Predators of Fig Wasps

Abstract

Predators inflict high mortality on the four species of wasps associated with the fig Ficus pertusa L. in Monteverde, Costa Rica. Because one of these wasps is the obligate pollinator of the fig, predation may have a strong impact on successful pollen donation by the plant. The natural histories of several predators are described: an ant that feeds on wasps arriving to oviposit, moth and weevil larvae that destroy wasps as they develop within the fruits, a staphylinid beetle that feeds on mature wasps before they leave the fruits, and a group of birds that gleans wasps as they leave. The synchrony of arrival and departure of pollinators from the fig trees probably make them the species least vulnerable to predation. FIGS (Ficus SPP.) AND THEIR POLLINATOR WASPS form a keystone (Gilbert 1980), an interaction upon which other species depend and around which they accumulate. The dependence of frugivorous birds (Snow 1981, Beehler 1985), bats (Heithaus et al. 1975, Morrison 1978), and primates (Raemaekers 1979, Milton 1980, Terborgh 1983) on ripe figs is well known. Several insects (Smilanick & Ehler 1976, Janzen 1979, Frank 1983) and birds (Janzen 1981) are major seed predators when fruits are still on the tree, and a large group of lygaeid bugs feeds exclusively on seeds of fallen figs (Slater 1972). Such interactions have a major impact on the female reproductive function of seed production in figs. Less well known are species that interact with the mutualism via their impact on the pollinator wasps (Hymenoptera: Chalcidoidea: Agaonidae), and thus potentially limit the figs' male reproductive function of pollen donation. The larvae of certain chalcidoid wasps are known to kill developing agaonid larvae (Kuttamathiathu 1955, Galil & Eisikowitch 1968), and ants (Frank 1983), dragonflies, and birds (Janzen 1979) have been observed to prey upon adults. Here I describe the suite of insects and birds that are major predators of four wasp species associated with one Costa Rican fig, and speculate on the extent to which they specialize on fig wasps. I then consider how great an impact predation has on the pollinator species, and thus indirectly on the fig itself. STUDY SITE AND NATURAL HISTORY Ficus pertusa, a small (5-12 m), hemiepiphytic or freestanding tree, is one of the two most common Ficus species in Central America (Condit 1969). It is found from 0 to 2000 m in moist highland to lowland forests and savannas and in both disturbed and undisturbed habitats (Burger 1977). F. pertusa grows abundantly in pastures and remnant patches of primary and secondary forest throughout the community of Monteverde, Costa Rica, located just below the Continental Divide on the Pacific slope of the Cordillera de Tilaran (10?12'N, 84?42'W, elevation 13501450 m). Undisturbed forest in the area is transitional between lower montane wet and moist forest (Holdridge