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Two new monospecific genera of filamentous red algae from New Zealand are described, Dione arcuata and Minerva aenigmata (Bangiales, Rhodophyta). Although these taxa conform to the morphological concept of the genus Bangia that is in current use, analyses of nuclear small-subunit ribosomal RNA gene (nSSU) sequences have revealed that these taxa are basal in the order Bangiales and differ significantly from each other and all other filamentous species in the order Bangiales for which nSSU sequence data exist (Broom et al. 2004). Dione arcuata can be distinguished in the field by its width, growth habit and the niche it occupies in the upper subtidal zone, whereas Minerva aenigmata is found on upper intertidal rocks in areas of sand abrasion, and is indistinguishable morphologically from other filamentous Bangiales taxa.
INTRODUCTION
In the red algal order Bangiales, two morphologically defined genera are recognized: those with filaments are placed in the genus Bangia Lyngbye (Lyngbye 1819) and bladed taxa in Porphyra C. Agardh (Agardh 1824). A critical turning point in the understanding of relationships amongst taxa within the Bangiales was the publication by Oliveira et al. (1995) of phylogenetic analyses using nuclear small-subunit ribosomal RNA gene (nSSU) sequences. This provided evidence that there is not a simple sister-group relationship between Bangia and a monophyletic Porphyra. Although making no formal nomenclatural or taxonomic decisions, Oliveira et al. (1995) explored the consequences of their findings. They observed that synonymizing Porphyra with Bangia could create havoc for commercial trade in nori seaweed and would result in a monophyletic but molecularly divergent concept of Bangia.
The concept of the order Bangiales as a monophyletic lineage is consistently supported by all recent phylogenetic treatments (e.g. Ragan et al. 1994; Oliveira & Bhattacharya 2000; Millier et al. 2001). The majority of studies on the Bangiales have been centred in the North Pacific and North Atlantic Oceans (e.g. Lindstrom & Cole 1992a, b; Miyata & Kikuchi 1997; Brodie et al. 1998; Müller et al. 1998, 2001; Klein et al. 2003; Lindstrom & Fredericq 2003), with relatively few authors including southern hemisphere taxa (e.g. Oliveira & Coll 1975; Woolcott & King 1998; Broom et al. 1999; Nelson et al. 2001a; Farr et al. 2003; Jones et al. 2004). As collections from a wider geographical region...