- 學位論文
利用外來植物阿勃勒對入侵動物黃頸蜷蚓進行生物防治
Using the Exotic Plant Cassia fistula to Biologically Control the Invasive Animal Pontoscolex corethrurus
摘要
本研究致力於發掘外來植物阿勃勒（Cassia fistula）作為防治入侵動物黃頸蜷蚓（Pontoscolex corethrurus）的生物防治方法（biological control）。黃頸蜷蚓原產於中南美洲，近年來在世界各地及臺灣迅速擴散，已成為一嚴重入侵種，並壓縮本土蚯蚓的生存空間。此外，黃頸蜷蚓也會改變土質，嚴重影響植物生長，但目前尚未有專一性的防治方式。然而，本實驗室過去的調查意外發現，在阿勃勒的周遭，黃頸蜷蚓的族群密度遠較其他植物周遭低，推測是由阿勃勒植株內所含的生物鹼（alkaloids）等成分造成此一現象。有鑑於此，阿勃勒便成為此次生物防治的主角。本研究在野外調查中發現幾乎沒有黃頸蜷蚓棲息在阿勃勒周遭。我們隨後以阿勃勒的乾燥葉子粉末以及阿勃勒主要成份之一的番瀉苷（sennoside）進行研究，發現這些物質皆會對黃頸蜷蚓造成驅逐作用，並出現類似腹瀉（diarrhea）之特殊毒理現象，然而它們對本土蚯蚓卻較無顯著之負面影響。由於阿斯匹靈（aspirin）是番瀉苷腹瀉效應的抑制劑之一，我們亦取阿斯匹靈進行測試，發現它確實能夠延長這些黃頸蜷蚓的壽命，此結果進一步證實番瀉苷所造成之腹瀉症狀，確實是黃頸蜷蚓的關鍵死因。最後，我們進行了阿勃勒對蚯蚓的野外驅逐測試，結果顯示阿勃勒乾葉粉末可以於短期內有效降低黃頸蜷蚓的族群量。由於阿勃勒的葉子在臺灣取得容易，且本實驗結果表現出高度的種間差異，顯示阿勃勒作為生物防治對非目標生物的影響不大，因此是極為理想的生物防治媒介（biological control agent）。我們期盼未來能將本研究結果應用於防治黃頸蜷蚓的入侵，並開創利用外來植物防治入侵動物的新概念。
並列摘要
This research investigates applying Cassia fistula to expelling Pontoscolex corethrurus. P. corethrurus is an invasive species that has caused negative influence on native biodiversity and soil structure in many areas around the world (Barros, Curmi, Hallaire, Chauvel, & Lavelle, 2001; Chapuis-Lardy et al., 2010; Hendrix et al., 2008). However, there have been only scant studies exploring the control of earthworms, and most strategies are mainly based on chemical pesticides and land management practices. To bridge this research gap, the present study explores P. corethrurus-targeted biological control using C. fistula. Previous research has indicated that P. corethrurus tend to keep away from C. fistula by nature (Chen, 2015). Based on this instinct of P. corethrurus, we carried out a secession of experiments, including burrowing tests, taxis tests, survival rate tests, histological analysis, aspirin rescue-effect test, and field expulsion test, to identify the ingredients of C. fistula and observe the behavior of P. corethrurus when treated with substances extracted from the plant. The results demonstrate that alkaloids, especially sennoside, in C. fistula produced a marked effect on repelling P. corethrurus. Specifically, when C. fistula leaf powder was applied to P. corethrurus, this earthworm displayed a negative chemotactic response to the plant, and it turned out that the density of the earthworm reduced significantly within two weeks. However, populations of native earthworms remained stable and unaffected. We suggest that the key reason for the phenomenon may be that P. corethrurus lacks the key enteric bacteria required for the metabolism of sennoside in C. fistula, which caused a laxative effect on it. Since the C. fistula-treatment test reflects a significant interspecies difference, we propose that it is ideal to use C. fistula as a biological control agent against P. corethrurus. Moreover, since C. fistula is easy to cultivate and limited in self-propagation, related control programs could be eco-friendly and cost-effective. This study contributes to solution of earthworm invasion and contemporary investigation of biological control.