INTERGENERIC HYBRIDIZATION AMONG 5 GENERA OF THE FAMILY LESSONIACEAE (PHAEOPHYCEAE) AND EVIDENCE FOR POLYPLOIDY IN A FERTILE PELAGOPHYCUS XMACROCYSTIS HYBRID

Hybridization was attempted by combining gametophytes between intergen eric pairs among the following taxa in the Lessoniaceae: Macrocystis p yrifera (L.) C. Agardh, M. integrifolia Bory, M. angustifolia Bory, Pe lagophycus porra (Leman) Setch., Nereocystis luetkeana (Mert.) Post & Rupr., Dictyoneurum californicum Rupr., and Dictyoneuropsis reticulata (Saud.) Smith. Hybrid sporophytes were produced in some combinations involving Macrocystis x Pelagophycus and Macrocystis x Dictyoneurum, a nd in all combinations of Dictyoneuropsis x Dictyoneurum. This is the first report of intergeneric hybrids involving Dictyoneurum. Gametophy tes of P. porra had 16-24 chromosomes. Gametophytes from a fertile Mac rocystis-Pelagophycus hybrid were crossed with Macrocystis and Pelagop hycus gametophytes. Hybrid male gametophytes and Pelagophycus female g ametophytes produced sporophyte progeny, but hybrid males with Macrocy stis females did not. A single hybrid female gametophyte did not produ ce gametophytes in combination with hybrid males, Pelagophycus males o r Macrocystis males. The hybrid gametophytes had approximately 30 chro mosomes. It is hypothesized that the hybrid is an alloploid, containin g a complete set of Macrocystis and Pelagophycus chromosomes, which ma y have allowed meiosis and sporogenesis to proceed normally in the hyb rid sporophyte found in the sea. Thus, reproductive isolating mechanis ms appear to operate at both pre- and postzygotic stages, and both can be overcome in intergeneric hybrids.