PATTERNS OF FLOWERING AND FRUIT PRODUCTION IN A NATURAL-POPULATION OFBANKSIA-SPINULOSA

Flowering and fruiting patterns for a population of Banksia spinulosa investigated over three years exhibited a great deal of variability, b oth amongst plants in a given season and over seasons. Inflorescence p roduction was greatest in 1987, reflecting an increase in numbers of p lants flowering and numbers of inflorescences per plant. In contrast, infructescence numbers were similar for the three years. However, seed output was greatest in 1988, due to increased numbers of follicles pe r infructescence. For all years, considerably fewer inflorescences flo wered late in the season. Late-flowering inflorescences also contained fewer flowers with pollen tubes, fewer pollen tubes per flower and pr oduced fewer infructescences. Variability amongst plants was evident i n the onset and timing of inflorescence production, rates of flower op ening, levels of pollen tube growth and infructescence production. For example, some plants consistently had higher reproductive output than others. These plants produced seed each year, and had a greater numbe r of mature infructescences each year and overall. The total reproduct ive output of these plants was approximately double that of other plan ts. Another group of plants never produced seed during the study, even though they flowered each year. These results illustrate the importan ce of considering individual variability in the population, rather tha n the more commonly measured, total, or mean reproductive success.