| 其他摘要 | The montane regions of southwestern China are characterized by complicated
geological and climatic history. Previous phylogeographic studies found that genetic
structures of species related to lotic environment from this region are consistent with
paleo-river system or contemporary river system, and historical geologic events such
as the uplift of Qinghai-Tibetan Plateau are the main factors that leading to the lineage
divergences of amphibian species from southwestern montane regions. Same
geological events may have same impact on sympatric species, but genetic structure
of species is also affected by its life history and ecological trait. To investigate the
effects of drainage system and climatic change during Quaternary on genetic structure
and lineage divergence of amphibian species from montane regions of southwestern
China, patterns of genetic variation in Babina pleuraden and Tylototriton shanjing,
both of which are endemic to southwestern China, are investigated based on
mitochondrial DNA in this study.
Fragments of Cyt b and COI genes of 262 individuals from 22 populations of B.
pleuraden and Fragments of Cyt b, D-loop, tRNA-Phe, and 12S rRNA genes of 146
individuals from 19 populations of T. shanjing were examined in this study. Our
results demonstrated that B. pleuraden is comprised of five distinct mitochondrial
lineages roughly corresponding to five geographical areas including western Yunnan,
northwestern Yunnan, central Yunnan, eastern Yunnan, and southwestern Sichuan, and
divergence among them occurred 0.36‒2.44 Mya. Its phylogeographic structure has
been shaped primarily by the unique regional responses of the Yunnan Plateau to the
rapid uplift of the Qinghai-Tibetan Plateau occurred c. 2.5 Mya (B phrase of
Qingzang Movement) and climatic oscillation during middle Pleistocene (0.36‒0.64
Mya), rather than by the paleo-drainage system. Tylototriton shanjing is comprised of
four maternal lineages corresponding to four population groups including southern
Yunnan, middle-western Yunnan, northwestern Yunnan, and the border region of
western Yunnan with Myanmar, and divergence of them occurred 0.71‒0.83 Mya.The paleo-drainage system also had no contribution to the current genetic structure of
T. shanjing and major glaciation events during the Pleistocene have triggered its
intra-specific divergence. Likely the reason that the paleo-river system had no impact
on genetic structures of B. pleuraden and T. shanjing is the preference for standing
water of these two species.
Coalescent simulations supported that B. pleuraden retreated to three refugia
located in northwestern Yunnan, central Yunnan, and eastern Yunnan, respectively,
and T. shanjing retreated to four refugia located in southern Yunnan, northwestern
Yunnan, the border region of western Yunnan with Myanmar, and middle-western
Yunnan, respectively, during glacial periods in the Pleistocene. Some of these regions
(e.g., northwestern Yunnan, southern Yunnan, and eastern Yunnan) have also been
suggested as glacial refugia for other species, meaning that these regions should be
important for consideration when developing sound conservation policies. Both B.
pleuraden and T. shanjing experienced population expansion and expansions occurred
prior to the Last Glacial Maximum (0.018‒0.023 Mya), reflecting the asynchronicity
between glaciations of the montane regions in southwestern China and Northern
Hemisphere glaciation events and complexity of topography, geomorphology, and
climate in montane regions of southwestern China. In addition, T. shanjing
experienced declines of population sizes, which occurred after the beginning of the
Last Glacial Maximum.
Results in the present study suggest that phylogeographic studies of species with
different life histories and ecological traits are necessary to completely understand the
phylogeographic patterns and their shaping mechanisms of amphibian species in
montane regions of southwestern China from a perspective of comparative
phylogeography. |
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