Molecular and Ecological Aspects of Heliothis Armigera

Abstract

The species status and host range of Heliothis armigera was investigated. DNA profiling, mitochondrial DNA sequencing, RAPD's, along with traditional morphological and crossing methods were used to investigate micro, macro and mega-population structuring. Thirty-six new host records were added, of which a number are important common weeds and crops. Mortality due to parasitoids and fungal infections were quantified on many host species. Genetic analysis of the COII and the AT-rich regions of the mitochondrial DNA showed very high levels of variation, as did the DNA profiling using the probes (CA)n and 33.15. The morphological analyses also showed variation, but to a lesser degree and without statistical significance. The variation found at all levels and in all aspects is discussed with respect to caterpillar host-plants and geographical location. All host-plant populations of caterpillars showed very high levels of genetic variability. However, the population of caterpillars found on Sulla (Hedysarium coronarium) was significantly more variable than those found on Lotus and Lucerne when compared using DNA profiling. The sequences obtained from the two mtDNA regions also showed considerable variation, a great percentage of which was uninformative. This variation did not allude to any structuring of caterpillar populations with respect to host-plant or geographical location. H. armigera is genetically a very variable species which does not equate with any population structuring present in the host-plant or geographical populations investigated here. This study has greatly increased the general understanding of this insect, and has elucidated a portion of the genetic makeup, but not helped in the development any new control methods.