十种菊科外来入侵种连萼瘦果风力传播的特性

借助风力传播连萼瘦果, 是菊科入侵种最普遍的自然扩散方式, 而其适应风力传播的特性与入侵性关系的研究还未得到足够的重视。阐明种子本身的风力传播特性与入侵潜力间的关系, 可以为深入理解外来入侵种的入侵机制以及入侵种的控制提供理论依据。该研究以10种菊科入侵种为研究对象, 测量其连萼瘦果的形态特征, 测定它们在静止空气中的垂直沉降速度和模拟风力条件下的水平扩散距离, 分析比较连萼瘦果的形态性状与沉降速度、水平扩散距离以及这些菊科入侵种在国内入侵范围的相关性。结果表明, 根据连萼瘦果的形态特征, 将这10个入侵种分为强、中和弱风传播3类; 连萼瘦果的重量和冠毛特征对垂直沉降速度和水平扩散距离均有显著影响, 对垂直沉降速度影响最大的因素是冠毛长度和冠毛上的小刺对数, 对水平扩散距离影响最大的因素是连萼瘦果的重量和冠毛长度。在垂直沉降速度和水平扩散距离间存在极显著负相关性(r = -0.806, p = 0.005), 表明沉降速度越慢, 借风力水平移动的距离越远。这些入侵种的发生程度与沉降速度间存在显著负相关性(r = -0.721, p = 0.019), 而与水平扩散距离之间存在着极显著正相关性(r = 0.927, p = 0.000), 说明水平扩散距离比垂直沉降速度更适合作为评估菊科入侵种入侵能力的指标。根据上述研究结果, 提出了南京市需重点防范胜红蓟(Agratum conyzoides)和牛膝菊(Galinsoga parviflora)等菊科入侵种的建议。

Wind-dispersed traits of cypselas in ten Asteraceae alien invasive species

Aims Wind dispersal of cypsela is the prevailing natural dispersal pattern in Asteraceae alien invasive species, but few studies have addressed the relationship between the characteristics of cypsela adapted to wind-dispersal and invasiveness. Our objective is to study the relationship between wind-dispersal traits and invasiveness to provide insight into invasion mechanisms and control of alien invasive species. Methods We selected ten wind-dispersed Asteraceae invasive species with cypselas, observed morphological traits of cypsela such as pappus number, pappus length, barb number on pappus and 1000-grain weight of cypsela and measured vertical settlement velocity in still air and horizontal dispersal distance in moving air. Correlations between morphological traits of cypsela and settlement velocity and horizontal dispersal distance were analyzed in relation to invasive range. Important findings We categorized the ten Asteraceae invasive species into three classes with strong, medium and weak dispersal-wind potential according to morphological traits of cypsela. Correlation analysis showed that pappus traits and weight of cypsela significantly affected both the settlement velocity and the horizontal dispersal distance. The settlement velocity was significantly affected by both pappus length (r = –0.483, p < 0.001) and barb numbers on pappus (r = –0.282, p = 0.002). Factors most affecting horizontal dispersal distance were cypsela weight and pappus length. Settlement velocity and horizontal dispersal distance were negatively correlated (r = –0.806, p = 0.005). The occurrence of these Asteraceae invasive species was significantly negatively correlated with settlement velocity (r = –0.721, p = 0.019) and significantly positively correlated with horizontal dispersal distance (r = 0.927, p = 0.000), suggesting that the horizontal dispersal distance better reflected invasiveness. Agratum conyzoides and Galinsoga parviflora with high invasiveness should be primary targets for invasive species management in Nanjing, China based on our results.