenotypic organs simultaneously, and show adaptive plasticity through the optimum biomass allocation, which help it survive, grow and propagate under diverse environments successfully.