In recent years, several highly sensitive molecular markers have been developed to study the genetic structure of aphid natural populations and in several cases, the genetic variation has been associated with strong differential selection by different plant hosts.
Mitochondrial DNA has been frequently used to assess genetic diversity in many insect species, so that at present it is considered as a highly competent tool for the distinction between insect host races, even in the presence of gene flow at the genomic level. Indeed, the absence of mtDNA divergence between insect populations is consistent with the hypothesis of ongoing maternally derived gene flow, while mtDNA differentiation between races indicates that gene flow is restricted.
A recent paper published by Mezghni-Khemakhen and colleagues reported, using DNA barcoding, the occurrence of two haplotypes of the aphid Aphis spiraecola in association with the host-plant (Rutaceae vs Rosaceae). The present work revealed evidence for patterns of genetic structuring within A. spiraecola populations related to their host-plants, suggesting a possible host race status. This result, implying a limited gene flow between A. spiraecola populations from Rosaceae and Rutaceae, could be considered in the development of an integrated controlling strategy. Nevertheless, such a host race status has to be confirmed by further research involving host–plant transfer experiments to quantify the feeding preference and performance of insects.
Maha MEZGHANI-KHEMAKHEM, Dhia BOUKTILA, Imen KHARRAT, Mohamed MAKNI, Hanem MAKNI (2012). Genetic variability of green citrus aphid populations from Tunisia, assessed by RAPD markers and mitochondrial DNA sequences. Entomological Science, 15, 171-179.