REPRODUCTION OF THE RARE MONOCARPIC SPECIES SAXIFRAGA-MUTATA L

The aim of the study is to investigate the impact of reproduction and genetic variation on the persistence of populations of the prealpine, monocarpic Saxifraga mutata L. The species grows on erosion slopes or rocks, and its local populations are often small and isolated. Crossin g experiments resulted in better seed-set than selfing, but both yield ed viable seeds. Agamospermy did not occur. In an early-successional s pecies like S. mutata, successful selfing is important in the coloniza tion of new habitats. Flowers of S. mutata were visited by Syrphidae a nd unspecialized Hymenoptera. A germination rate of 40% was reached in cultivation after 20 weeks but germination continued until the end of the experiment after 92 weeks. Seeds stored dry for 30 months at room temperature mostly lost their germinability. In natural habitats, see dlings were found almost throughout the year with a peak in spring. Su itable safe sites were small patches of open soil, bare marl on erosio n slopes, and rock crevices. AU individuals investigated were diploid with 2n = 26. Allozyme electrophoresis showed a lack of segregation wi thin the populations. Intra- and interpopulation genetic variation was low. These results were in partial disagreement with theoretical expe ctations in a mixed mating species. It is concluded that demographic r ather than generic processes are the main cause of extinction of popul ations of S. mutata, at least in the short-term. (C) 1996 The Linnean Society of London