Between-species facilitation by male fig wasps in shared figs

1. Facilitation, where one species helps another without cost or benefit to itself, is recorded from diverse plant-insect interactions, including pollination and herbivory. We investigated the significance of facilitation resulting from the behaviour of pollinator fig wasps inside figs shared with other species. Fig wasp females emerge from natal figs via exit holes dug by pollinator and some other fig wasp males. When no males are present the females struggle to escape and may die. 2. Ficus microcarpa is a widely-established invasive fig tree from SE Asia. Its pollinator is absent in South Africa, so the tree cannot reproduce, but two non-pollinating fig wasps (NPFW) Walkerella microcarpae and Odontofroggatia galili occupy its figs. We compared abundance patterns of the two NPFW and the proportion of male-free figs in South Africa, Spain (where the pollinator is introduced), and in China, where the native fig wasp community is diverse, to determine the consequences of reduced facilitation for insect survival. 3. The presence of pollinators in Spain allowed most NPFWs to develop in figs containing males. Far more male-free figs were present in South Africa, elevating mortality rates among female NPFW. Facilitation of female release by males of the more common NPFW species nonetheless benefitted the rarer species. 4. In the absence of pollinators (and specialist parasitoids) selection in South Africa should favour greater aggregation of NPFW offspring into a smaller numbers of figs, a preference for shared figs and less female-biased offspring sex ratios. The system provides an opportunity to investigate the plasticity of