Host Specificity of Fig Wasps (Agaonidae)

Studies of New World figs have shown that each species of fig (about 40) collected in Venezuela, Panamá, Costa Rica, San Andrés Island, México, and Florida has its own specific pollinator, with the exception of Ficus tuerckheimii which is always the host of two species of Blastophaga and the equivocal case of F. costaricana. Furthermore it was found that the two subgenera of New World figs each has its own group of related pollinators; Pharmacosycea is the host of Tetrapus wasps, while Urostigma is the host of Blastophaga. It is also well known that in the Old World each species of fig has its own agaonid symbiont, with only a few known exceptions (in which one species of fig is the host of two agaonids). Furthermore, each group of related figs (sections, subsections, series and subseries) has its own group of related pollinators. Hybrids are not common in figs. That each species of fig requires its own pollinator is revealed by the inability of species of figs introduced into new areas to set viable seeds when their symbionts are absent. Introduced figs begin producing seeds only when their specific pollinators are established. The relationship, one species of fig-one species of wasp, has evolved as a result of reciprocal development of features which favor monotropism. The conformation of the ostiole and size of styles in each species of fig, and the conformation of the head, especially of the mandibles, mandibular appendages, size of the ovipositor in each species of wasp and the presence of corbiculae to carry pollen in many Agaonidae (Ramírez, 1969) are apparently the most remarkable events associated with monotropism in Ficus and agaonids. Accounts are given of the few known cases of agaonids entering "wrong" figs. The theory is put forward that there is a causal relation between the closed pollinating mechanism of Ficus and the extraordinary amount of speciation (900 + species) found in the genus.