Host specificity of gall midges (Diptera: Cecidomyiidae) on ten species of inga (Fabaceae)

Abstract

Studies of host specificity in gall-inducing Cecidomyiidae are hindered by the difficulties encountered in obtaining adult stages, which are essential for species identifications, and even when adults are reared from galls, the vast majority of species are undescribed. For this reason gall morphotypes (morphospecies based on the extended phenotype) are commonly used as a surrogate for species. We used this methodology to examine the host-specificity of gall-inducing Cecidomyiidae associated with ten species of Inga, one of the most species-rich genera of trees in the Neotropics. A total of 5,756 galls were collected, which were conservatively classified into 30 gall morphotypes. Species richness of gall-inducers was highest on I. oerstediana, with 14 morphospecies. Thirteen cecidomyiid morphospecies were restricted to just one species of Inga. Of the 17 morphospecies found on more than one species of Inga, only three were restricted to a single section of the genus. We discuss possible reasons for these results, as well as the complications involved in using gall morphotypes as a surrogate for species.