Soil substrates affect responses of root feeding larvae to their hosts at multiple levels: Orientation, locomotion and feeding

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• 作者：Elisabeth J. Eilers^a ; ^b ; Daniel Veit^c ; Matthias C. Rillig^d ; ^e ; Bill S. Hansson^b ; Monika Hilker^a ; ^e ; Andreas Reinecke^b ; ^f ; ^{andrein@zedat.fu-berlin.de" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Belowground ; Cockchafer larvae ; Melolontha melolontha ; Scarabaeidae ; Soil ; Sand ; Vermiculite ; Taraxacum sectio ruderalia ; Chemical cues ; Biotest
• 刊名：Basic and Applied Ecology
• 出版年：2016
• 出版时间：March 2016
• 年：2016
• 卷：17
• 期：2
• 页码：115-124
• 全文大小：1387 K

文摘

The role of soil characteristics for cue-directed behaviour of rhizophagous insects remains largely unexplored to date. Here, we studied behavioural responses of polyphagous cockchafer larvae (Melolontha melolontha; Scarabaeidae) to roots of one of its preferred host plants, dandelion (Taraxacum sectio ruderalia; Asteraceae). Plants were grown in substrates with different adsorptive capacities, i.e. in vermiculite or sand. A behavioural assay was developed which allowed both monitoring the release of attractive CO₂ from roots and observation of larval behaviour at the same time. In sand, larvae got closer to the roots than in vermiculite where they eventually stopped orienting towards the roots: However, their total locomotory activity and the number of turning events/stationary points were higher in vermiculite. Larval behaviour was not correlated with CO₂ concentrations in both vermiculite and sand. On average, larvae kept a greater distance to vermiculite-grown roots. However, a feeding bioassay revealed that the larvae consumed more of vermiculite-grown roots than of sand-grown ones. This result showed that the weaker orientation of larvae towards vermiculite-grown roots was not due to the lower palatability of these roots. Vermiculite might adsorb foraging-relevant cues of dandelion roots, alter composition of root exudates, and/or physically impair oriented movements of soil-dwelling insects. Our study shows that the type of substrate affects responses of rhizophagous larvae to host roots at multiple levels independently of root-derived CO₂ gradients.