Structural conservation and variation in the mitochondrial control region of fringilline finches (Fringilla spp.) and the greenfinch (Carduelis chloris

We sequenced the entire control region and portions of flanking genes (tRNAPhe, tRNAGiu, and ND6) in the common chaffinch (Fringilla coelebs), blue chaffinch (F. teydea), brambling (F. montifringilla), and greenfinch (Carduelis chloris). In these finches the control region is similar in length (1,223-1,237 bp) and has the same flanking gene order as in other birds, and contains a putative TAS element and the highly conserved CSB-1 and F, D, and C boxes recognizable in most vertebrates. Cloverleaf-like structures associated with the TAS element at the 5′ end and CSB-1 at the 3′ end of the control region may be involved with the stop and start of D-loop synthesis, respectively. The pattern of nucleotide and substitution bias is similar to that in other vertebrates, and consequently the finch control region can be subdivided into a central, conserved G-rich domain (domain II) flanked by hyper- variable 5′-C-rich (domain I) and 3′-AT-rich (domain III) segments. In pairwise comparisons among finch species, the central domain has unusually low transition/transversion ratios, which suggests that increased G+T content is a functional constraint, possibly for DNA primase efficiency. In finches the relative rates of evolution vary among domains according to a ratio of 4.2 (domain III) to 2.2 (domain I) to 1 (domain II), and extensively among sites within domains I and II. Domain I and III sequences are extremely useful in recovering intraspecific phylogeographic splits between populations in Africa and Europe, Madeira, and a basal lineage in Nefza, Tunisia. Domain II se- quences are highly conserved, and are therefore only useful in conjunction with sequences from domains I and III in phylogenetic studies of closely related species.

H.D. Marshall and A.J. Baker, Mol. Biol. Evol., Feb 1997; 14:173-184