THE STRUCTURE OF A TROPICAL HOST PARASITOID COMMUNITY

1. A parasitoid web is a subset of a food web containing data on parasitoids and their hosts; connectance parasitoid webs embody information only about the presence or absence of an interaction, while quantitative parasitoid webs include information about the relative densities of all species.

2. Connectance and quantitative parasitoid webs are described for a community of leaf-mining insects and their parasitoids in regrowth tropical dry forest in Costa Rica. The webs were centred on a study site that contained 88 species of plants, 92 species of leaf miners and 93 species of parasitoids.

3. An average of 1.22 species of miner were found per species of plant, with more species on monocots than on plants with other growth forms. Leaf-miners were highly host-specific.

4. An average of 32% mortality of leaf-miners was caused by parasitoids; dipteran miners were more heavily attacked than lepidopteran species, with coleopteran miners the least attacked. The number of parasitoid species per host was strongly influenced by sample size with no evidence of an asymptote as sample size increased. Host breadth of parasitoid species was strongly influenced by mode of parasitism (ectoparasitism versus endoparasitism).

5. The parasitoid web did not appear to be compartmentalized. Examination of the quantitative web suggested that a number of different forms of indirect interaction between host species may occur. There was also evidence that some species in the web may have a major influence on system dynamics by virtue of their numerical preponderance.