Fig. 1. The rate of cytochrome b evolution (Scytb) modulates the
relationships between body mass (M), basal metabolic rate (BMR),
mass-specific basal metabolic rate (BMRw) and longevity
(L) in Neognathae birds. Data are from Table S2 in supplementary
material. Linear regressions of the power laws for the 59 genera of Neognathae
birds for which there are complete cytochrome b sequences available,
and the M, L and BMRw values, are shown by solid lines.
Linear regressions of the genera with the lowest values of Scytb (the lower
quadrant of the rate distribution, Scytb<0.069, N=15, full
symbols) are shown by dotted lines. The linear regressions of the genera with
the highest values of Scytb (the upper quadrant of the rate distribution,
Scytb>0.1345, N=15, empty symbols) are shown by
dash–dot–dash lines. When the regression was not significant
(P>0.05) the lines were omitted. (A) lnBMR as a function of
lnM: for the Neognathae clade lnBMR=3.712+0.6633lnM
(N=59, r2=0.973, P<0.001); for the
high Scytb group lnBMR=3.283+0.8263lnM (N=15,
r2=0.903, P<0.001); for the low Scytb group
lnBMR=3.715+0.6663lnM (N=15, r2=0.942,
P<0.001). The difference in the slopes between the low Scytb group
0.666±0.046 and the high Scytb group 0.826±0.075 is significant
(P<0.001). The curves for the low Scytb and the whole clade are
nearly identical. (B) LnBMRw as a function of M:
for the whole clade lnBMRw=3.712–0.3373lnM
(N=59, r2=0.904, P<0.001); for the
high Scytb group lnBMRw=3.283–0.1743lnM
(N=15, r2=0.291, P=0.038); for the low
Scytb group lnBMRw=3.715–0.3343lnM (N=15,
r2=0.804, P<0.001). The difference in the
slopes between the low Scytb group, –0.334±0.046, and the high
Scytb group, –0.175±0.075, is significant. The curves for the low
Scytb and the whole clade are nearly identical. (C) lnL as a function
of lnM: for the whole clade
lnL=1.742+0.193xlnM (N=59,
r2=0.473, P<0.001); for the high Scytb group
lnL=1.616+0.27xlnM (N=15,
r2=0.058, P=0.384); for the low Scytb group
lnL=2.23+0.153xlnM (N=15,
r2=0.551, P=0.002). (D) lnL as a
function of BMRw: for the whole clade
lnL=3.733–0.513xlnBMRw (N=59,
r2=0.417, P<0.001); for the high Scytb group
lnL=3.63–0.451xlnBMRw (N=15,
r2=0.017, P=0.643); for the low Scytb group
lnL=3.859–0.408xlnBMRw (N=15,
r2=0.547, P=0.002).