Molecular Evolutionary Genetics Of The Baiji, Finless Porpoise And Tiger

Both PCR directed DNA sequencing method and silver staining DNA sequencing techniques are applied to determine partial sequence of mitochondrial cytochrome b gene of the baiji, three subspecies of finless porpoise and two subspecies of tiger. Together with other published relative DNA sequence data, phylogeny of these taxa are analyzed by using appropriate program in software package PHYLIP.Total DNA is extracted from tissue preserved under -20X3 for a period of as short as several months to as long as 7 years, specific fragment of gene sequence can be successfully amplified, and also can be sequenced by silver staining DNA sequencing techniques. The results suggest that, it is not necessary to preserve tissues under strict conditions, and it is able to determine specific gene sequence of species both within short time and at lower expense.The difference of cytochrome b gene seqences between P. t. altaica and P. t. amoyensis is 1.53% (5/324bp), between P. t. altaica and P. tigris (Arnason et al., 1995) is 1.53% (5/534bp), between P. t. altaica and P. t. sumatrae is 6.79% (22/324bp); the difference between P. t. amoyensis and P. tigris (Arnason et al., 1995) is 3.09% (10/324bp), between P. t. amoyensis and P. t. sumatrae is 8.02% (26/324bp). On the basis of nucleotide substitutions, the divergences of P. t. altaica from P. t. amoyensis are estimated to have occurred around 0.61 million years ago.Among the three specimens of the baiji, no sequence difference is detected between LVE1 and LVE2, however the sequence of LVE3 has two nucleotide substitutions, they are C→T at 14989 site and C→A at 15022 site. The sequence difference of cytochrome b gene between Lipotes vexillifer and Inia geoffrensis is 17.18% (56/326bp), and between L. vexillifer and Neophocaena phocaenoides is 15.03% (49/326bp). Two phylogenetic trees, constructed by using sequence data, suggest that Lipotes vexillifer does not share a direct common ancestor with Inia geoffrensis, thus provide molecular evidence in favor of the establishment of family Lipotidae; extant river dolphins might be a group of (?)es with...