On the occurrence of sexual reproduction in Saxifraga cernua and S. foliolosa (Saxifragaceae)

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Abstract
In all contemporary floras, the two circumpolar arctic species Saxifraga cernua and S. foliolosa are claimed to reproduce only by vegetative means (bulbils) and to have abandoned sexual reproduction. Scattered records in the literature indicate that this is erroneous, and that seed is set irregularly and at a low rate in both species. An inventory of herbarium material supports this view. Field studies at Latnjajaure, N Swedish Lapland, demonstrate that both species have an androdioecious mating system, a phenomenon which is extremely rare in natural plant populations. The two gender classes within each species are maintained by self‐incompatibility in hermaphorodites and a higher rate of vegetative propagation in female‐sterile plants. Hermaphrodites are rare, especially in S. cernua, and most populations consist exclusively of female‐sterile plants. The sparsity of fruiting material in herbaria is regarded to be, in part, a result of low frequency of collecting, due to the in‐conspicuousness of the plants in this stage. Scanning electron micrographs of seeds of the two species are provided.Flora Nordica Notes no. 5.