Two centuries of monarch butterfly collections reveal contrasting effects of range expansion and migration loss on wing traits
Two centuries of monarch butterfly collections reveal contrasting effects of range expansion and migration loss on wing traits
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DOI：
10.1073/pnas.2001283117
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发表时间：
2020-11-17
影响因子：
11.1
通讯作者：
Ramirez, Santiago R.
中科院分区：
文献类型：
--
作者：
Freedman, Micah G.;Dingle, Hugh;Ramirez, Santiago R.
迁徙动物表现出的特征使它们能够利用季节性变化的栖息地。在环境中，迁移不再是有益的，如海洋岛屿，迁移协会性状可能会选择反对或放松选择。单拱蝶以其在北美大陆范围内的迁徙而闻名，但在热带美洲以及大西洋和太平洋岛屿上一再成为非移民。这些复制的非迁徙种群为理解迁徙相关性状的进化速率提供了天然实验室。我们测量了从1856年到现在收集的6,000多个帝王蝶博物馆标本，以及来自世界各地的当代野生帝王蝶。我们确定了1）翅膀形态如何在君主的全球范围内变化，2）最初的长途创始人是否特别适合迁移，以及3）最近建立的nonmigrants是否显示当代表型进化的证据。我们进一步在受控条件下饲养了来自世界各地六个种群的1,000多只帝王蝶，并测量了与迁徙相关的特征。历史标本表明，1）最初的创始人非常适合长距离移动，2）季节性迁移的损失与前翅尺寸和伸长的减少有关。在一个共同的花园从四个衍生的nonmigrating种群提出的帝王蝶表现出遗传基础上减少前翅大小，与以前的研究一致。我们的研究结果提供了一个令人信服的例子，说明在范围扩展的早期阶段，与迁移相关的性状可能会受到青睐，以及在失去迁移后，这些相同性状的减少率。
Migratory animals exhibit traits that allow them to exploit seasonally variable habitats. In environments where migration is no longer beneficial, such as oceanic islands, migration-association traits may be selected against or be under relaxed selection. Mon-arch butterflies are best known for their continent-scale migration in North America but have repeatedly become established as non migrants in the tropical Americas and on Atlantic and Pacific Islands. These replicated nonmigratory populations provide natural laboratories for understanding the rate of evolution of migration associated traits. We measured >6,000 museum specimens of monarch butterflies collected from 1856 to the present as well as contemporary wild-caught monarchs from around the world. We determined 1) how wing morphology varies across the monarch's global range, 2) whether initial long-distance founders were particularly suited for migration, and 3) whether recently established nonmigrants show evidence for contemporary phenotypic evolution. We further reared >1,000 monarchs from six populations around the world under controlled conditions and measured migration-associated traits. Historical specimens show that 1) initial founders are well suited for long-distance movement and 2) loss of seasonal migration is associated with reductions in fore wing size and elongation. Monarch butterflies raised in a common garden from four derived nonmigratory populations exhibit genetically based reductions in forewing size, consistent with a previous study. Our findings provide a compelling example of how migration-associated traits may be favored during the early stages of range expansion, and also the rate of reductions in those same traits upon loss of migration.