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In this study, we document two species of the genus Gelidiella from Taiwan including a new species, Gelidiella fanii sp. nov., from eastern and southern Taiwan. Although the type specimen of Gelidiella acerosa from Yemen was not available during this study, analyses of rbcL sequences indicate that specimens identified as G. acerosa from the Caribbean Sea, southeastern Australia, and the Indo-Pacific oceans and G. fanii from Taiwan are clearly separate species. Gelidiella fanii differs morphologically from Taiwan G. acerosa specimens in having strict unilateral branching, cylindrical to compressed erect axes, numerous surface hairs on the distal ends of branches and branchlets, iridescent thalli, and smaller tetrasporangia.
KEY WORDS: Gelidiella acerosa, Gelidiella fanii sp. nov., rbcL, Taiwan
INTRODUCTION
The genus Gelidiella was established by Feldmann and Hamel (1934) based on Gelidiella acerosa from the Red Sea (Yemen). A historical review of the genus was provided by Santelices in 2004. Fan (1961) placed Gelidiella in his monotypic family Gelidiellaceae, characterized by lack of thick-walled, delicate fibers (= rhizines or internal hyphae) in the cortex or medulla and the absence of a known sexual generation; however, the consistency of both these characters within Gelidiella has been questioned. The total absence of rhizines in G. acerosa (Melo 1992) and probable incorrect assignment of species with rhizines in Gelidiella, as discussed in Millar & Freshwater (2005), confirms the absence of rhizines as a synapomorphy for the Gelidiellaceae. In contrast, numerous studies have shown that the absence of a gametophyte stage in the life history can no longer be considered a diagnostic character of the family. Sreenivasa Rao & Trivedi (1980) provided the only description of the structure of a cystocarp based on an undescribed species of Gelidiella from Diu Island, India; however, this report has not been generally accepted (e.g. Santelices & Flores 2004). In contrast, meiotic divisions and alternating haploid and diploid DNA amounts have been reported for G. acerosa (Sreenivasa Rao 1974; Kapraun et al. 1994), and male gametophytes have been described for two species in the Gelidiellaceae (Santelices 1997; Rico et al. 2002; Santelices & Flores 2004).
Consistent differences in tetrasporangial stichidia among Gelidiella species were first reported by Feldmann & Hamel (1934). Santelices (2002) recognized additional differences in the pattern of apical division and internal...