What fig wasp sex ratios may or may not tell us about sex allocation strategies

Fig wasps (Hymenoptera. Agaonidae) have been widely utilized in studies of sex ratio evolution, especially local mate competition (LMC), and good fits have been obtained between empirical data;ind model predictions incorporat ing LMC and inbreeding effects. These models assume that foundress females within a patch (a fig) oviposit synchronously, producing roughly equal numb ers or offspring with the same progeny sex ratios. Working with the fig was p Eupristina belagaumensis, which pollinates the fig tree Ficus drupacea in India, we investigated whether these assumptions valid. and then produced an alternative model which incorporates revised biological assumptions. Egg loads at adult emergence were compared with those remaining in females aft er they had completed their egg-laying and had died. As foundress numbers i ncreased. so did variation in the numbers of eggs which the females managed to lay. In multi-foundress figs certain females (most likely the first one s to enter) often contributed almost complete egg loads while others (which may have entered when most of the oviposition sites had been utilised) con tributed relatively few eggs. Assumptions of previous models were therefore violated. Our model assumes totally sequential oviposition by foundresses and differential contributions to broods. The predicted overall sex ratios of the fig wasp progeny are qualitatively similar to models based on LMC an d inbreeding effects, despite being based on different biological assumptio ns. suggesting that previous models may have given the right answers for th e wrong reasons. Explicit tests between the models are possible. as the seq uential oviposition model predicts that the progeny sex ratios of individua l foundresses should vary depending on where in the sequence they enter a f ig.