No evidence for simultaneous pollen and resource limitation in Aciphylla squarrosa:: A long-lived, masting herb

For successful reproduction animal pollinated plants must provide resources for both pollinator attraction and offspring production, and theory suggests that resources and pollen delivery limit reproduction simultaneously. We conducted a series of experiments involving supplemental pollination, flower removal, fertilizer addition and foliage removal to investigate the interaction of resources and pollen on fruit-set of Aciphylla squarrosa, a long-lived, dioecious, masting herb in Wellington, New Zealand. Reducing floral display decreased open-pollinated fruit-set, suggesting that display size is a reflection of an optimal investment between attraction and fecundity. In combination with supplemental pollination, resource reduction and fertilization addition did not alter fruit-set, suggesting that changes in resource availability did not limit reproduction in the current year. In addition, supplemental pollination of non-manipulated treatments did not increase fruit-set, demonstrating that plants were not naturally pollen limited. While we found that simultaneous pollen and resource limitation did not occur within a season, this is possibly mitigated by life history patterns including mast flowering and a storage taproot. Multiple year studies are required to further examine simultaneous resource and pollen limitation.