Phylogenetic Researches On 21 Passerine Species Based On Cytochrome-b Gene Sequences

Passeriformes is the largest group in aves. It has broad adaptive radiations in the nature. The origin and evolution of Passeriformes have been major arguments in ornithology. With the advantages of molecular systematics, more and more schlors tend to use molecular systematic methods in avian phylogenetic researches. In this research, we applied DNA sequencing method to study the phylogeny and evolution of 21 passerine species. Partial cytochrome b gene sequences of these birds were sequenced and analyzed. Also, phylogenetic trees were constructed using Mega 3. The results are as follows:1. Nuclear mitochondrial pseudogene copies probably exsited in marsh tit (Parus palustris). Also, in grey-backed thrush (Turdus hortulorun) and coal tit(Parus ater), abnormal fragments were amplified out. But it needs further studies to verify what these abnormal fragments are.2. The characteristics of partial cytochrome b gene sequences (455bp) are as follows: average base frequencies of T, C, A and G are 24.2%, 32.2%, 28.5% and 15.1%, respectively; total frequency of G and C is 47.3%; there are strong base usage bias in the third coden sites with total frequency of A and C being 86.4% and G's frequency 2.7%; transtions and transversions are the major types of nucleotide substitutions and the number of transtions are larger than that of transversions; the average ratio of transtions to transversions is 1.5; the ratios of transtions to transversions in the first and third coden sites are 2.3 and 1.3 and there are no transversions in the second coden sites; there are also strong bias in the synonymous coden usage; the overall genetic distance between sequences is 0.176.3. The results show that fringillids and emberizids should be listed into two families (Fringillidae and Emberizidae), not two subfamilies; also the muscicapids, turdids, long-tailed prrids, sylviids and prunellids should all be listed into families. Through the constructions of phylogenetic trees, the interfamiliar rlationships were defined as follows:( ( Muscicapidae, Turnidae), ( ( ( Aegithalidae, Sylviidae ), Paridae), ( (1) ( Prunelldae, (Emberizidae, Fringillidae))))).4. A new sunfamily- Coccothraustinae is suggested to be founded parallel to Fringillnae and Carduelinae.5. The substitution rates of major clades are thought to be the same according to relative rate tests. The divergence time of major clades is estimated at the rate of 2% per million years. Thus the estimated divergence time of Fringillidae and Emberizidae is 8.0 million years, Muscicapidae and Turnidae 8.0 Myr, Aegithalidae and Sylviidae 9.3 Myr, Coccothraustinae and Carduelinae 7.3 Myr, Pallas's rosefinch and long-tailed rosefinch 5.0 Myr, two outgroups 12.4 Myr.