IRFP: Elucidating Incipient Coevolutionary Speciation Through Experimental and Transcriptomic Approaches

国际研究奖学金项目使美国科学家和工程师能够在国外进行9至24个月的研究。该计划的奖励为联合研究提供了机会，并利用独特或互补的设施、专业知识和国外的实验条件。该奖项由国际科学与工程办公室和环境生物学部的进化生态学项目共同资助。该奖项将支持David H. Hembry博士与日本大江京都大学的川喜多（Atsushi Kawakita）博士进行为期18个月的研究，随后将支持Hembry博士与加州大学伯克利分校的Michael B. Eisen博士进行为期6个月的研究。物种间的共同进化在地球生命多样化中的作用是进化生物学的主要问题之一。特别是，在互惠关系中的物种之间的共同进化（其中两个物种的成员都受益）促进多样化的证据，以及它可能这样做的机制，仍然是模棱两可的。昆虫和植物之间的特殊传粉互助关系，特别是无花果和无花果黄蜂以及丝兰和丝兰蛾之间的互助关系，长期以来一直被用作本研究的模型，因为传粉媒介在运输寄主配子方面所起的作用使它们特别有可能成为共同进化多样化的候选者。然而，从经验和理论的角度来看，共同进化驱动这些系统多样化的证据都是模棱两可的，并且很少有研究明确地调查这些系统中的物种形成。本研究的目的是利用实验和转录组学方法的结合，来研究最近在法属波利尼西亚海洋岛屿上多样化的一种特殊的昆虫-植物共生关系中新生的共同进化物种形成的假设案例。叶蛾（鳞翅目：细叶蛾科：叶蛾）是其叶花植物寄主（Phyllanthaceae: Phyllanthus s.l . [Glochidion]）的唯一传粉者，但它们的幼虫消耗寄主的一部分种子以换取授粉服务。该项目将探讨在这种互惠关系中是否存在促进相互专门化的机制，这种专门化是否导致了叶蛾传粉媒介的种群分化，以及随着这种相互专门化而进化的基因表达或基因组序列的哪些差异。这些问题将通过生物测定、花气味分析（GC-MS）、群体遗传学和转录组学等方法的组合来解决。在此过程中，本研究将明确研究共同进化生物之间的新生共同进化物种形成，以及这种新生物种形成发生的机制。了解生物多样性产生的机制，特别是在热带地区，对于保护物种多样性和相互作用多样性至关重要。由于余甘子树是南太平洋地区主要的特有辐射植物之一，许多珍稀类群受到外来物种入侵和栖息地破坏的威胁，本研究具有长期和短期的双重价值。此外，利用转录组学研究昆虫寄主小种形成具有明确的农业应用价值。该计划将促进首席研究员在进化生物学的下一代测序方法方面的培训，以及他的国际研究经验。最后，本项目将促进日本京都大学（Atsushi Kawakita博士、Makoto Kato博士、Tomoko Okamoto博士和Hirokazu Toju博士）、日本京都立大学（Issei Ohshima博士）、加州大学伯克利分校（Michael Eisen博士）和法属波利尼西亚的daca Recherche （Jean-Yves Meyer博士）的首席研究员和研究小组之间的国际合作。

The International Research Fellowship Program enables U.S. scientists and engineers to conduct nine to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad. This award is co-funded by the Office of International Science and Engineering and by the Evolutionary Ecology Program in the Division of Environmental Biology. This award will support an eighteen-month research fellowship by Dr. David H. Hembry to work with Dr. Atsushi Kawakita at Kyoto University in Otsu, Japan, followed by a six-month research fellowship for Dr. Hembry to work with Dr. Michael B. Eisen at the University of California, Berkeley. The role of coevolution between species in the diversification of life on earth is one of the major questions in evolutionary biology. In particular, evidence that coevolution between species in mutualistic relationships (in which members of both species benefit) promotes diversification, as well as the mechanisms by which it might do so, remains equivocal. Specialized pollination mutualisms between insects and plants, particularly those between figs and fig wasps and yuccas and yucca moths, have long been used as models for this research because the role that pollinators play in transporting their hosts' gametes makes them especially likely candidates for coevolutionary diversification. However, evidence for coevolution driving diversification in these systems is equivocal from both empirical and theoretical angles, and few studies have explicitly investigated speciation in these systems.The goal of this proposal is to use a combination of experimental and transcriptomic approaches to examine a putative case of nascent coevolutionary speciation in a specialized, insect-plant mutualism that has recently diversified on oceanic islands in French Polynesia. Leafflower moths (Lepidoptera: Gracillariidae: Epicephala) are the sole pollinators of their leafflower plant hosts (Phyllanthaceae: Phyllanthus s. l. [Glochidion]) but their larvae consume a subset of the host's seeds in return for the service of pollination. This project will ask whether mechanisms exist that promote reciprocal specialization in this mutualism, whether such specialization leads to population differentiation in the leafflower moth pollinators, and what kinds of differences in gene expression or genome sequence are evolving in tandem with this reciprocal specialization. These questions will be addressed through a combination of methods including bioassays, flower odor analysis (GC-MS), population genetics, and transcriptomics. In doing so, this study will explicitly investigate both nascent coevolutionary speciation between coevolving organisms, and the mechanisms by which such nascent speciation occurs.An understanding of the mechanisms that give rise to biodiversity, particularly in the tropics, is vital to conserving both species diversity and interaction diversity. This research has both long-term value and short term value in this regard, since Phyllanthus trees are one of the major endemic plant radiations in the South Pacific, with many rare taxa threatened by invasive species and habitat destruction. Additionally, the use of transcriptomics in the study of host-race formation in insects has clear agricultural applications. This program will facilitate the Principal Investigator's training both in next-generation sequencing methods in evolutionary biology, and his international research experience. Finally, this project will facilitate international collaboration between the Principal Investigator and research groups at Kyoto University, Japan (Dr. Atsushi Kawakita, Dr. Makoto Kato, Dr. Tomoko Okamoto, and Dr. Hirokazu Toju), Kyoto Prefectural University, Japan (Dr. Issei Ohshima), the University of California, Berkeley (Dr. Michael Eisen), and the Délégation à la Recherche, French Polynesia (Dr. Jean-Yves Meyer).