Lozada-Troche, Chad A.

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    Molecular systematics of tropical Rhodymeniales (Rhodophyta) from Puerto Rico
    (2009-05) Lozada-Troche, Chad A.; Ballantine, David L.; College of Arts and Sciences - Sciences; Schizas, Nikolaos V.; Kolterman, Duane A.; Aponte, Nilda E.; Department of Marine Sciences; Diffoot Carlo, Nanette
    The Rhodymeniales is one of twenty-four orders within the class Florideophyceae in the Division Rhodophyta. The application of molecular systematics to Rhodymeniales taxonomy has helped to recognize the order as a monophyletic group as well as clarify familial relationships within the order. Despite advances and the elucidation of phylogenetic relationships, there are genera whose taxonomic placement remains uncertain or their generic delimitation is not well defined. The present study addresses phylogenetic relations among rhodymenialean species reported from Puerto Rico using the small ribosomal subunit (18s) and the rubisco large subunit (rbcL) genes. Results from analyses of eighty-six 18s gene sequences highly supported all six families currently recognized within the order. In addition 18s sequence results have provided molecular evidence for the first time for inclusion of the genus Chamaebotrys within the Erythrocolon group in the family Rhodymeniaceae and supported the recognition of a new genus that based on morphological and reproductive characters was initially classified as a new Chrysymenia species. The new genus also belongs in the Erythrocolon group despite the possession of a non-septate thallus. Furthermore molecular data highly supported and provided evidence of the close phylogenetic relation between Gloiocladia atlantica (Searles) R.E. Norris and Gloioderma fruticulosum (Harv.) De Toni, which represent sister taxa. Nevertheless no formal transfer can be suggested because there is no molecular data available for Gloioderma australis (J. Agardh) R.E. Norris (the type species of the genus), to relate the species to either genus. Sequences for both the 18s and rbcL genes confirm the polyphyletic nature of the genus Chrysymenia, revealing that Chrysymenia enteromorpha Harv. and C. wrightii (Harv.) Yamada are more closely related to the genus Botryocladia than to the other Chrysymenia species included in the analyses. Also data from the rbcL gene indicated that the recently described Botryocladia iridescens D.L. Ballant. et Ruiz is closely related to B. madagascariensis G. Feldmann. DNA sequence analyses from both genes highly supported the transfer of Coelothrix irregularis (Harv.) Børgesen to the Champiaceae despite some morphological and reproductive differences with members of the family, indicating that broadening of the defining characters of the family are needed. A new Champia species that superficially resembles Champia parvula (C. Agardh) Harv. was recognized. The new species can be distinguished externally on the bases of branch origin: between the septa in the new species and from the nodal region in the latter, and the number of axes arising from the holdfast. Analysis of 18s sequence and divergence indicated that Chylocladia verticillata (Lightf.) Bliding and Gastroclonium ovatum (Huds.) Papenfuss might be congeneric, nevertheless a larger species sampling is required prior to proposal of a formal transfer. Finally rbcL sequence analysis and divergence provided further evidence to maintain Champia compressa Harv. and C. vieillardii Kütz. as separate species.