Resource defence in female pollinating fig wasps: two's a contest, three's a crowd

Female pollinating fig wasp (foundress) reproduction is often reduced when multiple foundresses oviposit in figs, owing to oviposition site limitation or the extra time spent searching for unused sites. In species where foundresses cannot re-emerge from figs (meaning that all reproduction takes place in a single fig), they might therefore be expected to defend sites from competitors. For the first time, we explicitly documented defence by foundresses. Larger Platyscapa awekei foundresses (pollinators of Ficus salicifolia) in two-foundress figs prevented smaller foundresses from ovipositing by holding them in their mandibles while ovipositing themselves, and deposited the same number of eggs as when ovipositing in isolation. Smaller foundresses deposited around 30% fewer eggs. The onset of defence in two-foundress figs depended on larger foundress body size, implying that they made decisions based on their own size relative to the population mean (i.e. the average probability of being successful). Defence was less common in three- than in two-foundress figs, probably because the presence of a third competitor reduced the benefits accrued. We discuss why foundresses use such tactics, and identify other species in which defence may occur. Qualitative behavioural observations and comparative morphology suggest that defence is common, occurring in four pollinator genera. (C) 2003 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.