| 其他摘要 | In spite of several classification attempts within the genus Lepus, phylogenetic relationships still remain poorly understood. Here we present molecular genetic data that help sorts out some of the present incongruities in the phylogeny of the genus Lepus. The complete mitochondrial cytb, 12S genes, and parts of ND4 and control region genes were sequenced to examine phylogenetic relationships within Chinese hare taxa and other Leporids throughout the World using maximum parsimony, maximum likelihood and Bayesian phylogenetic reconstruction approaches. Using reconstructed phytogenies, we observed that the Chinese hare is not a single monophyletic group as originally thought. Instead, the data suggests that the genus Lepus is monophyletic with three unique species groups: North America, Eurasia and South Africa. The data also infers that the 29 Lepus species currently recognized as valid taxa is a gross overestimate of the number that actually exists. Ancestral area analysis indicated that ancestral Lepus arose in North America, and then dispersed into Eurasia via the Bering Land Bridge eventually reaching Africa. Brooks Parsimony analysis (BPA) showed that dispersal events followed by subsequent speciation have occurred in other geographic areas as well and resulted in the rapid radiation and speciation of Lepus. A Bayesian relaxed molecular clock approach based on the continuous autocorrelation of evolutionary rates along branches estimated the divergence time between the three major groups within Lepus. The genus speciation events occurred during the Pliocene epoch (4.29-5.39 MYA). We examined the genetic structure and phylogeographical patterns of the Yunnan hare {L. comus G Allen 1927) by using the first hypervariable domain of the mitochondrial control region genealogies obtained from 22 sampling localities to explain the geographical distributions of the mtDNA haplotypes in this species. A 505-base-pair (bp) segment of the mitochondrial control region was sequenced from 85 individuals representing three morphological recognized subspecies, L. c. comus, L c. pygmaeus and L c. pent. An analysis of molecular variance (AMOVA) shows significant genetic differentiation in the total samples and also between regions. There is a positive correlation between geographic distance and pairwise differences. Mismatch analysis did not indicate that the Yunnan hare populations experienced a recent range expansion. Nested clade analyses revealed significant associations between genetic structure and geographical division, thereby suggesting that restricted gene flow was a major phylogeographical event shaping the geographical distribution of the Yunnan hare in the Yunnan Plateau. Molecular phylogenetic analyses and population genetic structure suggest two subspecies of the Yunnan hare (L c. comus and ?. c. peni) Mitochondrial DNA control region sequence analysis was used to examine the phylogeographical patterns and population structure, the extant of genetic differentiation and their phylogenetic relationships within the timidus species complex (L timidus, L. othus^ L. arctic^ L. capensis and L corsicanus) in the Holarctic. Chinese samples were collected at twelve localities from the origin and distributional center of the Chinese cape hare according to previously comparative studies. Comparison with other Lepus species, the timidus species group has a relative low level of genetic variation. Based on the combined sequence data, phylogenetic analysis for the haplotypes of the timidus species group was constructed using Lepus comus and. L* oiostolus as outgroup. From the tree topology, two clades or phylogeographical groups were identified, and derived from a common ancestor about 0.806-0.242 million years (Myr) ago. However, of the two phylogeographical groups, no obvious phylogeographical structure existed due to the population expansion and the Bering Stait Land Bridge, and also no obvious physical barriers in Chinese mainland. Based upon mitochondrial cytochrome b gene sequence analysis, the history of true sheep Ovis began approximately 3.12 million years ago (MYA). The evolution of the genus Ovis has resulted in three generally accepted groups; namely, Argaliforms, Moufloniforms and Pachyceriforms. The Pachyceriforms of the subgenus Pachyceros comprise the thin-horn sheep 0. nivicola (snow sheep) and O. dalli and the Rocky Mountain bighorn 0. canadensis. North America wild sheep (0. canadensis and 0. dalli) evolved separately from Eurasian wild sheep and diverged from each other about L41 MYA. Ancestral stock that gave rise to snow sheep, Moufloniforms, and Argaliforms occurred 2.3 MYA, which then gave rise to two different extant lines of snow sheep which diverged from each other about 1.96 MYA. The more recent nivicola line is genetically closer to the North American wild sheep and may represent close association during the refugium when Alaska and Siberia were connected by the Bering Land Bridge. The earlier period of evolution of the Pachyceriforms suggest they may have first evolved in Eurasia, the oldest ancestor then giving rise to North American wild sheep, and that a canadensis-liko ancestor most likely gave rise to nivicola. Cytogenetic analysis further validates that the standard diploid number for modern nivicola is 52. Subspecies phylogeny among the argaliform wild sheep (Ovis ammori) has special interest due to its endangered species status and unresolved taxonomic classification. Using a molecular level approach, we fiirther clarify the phylogenetic relationships of several subspecies of ammon by comparing the sequences of mitochondrial DNA in the displacement (D)-loop region. Five putative subspecies of ammon (0. dalai-lamae, 0. darwini, 0. hodgsoni, 0. sairensis and 0. Httledalei) were sampled from four Chinese provinces [Xinjiang, Qinghai, Gansu and XiZang (Tibet)] and two (0. servertzovi and 0. nigrimontana) from Uzbekistan. These samples are representative of most of the currently recognized putative subspecies of argali. mtDNA fragments containing the entire D-loop (approximately 1,100 bases) were amplified by PCR and sequenced. Analysis of mtDNA sequences revealed high variability within ammon (77%), ranging in divergence from 2.4 to 11.52%. Phylogenetic relationships based on Maximum-likelihood (ML) infer that there are two major clades or clusters of argalis: one is the western clade from Uzbekistan and the other the eastern clade of China. Parsimony (MP) analysis show three subclades were identified within the Chinese clade. One subclade includes 0. a. sairensis and 0. a. Httledalei located in Tuoli, Bayinburuke of Xinjiang Prov.; the second subclade consists of only one subspecies (0. a. darwini) from Mazong Mountain, Gansu Prov.; and the third subclade consists of O. a. hodgsoni distributed in Dulan, Qinghai-Tibet plateur, and O. a. dalai-lamae Subei, Gansu Prov. |
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