Data from: Experimental assemblage of novel plant-herbivore interactions: ecological host shifts after 40 million years of isolation

Geographic isolation is the first step in insect herbivore diet specialization. Such specialization is postulated to increase insect fitness, but may simultaneously reduce insect ability to colonize novel hosts. During the Paleocene-Eocene, plants from the order Zingiberales became isolated either in the Paleotropics or in the Neotropics. During the Cretaceous, rolled-leaf beetles diversified in the Neotropics concurrently with neotropical Zingiberales. Using a community of Costa Rican rolled-leaf beetles and their Zingiberales host plants as study system, we explored if previous geographic isolation precludes insects to expand their diets to exotic hosts. We recorded interactions between rolled-leaf beetles and native Zingiberales by combining DNA barcodes and field records for 7450 beetles feeding on 3202 host plants. To determine phylogenetic patterns of diet expansions, we set 20 field plots including five exotic Zingiberales, recording beetles feeding on these exotic hosts. In the laboratory, using both native and exotic host plants, we reared a subset of insect species that had expanded their diets to the exotic plants. The original plant-herbivore community comprised 24 beetle species feeding on 35 native hosts, representing 103 plant-herbivore interactions. After exotic host plant introduction, 20% of the beetle species expanded their diets to exotic Zingiberales. Insects only established on exotic hosts that belong to the same plant family as their native hosts. Laboratory experiments show that beetles are able to complete development on these novel hosts. In conclusion, rolled-leaf beetles are pre-adapted to expand their diets to novel host plants even after millions of years of geographic isolation.

地理隔离是植食性昆虫食性特化的首要环节。此类食性特化被推测可提升昆虫适合度，但同时可能削弱其定殖新型寄主的能力。古新世-始新世时期，姜目（Zingiberales）植物在古热带区与新热带区间发生了地理隔离。白垩纪期间，卷叶甲虫（rolled-leaf beetles）与新热带姜目植物在新热带区同步发生物种分化。本研究以哥斯达黎加卷叶甲虫及其姜目寄主植物类群为研究系统，旨在探究既往地理隔离是否会阻碍昆虫将食性拓展至外来寄主。研究人员结合DNA条形码（DNA barcodes）与野外调查记录，对取食3202株寄主植物的7450头甲虫开展了交互作用普查，明确了卷叶甲虫与本土姜目植物的取食关联。为明确食性拓展的系统发育模式，我们设置了包含5种外来姜目植物的20个野外样地，记录取食这些外来寄主的甲虫类群。在实验室条件下，我们选取部分已实现食性拓展至外来植物的昆虫物种，分别以本土与外来寄主植物开展饲养实验。原始植物-植食性昆虫群落包含24种甲虫，取食35种本土寄主，共计103组植物-植食者互作关系。引入外来寄主植物后，20%的甲虫物种完成了食性拓展，可取食外来姜目植物。且昆虫仅能定殖与本土寄主同科的外来寄主植物。实验室实验证实，甲虫可在这些新型寄主上完成完整生长发育周期。综上，即便经历了数百万年的地理隔离，卷叶甲虫仍具备预适应能力，可将食性拓展至新型寄主植物。