Figure 1.1 Tree topology for the species used in this study. Labels and numbers on the branches
represent taxonomic categories and divergence times, respectively. Nicotiana and Scaptomyza
species are N. tabacum for G6pd and N. plumbaginifolia for Sod; S. adusta for Amd, Ddc, and Sod; and S.
albovittata for Adh. a: Gpdh sequences from Kwiatowski and Ayala (1999); b: Ddc sequences from
Tatarenkov et al. (1999).
MOLECULAR CLOCKS: WHENCE AND WHITHER? 9