Evolution of nuchal glands, unusual defensive organs of Asian natricine snakes (Serpentes: Colubridae), inferred from a molecular phylogeny
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- Hirohiko Takeuchi
- Seto Marine Biological Laboratory Field Science Education and Research Center Kyoto University Shirahama Japan
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- Alan H. Savitzky
- Department of Biology Utah State University Logan Utah
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- Li Ding
- Chengdu Institute of Biology Chinese Academy of Sciences Chengdu China
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- Anslem de Silva
- Gampola Sri Lanka
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- Indraneil Das
- Institute of Biodiversity and Environmental Conservation University Malaysia Sarawak Sarawak Malaysia
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- Tao Thien Nguyen
- Vietnam National Museum of Nature Vietnam Academy of Science and Technology Hanoi Vietnam
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- Tein‐Shun Tsai
- Department of Biological Science and Technology National Pingtung University of Science and Technology Neipu Township Taiwan
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- Teppei Jono
- Chengdu Institute of Biology Chinese Academy of Sciences Chengdu China
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- Guang‐Xiang Zhu
- College of Life Science Sichuan Agricultural University Ya'an China
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- Dharshani Mahaulpatha
- University of Sri Jayewardenepura Nugegoda Sri Lanka
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- Yezhong Tang
- Chengdu Institute of Biology Chinese Academy of Sciences Chengdu China
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- Akira Mori
- Department of Zoology Graduate School of Science Kyoto University Kyoto Japan
抄録
<jats:title>Abstract</jats:title><jats:p>A large body of evidence indicates that evolutionary innovations of novel organs have facilitated the subsequent diversification of species. Investigation of the evolutionary history of such organs should provide important clues for understanding the basis for species diversification. An Asian natricine snake, <jats:italic>Rhabdophis tigrinus</jats:italic>, possesses a series of unusual organs, called nuchal glands, which contain cardiotonic steroid toxins known as bufadienolides. <jats:italic>Rhabdophis tigrinus</jats:italic> sequesters bufadienolides from its toad prey and stores them in the nuchal glands as a defensive mechanism. Among more than 3,500 species of snakes, only 17 Asian natricine species are known to possess nuchal glands or their homologues. These 17 species belong to three nominal genera, <jats:italic>Balanophis</jats:italic>,<jats:italic> Macropisthodon</jats:italic>, and <jats:italic>Rhabdophis</jats:italic>. In <jats:italic>Macropisthodon</jats:italic> and <jats:italic>Rhabdophis</jats:italic>, however, species without nuchal glands also exist. To infer the evolutionary history of the nuchal glands, we investigated the molecular phylogenetic relationships among Asian natricine species with and without nuchal glands, based on variations in partial sequences of Mt‐<jats:styled-content style="fixed-case">CYB</jats:styled-content>, Cmos, and <jats:styled-content style="fixed-case">RAG</jats:styled-content>1 (total 2,767 bp). Results show that all species with nuchal glands belong to a single clade (<jats:styled-content style="fixed-case">NGC</jats:styled-content>). Therefore, we infer that the common ancestor of this clade possessed nuchal glands with no independent origins of the glands within the members. Our results also imply that some species have secondarily lost the glands. Given the estimated divergence time of related species, the ancestor of the nuchal gland clade emerged 19.18 mya. Our study shows that nuchal glands are fruitful subjects for exploring the evolution of novel organs. In addition, our analysis indicates that reevaluation of the taxonomic status of the genera <jats:italic>Balanophis</jats:italic> and <jats:italic>Macropisthodon</jats:italic> is required. We propose to assign all species belonging to the <jats:styled-content style="fixed-case">NGC</jats:styled-content> to the genus <jats:italic>Rhabdophis</jats:italic>, pending further study.</jats:p>
収録刊行物
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- Ecology and Evolution
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Ecology and Evolution 8 (20), 10219-10232, 2018-09-21
Wiley