Genetic introgression between tetraploid Dactylis glomerata subspp. reichenbachii and glomerata in the French Alps. Insight from morphological and allozyme variation

The morphology, phenology and allozyme polymorphism in seven tetraploid Dac tylis glomerata populations growing in the French Alps were studied. Based on habitat and morphological characteristics, two of the populations could be classified as D. glomerata subsp. reichenbachii, which is known to compr ise diploid and tetraploid plants growing exclusively on dolomite, on south -facing meadows. This subspecies has been previously recorded in the Italia n and Swiss Alps but not in the French Alps. The remaining five populations were morphologically intermediate but more similar to the cosmopolitan D. glomerata subsp. glomerata. On the basis of allozyme variation, all populat ions were more related to subsp. reichenbachii than to the cosmopolitan sub sp. glomerata, suggesting that gene flow has occurred between the two tetra ploid subspecies. The possibility that selection has acted differently on m orphological and allozyme characters is discussed.