A muscoides-like Fucus from a Maine salt marsh: Its origin, ecology, and taxonomic implications.

The morphology and habitat of a dwarf moss-like or muscoides-like fucoid br own alga were studied in the Brave Boat Harbor salt marsh of York-Kittery, Maine, U.S.A. using transect studies and transplant experiments. The plant, which lacks a holdfast, forms a dense embedded turf amongst sparse Spartin a parens populations in the high marsh, particularly on well-drained sandy sediments near the Harbor's mouth. The plant's dichotomously branched frond s were smaller than those previously reported for muscoides-like population s from Europe (mean = 13.2 mm long, 1.1 mm wide, and 0.1 g damp-dried weigh t), while they had a similar dominance of marginal hair pits or cryptostoma ta. Transplantation of in situ Fucus spiralis from the lower to the upper m arsh resulted in enhanced fragmentation, stunting, proliferation, and reduc ed reproduction. Reciprocal transplantation of the muscoides-like Fucus fro m upper to lower elevations caused enhanced frond length and proliferation. Based upon detailed transplant and morphological studies, we conclude that the muscoides-like Fucus plants from Brave Boat Harbor represent a phenoty pic variant of F. spiralis, caused by detachment, extensive proliferation, and subsequent degeneration of detached fragments. The plant's dwarf morpho logy is primarily linked to a series of unique environmental conditions (de siccation and low nutrients), plus the type of attached parental material a vailable. Thus, the dwarf muscoides-like Fucus in Europe and some Northwest Atlantic sites may be derived from F. vesiculosus, while in Brave Boat Har bor the parental material is F. spiralis. An analogous pattern is also evid ent between Ascophyllum nodosum and its detached ecad scorpioides, with the presence of dwarf specimens and the occurrence of a conspicuous morphologi cal continuum between the two plants.