Reproductive biology and population molecular genetics of the scrub morning glory Bonamia grandiflora.

摘要

The Florida scrub is an ancient ecosystem that appeared twenty million years ago and has persisted to the present. Bonamia grandiflora, the scrub morning glory, is one of the many threatened or endangered species endemic to the Florida scrub. This study assessed the phenotypic variation, reproductive biology and molecular genetic diversity of B. grandiflora throughout its geographic range.; Variation in morphology was assessed in wild populations of B. grandiflora. The number of stems per plant and stem length were variable between populations; the reproductive output, leaf pubescence (number of hairs/mm2) and flower dimensions were not. There was no geographic pattern associated with any of the variables. Variation in number and length of stems may be due to habitat differences. Although reproductive output is associated with the number and length of stems, other unknown factors have as much influence as plant size.; The breeding system of B. grandiflora was investigated through hand-pollinations in three populations in the Ocala National Forest. B. grandiflora has a mixed mating system; that is, its seeds form both by selfing and by cross-pollination of the flowers. Natural pollinators are necessary to ensure substantial seed production. B. grandiflora shows some inbreeding depression in selfed fruits and seeds but this does not appear to hinder the present populations; however, germination percentages are generally low. Seed herbivory rarely occurs and does not endanger this species.; The genetic diversity in B. grandiflora was assessed by isozymes, RAPD markers and AFLP markers. Genetic variation in this morning glory is reduced and comparable to near-isogenic agronomic lines and some very rare species. The genetic diversity is allocated mainly within rather than between populations. This results in poor structure of the genetic richness and a very weak geographic pattern of this diversity. Two populations have the greatest genetic diversity but no single population covers the entire gamut of genetic variation.; B. grandiflora does not appear in immediate danger of extinction but it has poor genetic diversity and it shows some inbreeding depression. Further reduction of its natural populations could exacerbate these problems and impede the long-term survival of the scrub morning glory.