Anthropogenic impacts and subsequent pollen limitation has been demonstrated in a divers range of pollination systems. Although vital in understanding the role of pollination in the entire life cycle of a plant, to our knowledge no field studies exists determine the strength of the link between pollination and population persistence. Demographic studies are one way of addressing this question. In this study we attempt to fill this gap by monitoring 240 Brunsvigia orientalis (Amaryllidaceae) plants for 9 years, starting the year after a fire. Dormancy, flowering (April), seed set and number of leaves (August) for all mapped individuals were recorded. From this, annual matrices were developed to obtain estimates of reproduction, growth and survival. Deterministic stage based population projection matrix models, elasticity analysis and simulations were used to explore population dynamics. This model was then used to predict demographic population structure at differing abundances of pollinating sunbirds and verified against observed population structure in populations differing in sunbird abundance.

Results/Conclusions Initially population growth rates were high (highest λ = 2.24) but decreased (lowest λ = 1.18) as time since fire increased with stasis and growth the most important stages. Lambda for shaded plants was significantly lower than for unshaded plants. There was no significant effect of flowering on leaf gain of the next year but leaf gain in the previous year significantly depressed leaf gain in the current year. There was no correlation between rainfall and population growth rates. In pollinator deficient environments few seeds are produced but population growth rate is still positive due to a small amount of selfing. Pollinator simulations could predict population structure in populations differing in pollinator abundance. Increased shade coupled with a complete loss of pollination in small conservation areas results in declining populations (λ < 1). Capable of long distances dispersal B. orientalis relies on quickly colonizing new disturbed areas, which necessitates large quantities of seeds. We conclude therefore that pollination rate impacts the demographic population structure of B. orientalis, suggesting that pollination is a vital component of the life history of this species.