Prudic Kathleen L, Oliver Jeffrey C, Bowers M Deane
Ecology and Evolutionary Biology, University of Colorado, 334 UCB, Boulder, CO 80309, USA.
Oecologia. 2005 May;143(4):578-87. doi: 10.1007/s00442-005-0008-5. Epub 2005 Mar 24.
This study examined the effects of increased leaf nitrogen in natural host-plants (Plantago spp.) on female oviposition preference, larval performance, and larval chemical defense of the butterfly Junonia coenia. Increased availability of soil nutrients caused the host-plant's foliar nitrogen to increase and its chemical defense to decrease. Larval performance did not correlate with increases in foliar nitrogen. Larval growth rate and survival were equivalent across host-plant treatments. However, larvae raised on fertilized host-plants showed concomitant decreases in chemical defense as compared to larvae reared on unfertilized host-plants. Since most butterfly larvae cannot move long distances during their first few instars and are forced to feed upon the plant on which they hatched, J. coenia larval chemical defense is determined, in large part, by female oviposition choice. Female butterflies preferred host-plants with high nitrogen over host-plants with low nitrogen; however, this preference was also mediated by plant chemical defense. Female butterflies preferred more chemically defended host-plants when foliar nitrogen was equivalent between host-plants. J. coenia larvae experience intense predation in the field, especially when larvae are not chemically well defended. Any qualitative or quantitative variation in plant allelochemical defense has fitness consequences on these larvae. Thus, these results indicate that females may be making sub-optimal oviposition decisions under a nutrient-enriched regime, when predators are present. Given the recent increase in fertilizer application and nitrogen deposition on the terrestrial landscape, these interactions between female preference, larval performance, and larval chemical defense may result in long-term changes in population dynamics and persistence of specialist insects.
本研究调查了天然寄主植物（车前草属植物）叶片氮含量增加对苎麻珍蝶雌蝶产卵偏好、幼虫生长性能及幼虫化学防御的影响。土壤养分有效性增加导致寄主植物叶片氮含量上升，化学防御能力下降。幼虫生长性能与叶片氮含量的增加并无关联。在不同寄主植物处理组中，幼虫的生长速率和存活率相当。然而，与在未施肥寄主植物上饲养的幼虫相比，在施肥寄主植物上饲养的幼虫化学防御能力同时下降。由于大多数蝴蝶幼虫在最初的几龄期内无法远距离移动，只能取食孵化所在的植物，苎麻珍蝶幼虫的化学防御在很大程度上取决于雌蝶的产卵选择。雌蝶更喜欢氮含量高的寄主植物而非氮含量低的寄主植物；然而，这种偏好也受到植物化学防御的影响。当寄主植物之间叶片氮含量相当时，雌蝶更喜欢化学防御能力更强的寄主植物。苎麻珍蝶幼虫在野外面临强烈的捕食压力，尤其是当幼虫化学防御能力不足时。植物化感物质防御的任何质或量的变化都会对这些幼虫的适合度产生影响。因此，这些结果表明，在有捕食者存在且养分充足的情况下，雌蝶可能会做出次优的产卵决策。鉴于近期陆地景观中肥料施用量和氮沉降的增加，雌蝶偏好、幼虫生长性能和幼虫化学防御之间的这些相互作用可能会导致专食性昆虫种群动态和持久性的长期变化。
