为什么有些植物能够比其他植物更好地抵御虫害？新的证据表明，这可能取决于这种植物是否能得到任何“植物之爱”。
在美国《国家科学院院刊》（PNAS）上发表的一项研究中，来自美国北卡罗莱纳州立大学和杜克大学的科学家发现，有性生殖的月见草（evening primrose plant）比同科无性生殖的植株能更好的抵御食草昆虫（如毛毛虫）的侵害。
美国北卡罗莱纳州植物生物学助理教授马尔科·约翰森博士说，这一发现对于我们更好地了解植物是如何演化，从而进一步抵御食草昆虫害，是非常重要的一步。约翰森还是这篇研究论文的第一作者。
约翰森说，有性繁殖与否很大程度上影响着植物的进化并抵御虫害的能力。
在这项研究中，研究人员分别在室内和野外对月见草（菜科）进行了试验。这一科植物包含259个品种，其中85%都是有性生殖，其余为无性生殖。研究人员用这种植物进行研究就是想测试一下有性生殖与无性生殖对于植物抵御虫害的效果有什么不同。研究人员发现，所谓的广食性昆虫——即吃多种植物的昆虫——更青睐无性植株，而且也因此活得更久。
然而这一研究结果与所谓的“专一”食草昆虫有所不同。那些只喜欢一种植物的昆虫，更青睐有性生殖的植株。约翰逊说，之所以会出现这样的结果，是因为专一食草昆虫与它们的宿主一起进化，并且不断发展出新的方法以攻破宿主的防御。因此，他们不会惧怕植株产生的防御虫害的化学物质并远离植株，相反它们会被这种物质所吸引。
约翰逊说，这些差别微小的研究结果很有科学价值。
“有性生殖会使基因混合，这样个体植株就可以去掉一些不好的基因，保留好的基因。”约翰逊如此说道，“这有助于他们不断发展新的方法以抵御虫害。尽管无性生殖在短期内也有一定的益处，比如说当无法授粉时，植株仍然可以快速繁殖和生长，但从长期来讲，无性生殖还是有很大缺陷。（生物谷Bioon.com）
生物谷推荐原始出处：
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.
