Hybridization between Atlantic and Pacific representatives of the Simplices section of Laminaria (Phaeophyta)

Hybrids were successfully produced in crosses between Laminaria saccharina from the north-east Pacific, smooth and bullate Atlantic forms of the same species, and Atlantic L. longicruris. The lack of crossing barriers further justifies the placing of the Pacific plants in L. saccharina. Hybrid macrosporophytes were also produced between Japanese L. ochotensis and various races of L. saccharina, although in crosses between L. ocholensis and L. longicruris only those involving L. ochotensis females were successful. A cross between Helgoland L. saccharina and eastern Canadian L. longicruris became fertile in the laboratory and normal F2 gametophytes were produced. The contribution of these findings to the understanding of relationships between Atlantic and Pacific non-digitate Laminaria spp. is discussed.