POPULATION-STRUCTURE AND SPATIAL PATTERN IN THE DIOECIOUS SHRUB CERATIOLA-ERICOIDES

The dioecious shrub Ceratiola ericoides (Florida rosemary) dominates x eric, infrequently burned Florida scrub vegetation, often to the near- exclusion of other woody species. We studied the spatial pattern, age, sex and size structure of four populations in Florida, USA: two coast al scrub populations subject to recurrent local disturbances due to sa nd movement, and two inland scrub populations in sites periodically bu rned by stand-replacing fires. The age structure of individual genets was estimated from node counts and used to describe the age structure of the populations. The sex ratio of males to females was not signific antly different from 1:1, except within a female-biased coastal popula tion subject to frequent sand movement. Node counts indicated that the mean age for reproductive individuals was 15 - 16 yr for the inland p opulations and 13 - 16 yr for the coastal populations. In all sites, t here was no difference in mean age between males and females. Vegetati ve reproduction was uncommon except for the least-disturbed coastal po pulation where 72 % of the reproductive individuals originated through layering. Individuals were generally randomly dispersed at the coasta l sites, whereas significant aggregation of males and females occurred in the inland sites where the populations were initiated following fi re. Seedling recruitment was continuous in the disturbed coastal scrub site, where 35 % of the individuals were juveniles. Most juveniles we re dispersed from 0.5 to 0.75 m around females. At one of the inland s ites, where juveniles comprised 11 % of the population, juveniles were clustered at 0.25 to 5.75 m around females. Coastal populations were all-aged, while inland populations were uneven-aged. Recruitment appea rs to follow periods of disturbance; infrequent fire in the inland pop ulations and continuous sand movement on the coast are factors initiat ing recruitment.