THE ROLE OF SEXUAL AND CLONAL REPRODUCTION IN MAINTAINING POPULATION IN FRITILLARIA-CAMTSCHATCENSIS (L.) KER-GAWL. (LILIACEAE)

Fritillaria camtschatcensis can reproduce by means of both sexual repr oduction and clonal multiplication. Despite prolific seed production, no seedlings have been found for several years in natural populations on Mt Hakusan. The purposes of this paper are to clarify: (i) whether population size is maintained mainly by clonal multiplication; and (ii ) if this is the case, to what extent occasional seedling establishmen t affects population growth rate and population structure. Two permane nt quadrats were placed in subalpine meadows in 1992 on Mt Hakusan. Pl ant size, location and reproductive states for all ramets in the quadr ats were recorded every year. Projection matrices were created based o n field census, and computer simulation experiments were performed. Fr itillaria camtschatcensis had two types of flower, male flower and cos exual flower, and they were changeable. This is the first report on se x lability in Fritillaria. Clonal growth was more closely correlated w ith life-history stages, especially with sexual states than with plant size. The population growth rate, lambda, was 1.006 for the Mizuyajir i population and 1.047 for the Nanryu population, respectively. Seedli ngs were found in 1996 for the first time. These facts indicate that p opulations of F. camtschatcensis on Mt Hakusan can usually be maintain ed by clonal multiplication. However, it is not yet certain whether se eds germinate every pear or whether a flush of seedling emergence occu rs once in every few years in natural populations. Computer simulation revealed that: (i) there was a critical germination rate above which population growth rate suddenly increased; and (ii) occasional seedlin g establishment could provide almost the same contribution to populati on growth rate as that of annual seedling establishment. These results suggest that population size can be maintained mainly by clonal multi plication, and the role of sexual reproduction lies beyond maintaining the population size in F. camtschatcensis.