很多研究表明，在入侵地外來種缺少原產(chǎn)地的專性天敵（Specialists）,，入侵地的廣普天敵（Generalists）又因各種原因很少危害外來種,，致使天敵逃逸，這可能是外來種成功入侵的重要原因,。天敵逃逸不僅可以直接提高外來入侵種對(duì)本地種（有天敵）的競(jìng)爭(zhēng)能力,，而且還可以通過影響外來入侵種的進(jìn)化提高其入侵能力,。增強(qiáng)競(jìng)爭(zhēng)能力的進(jìn)化（EICA）假說認(rèn)為，入侵地的天敵缺乏將使外來種通過進(jìn)化降低天敵防御能力,，而把原來用于天敵防御的資源用于生長(zhǎng)和繁殖等過程,，從而提高競(jìng)爭(zhēng)力，促進(jìn)入侵,。該假說的前提是植物的防御是有成本的,，生長(zhǎng)和防御有權(quán)衡關(guān)系，而這種權(quán)衡關(guān)系也已被很多研究所證實(shí),。
然而,，最近美國蒙大拿大學(xué)、科羅拉多州立大學(xué)和中科院西雙版納熱帶植物園生物入侵生態(tài)學(xué)研究組的合作研究表明,，外來入侵植物斑點(diǎn)矢車菊（Centaurea maculosa）入侵種群的生長(zhǎng)速度和競(jìng)爭(zhēng)能力高于原產(chǎn)地種群,，但是入侵種群高的競(jìng)爭(zhēng)能力并不是以天敵防御能力降低為代價(jià)的。相反,，入侵種群對(duì)廣普天敵和專性天敵的防御能力要高于原產(chǎn)地種群,，它們不僅能更好地抑制天敵取食（抗性），也能更好地忍耐天敵的攻擊（耐性）,。入侵種群高的天敵防御能力與其高的化防物質(zhì)前體含量,、堅(jiān)韌的葉片和多的葉毛有關(guān)。入侵種群的這些特性是由遺傳因素決定的,。該研究表明,，增強(qiáng)競(jìng)爭(zhēng)能力的進(jìn)化并不總是由能量或資源向生長(zhǎng)和防御分配的生理權(quán)衡造成的，這與傳統(tǒng)的生態(tài)學(xué)理論不同,，與Blossey等提出的EICA假說也不同,，與中國科學(xué)院西雙版納熱帶植物園馮玉龍等提出的氮分配進(jìn)化假說也不一致，必將促進(jìn)今后相關(guān)領(lǐng)域的研究,。
該研究成果發(fā)表在世界著名生態(tài)學(xué)期刊《生態(tài)學(xué)專論》（Ecological Monographs）上,。（生物谷Bioon.com）
生物谷推薦原始出處：
Ecological Monographs,，Volume 78, Issue 3,，pp. 369–386，Wendy M. Ridenour,，Ragan M. Callaway
NO EVIDENCE FOR TRADE-OFFS: CENTAUREA PLANTS FROM AMERICA ARE BETTER COMPETITORS AND DEFENDERS
Wendy M. Ridenour1,4, Jorge M. Vivanco2, Yulong Feng3, Jun-ichiro Horiuchi2, and Ragan M. Callaway1
1 Division of Biological Sciences, The University of Montana, Missoula, Montana 59812 USA
2 Department of Horticulture, Colorado State University, Fort Collins, Colorado 80523 USA
3 Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Kunming 650223 Yunnan Province, China
The natural enemies hypothesis has led to a number of ideas by which invaders might evolve superior competitive ability. In this context, we compared growth, reproduction, competitive effect, competitive response, and defense capabilities between invasive North American populations of Centaurea maculosa and populations in Europe, where the species is native. We found that Centaurea from North America were larger than plants from European populations. North American Centaurea also demonstrated stronger competitive effects and responses than European Centaurea. However, competitive superiority did not come at a cost to herbivore defense. North American plants were much better defended against generalist insect herbivores and slightly better defended against specialists. North Americans showed a stronger inhibitory effect on the consumers (resistance) and a better ability to regrow after attack by herbivores (tolerance). Better defense by North Americans corresponded with higher constitutive levels of a biochemical defense compound precursor, tougher leaves, and more leaf trichomes than Europeans. North American F1 progeny of field collected lines retained the traits of larger size and greater leaf toughness suggesting that genetic differences, rather than maternal effects, may be the cause of intercontinental differences, but these sample sizes were small. Our results suggest that the evolution of increased competitive ability may not always be driven by physiological trade-offs between the allocation of energy or resources to growth or to defense. Instead, we hypothesize that Centaurea maculosa experiences strong directional selection on novel competitive and defense traits in its new range.
