Reproductive features of Hawaiian Halimeda velasquezii (Bryopsidales, Chlorophyta), and an evolutionary assessment of reproductive characters in Halimeda

Reproductive features form the basis of many taxonomic and phylogenetic classification schemes, yet their relative obscurity among many green algae has led researchers to form evolutionary hypotheses based primarily on vegetative features. Here we describe reproductive characters of Halimeda velasquezii for the first time and assemble descriptive information for 19 other species of Halimeda to assess the importance of reproductive structures for delineation of species and phylogenetic hypotheses within the genus. Multivariate analyses reveal reproductive structures of sand-dwellings species to form a group distinct from at least one other evolutionary lineage within the genus, suggesting that reproductive characters may be evolutionarily informative. Gametophore length appears to be the most phylogenetically informative character, accounting for over 75 % of differences between lineages. Most Halimeda species with multiple descriptions of reproductive characters exhibit widely divergent, nonoverlapping size characteristics between geographic locations. This may be explained by possible nonmonophyly of historical species from distant areas or specimens having been collected at different developmental stages.