ABSTRACT
The ability to sense and respond to chemical stimuli in the environment was a fundamental evolutionary development. Many complex insect behaviors, including foraging, host seeking and selection, feeding, oviposition, nesting, hygiene, mating, and kin selection behaviors, are mediated by the chemical senses. Research during the last decade is revealing an equally complex molecular genetic and neural system for detecting and discriminating chemical stimuli. Much of the recent progress toward understanding the molecular mechanisms of the chemical senses has been facilitated by the whole genome sequence of Drosophila melanogaster completed in 2000 (Adams et al. 2000). For the rst time, insect chemoreceptor (Cr) genes were identied using bioinformatics tools to search the fruit y genome (Clyne et al. 1999; Gao and Chess 1999; Vosshall et al. 1999). The rapid advance of whole genome sequencing is helping to extend this progress broadly to nonmodel and emerging model species such as the silkworm Bombyx mori (Goldsmith, Shimada, and Abe 2005; see Chapter 2 for silkworm genomics). The rst drafts of the silkworm genome sequence were published in 2004 (Mita et al. 2004; Xia et al. 2004), providing an insight into the chemoreceptor sequences of the Lepidoptera (Wanner et al. 2007; Wanner and Robertson 2008). Although this eld is progressing rapidly, it remains in its infancy. When an insect genome is sequenced, one of the rst steps toward chemosensory research is the annotation of its chemoreceptors. Almost all species of Lepidoptera are herbivorous and therefore represent a large proportion of the insect pests of food and ber crops worldwide. An analysis of Lepidoptera Cr genes will not only provide interesting insights into the evolution of plant host interactions (see Chapter 11 for evolution of host range), but it will also provide new gene targets for the development of insect management tools. In this chapter we will review the phylogenetics of the lepidopteran Cr superfamily within the broad context of knowledge gained from D. melanogaster research.
