Sc. Lougheed et al., MITOCHONDRIAL-DNA HYPERDIVERSITY AND VOCAL DIALECTS IN A SUBSPECIES TRANSITION OF THE RUFOUS-COLLARED SPARROW, The Condor, 95(4), 1993, pp. 889-895
The Rufous-collared Sparrow, Zonotrichia capensis, is widely distribut
ed in neotropical America and shows extensive variation in its learned
song. In northwestern Argentina it exhibits song dialects which map c
losely onto the distribution of natural vegetation assemblages. To dat
e, there is no evidence of a correlation between genetic (allozyme) va
riation and dialects. However, recent genetic structuring produced thr
ough philopatry and assortative mating by dialect is difficult to demo
nstrate statistically with such protein-encoding nuclear genes. Theref
ore, we assayed variation in more rapidly evolving mitochondrial DNA a
long a 50 km transect, which spans three dialect boundaries between fo
ur adjacent habitat-types (from similar to 1,800 m to similar to 3,000
m), using restriction fragment length polymorphism analysis. This rev
ealed exceptional diversity (41 clones from 42 individuals), a level c
omparable with DNA-fingerprinting, and higher than reported in any pas
serine over such a small area to date. The degree of nucleotide diverg
ence between the two main clusters of mtDNA haplotypes implies a separ
ation time in excess of one million years. The mtDNA variability is no
t related to song dialects; rather it is interpreted as a reflection o
f secondary introgression between two well-differentiated subspecies w
hose ranges about in this region.