Patterns of Flowering and Fruit Production in a Natural-Population of Banksia spinulosa

Abstract

Flowering and fruiting patterns for a population of Banksia spinulosa investigated over three years exhibited a great deal of variability, both amongst plants in a given season and over seasons. Inflorescence production was greatest in 1987, reflecting an increase in numbers of plants 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 per infructescence. For all years, considerably fewer inflorescences flowered late in the season. Late-flowering inflorescences also contained fewer flowers with pollen tubes, fewer pollen tubes per flower and produced fewer infructescences. Variability amongst plants was evident in the onset and timing of inflorescence production, rates of flower opening, 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 number of mature infructescences each year and overall. The total reproductive output of these plants was approximately double that of other plants. Another group of plants never produced seed during the study, even though they flowered each year. These results illustrate the importance of considering individual variability in the population, rather than the more commonly measured, total, or mean reproductive success.