School of Biological Sciences, Royal Holloway, University of London, Egham, Surrey TW20 0EX, UK.
Biol Lett. 2012 Aug 23;8(4):628-30. doi: 10.1098/rsbl.2012.0271. Epub 2012 May 2.
Plant defences against herbivores include direct defences such as secondary metabolites or physical structures (e.g. trichomes) as well as indirect defences mediated via mutualistic interactions with other organisms including ants. Production of both direct defences and rewards for mutualistic ants may be costly for a plant, and it has been suggested that trade-offs may exist between direct and ant-mediated defences. We have conducted a meta-analysis of 25 studies testing the above hypothesis and found a significant negative correlation between plant allocation to direct and ant-mediated defences. The strength of correlation was similar for across- and within-species comparisons, and for chemical and physical direct defences. However, trade-offs with direct defences were significant only in plants which offered to ants more costly rewards such as food bodies and/or domatia, but not in plants which attracted ants with relatively cheap extrafloral nectaries. Our results therefore support the hypothesis that plant investment in ant-mediated defences may reduce the requirement for direct chemical and physical defences, but only in plants which offer more costly rewards to their bodyguards.
植物防御草食动物的策略包括直接防御，如次生代谢物或物理结构（如毛状体），以及通过与包括蚂蚁在内的其他生物的互利共生相互作用介导的间接防御。植物生产直接防御和互惠互利的蚂蚁奖励可能是昂贵的，有人认为，直接防御和蚂蚁介导的防御之间可能存在权衡。我们对 25 项研究进行了荟萃分析，以检验上述假设，结果发现植物对直接防御和蚂蚁介导的防御的分配之间存在显著的负相关。种间和种内比较、化学防御和物理防御的相关性强度相似。然而，只有在那些向蚂蚁提供食物体和/或栖所等代价更高的奖励的植物中，与直接防御的权衡才具有显著意义，而在那些利用相对便宜的额外花蜜腺吸引蚂蚁的植物中，这种权衡则不显著。因此，我们的研究结果支持这样一种假设，即植物对蚂蚁介导的防御的投资可能会降低对直接化学和物理防御的需求，但仅限于那些向其“保镖”提供更高代价奖励的植物。
