Phylogenetic relationships of Dichotomaria (Nemaliales, Rhodophyta) with the proposal of Dichotomaria intermedia (R.C.Y. Chou) comb. nov.

Abstract

Species delineation in the calcified red algal genus Dichotomaria is difficult due to the high degree of morphological similarity observed in these algae; thus, species descriptions are based on a limited set of morphological characters. In this study, we conducted phylogenetic analyses of plastid rbcL and mitochondrial cox1 sequences and detailed morphological observations on 28 specimens of Dichotomaria from the Indo-Pacific, Bermuda, the Galápagos Islands, and the Lesser Antilles. As a consequence, we propose the new combination Dichotomaria intermedia (R.C.Y. Chou) comb. nov. based on Galaxaura intermedia. This species has flattened branches, three to four cortical cell layers, four sterile branches issuing from the hypogynous cell, and a pericarp formed from the basal cell, as in the genus Dichotomaria. In the rbcL tree, D. intermedia formed a group with Dichotomaria tenera from South Africa. Our results confirmed the occurrence of 11 species and one variety: Dichotomaria apiculata, Dichotomaria australis, Dichotomaria diesingiana, Dichotomaria falcata, Dichotomaria hommersandii, Dichotomaria intermedia, Dichotomaria marginata, Dichotomaria obtusata, D. obtusata var. major, Dichotomaria papillata, Dichotomaria spathulata, and D. tenera. Further study is required to address unidentified genetic groups that cannot currently be assigned to known species groups.

Notes on the marine algae of the Bermudas. 15. Dichotomaria huismanii (Galaxauraceae, Rhodophyta), a new species in the D. marginata complex from the western Atlantic

“…The second species that genetically clusters with Dichotomaria huismanii (Figure 2) (Wiriyadamrikul et al 2014), as compared to those for D. huismanii, 28-50 μm tall and 22-48 μm diameter (Table 2), but unlike the new species, these cells are apiculate.…”

“…Specimens were likewise sequenced Brought to you by | MIT Libraries Authenticated Download Date | 5/12/18 3:10 PM for the plastid-encoded rbcL operon. Amplification and/ or sequencing reactions for rbcL were conducted using the primers (F43-R753; F615-RrbcS start) and the thermal profile referenced in Wiriyadamrikul et al (2014). All amplified DNA was treated with the Qiagen (Redwood City, CA, USA) QIAquick PCR Purification Kit following the manufacturer's protocol.…”

“…major W.R. Taylor (Taylor 1960) were based on the larger habits they displayed in the islands as compared to the nominate variety, and sequences we have generated from recent collections match those derived from isotype material of D. obtusata var. major by Wiriyadamrikul et al (2014). Whether they are representative of the species remains to be seen, as material of D. obtusata from the region of the type locality (Bahamas Is.)…”

“…Along with four others, they reassigned two species originally included by Lamarck (1816) in his new genus Dichotomaria, Dichotomaria marginata (J. Ellis et Solander) Lamarck and Dichotomaria obtusata (J. Ellis et Solander) Lamarck, species known during the 20th century as Galaxaura, both being widely reported in the western Atlantic as well as other seas. Pantropical D. obtusata has been shown to be a complex of species, but authentic material from the West Indies has not been sequenced and compared with the various genetic species now known from distant seas (Wiriyadamrikul et al 2014). Bermuda specimens designated as D. obtusata var.…”

“…Lamouroux, and all subsequent reports in Bermuda followed their lead (see Schneider 2003). In the present study, we have made several recent collections of D. marginata in Bermuda and St. Croix, Virgin Is., to compare genetically with other species in the complex, in particular specimens attributed to this species from Puerto Rico analyzed by Huisman et al (2004) and Guadeloupe by Wang et al (2005) and Wiriyadamrikul et al (2014).…”