Department of Ecology and Evolutionary Biology, Cornell University, 215 Tower Road, Ithaca, NY 14853, USA.
Proc Biol Sci. 2023 Aug 9;290(2004):20230987. doi: 10.1098/rspb.2023.0987.
Plant toxicity shapes the dietary choices of herbivores. Especially when herbivores sequester plant toxins, they may experience a trade-off between gaining protection from natural enemies and avoiding toxicity. The availability of toxins for sequestration may additionally trade off with the nutritional quality of a potential food source for sequestering herbivores. We hypothesized that diet mixing might allow a sequestering herbivore to balance nutrition and defence (via sequestration of plant toxins). Accordingly, here we address diet mixing and sequestration of large milkweed bugs () when they have differential access to toxins (cardenolides) in their diet. In the absence of toxins from a preferred food (milkweed seeds), large milkweed bugs fed on nutritionally adequate non-toxic seeds, but supplemented their diet by feeding on nutritionally poor, but cardenolide-rich milkweed leaf and stem tissues. This dietary shift corresponded to reduced insect growth but facilitated sequestration of defensive toxins. Plant production of cardenolides was also substantially induced by bug feeding on leaf and stem tissues, perhaps benefitting this cardenolide-resistant herbivore. Thus, sequestration appears to drive diet mixing in this toxic plant generalist, even at the cost of feeding on nutritionally poor plant tissue.
植物毒性会影响草食动物的饮食选择。特别是当草食动物从植物中摄取毒素时，它们可能会在获得天敌保护和避免毒性之间做出权衡。可供摄取的毒素的可用性可能会与草食动物摄取的潜在食物源的营养价值相互权衡。我们假设，饮食混合可能允许摄取毒素的草食动物在营养和防御之间取得平衡（通过摄取植物毒素来实现）。因此，在这里，我们研究了大型乳草盲蝽（）在饮食中存在毒素（卡烯内酯）差异时的饮食混合和摄取情况。在缺乏偏好食物（乳草种子）中的毒素的情况下，大型乳草盲蝽以营养充足但无毒的种子为食，但通过食用营养较差但富含卡烯内酯的乳草叶和茎组织来补充其饮食。这种饮食转变与昆虫生长减少相对应，但促进了防御性毒素的摄取。昆虫对叶和茎组织的取食也显著诱导了植物产生卡烯内酯，也许使这种对卡烯内酯具有抗性的草食动物受益。因此，摄取似乎在这种有毒植物的杂食者中驱动了饮食混合，即使这是以食用营养较差的植物组织为代价的。
