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 have received much attention from conservation and evolutionary biologists. However, plants on islands in the Mediterranean region have received very little attention. In the present study, we examine the floral biology and mating system of Cyclamen creticum, a diploid perennial herb endemic to Crete and Karpathos. Our purpose is to quantify (1) variation and covariation of floral traits related to the mating system, (2) the ability of the species to self in the absence of pollinators and its relative performance on selfing and outcrossing and (3) genetic diversity within and among populations. Pollen/ovule ratios were indicative of a xenogamous species. A controlled pollination experiment showed that the species is self-compatible but is unable to set seed in the absence of pollinators, probably due to stigma-anther separation. A multiplicative estimate of inbreeding depression based on fruit maturation, seed number and percentage seed germination gave delta = 0.38. Population genetic diversity was high, 54.76 % polymorphic loci, a mean of 1.78 alleles per locus and a mean observed heterozygosity of 0.053. F-statistics nevertheless indicated high inbreeding rates (mean F-st = 0.748) in natural populations, and low levels of population differentiation (mean F-st = 0.168). C. creticum thus appears to have a mixed-mating system with high levels of (pollinator) mediated inbreeding (either by facilitated selfing, geitonogamy or biparental inbreeding) in natural populations. (C) 1997 The Linnean Society of London.