• Plants are often attacked by multiple insect herbivores. How plants deal with an increasing richness of attackers from a single or multiple feeding guilds is poorly understood.
• We subjected black mustard (Brassica nigra) plants to 51 treatments representing attack by an increasing species richness (one, two or four species) of either phloem feeders, leaf chewers, or a mix of both feeding guilds when keeping total density of attackers constant and studied how this affects plant resistance to subsequent attack by caterpillars of the diamondback moth (Plutella xylostella).
• Increased richness in phloem-feeding attackers compromised resistance to P. xylostella. By contrast, leaf chewers induced a stronger resistance to subsequent attack by caterpillars of P. xylostella while species richness did not play a significant role for chewing herbivore induced responses. Attack by a mix of herbivores from different feeding guilds resulted in plant resistance similar to resistance levels of plants that were not previously exposed to herbivory.
• We conclude that B. nigra plants channel their defence responses stronger towards a feeding-guild specific response when under multi-species attack by herbivores of the same feeding guild, but integrate responses when simultaneously confronted with a mix of herbivores from different feeding guilds.

中文翻译：

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昆虫物种丰富度影响植物对多食草动物攻击的反应

• 植物经常受到多种昆虫食草动物的攻击。植物如何应对来自单个或多个饲养行会的越来越多的攻击者，我们知之甚少。
• 我们对黑芥菜（Brassica nigra）植物进行了 51 种处理，这些处理代表在保持攻击者的总密度恒定的情况下，韧皮部饲养者、叶咀嚼者或两种饲养者的混合物的物种丰富度不断增加（一种、两种或四种）的攻击。研究了这如何影响植物对小菜蛾（Plutella xylostella）毛虫随后攻击的抵抗力。
• 以韧皮部为食的攻击者的丰富度增加削弱了对小菜蛾的抵抗力。相比之下，叶咀嚼者对小菜蛾毛虫的后续攻击产生更强的抵抗力，而物种丰富度对咀嚼食草动物诱导的反应没有发挥重要作用。来自不同饲养行会的食草动物的混合攻击导致植物抵抗力类似于以前未接触过食草动物的植物的抵抗力水平。
• 我们的结论是黑芥植物引导他们的防御反应向进给公会特异性反应强烈时，下多品种由同喂养公会的草食动物攻击，而是集成响应时从不同的饲养行会食草动物的混合同时面对。