This paper describes two species previously confused under the name Porphyra purpurea (Roth) C. Ag. sensu lato: Porphyra dioica sp. nov. and P. purpurea sensu stricto. The holotype(BM) of P. dioica is from Sidmouth, Devon, England and the proposed neotype (BM) of P. purpurea is from Nord-Ost Watt, Helgoland. Porphyra dioica is characterised by having olive-green to purplebrown, frequently laciniate, lanceolate to broadly ovate fronds which fold in half when held vertically; it is dioecious with marginal sori; spermatangial packets contain 64 spermatangia; carposporangial packets contain 8 carpospores. Porphyra purpurea sensu stricto is characterised by having brown to reddish-brown, usually entire, elliptical to obovate fronds; it is monoecious with male and female sori separated by a distinct line; spermatangial packets contain 64-128 spermatangia; carposporangial packets contain 16 carpospores. Carpospores of both species develop into a filamentous "Conchocelis" -phase. Ecological differences are also apparent, with P. dioica occurring in the lower midlittoral of more exposed shore regions, and P. purpurea in the midlittoral of more shelteredlocations. |
