The genus Leptophytum (Melobesioideae, Corallinales, Rhodophyta) on the Pacific coast of North America

Abstract

A. Athanasiadis and W.H. Adey. 2006. The genus Leptophytum (Melobesioideae, Corallinales, Rhodophyta) on the Pacific coast of North America. Phycologia 45: 71–115. DOI: 10.2216/04-38.1We provide a first account of the genus Leptophytum on the Pacific coast of North America, after re-examining the types and representative collections of species previously associated with Leptophytum, Mesophyllum and Lithothamnion of the Melobesioideae. Six species are recognized, distributed between Alaska (Port Clarence) and Baja California (Isla Magdalena), viz.: Leptophytum tenue (Kjellman) comb. nov. from Port Clarence and Orcas Island in Puget Sound (Washington State), L. adeyi from Tatoosh Island (Washington State), L. lamellicola sp. nov. from California (Monterey and San Mateo Counties) and southern Vancouver Island, L. julieae sp. nov. from SW and SE Vancouver Island and the Queen Charlotte Islands, L. foecundum var. sandrae var. nov. from southern Vancouver Island and Seattle (the typical variety foecundum being restricted to the Arctic and North Atlantic Oceans), and L. microsporum (Foslie) comb. nov. from southern California (Santa Catalina I.) to Baja California (Isla Magdalena). All species display the following characters, which unite them with North Atlantic congeners: noncoaxial (or predominantly noncoaxial) hypothallium, flattened epithallial cells, shedding conceptacles, and no perithallial protuberances. Sexual species (L. lamellicola and L. tenue in the North Pacific, and L. laeve and L. elatum in the North Atlantic) develop predominantly simple spermatangial mother cells with few branched ones occurring centrally or in other places on the chamber floor. Chambers of carposporangial conceptacles display a flattened floor with peripheral development of carposporangia. The NE Pacific species differ from each other in: (1) thallus adhesion (L. lamellicola and L. julieae grow partly unattached), (2) hypothallial growth (patches of coaxial cells occur regularly in L. lamellicola and less frequently in L. foecundum, L. tenue and L. microsporum), (3) perithallial stratification (present in L. lamellicola, L. julieae and L. foecundum), (4) size of subepithallial meristematic cells (distinctively elongateovate in L. julieae), (5) embedded multiporate conceptacles (present in L. lamellicola, L. julieae and L. microsporum), and (6) pore cell morphology of multiporate conceptacles. Each taxon is formally described, and its features are illustrated, tabulated and discussed. A dichotomous key to the six NE Pacific species is also provided together with an emended generic description that encompasses nine Northern and three Southern Hemisphere species.