HYBRIDIZATION OF SAXIFRAGA-OPPOSITIFOLIA AND SAXIFRAGA-BIFLORA (SAXIFRAGACEAE) IN A MIXED ALPINE POPULATION

Saxifraga oppositifolia, S. biflora, and their hybrid S. x kochii were studied in a mixed population in the Swiss Alps. Qualitative morpholo gical characters did not allow to clearly separate the hybrid S. x koc hii from its parental species. All quantitative characters were interm ediate in S. x kochii, but the ranges of these characters overlapped w ith those of S. oppositifolia and S. biflora. A hybrid index and canon ical discriminant analysis allowed a clear separation of the three gro ups and strongly confirmed a priori grouping. Phenological observation s showed that the three groups were not temporally separated within th e investigated mixed population. Reciprocal hand pollinations between S. oppositifolia and S. biflora yielded higher seed set with S. opposi tifolia than with S. biflora as maternal plant. Germination rate of se eds from these crossing experiments varied in the same way as seed yie lds, whereas germination rate was intermediate for seeds from naturall y pollinated S. x kochii. Considering its ecological and reproductive properties, S. x kochii has good prerequisites for evolving into a dis tinct species.