Fueling the fall migration of the Monarch butterfly
Fueling the fall migration of the Monarch butterfly
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DOI：
10.1093/icb/icl029
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发表时间：
2006-12-01
影响因子：
2.6
通讯作者：
Walford, Peter
中科院分区：
文献类型：
--
作者：
Brower, Lincoln P.;Fink, Linda S.;Walford, Peter
北美东部的帝王蝶在秋季迁徙到墨西哥中部的过程中积累了脂肪，并在5个月的越冬期间将其作为能量来源。蝴蝶在迁徙途中何时何地积累了这些脂肪，这对北美秋季花蜜来源的重要性有一定的影响。我们分析了4年来(1998-2001年)在弗吉尼亚州中部1个蜜腺产卵点收集的765只夏季繁殖和秋季迁徙的帝王蝶的脂肪含量，并将它们与1941年以来其他地点的16个已公布和未公布的数据集进行了比较。弗吉尼亚州的候鸟储存的脂肪明显多于夏季蝴蝶，并且表现出显著的季节内和年际变化。弗吉尼亚州的样本和历史样本中，除了一个例外，没有一个样本的血脂水平与抵达德克萨斯州和墨西哥北部的移民的血脂水平相当。这一证据表明，在到达德克萨斯州后，蝴蝶的行为发生了变化，花在蜜腺上的时间更多。一个例外的样本让我们发现，在迁徙路线上形成栖息地的君主比在花蜜中收集的君主的脂肪含量更高。我们认为，在它们旅途的大部分时间里，帝王都是机会主义的候鸟，样本内部和样本之间的差异反映了蝴蝶的个人经历。储存的脂肪对蝴蝶迁徙的重要性似乎小于对它们在越冬期间生存的重要性，部分原因是在有利的风向下飞行降低了飞行的能量成本。保护得克萨斯州和墨西哥北部的花蜜植物对于维持帝王的迁徙景象至关重要，整个北美东部的花蜜丰富也很重要。作为选择花蜜来源和蜜汁栖息地的多面手，帝王不太可能受到植物群落微小变化的影响。然而，美国东部和大平原自然群落的农业转型，特别是转基因抗除草剂大豆和玉米的广泛种植，可能正在改变君主和其他传粉者的花蜜供应。这项新技术正在消除农田及其周围的几乎所有杂草，包括君主的幼虫寄主植物(乳草)以及本地和标准的花蜜来源。为了评估花蜜供应的变化是否改变了蝴蝶积累能量的能力，我们建议每年在北美东部的地点检测帝王蝶的脂肪含量。
Monarch butterflies in eastern North America accumulate lipids during their fall migration to central Mexico, and use them as their energy source during a 5 month overwintering period. When and where along their migratory journey the butterflies accumulate these lipids has implications for the importance of fall nectar sources in North America. We analyzed the lipid content of 765 summer breeding and fall migrant monarch butterflies collected at 1 nectaring site in central Virginia over 4 years (1998-2001), and compared them with 16 additional published and unpublished datasets from other sites, dating back to 1941. Virginia migrants store significantly more lipid than summer butterflies, and show significant intraseason and between-year variation. None of the Virginia samples, and none of the historical samples, with one exception, had lipid levels comparable with those found in migrants that had reached Texas and northern Mexico. This evidence suggests that upon reaching Texas, the butterflies undergo a behavioral shift and spend more time nectaring. The one exceptional sample led us to the discovery that monarchs that form roosts along their migratory routes have higher lipid contents than monarchs collected while nectaring at flowers. We propose that for much of their journey monarchs are opportunistic migrants, and the variation within and between samples reflects butterflies' individual experiences. The stored lipids appear to be of less importance as fuel for the butterflies' migration than for their survival during their overwintering period, in part because soaring on favorable winds reduces the energetic cost of flying. The conservation of nectar plants in Texas and northern Mexico is crucial to sustaining the monarch's migratory spectacle, and nectar abundance throughout eastern North America is also important. As generalists in their selection of nectar sources and nectaring habitats, monarchs are unlikely to be affected by small changes in plant communities. Agricultural transformations of natural communities in the eastern United States and Great Plains, however, and especially the extensive planting of genetically modified herbicide-resistant soybeans and corn, may be changing the availability of nectar for monarchs and other pollinators. This new technology is eliminating virtually all forbs in and surrounding agricultural fields, including the monarch's larval hostplants (milkweeds) and native and normative nectar sources. To evaluate whether changes in nectar availability are altering the butterflies' ability to accumulate energy, we recommend that monarchs' lipid contents be assayed annually at sites throughout eastern North America.