Molecular Mechanisms Underlying Insect Adaptation
Diamondback Moth, Plutella xylostella
Insecticide application can provide the ultimate selective pressure on targeted pests: death upon exposure or survival through the evolution of resistance. The research in my laboratory focuses on;
- identifying mutations that cause insecticide resistance
- determining their fitness costs
- measuring genetic diversity after selection for resistance
Diamondback moth, Plutella xylostella, is a worldwide pest of brassica crops, which include cabbage, broccoli and canola(oilseed rape). They are often the first insect species to evolve resistance to new insecticides in the field (e.g. DDT, Bt toxins), so they are a good model for studying molecular mechanisms of resistance. Identifying the genetic mutations that cause resistance in diamondback moth enables parallel mechanisms to be investigated in other pest species.
Figure 1. P. xylostella (A) larvae feeding on cabbage and (B) a pupae nearly ready to eclose.
Neo-tropical Heliconius butterflies display striking wing phenotypes that are often convergent between unrelated species. The best example is probably between Müllerian mimics H. melpomene and H. erato, which share very similar wing pattern phenotypes where their ranges overlap (e.g. Figure 2).
Geographic races of H. melpomene display incredible phenotypic diversity across South America, and these bright patterns deter predator attack and are used as mating signals. Wing patterns are controlled by few loci of major effect, and we are currently analysing whole genome sequences of individuals to identify key regulatory elements controlling the evolution of these phenotypes.
Figure 2. Müllerian mimics H. melpomene and H. erato east of the Ecuadorian Andes.
The H. melpomene hybrid, collected by Dr. P. Salazar, displays a combination of patterns found in pure breeding populations.