POPULATION GENETIC-STRUCTURE AND LEVELS OF INBREEDING DEPRESSION IN THE MEDITERRANEAN ISLAND ENDEMIC CYCLAMEN CRETICUM (PRIMULACEAE)

The variation and evolution of reproductive traits in island plants ha ve received much attention from conservation and evolutionary biologis ts. However, plants on islands in the Mediterranean region have receiv ed very little attention. In the present study, we examine the floral biology and mating system of Cyclamen creticum, a diploid perennial he rb endemic to Crete and Karpathos. Our purpose is to quantify (1) vari ation and covariation of floral traits related to the mating system, ( 2) the ability of the species to self in the absence of pollinators an d its relative performance on selfing and outcrossing and (3) genetic diversity within and among populations. Pollen/ovule ratios were indic ative of a xenogamous species. A controlled pollination experiment sho wed that the species is self-compatible but is unable to set seed in t he absence of pollinators, probably due to stigma-anther separation. A multiplicative estimate of inbreeding depression based on fruit matur ation, seed number and percentage seed germination gave delta = 0.38. Population genetic diversity was high, 54.76 % polymorphic loci, a mea n of 1.78 alleles per locus and a mean observed heterozygosity of 0.05 3. F-statistics nevertheless indicated high inbreeding rates (mean F-s t = 0.748) in natural populations, and low levels of population differ entiation (mean F-st = 0.168). C. creticum thus appears to have a mixe d-mating system with high levels of (pollinator) mediated inbreeding ( either by facilitated selfing, geitonogamy or biparental inbreeding) i n natural populations. (C) 1997 The Linnean Society of London.