Lessonia adamsiae sp. nov. (Phaeophyta: Laminariales) from the Snares Islands, New Zealand

A new species of Lessonia Bory, L. adamsiae C. H. Hay, with wide, conspicuously corrugated blades, a massive, woody, buttressed base, long, terete branches, and a lacunate cortex is described from Snares Island, New Zealand. This, the only species of Lessonia growing on the Snares, is compared in detail with the following species: - L. corrugala Lucas, which is endemic to Tasmania and hitherto the only Lessonia species previously described with corrugated blades; L. variegata J. Ag. from mainland New Zealand, L. brevifolia J. Ag., so far recorded from Auckland, Campbell, Antipodes, and Bounty Islands; L. nigrescens Bory from Chile and southern Peru; L. flavicans from the Falkland Islands and the Fuegian region of South America; L. vadosa Searles from Fuegia and the Falklands, and L. trabeculata Villouta et Santelices from northern and central Chile. The occurrence of this very distinctive species on an island so close to the much larger and more widely dispersed population of L. variegata on the New Zealand mainland is discussed in terms of recent geology and ocean circulation patterns.