Beyond mutations at the domain and protein level, regulation of protein expression provides another vital mechanism through which protein networks can evolve. Microarray studies are now well under way to map genome-wide ex-pression levels of related and non-related genes under a variety of conditions [91, [94] [95] [96] . For example, transcriptional comparisons have investigated aging [106] and pathogenicity [107] . Unfortunately, given the highly variable nature of gene expression and the fact that different species may respond different to external stimuli, such comparisons can only be performed under strictly controlled research conditions. To date most studies have therefore focused on the embryogenesis, metamorphosis, sex-dependency and mutation rates of subspecies [94, [108] [109] [110] [111] . Other studies have revealed valuable information on promoter types and duplication events [91] [92] [93] [94] .