The conspecificity of Galaxaura apiculata and G. hystrix (Nemaliales, Rhodophyta) inferred from comparative morphology and rbcL and ITS1 sequences

In order to elucidate possible relationships among tetrasporophytic and gametophytic species of the red algal genus Galaxaura (Galaxauraceae, Nemaliales), we studied some tetrasporophytic and gametophytic species from Japanese waters, using morphological data, partial sequences of the large subunit of the RUBISCO (rbcL) gene and the nuclear rDNA internal transcribed spacer 1 (ITS1). Two morphologically similar species, G. apiculata Kjellman (tetrasporophytic species whose tetrasporangia are reported for the first time) and G. hystrix Kjellman (gametophytic species). Both of these were originally described from Japan and shared identical rbcL and ITS1 sequences. We conclude that these two algae constitute a single species, although their internal structures are distinct (particularly the shape of the cortical cells). Galaxaura hystrix is subsumed in G. apiculata and we provide an emended description of the species. Structural dimorphism among tetrasporophytic and gametophytic individuals within a single species was also confirmed in two additional species, G. falcata Kjellman and G. papillata Kjellman, whose type localities are also in Japan.