Data from: Diet specialization in an extreme omnivore: nutritional regulation in glucose-averse German cockroaches

Organisms have diverse adaptations for balancing dietary nutrients, but often face trade-offs between ingesting nutrients and toxins in food. While extremely omnivorous cockroaches would seem excluded from such dietary trade-offs, German cockroaches (Blattella germanica) in multiple populations have rapidly evolved a unique dietary specialization – an aversion to glucose, the phagostimulant in toxic baits used for pest control. We used factorial feeding experiments within the geometric framework to test whether glucose-averse (GA) cockroaches with limited access to this critical metabolic fuel have compensatory behavioural and physiological strategies for meeting nutritional requirements. GA cockroaches had severely constrained intake, fat and N mass, and performance on glucose-based diets relative to wild-type (WT) cockroaches and did not appear to exhibit digestive strategies for retaining undereaten nutrients. However, a GA × WT ‘hybrid’ had lower glucose aversion than GA and greater access to macronutrients within glucose-based diets – while still having lower intake and survival than WT. Given these intermediate foraging constraints, hybrids may be a reservoir for this maladaptive trait in the absence of positive selection and may account for the rapid evolution of this trait following bait application.

生物拥有多样的适应性策略以平衡膳食营养，但在摄取营养与摄入食物中的毒素之间，往往需要做出权衡取舍。尽管极度杂食性的蟑螂看似不会受这类膳食权衡的限制，但多个种群的德国小蠊（Blattella germanica）却快速演化出了独特的膳食特化现象——对葡萄糖产生厌恶感，而葡萄糖正是害虫防治所用毒饵中的取食刺激剂（phagostimulant）。我们采用几何框架（geometric framework）下的析因摄食实验，探究对葡萄糖产生厌恶的（glucose-averse, GA）蟑螂——这类个体难以获取这种关键代谢燃料——是否存在补偿性的行为与生理策略以满足自身营养需求。与野生型（wild-type, WT）蟑螂相比，GA蟑螂在基于葡萄糖的膳食中，摄食量、脂肪与氮含量以及生理表现均受到严重限制，且似乎并未演化出留存未摄取营养的消化策略。不过，GA与WT的"杂交个体"对葡萄糖的厌恶程度低于GA蟑螂，且在基于葡萄糖的膳食中能更多获取宏量营养素——尽管其摄食量与存活率仍低于WT个体。鉴于这类介于两者之间的觅食限制条件，在缺乏正向选择的情况下，杂交个体或许可成为这种适应不良性状的储存库，同时也能解释毒饵施用后该性状快速演化的现象。