J Exp Biol. 2010 Jan 15;213(2):237-41. doi: 10.1242/jeb.037127.
By comparison with studies of herbivore physiological adaptation to plant allelochemicals, work on predator physiological adaptation to potentially toxic prey has been very limited. Such studies are important in understanding how evolution could shape predator diets. An interesting question is the specificity of predator adaptation to prey allelochemicals, given that many predators consume diverse prey with different chemical defences. The ladybird Harmonia axyridis, an invasive species in America, Europe and Africa, is considered a significant predatory threat to native invertebrates, particularly other aphid-eating ladybirds of which it is a strong intraguild predator. Although ladybirds possess species-specific alkaloid defences, H. axyridis exhibits high tolerance for allospecific ladybird prey alkaloids. Nonetheless, it performs poorly on species with novel alkaloids not commonly occurring within its natural range. We examined alkaloid fate in H. axyridis larvae after consumption of two other ladybird species, one containing an alkaloid historically occurring within the predator's native range (isopropyleine) and one containing a novel alkaloid that does not (adaline). Our results indicate that H. axyridis rapidly chemically modifies the alkaloid to which it has been historically exposed to render it less harmful: this probably occurs outside of the gut. The novel, more toxic alkaloid persists in the body unchanged for longer. Our results suggest metabolic alkaloid specialisation, in spite of the diversity of chemically defended prey that the predator consumes. Physiological adaptations appear to have made H. axyridis a successful predator of other ladybirds; however, limitations are imposed by its physiology when it eats prey with novel alkaloids.
与研究草食动物对植物化感物质的生理适应相比，对捕食者对潜在有毒猎物的生理适应的研究非常有限。这些研究对于理解进化如何塑造捕食者的饮食非常重要。一个有趣的问题是，捕食者对猎物化感物质的适应特异性，因为许多捕食者会消耗具有不同化学防御的不同猎物。异色瓢虫 Harmonia axyridis 是一种入侵物种，分布于美洲、欧洲和非洲，被认为是对本地无脊椎动物的重大捕食威胁，尤其是其他以蚜虫为食的异色瓢虫，它是一种强有力的种间捕食者。虽然异色瓢虫具有特定于物种的生物碱防御机制，但 H. axyridis 对同种异体异色瓢虫猎物生物碱具有很高的耐受性。尽管如此，它在具有新颖生物碱的物种上表现不佳，而这些生物碱在其自然分布范围内并不常见。我们研究了异色瓢虫幼虫在食用另外两种异色瓢虫后的生物碱命运，一种含有历史上存在于捕食者原生范围内的生物碱（异丙烯基碱），另一种含有一种不在其自然范围内的新颖生物碱（阿达林）。我们的结果表明，H. axyridis 会迅速对其历史上暴露过的生物碱进行化学修饰，使其毒性降低：这可能发生在肠道之外。对于在体内持续时间更长且未发生变化的新颖、毒性更大的生物碱则保持不变。我们的研究结果表明，尽管捕食者消耗了多种具有化学防御能力的猎物，但它们存在代谢生物碱特化现象。生理适应使 H. axyridis 成为其他异色瓢虫的成功捕食者；然而，当它吃具有新颖生物碱的猎物时，其生理机能会受到限制。
