二色仙人掌，中国仙人掌科一新归化种

Opuntia cespitosa Rafinesque, A New Naturalized Species of Cactaceae from China

摘要:

2019年4-6月，在江苏省西南部句容市郭庄镇虬山，首次发现二色仙人掌（Opuntia cespitosa Rafinesque）归化种群。该种群主要生长在海拔46~90 m的废弃采石场上，分布范围东西长510 m，南北宽260 m，面积约13.26 hm²。二色仙人掌开花结实的成年植株共计910棵，其中最大灌木平卧茎长轴上叶状茎10个，树龄可达10 a，大概在2010年就生长于虬山。在句容虬山采石场关闭时，采石场工作人员可能将盆栽的二色仙人掌就地丢弃，从而导致该归化种群的发展。比较了二色仙人掌与中国仙人掌属已知其余4种归化植物的形态特征，并编制了分种检索表。此外，讨论了二色仙人掌的传播机制及其入侵风险。

Abstract:

From April to June in 2019, a naturalized population of Opuntia cespitosa was first found at Qiushan Hill, Guozhuang Town, Jurong City, southwestern Jiangsu. The population mainly occurs on an abandoned quarry at elevations of 46-90 m, covering an area of ca. 13.26 hm², 510 m long from east to west, and 260 m wide from north to south. A total of 910 mature shrubs bearing flowers and fruits have been recorded there, among which the longest axis of the largest shrub consists of 10 continuous cladodes, indicating an age of 10 years, which probably appeared at Qiushan Hill in 2010. This naturalized population may be derived from the pot plants of O. cespitosa, which were possibly discarded in situ by the staff of Qiushan quarry, when the quarry became abandoned. The morphological features are compared between O. cespitosa and known other four naturalized species of Opuntia in China, and a key to these species is prepared. Furthermore, the dispersal mechanisms and its invasion risk of O. cespitosa are also discussed.