福寿螺对稻田水生植物群落结构的影响

Effects of Pomacea canaliculata on aquatic macrophyte community structure in paddy fields

福寿螺是在我国南方地区危害水稻生产的一种外来入侵软体动物,已被世界自然保护联盟入侵生物专家组列为100种危害最为严重的外来入侵物种之一。在水域生态系统中福寿螺主要以摄食各种水生植物而生存。以水稻、大薸、水葫芦、粉绿狐尾藻、水花生和鸭舌草构成的稻田水生植物群落为对象,研究了低密度(4株/m2)、中密度(8株/m2)和高密度(12株/m2)福寿螺处理对稻田水生植物群落的影响,同时结合福寿螺的食物选择性实验分析其相关行为特性。结果表明:1)低密度、中密度和高密度福寿螺处理1周内水稻密度均急剧下降,高密度福寿螺造成水稻密度下降超过70%,2周后福寿螺危害水稻秧苗的程度减轻;2)各密度处理福寿螺均抑制了水花生和鸭舌草扩散,第8周时高密度福寿螺处理中水花生和鸭舌草的密度仅为对照的30%和25%。同时,低密度福寿螺处理中的水花生和鸭舌草的密度显著高于中密度和高密度处理。不同密度福寿螺处理对水葫芦、大薸和粉绿狐尾藻影响不明显;3)水稻的日均密度增长率为负值,低密度、中密度和高密度福寿螺处理间存在明显差异,且均显著低于对照。水花生和鸭舌草的日均密度增长率虽为正值,但显著低于对照,水葫芦、大薸和粉绿狐尾藻的日均密度增长率和对照无差异。福寿螺日均密度增长迅速,各密度处理无显著差异。福寿螺对水稻、水花生、鸭舌草的选择性显著高于水葫芦、粉绿狐尾藻和大薸;4)福寿螺引入8周后稻田水生植物群落物种多样性Simpson指数、Shannon指数和均匀度指数均显著降低。Simpson指数的大小顺序为:对照>低密度>中密度、高密度,Shannon指数和均匀度指数的大小顺序为:对照>低密度>中密度>高密度。说明福寿螺对供试水生植物有明显的选择性,其入侵会严重危害稻田水生植物群落的物种多样性。

Pomacea canaliculata （Lamarck） is an invasive aquatic gastropod endangering rice production in Southern China, with a feeding preference for rice seedlings in paddy fields. P. canaliculata is listed as one of the top 100 invasive species by the Invasive Species Group of the World Conservation Union. P. canaliculata mainly feeds on a diverse range of macrophyte species. We investigated the invasive effects of P. canaliculata on the aquatic macrophyte plant community in paddy fields. Our experimental macrophyte community consisted of Oryza sativa L., Pistia stratiotes L., Eichhornia crassipes, Myriophyllum aquaticum, Alternanthera philoxeroides, Monochoria vaginalis. The control and three treatments used different P. canaliculata densities： control （P. canaliculata-free）; low （4 individuals/m^2）; medium （8 individuals/m^2） and high （12 individuals/m^2）. We analyzed the effect that P. canaliculata had on the macrophyte community using the compound food preference test. Our results showed： 1） O. sativa densities in the three treatments decreased rapidly one week after P. canaliculata was introduced. In herbivore, in the P. canaliculata high-density treatment, O. sativa density declined approximately 70%. However, two weeks after P. canaliculata was introduced, the herbivore effect on O. sativa density decreased. 2） After eight weeks P. canaliculata reduced A. philoxeroides and M. vaginalis densities （30% and 25%, respectively） in the high-density herbivore treatment and inhibited the growth of A. philoxeroides and M. vaginalis. The plant densities of A. philoxeroides and M. vaginalis were higher in the low-density herbivore treatment compared with those in the medium and high-density herbivore treatments. However, P. canaliculata showed no significant effect on the plant densities of E. crassipes, P. stratiotes and M. aquaticum. 3） The daily density rate of increase was negative for O. sativa, and significantly different in the low, medium and high-density herbivore treatments. The daily density rate of increase for O. sativa showed a significant decrease compared with the P. canaliculata-free control. The daily density rate of increase for A. philoxeroides and M. vaginalis was positive, where the rate was significantly lower compared with the P. canaliculata-free control. Concurrently, the daily density rates of increase were not significantly influenced by P. canaliculata for P. stratiotes, E. crassipes and M. aquaticum. We found that P. canaliculata populations increased rapidly. The daily density rate of increase for P. canaliculata populations in the three different density treatments were all high, but not significantly different. The food preference frequencies of P. canaliculata on O. sativa, A. philoxeroides and M. vaginalis were all significantly higher compared with E. crassipes, P. stratiotes and M. aquaticum. 4） Eight weeks after the introduction of P. canaliculata the Simpson, Shannon and Homogeneity biodiversity indices showed a significant decline in the aquatic macrophyte community. The Simpson index values showed the decline in order of： the control 〉 low- 〉 medium-and high-densities. The Shannon and Homogeneity indices showed the decline in order of： the control 〉 low- 〉 medium- 〉 high-densities. We conclude that P. canaliculata showed significantly different feeding preference on macrophyte plants species. The invasion of P. canaliculata would significantly endanger aquatic macrophyte community biodiversity in the paddy fields of China.