18. Glaciation and Avian Evolution
281
2.2 Intraspecific Analyses
Data for the Song Sparrow comprise 700 bp of the "control region" for 95 individuals sampled from throughout the breeding range (Fry and Zink 1998). Computation of nucleotide diversity (n) and the neighbor joining (NJ) tree is described in
Fry and Zink (1998). We computed a mismatch distribution, defined as the distribution of pairwise raw sequence differences between all pairs of 95 individuals. We
computed the mismatch distribution expected for an exponentially growing population as a poisson distribution with the same mean as the observed distribution
(Slatkin and Hudson 1991). We compared distributions with a Kolmogorov-Smirnov
one-sample test. On the NJ tree we computed the In number of lineages vs. time,
with time taken as the overall mtDNA distance (Nee et al. 1995).
3 Results
3.1 Interspecific Analyses
The LRT for the molecular clock revealed no evidence of deviations from clocklike sequence evolution (In-likelihood with clock = 6788.0, without clock = 6773.2,
X = 29.6, df = 19, P > 0.05). The average gamma-K2P distance was 7.1 % (Table 1).
Use of either calibration (Fig. 2) provides no support for the LPO model; over 90%
of values exceed 500,000 years.
if! 5
ro
Pleistocene
0..
· . . . . . . . . . . ~i
1.6%/MY
'" 4
Cl>
i3
~ '3
if)
a
Q;
2
.c 1
E
::l
Z
2
3
4
5
6
7+
7
6
if!
' ro
0..
'" 4
3.5%/MY
Cl>
i3
Cl>
3
a.
if)
Fig. 2. Divergence dates
a 2
Cii
(data from Table 1) plotted
.c 1
E
according to calibrations
::l
z
for songbirds (top) and
2
3
4
5
6
7+
galliform birds (bottom)
Estimated Divergence Times (Millions of years)