Janice Lord

Department of Botany, University of Otago


Saturation or stimulation? The effect of mast flowering on pollinators

Masting is a pattern of reproduction in plants in which years of very high seed production are separated by several years with little or no seed production. Satiation of seed predators, typically invertebrates, during mast years, is thought to be a major advantage of masting behaviour. Little is known, however, of the consequences of masting for insects that utilise floral resources, as the plants that have been most researched in New Zealand and worldwide are wind-pollinated. In New Zealand alpine ecosystems, Aciphylla species (taramea, speargrasses), some Celmisia species (mountain daisies) and Dolichoglottis species (alpine groundsels) show mast-flowering behaviour and are insect-pollinated. This talk presents multi-year data from summer surveys of visitors to flowers on the Remarkables Range, Otago. Several of those surveys occurred in years where Aciphylla and Dolichoglottis species were flowering heavily. As expected, these masting species attracted large numbers of flower-visiting insects. However, the numbers of insects visiting flowers of all species was also significantly higher. Hoverflies and native bees in particular showed significant increases in local abundance in heavy masting years. These results suggest firstly that insect-pollinated masting plants could be critical drivers of community-wide pollinator services, and furthermore, that the ability to detect trends in New Zealand insect numbers could be strongly affected by the frequency of masting in the native flora.

Syrphid fly accessing Aciphylla aurea flowers, Rastus Burn Recreation Reserve, Remarkables Range.