Phylogenetic relationships and distribution of Gelidium crinale and G. pusillum (Gelidiales, Rhodophyta) using cox1 and rbcL sequences

The taxonomic distinctiveness and cosmopolitan distributions of the red algae Gelidium crinale and G. pusillum remain unclear. Both species were first described in Devon in southwestern England; namely in Ilfracome for G. crinale and Sidmouth for G. pusillum. We analyzed mitochondrial cox1 and plastid rbcL sequences from specimens collected in East Asia, Australia, Europe and North America. In all phylogenetic analyses of cox1 and rbcL sequences, G. crinale was distinct from congeners of the genus. The analyses also revealed a sister relationship with the G. coulteri and G. capense clade. Nineteen cox1 haplotypes were identified for G. crinale, and they were likely geographically structured. Despite the distinctiveness in both cox1 and rbcL datasets, the sister relationship of G. pusillum in the genus was not resolved. Our cox1 and rbcL datasets indicate that G. crinale is a cosmopolitan species, found in East Asia, Australia, Europe and North America, while the distribution of G. pusillum is restricted to Europe and Atlantic North America. Our results suggest that infraspecific classification of G. pusillum may be abandoned.