Mason Peri A, Deane Bowers M
Department of Ecology and Evolutionary Biology, University of Colorado, UCB 334, Boulder, CO, 80309, USA.
Bard High School Early College, Queens 30-20 Thompson Avenue, Long Island City, NY, 11101, USA.
J Chem Ecol. 2017 May;43(5):480-486. doi: 10.1007/s10886-017-0841-0. Epub 2017 Apr 10.
Many insect species sequester compounds acquired from their host plants for defense against natural enemies. The distribution of these compounds is likely to affect both their efficacy as defenses, and their costs. In this study we examined the distribution of sequestered iridoid glycosides (IGs) in two congeneric species of nymphalid butterfly, Euphydryas anicia and E. phaeton, and found that the pattern of localization of IGs differed between the two species. Although IG concentrations were quite high in the heads of both species, the relative concentrations in wings and abdomens differed substantially. Euphydryas anicia had relatively high IG concentrations in their abdomens and low IG concentrations in their wings, whereas the reverse was true in E. phaeton. We interpret these results in light of two current hypotheses regarding where sequestered chemicals should be localized: that they should be found in wings, which would allow non-lethal sampling by predators; and that their distribution is constrained by the distribution of tissue types to which sequestered compounds bind. We also offer the third hypothesis, that costs of storage may differ among body parts, and that the localization of compounds may reflect a cost-reduction strategy. Results from E. phaeton were consistent with all three of these non-mutually exclusive hypotheses, whereas results from E. anicia were only consistent with the notion that tissue bias among body parts plays a role in IG distribution. The finding that these two congeneric butterflies exhibit different patterns of IG localization suggests that they have been shaped by different selection regimes.
许多昆虫物种会摄取从寄主植物中获取的化合物来抵御天敌。这些化合物的分布可能会影响它们作为防御手段的功效及其成本。在本研究中，我们检测了蛱蝶科两种同属蝴蝶——阿尼西亚优蚬蝶（Euphydryas anicia）和辉蚬蝶（E. phaeton）——中螯合环烯醚萜苷（IGs）的分布情况，发现这两种蝴蝶中IGs的定位模式有所不同。尽管两种蝴蝶头部的IG浓度都相当高，但翅膀和腹部的相对浓度差异很大。阿尼西亚优蚬蝶腹部的IG浓度相对较高，翅膀中的IG浓度较低，而辉蚬蝶的情况则相反。我们根据目前关于螯合化学物质应定位在何处的两种假设来解释这些结果：一种假设是它们应存在于翅膀中，这将允许捕食者进行非致命性取样；另一种假设是它们的分布受螯合化合物所结合的组织类型分布的限制。我们还提出了第三种假设，即身体各部位的储存成本可能不同，化合物的定位可能反映了一种降低成本的策略。辉蚬蝶的结果与所有这三种并非相互排斥的假设一致，而阿尼西亚优蚬蝶的结果仅与身体各部位的组织偏好对IG分布起作用这一观点一致。这两种同属蝴蝶表现出不同的IG定位模式这一发现表明它们受到了不同选择机制的影响。
