起源于東亞和東南亞的環(huán)毛類蚯蚓與起源于歐洲的正蚓科蚯蚓是兩類主要的世界性入侵蚯蚓,。值得注意的是，雖然外來的歐洲正蚓也廣泛分布于我國北方,，但由北至南，數(shù)量逐漸減少,，而土著的亞洲環(huán)毛類蚯蚓卻逐漸增多,。這種南北分異的蚯蚓分布格局，可能是氣候,、生境和蚯蚓本身的特性共同作用的結果,。但是，傳統(tǒng)的入侵生態(tài)學研究方法無法將氣候,、生境和生物本身的特性對生物入侵的貢獻區(qū)分開來,，所以難以確切了解蚯蚓本身的入侵或抵御入侵的能力。
中科院華南植物園恢復生態(tài)學團隊張衛(wèi)信博士在傅聲雷研究員和美國佐治亞大學奧德姆生態(tài)學院Paul F. Hendrix教授的指導下,，提出了一種“第三方生境”的研究方法,，即在一個相對陌生的第三方生境中，研究環(huán)毛類蚯蚓與歐洲正蚓的相互作用,。因為,，在第三方生境中兩類蚯蚓都是外來種，沒有漫長的“物種-生境”相互適應過程,，從理論上說,，彼此碰上適宜或不適宜生境的機會均等。這種情況下,，蚯蚓的生物學特性將決定其是否能成功入侵,。
應用這種新的方法，張衛(wèi)信等研究了美國溫帶落葉闊葉林中的兩種外來蚯蚓,，一種歐洲正蚓（Lumbricus rubellus）與一種亞洲環(huán)毛類（Amynthas agrestis）之間的相互作用,，成功區(qū)分了蚯蚓本身的入侵性（Invasiveness）和生境的可入侵性（Invasibility）在蚯蚓入侵過程中的貢獻。借助于穩(wěn)定性同位素（13C和15N）和微生物磷脂脂肪酸技術,，研究人員發(fā)現(xiàn)蚯蚓的食性特點對其入侵能力影響巨大,，而且亞洲環(huán)毛類蚯蚓的取食過程對于歐洲正蚓的生存非常不利。具體說來,，雖然亞洲環(huán)毛類蚯蚓偏好取食土壤（包括其中的生物）,，而歐洲正蚓偏好取食凋落物，但是,，歐洲正蚓取食凋落物的過程需要土壤微生物(G+菌)的參與,；亞洲環(huán)毛類蚯蚓攝食能力強且富于變化,，其強勢的取食過程打破了歐洲正蚓與土壤微生物(G+菌)間的關鍵聯(lián)系，進而嚴重影響了歐洲正蚓對凋落物的取食,，最終抑制了歐洲正蚓在北美溫帶落葉自然林的生存,。
此項工作揭示了蚯蚓入侵的一種新機制，發(fā)展了入侵生態(tài)學的研究方法,，同時也顯示了研究多個入侵物種間相互作用的重要性,。這對研究我國南方自然林中環(huán)毛類蚯蚓對外來種的抵御機制也有重要的啟發(fā)和借鑒作用。相關內容已在國際生態(tài)學權威期刊《生態(tài)學》（Ecology）在線發(fā)表(生物谷Bioon.com)
生物谷推薦原文出處：
Ecology doi: 10.1890/09-0979
Dietary flexibility aids Asian earthworm invasion in North American forests
Weixin Zhang1, Paul Hendrix2, Bruce Snyder3, Marirosa Molina4, Jianxiong Li5, Xingquan Rao6, Evan Siemann7, and Shenglei Fu8,¤
1Chinese Academy of Sciences, Guangzhou, Guangdong, China
2University of Georgia, Athens, GA, United States of America
3University of Georgia, Athens, GA, United States of America
4USEPA, Athens, GA, United States of America
5Guangdong entomological institute, Guangzhou, Guangdong, China
6Chinese Academy of Sciences, Guangzhou, Guangdong, China
7Rice University, Houston, TX, United States of America
8Chinese Academy of Sciences, Guangzhou 510650, China
On a local scale, invasiveness of introduced species and invasibility of habitats together determine invasion success. A key issue in invasion ecology has been how to quantify the contribution of species invasiveness and habitat invasibility separately. Conventional approaches, such as comparing the differences in traits and/or impacts of species between native and/or invaded ranges, do not determine the extent to which the performance of invaders is due to either the effects of species traits or habitat characteristics. Here we explore the interaction between two of the most widespread earthworm invaders in the world (Asian Amynthas agrestis and European Lumbricus rubellus) and study the effects of species invasiveness and habitat invasibility separately through an alternative approach of "third habitat" in Tennessee, USA. We propose that feeding behaviors of earthworms will be critical to invasion success because trophic ecology of invasive animals plays a key role in the invasion process. We found that (1) the biomass and isotopic abundances (δ13C and δ15N) of A. agrestis were not impacted by either direct effects of L. rubellus competition or indirect effects of L. rubellus-preconditioned habitat; (2) A. agrestis disrupted the relationship between L. rubellus and soil microorganisms and consequently hindered litter consumption by L. rubellus; and (3) compared to L. rubellus, A. agrestis shifted its diet more readily to consume more litter, more soil G+ bacteria (which may be important for litter digestion), and more non-microbial soil fauna when soil microorganisms were depleted. In conclusion, A. agrestis showed strong invasiveness through its dietary flexibility through diet shifting and superior feeding behavior and its indirectly negative effect of habitat invasibility on L. rubellus via changes in the soil microorganism community. In such context, our results expand on the resource fluctuation hypothesis and support the superior competitor hypothesis. This work presents additional approaches in invasion ecology, provides some new dimensions for further research, and contributes to a greater understanding of the importance of interactions between multiple invading species.
