Abstract
Results of recent molecular phylogenetic analyses have shown that the previous separation of Trillium into two subgenera based on pedicellate or sessile flowers is untenable. An updated infrageneric classification is presented recognising four subgenera in the genus, consistent with phylogenetic analyses. The three clades of pedicellate-flowered species are recognised here as subgenera: subgen. Trillium, Delostylis and newly named Callipetalon. The fourth, Trillium subgen. Sessilia, includes all sessile-flowered species. Orthographic considerations necessitate corrections to two previously published subgeneric names: Delostylium and Sessilium should be Delostylis and Sessilia.
References
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<p>Haga, T., Watanabe, H. & Kanazawa, H. (1974) Hybridization in natural populations of Japanese trilliums. <em>The Japanese Journal of Genetics</em> 49: 399–412. https://doi.org/10.1266/jjg.49.399</p>
<p>Harbison, T.G. (1901) New or little known species of <em>Trillium</em>. <em>Biltmore Botanical Studies</em> 1: 19 –24.</p>
<p>Ihara, K. & Ihara, M. (1982) A biosystematic study on the pedicellate-flowered species of North American <em>Trillium </em>(2) an interspecific relationship shown by karyotypes and mode of microsporogenesis. <em>Journal of Phytogeography and Taxonomy </em>30: 74–82.</p>
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<p>Ker Gawler, J.B. (1805) <em>Trillium camschatcense</em>. <em>Botanical Magazine</em> 22: pl. 855.</p>
<p>Kiger, R.W., Case, Jr., F.W. & Pires, J.C. (2001) New infraspecific names in North American Liliales. <em>Taxon</em> 50: 201. https://doi.org/10.2307/1224524</p>
<p>Kubota, S., Kameyama, Y. & Ohara, M. (2006) A reconsideration of relationships among Japanese <em>Trillium</em> species based on karyology and AFLP data. <em>Plant Systematics and Evolution </em>261: 129–137. https://doi.org/10.1007/s00606-006-0447-4</p>
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