Adaptive radiation and diversification in gall‐inducing insects in the Indian subcontinent: search for a pattern

Abstract

The most striking behaviour among gall-inducing insects is that a majority of them are specialist organisms that display a high level of fidelity to their host plants. In a context of discussing species diversity among and richness of gall-inducing insects, this paper attempts to discuss the patterns of adaptive radiation evident in different gall-inducing insects of the Indian subcontinent, which is characterized by profound geological, vegetation, and climatic variations. As a case study, in this paper I have analyzed and discussed patterns of adaptive radiation apparent in gall-inducing Cecidomyiidae on Indian Anacardiaceae with a particular reference to Mangifera indica. The possible absence of resistance-breaking genes in Indian Cecidomyiidae on different Anacardiaceae and M. indica explains why these elements have not radiated and diversified as aggressively as the gall-inducing Eulophidae have done on different Eucalyptus taxa introduced into India as commercial plantation crops. Alternatively, the host-plant populations are, in high likelihood, restricting the gene flow between specific gall-midge populations, through their secondary chemistry because, the host-plant mediated impediments on the breeding behaviours impact on the radiation of gall-inducing insects. A significant majority of Indian gall-inducing insects show features of conservative diversification, and based on available evidence their conservative diversification appears to be strongly plant mediated. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)