Fire effects on pollinators and pollination

© 2016 Dr. Julian MacPherson BrownOne of the most important knowledge gaps currently inhibiting biodiversity conservation in fire-prone landscapes concerns the interactions between fire and other ecosystem processes. Animal-mediated pollination, whereby animals transport pollen between the male and female parts of flowers, is an important ecosystem processes as it is required for approximately 80-90% of the Earth’s flowering plants to reproduce sexually. The aim of my thesis is to better understand fire effects on pollinators and pollination and their role in fire management. First I synthesise the literature to develop a conceptual model, and then describe my empirical work exploring the ideas underlying this model. The central idea is that fire can influence plant-pollinator interactions through multiple processes operating over different spatial scales, and this was supported by my empirical work (and a study (Ponisio et al. 2016) from North America published as I was finalising my thesis). I collected data from the Mediterranean climate zone of south-eastern Australia, employing a space-for-time substitution design with spatially independent sites along a 75 year post-fire successional gradient. I monitored pollinator visitation to the sexually-deceptive orchid Caladenia tentaculata, capsule set of the food-deceptive orchid Diuris maculata sensu lato, and sampled aerial invertebrate assemblages (focusing on known fly and wasp pollinator groups) across these sites. I found that visitation to C. tentaculata was greatest when the site was recently burnt but the surrounding landscape was long-unburnt. Diuris maculata s.l. capsule set was influenced mostly by rainfall in the growing and flowering season (winter and spring). Flies and wasps exhibited only moderate or weak responses to post-fire age. Interestingly, though, species richness was positively related to fire age diversity within 800 m of sample locations but negatively related to fire age diversity within 200 m. My model could form the basis for simulations of plant and pollinator population dynamics in fire-prone landscapes, parameterised with spatially-explicit empirical data as presented in my thesis