為什么有些植物能夠比其他植物更好地抵御蟲害,？新的證據(jù)表明，這可能取決于這種植物是否能得到任何“植物之愛”,。
在美國《國家科學(xué)院院刊》（PNAS）上發(fā)表的一項(xiàng)研究中，來自美國北卡羅萊納州立大學(xué)和杜克大學(xué)的科學(xué)家發(fā)現(xiàn),，有性生殖的月見草（evening primrose plant）比同科無性生殖的植株能更好的抵御食草昆蟲（如毛毛蟲）的侵害,。
美國北卡羅萊納州植物生物學(xué)助理教授馬爾科·約翰森博士說，這一發(fā)現(xiàn)對于我們更好地了解植物是如何演化,，從而進(jìn)一步抵御食草昆蟲害,，是非常重要的一步。約翰森還是這篇研究論文的第一作者。
約翰森說,，有性繁殖與否很大程度上影響著植物的進(jìn)化并抵御蟲害的能力,。
在這項(xiàng)研究中，研究人員分別在室內(nèi)和野外對月見草（菜科）進(jìn)行了試驗(yàn),。這一科植物包含259個(gè)品種,，其中85%都是有性生殖，其余為無性生殖,。研究人員用這種植物進(jìn)行研究就是想測試一下有性生殖與無性生殖對于植物抵御蟲害的效果有什么不同,。研究人員發(fā)現(xiàn)，所謂的廣食性昆蟲——即吃多種植物的昆蟲——更青睞無性植株,，而且也因此活得更久,。
然而這一研究結(jié)果與所謂的“專一”食草昆蟲有所不同。那些只喜歡一種植物的昆蟲,，更青睞有性生殖的植株,。約翰遜說，之所以會出現(xiàn)這樣的結(jié)果,，是因?yàn)閷Ｒ皇巢堇ハx與它們的宿主一起進(jìn)化,，并且不斷發(fā)展出新的方法以攻破宿主的防御。因此,，他們不會懼怕植株產(chǎn)生的防御蟲害的化學(xué)物質(zhì)并遠(yuǎn)離植株,，相反它們會被這種物質(zhì)所吸引。
約翰遜說,，這些差別微小的研究結(jié)果很有科學(xué)價(jià)值,。
“有性生殖會使基因混合，這樣個(gè)體植株就可以去掉一些不好的基因,，保留好的基因,。”約翰遜如此說道，“這有助于他們不斷發(fā)展新的方法以抵御蟲害,。盡管無性生殖在短期內(nèi)也有一定的益處,，比如說當(dāng)無法授粉時(shí)，植株仍然可以快速繁殖和生長,，但從長期來講,，無性生殖還是有很大缺陷。（生物谷Bioon.com）
生物谷推薦原始出處：
PNAS July 15, 2009, doi: 10.1073/pnas.0904695106
Plant sex and the evolution of plant defenses against herbivores
Marc T. J. Johnsona,1, Stacey D. Smithb and Mark D. Rausherb
aDepartment of Plant Biology, North Carolina State University, Raleigh, NC 27695; and
bDepartment of Biology, Duke University, Durham, NC 27612
Despite the importance of plant–herbivore interactions to the ecology and evolution of terrestrial ecosystems, the evolutionary factors contributing to variation in plant defenses against herbivores remain unresolved. We used a comparative phylogenetic approach to examine a previously untested hypothesis (Recombination-Mating System Hypothesis) that posits that reduced sexual reproduction limits adaptive evolution of plant defenses against arthropod herbivores. To test this hypothesis we focused on the evening primrose family (Onagraceae), which includes both sexual and functionally asexual species. Ancestral state reconstructions on a 5-gene phylogeny of the family revealed between 18 and 21 independent transitions between sexual and asexual reproduction. Based on these analyses, we examined susceptibility to herbivores on 32 plant species representing 15 independent transitions. Generalist caterpillars consumed 32% more leaf tissue, gained 13% greater mass, and experienced 21% higher survival on functionally asexual than on sexual plant species. Survival of a generalist feeding mite was 19% higher on asexual species. In a field experiment, generalist herbivores consumed 64% more leaf tissue on asexual species. By contrast, a specialist beetle fed more on sexual than asexual species, suggesting that a tradeoff exists between the evolution of defense to generalist and specialist herbivores. Measures of putative plant defense traits indicate that both secondary compounds and physical leaf characteristics may mediate this tradeoff. These results support the Recombination-Mating System Hypothesis and suggest that variation in sexual reproduction among plant species may play an important, yet overlooked, role in shaping the macroevolution of plant defenses against arthropod herbivores.
