THE HYBRID ORIGIN OF THE POLYPLOID LIVERWORT PELLIA-BOREALIS

Isozyme markers were used to investigate the origin of the polyploid l iverwort, Pellia borealis (gametophytic n = 18), which was believed to represent an autopolyploid form of Pellia epiphylla (n = 9). Enzyme v ariation was studied in four taxa: polyploid P borealis, two recently discovered sibling species of P. epiphylla complex, and the closely re lated P. neesiana (n = 9). Gametophytes of the polyploid showed a comp lex electrophoretic phenotype for three diagnostic enzymes (DIA1, MPI1 and AGO) in contrast to simple pattern in all haploid taxa. It was po stulated that the pattern found in the polyploid represents a 'fixed h eterozygous' phenotype resulting from allopolyploidy. Alleles present in the polyploid were found (with only one exception) in the two sibli ng species of the P. epiphylla complex, suggesting that they are the p arents of the allopolyploid. Pellia neesiana was excluded as a donor o f either of the genomes. Variation in the polyploid suggests at least three separate origins of P borealis.