土著昆虫素毒蛾对入侵植物互花米草地理种群的选择性

Preference of Laelia coenosa for native and introduced populations of invasive Spartina alterniflora

外来植物入侵后会改变其对入侵地植食性昆虫的防御能力以应对入侵地生物环境的变化,因此,对土著昆虫防御能力变化的研究将有助于解释外来植物成功入侵的机制。互花米草(Spartina alterniflora)是广泛入侵中国东部沿海地区的外来植物,研究其入侵后对本地植食性昆虫的响应,可从一个侧面部分地回答其成功入侵的生态机制。利用Y型嗅觉仪,结合室内取食实验,我们比较了中国的土著昆虫素毒蛾(Laelia coenosa)对互花米草3个原产地种群和5个入侵地种群的选择偏好,这些种群分别来自美国的德克萨斯(Texas Point)、卡纳维拉尔国家海岸(Canaveral National Seashore)、佛罗里达大西洋大学(Florida Atlantic University),以及中国的唐海、天津、盐城、崇明、珠海。结果表明,虽然素毒蛾幼虫对互花米草不同地理种群叶片气味没有显著的选择偏好,但对原产地种群的取食相对选择系数显著高于入侵地种群,说明互花米草入侵地种群对素毒蛾的抵抗能力相对较强。这从某种层面上可以推测互花米草入侵中国东部沿海地区以后,其对植食性昆虫取食的防御能力有所增强,而这种能力将在一定程度上减少素毒蛾等入侵地植食动物对它的攻击。

Exotic plants may modify their resistance to herbivory in response to new phytophagous insects in their introduced ranges. Studying the variation in such resistance may help us understand the in-depth mech- anisms of plant invasions. Spartina alterniflora is one of the most serious invasive plants in China＇s coastal salt marshes. Investigating how S. alterniflora responds to the phytophagous insects in the introduced ranges may partially explain the mechanism of its invasion success. We conducted choice tests under controlled conditions to compare the preferences of Laelia coenosa （native to China） for native （US） and introduced （China） S. alterniflora populations. In relation to smell, caterpillars of L. coenosa did not show any prefer- ence for native or introduced populations, but the relative choice index for taste of native populations was significantly higher than that of introduced populations. This feeding preference of the caterpillars for popu- lations of the plant from its native range suggests that S. alterniflora has altered its defense against the native phytophagous insects in their introduced range, thereby reducing insect herbivore attacks.