THE POPULATION BIOLOGY OF CHAMAELIRIUM LUTEUM, A DIOECIOUS MEMBER OF THE LILY FAMILY: TWO-SEX POPULATION PROJECTIONS AND STABLE POPULATION STRUCTURE'

Matrix projection models as typically applied to data from natural populations of an- imals and plants fail to distinguish between male and female contributions to population growth. The well-known Leslie model, for example, considers only females, and thereby ignores the interaction of females with males in the production of offspring. In the present paper, a two-sex size-specific population projection model is developed for Chamaelirium luteum, a long-lived dioecious plant. Application of this model to C. luteum is based on a 5-yr study of three large (N > 1000) natural populations of this forest-floor herb. Differences between sex classes (male, female, juvenile) in size- specific survivorship and size transitions are taken into account, as well as particular differences between males and females in age at first reproduction, flowering schedules, and reproductive output per individual. Projections of the three populations studied using this model generally showed a slight male bias in the adult sex ratio. Furthermore, comparison of observed size distribution and sex composition with projected stable populations indicated that the populations studied are near a stable structure and should show only modest changes in population size from year to year. These results are in accord with one's expectations for a long-lived species growing in an ecologically stable habitat.