Fire,food and sexual deception in the neighbourhood of some Australian orchids

The effective use of prescribed fire in biodiversity conservation is currently inhibited by a limited understanding of fire effects on ecosystem processes such as pollination. Orchids inhabiting fire‐prone landscapes are likely to be particularly sensitive because they often exhibit highly specialized pollination systems and provide no reward to pollinators, making them dependent on co‐flowering heterospecifics to attract and support pollinators. We investigated the hypothesis that fire‐driven changes in the local abundance of rewarding heterospecific flowers influence pollination in two rewardless Australian orchid species, Diuris maculata sensu lato and Caladenia tentaculata. Diuris maculata s.l. is thought to achieve pollination by mimicking papilionoid Fabaceae flowers. Caladenia tentaculata attracts male thynnine wasps through sexual deceit, and these wasps forage on the open‐access flowers of other taxa. We used a space‐for‐time substitution design with sites in different stages of post‐fire succession where we recorded capsule set in D. maculata s.l., pollinator visitation to C. tentaculata, the floral abundance of rewarding heterospecifics and abiotic conditions. Many rewarding taxa responded to fire age, but there was only weak evidence that capsule set in D. maculata s.l. was positively related to the local floral abundance of rewarding species. There was evidence of an overriding effect of rainfall on capsule set that may have obscured effects of the floral community. Visitation to C. tentaculata was not positively associated with any rewarding heterospecifics, and was negatively associated with rewarding Burchardia umbellata. Our preliminary findings highlight the need to account for multiple factors when trying to detect fire effects on pollination.