Resilience to summer bushfire in the threatened orchid, Caladenia tessellata, in terms of pollination success, herbivory, and mycorrhizal associations

Abstract

In some biogeographic regions, many threatened plant species occur in habitats that periodically experience bushfire. However, we currently have relatively little information on how important plant–animal and plant–fungus interactions are affected by these fires. For the threatened sexually deceptive orchid Caladenia tessellata we test whether pollination rate, frequency of florivory, and the species of mycorrhizae the plant associates with differ between burnt and unburnt sites. Interestingly, pollination rates were unaffected by fire, demonstrating that populations of the thynnine wasp pollinator can persist post-fire. However, there was a significant negative relationship between number of flowers in a population and pollination success, which is likely a by-product of a deceptive pollination strategy. Despite the presence of vertebrate herbivores, florivory rates were low in both burnt and unburnt sites. Caladenia tessellata associated primarily with the mycorrhiza Serendiptia australiana, regardless of fire history. While our results suggest resilience to a one-off summer fire for the ecological interactions that we measured, it would be interesting to investigate the effects of fire frequency and time of year. High reproductive rates in small populations of C. tessellata suggest these populations may be viable and that retaining them is a high priority for conservation.