Nobler Jordan D, Camp Meghan J, Crowell Miranda M, Shipley Lisa A, Dadabay Carolyn, Rachlow Janet L, James Lauren, Forbey Jennifer S
Boise State University, 1910 W. University Dr, Boise, ID, 83725, USA.
Washington State University, PO Box 64, Pullman, WA, 99164, USA.
J Chem Ecol. 2019 Jan;45(1):74-85. doi: 10.1007/s10886-018-1030-5. Epub 2018 Nov 6.
Herbivores that forage on chemically defended plants consume complex mixtures of plant secondary metabolites (PSMs). However, the mechanisms by which herbivores tolerate mixtures of PSMs are relatively poorly understood. As such, it remains difficult to predict how PSMs, singly or as complex mixtures, influence diet selection by herbivores. Although relative rates of detoxification of PSMs have been used to explain tolerance of PSMs by dietary specialist herbivores, few studies have used the rate of detoxification of individual PSMs to understand dietary preferences of individual herbivores for individual versus mixtures of PSMs. We coupled in vivo experiments using captive feeding trials with in vitro experiments using enzymatic detoxification assays to evaluate the dietary preferences and detoxification capacities of pygmy rabbits (Brachylagus idahoensis), dietary specialists on sagebrush (Artemisia spp.), and mountain cottontails (Sylvilagus nuttallii), dietary generalists. We compared preference for five single PSMs in sagebrush compared to a mixture containing those same five PSMs. We hypothesized that relative preference for individual PSMs would coincide with faster detoxification capacity for those PSMs by specialists and generalists. Pygmy rabbits generally showed little preference among individual PSMs compared to mixed PSMs, whereas mountain cottontails exhibited stronger preferences. Pygmy rabbits had faster detoxification capacities for all PSMs and consumed higher concentrations of individual PSMs versus a mixture than cottontails. However, detoxification capacity for an individual PSM did not generally coincide with preferences or avoidance of individual PSMs by either species. Cottontails avoided, but pygmy rabbits preferred, camphor, the PSM with the slowest detoxification rate by both species. Both species avoided β-pinene despite it having one of the fastest detoxification rate. Taken together our in vivo and in vitro results add to existing evidence that detoxification capacity is higher in dietary specialist than generalist herbivores. However, results also suggest that alternative mechanisms such as absorption and the pharmacological action of individual or mixtures of PSMs may play a role in determining preference of PSMs within herbivore species.
以化学防御植物为食的食草动物会摄入植物次生代谢产物（PSMs）的复杂混合物。然而，食草动物耐受PSMs混合物的机制相对来说了解较少。因此，仍然难以预测PSMs单独或作为复杂混合物如何影响食草动物的食物选择。尽管PSMs的相对解毒速率已被用于解释食性专一的食草动物对PSMs的耐受性，但很少有研究使用单个PSMs的解毒速率来了解个体食草动物对单个PSMs与PSMs混合物的食物偏好。我们将使用圈养喂食试验的体内实验与使用酶解毒测定的体外实验相结合，以评估侏兔（Brachylagus idahoensis，以蒿属植物为食的食性专一动物）和山地棉尾兔（Sylvilagus nuttallii，食性广泛的动物）的食物偏好和解毒能力。我们比较了与包含相同五种PSMs的混合物相比，对蒿属植物中五种单一PSMs的偏好。我们假设对单个PSMs的相对偏好将与专一动物和广泛动物对这些PSMs更快的解毒能力相吻合。与混合PSMs相比，侏兔通常对单个PSMs几乎没有偏好，而山地棉尾兔则表现出更强的偏好。侏兔对所有PSMs都有更快的解毒能力，并且与棉尾兔相比，消耗的单个PSMs浓度高于混合物。然而，单个PSMs的解毒能力通常与任何一个物种对单个PSMs的偏好或回避并不一致。棉尾兔回避，但侏兔偏好樟脑，这是两种物种解毒速率最慢的PSM。尽管β-蒎烯具有最快的解毒速率之一，但两种物种都回避它。综合我们的体内和体外结果，进一步证明了食性专一的食草动物的解毒能力高于食性广泛的食草动物。然而，结果也表明，诸如吸收以及单个PSMs或PSMs混合物的药理作用等其他机制可能在决定食草动物物种内对PSMs的偏好中起作用。
