Phylogeny of Hedyotis L. (Rubiaceae: Spermacoceae): Redefining a complex Asian-Pacific assemblage

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Abstract:

The genus Hedyotis (Rubiaceae: Spermacoceae) has long served as a repository for tropical herbaceous species that do not fit readily into other genera. Circumscribed broadly the genus becomes a highly heterogeneous assembly, but relationships of Hedyotis have been difficult to resolve and it has proven very difficult to circumscribe the genus in a more narrow sense. Here we present Bayesian phylogenetic analyses of Hedyotis using plastid (rps16, petD) and nuclear (ITS, ETS) sequence data to resolve monophyletic lineages, to test former taxonomic hypotheses, and to revise the taxa within a well-supported evolutionary framework. Four hundred and sixty-seven sequences representing 129 accessions, never previously included in any phylogenetic analyses, are newly reported. Hedyotis, as previously circumscribed, is polyphyletic, but all investigated species, except for Hedyotis coronaria, are resolved in one of three well-supported monophyletic groups. The largest clade includes all investigated species of Hedyotis from the Indian subcontinent as well as three groups of species with primarily Chinese distributions. The type species of Hedyotis (H. fruticosa) is resolved with the Indian subcontinent species and following previous suggestions this group is referred to as Hedyotis s.str. Species currently recognized under the generic names Metabolos and Pleiocraterium are resolved in Hedyotis s.str. The second-largest group comprises a series of smaller, but well-supported, clades including the Leptopetalum clade, the genus Kadua, an unnamed group distributed in Asia and the Pacific, and a large Asian group referred to here as the Exallage/Dimetia clade. The third group includes a few SE Asian Hedyotis, as well as all investigated species of the genus Neanotis. Hedyotis coronaria is not closely related to other species from Asia and is resolved with Spermacoce hispida. The analyses indicate that diplophragmous capsules and “fruticosa-type” seeds occur outside of Hedyotis s.str., and several species suggested to have these features are resolved in the Exallage/Dimetia clade. Species sug gested to have indehiscent capsules, a feature used by Bremekamp to characterize the genus Exallage, are also resolved in both the Exallage/Dimetia clade and in Hedyotis s.str., but a close examination indicates that the capsules are not truly indehiscent in the Hedyotis s.str. species. One species of Metabolos and one species of Pleiocraterium are given new species names, and one species of Pleiocraterium is transferred to Hedyotis and three species of Hedyotis are transferred to Neanotis.

Keywords: ASIA; HEDYOTIS; PHYLOGENETIC ANALYSIS; RUBIACEAE; SPERMACOCEAE

Document Type: Research Article

DOI: http://dx.doi.org/10.12705/622.2

Affiliations: 1: Bergius Foundation, The Royal Swedish Academy of Sciences and Department of Botany, Stockholm University, 10691 Stockholm, Sweden;, Email: niklas.wikstrom@bergianska.se 2: Department of Biological Sciences, Old Dominion University, Norfolk, Virginia 23529-0266, U.S.A. 3: The Linnaean Gardens of Uppsala, Uppsala University, Villavägen 8, 752 36 Uppsala, Sweden 4: Bergius Foundation, The Royal Swedish Academy of Sciences and Department of Botany, Stockholm University, 10691 Stockholm, Sweden

Publication date: April 20, 2013

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