Bradley Lauren E, Kelly Caitlin A, Bowers M Deane
Department of Ecology and Evolutionary Biology, 334 UCB, University of Colorado, Boulder, CO, 80309, USA.
Department of Ecology and Evolutionary Biology and University of Colorado Museum, 334 UCB, University of Colorado, Boulder, CO, 80309, USA.
J Chem Ecol. 2018 Nov;44(11):1051-1057. doi: 10.1007/s10886-018-1012-7. Epub 2018 Sep 3.
The checkerspot butterfly, Euphydryas anicia (Nymphalidae), specializes on plants containing iridoid glycosides and has the ability to sequester these compounds from its host plants. This study investigated larval preference, performance, and sequestration of iridoid glycosides in a population of E. anicia at Crescent Meadows, Colorado, USA. Although previous studies showed that other populations in Colorado use the host plant, Castilleja integra (Orobanchaceae), we found no evidence for E. anicia ovipositing or feeding on C. integra at Crescent Meadows. Though C. integra and another host plant, Penstemon glaber (Plantaginaceae), occur at Crescent Meadows, the primary host plant used was P. glaber. To determine why C. integra was not being used at the Crescent Meadows site, we first examined the host plant preference of naïve larvae between P. glaber and C. integra. Then we assessed the growth and survivorship of larvae reared on each plant species. Finally, we quantified the iridoid glycoside concentrations of the two plant species and diapausing caterpillars reared on each host plant. Our results showed that E. anicia larvae prefer P. glaber. Also, larvae survive and grow better when reared on P. glaber than on C. integra. Castilleja integra was found to contain two primary iridoid glycosides, macfadienoside and catalpol, and larvae reared on this plant sequestered both compounds; whereas P. glaber contained only catalpol and larvae reared on this species sequestered catalpol. Thus, although larvae are able to use C. integra in the laboratory, the drivers behind the lack of use at the Crescent Meadows site remain unclear.
北美花斑蝶（Euphydryas anicia，蛱蝶科）专门以含有环烯醚萜苷的植物为食，并能够从其寄主植物中摄取这些化合物。本研究调查了美国科罗拉多州新月草甸的北美花斑蝶种群对环烯醚萜苷的幼虫偏好、生长表现及摄取情况。尽管此前的研究表明科罗拉多州的其他种群会利用寄主植物全缘卡斯蒂利亚花（Castilleja integra，列当科），但我们没有发现北美花斑蝶在新月草甸在全缘卡斯蒂利亚花上产卵或取食的证据。虽然全缘卡斯蒂利亚花和另一种寄主植物光滑钓钟柳（Penstemon glaber，车前科）都出现在新月草甸，但主要使用的寄主植物是光滑钓钟柳。为了确定为何在新月草甸的地点不使用全缘卡斯蒂利亚花，我们首先研究了初孵幼虫在光滑钓钟柳和全缘卡斯蒂利亚花之间对寄主植物的偏好。然后我们评估了在每种植物上饲养的幼虫的生长和存活情况。最后，我们对这两种植物以及在每种寄主植物上饲养的滞育毛虫的环烯醚萜苷浓度进行了量化。我们的结果表明，北美花斑蝶幼虫更喜欢光滑钓钟柳。此外，在光滑钓钟柳上饲养的幼虫比在全缘卡斯蒂利亚花上饲养的幼虫存活和生长得更好。发现全缘卡斯蒂利亚花含有两种主要的环烯醚萜苷，即麦克法迪苷和梓醇，在这种植物上饲养的幼虫摄取了这两种化合物；而光滑钓钟柳只含有梓醇，在该物种上饲养的幼虫摄取了梓醇。因此，虽然幼虫在实验室中能够利用全缘卡斯蒂利亚花，但新月草甸地点不使用它的背后原因仍不清楚。
