The Role of Diversity and Functional Traits of Species in Community Invasibility

生物入侵已經成為一個普遍性的環境問題，但人們對之仍瞭解甚少。儘管一些理論分析和觀察研究表明生物多樣性豊富的群落不容易受到外來種的入侵，但後來有些實驗研究並沒能證實兩者的負相關性，多樣性－可入侵性假說仍是入侵生態學領域爭論比較多的一個焦點。本實驗以喜旱蓮子草（Alternanthera philoxerolides （Mart.）Griseb.）為入侵種，人為構建不同物種多樣性和物種功能群多樣性（16個物種分別屬於C3禾本科植物、C4植物、禾本科植物和豆科植物4個不同的能群）梯度的小尺度草地群落，同時盡可能把其他影嚮可入侵性的外在因素和多樣性效隔離開來，研究喜旱蓮子草在不通群落裏的入侵過程，驗證多樣性與可入侵性及其相關假說。研究結果顯示，物種功能群愈豊富的群落很可能通過降低資源可利用率從而表現出對入侵較強的抵抗力，而基於功能群數目的不同物種多樣性的群落可入侵性沒有顯著差異。物種功能群特徵不同的群落也表現出可入侵性的差異，生活史周期短的單一物種群落和有著生物固氮功能的豆科植物對入侵抵抗力較弱，和喜旱蓮子草屬於同一功能群且有著相似生態的土著種蓮子草（Alternanthera sessilis）對入侵的抵抗力最強。實驗結果暗示，群落可入侵性和物種多樣性並沒有很顯著的負相關，而是和物種特徵性基礎上的物種功能群多樣性呈負相關，群落中留給入侵種的生態位機會的多少很可能是決定群落可入侵性的一個關鍵因素。因為可入侵受到的影嚮因素太多，還需通過更為細緻的試驗設計和理論模型來進一步論證。

關鍵字

喜旱蓮子草；群落；多樣性；功能群；可入侵性；入侵。

並列摘要

The invasion of exotic species into assemblages of native plants is a pervasive and widespread phenomenon. Many theoretical and observational studies suggest that diverse communities are more resistant to invasion by exotic species than less diverse ones. However, experimental results do not always support such a relationship. Therefore, the hypothesis of diversity-community invasibility is still a focus of controversy in the field of invasion ecology. In this study, we established and manipulated communities with different species diversity and different species functional groups (16 species belong to C3, C4, forbs and legumes, respectively) to test Elton's hypothesis and other relevant hypotheses by studying the process of invasion. Alligator weed (Alternanthera philoxeroides) was chosen as the invader. We found that the correlation between the decrement of extractable soil nitrogen and biomass of alligator weed was not significant, and that species diversity, independent of functional groups diversity, did not show a significant correlation with invasibility. However, the communities with higher functional groups diversity significantly reduced the biomass of alligator weed by decreasing its resource opportunity. Functional traits of species also influenced the success of the invasion. Alternanthera sessilis, in the same morphological and functional group as alligator weed, was significantly resistant to alligator weed invasion. Because community invasibility is influenced by many factors and interactions among them, the pattern and mechanisms of community invasibility are likely to be far subtler than we found in this study. More careful manipulated experiments coupled with theoretical modeling studies are essential steps to a more profound understanding of community invasibility.

並列關鍵字

Alligator weed ； Community ； Diversity ； Functional groups ； Invasibility ； Invasion

國際替代計量

The Role of Diversity and Functional Traits of Species in Community Invasibility

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