Telling the Evolutionary Time: Molecular Clocks and the Fossil Record

Table 1.3

Normalized rates of evolution of GPDH, G6PD, PGD, SOD, TPI, and XDH for increasingly remote lineages

The species compared are listed in

Figure 1.1

. The plus/minus values are crude estimates of error for myr. Rate values are expressed in units of 10

−^10

per site

per year. Averages across loci are obtained by weighing the rate of each gene by the length of its sequence (i.e. 0.15, 0.23, 0

.13, 0.07, 0.05, and 0.

37,corresponding to 241, 367, 208, 107, 78, and 599 residues of GPDH, G6PDH, 6PGDH, SOD, TPI, and XDH, respectively); averages

for rows two,

three, and four are taken across the proteins in

Table 1.2

(i.e. ADH, AMD, DDC, GPDH, SOD, and XDH). The rates are estimated using the

α

values

obtained from the global dataset given in

Table 1.1

.

a For the comparison between the

melanogaster

group species in

Figure 1.1

.

b For the comparison between

Drosophila

and

Calliphora

assuming that the two dipteran families diverged at 120 Ma.

MOLECULAR CLOCKS: WHENCE AND WHITHER? 19