Not-so-forbidden fruit: the potential conservation role of toxic Pimelea microcephala subsp. microcephala fruits for native arid zone birds

ABSTRACT Food resources in arid habitats are important for the survival of native fauna, especially where resources provide water or key nutrients during dry periods. However, food resource plants can be susceptible to grazing species or may not be suitable for revegetating arid areas. Pimelea microcephala subsp. microcephala (P.m.microcephala) is an Australian dioecious shrub bearing bright fruit that are likely to attract birds. The plant is also noted for its production of simplexin, a compound toxic to mammals. The aims of our study were 1) to assess the nutrient and simplexin content of P.m.microcephala fruits, and 2) to confirm the identity of native avian species that consume the fruits. With both pieces of information, we could then determine the conservation utility of P.m.microcephala. Combining chemical analysis of fruit nutrients with field observations, we found that ripe fruits contain 60.5% water, 2.8% sugar, and potent antioxidants, which would likely be of nutritional benefit to consuming frugivores. The fruits also contain high levels of the toxin simplexin, which comprised 3.6% of ripe fruits by weight. We identified eight bird species interacting with P.m.microcephala, with at least five of these consuming ripe fruits. Our study demonstrates the potential for P.m.microcephala to contribute to revegetation and provide a food resource for arid zone birds, whilst being protected from grazing by the presence of simplexin. Further studies are needed to establish the species’ absolute significance in terms of fruits as a source of water and nutrients to arid zone bird diets.