The hypothesis of hybrid origin of Poa jemtlandica supported by morphometric and isoenzyme data

Abstract

Morphometric and isozyme data were used to test the hypothesis that the pseudoviviparous Poa jemtlandica has originated as a hybrid between the sexual P flexuosa and the facultative apomict P alpina. Plants were sampled from three localities in southern Norway. In addition, some Icelandic plants were included. Both morphometric and isozyme data clearly support the hybrid hypothesis. Poa jemtlandica was morphologically intermediate between its supposed parents in several individual characters as well as in a discriminant analysis. Seven enzyme systems were analysed. Eight areas of activity were interpreted as “loci”, each of which certainly represented several duplicated genes in these plants which all are polyploid. A total of 27 different multilocus phenotypes was observed: ten phenotypes in P alpina var. vivipara, eight phenotypes in I. alpina var. alpina, seven phenotypes in P jemtlandica, and three phenotypes in P flexuosa. The phenotype of Icelandic P jemtlandica was identical to that of P. jemtlandica from one of the Norwegian localities. Additive electrophoretic patterns were observed for P jemtlandica at four individual “loci”. At the remaining “loci” some phenotypes of P. jemtlandica were most similar to P. flexuosa, others to P alpina. The data also suggest that P jemtlandica has originated several times, but there is no indication of frequent or recent hybridization where the species coccur today.