Genetic segregation and differentiation of a common subtidal alga Pterocladia lucida (Gelidiales, Rhodophyta) between Australia and New Zealand

Pterocladia lucida (Gelidiales), an important agar source in New Zealand, commonly occurs subtidally in Australia and New Zealand and is very variable in morphology. In the present study, the genetic diversity of P. lucida was investigated for 33 specimens collected in Australia and New Zealand. Phylogenetic analyses of mitochondrial cox1 and plastid rbcL sequences revealed that P. lucida specimens formed a monophyletic clade but consisted of four distinct genealogical lineages: one from Australia and three from New Zealand. The pairwise divergences between these four lineages are equal to or higher than those between other species of the family. The Australian lineage is recognized as Pterocladia lucida sensu stricto because the type of the species is from southern Australia. Our results suggest that an ancestor of the P. lucida complex from New Zealand was segregated from the Australian species and then has likely diverged into three species.