| Summary: | 碩士 === 國立中山大學 === 生物科學系研究所 === 102 === Speciation is an important issue in evolutionary biology and species complex is a good model to test the pattern of speciation. Keteleeria (Pinaceae) is an Asian gymnosperm genus and restricted to subtropical to north tropical hill regions of South China, Taiwan, and Hainan. Fossil records have been wild distributed in Northern Hemisphere. Current distribution indicates that apparently affected by Quaternary climate shifts and almost extinction. The definition of species is difficult to consensus because taxonomists had different opinions based on morphological similarities. In this study, we build a transcriptome based on high-throughput Illumina RNA-seq sequencing technique using K. davidiana var. formosana as target taxa. We surveyed sequence variation for 4 chloroplast (cp) DNA fragments, and 27 nuclear genes among 91 individuals sampled from 12 taxa of Keteleeria.
The assignment test based on STRUCTURE show the best clustering was assumed at K=2, DE group in Yunnan and other species include in FP group. The RASP based on S-DIVA indicates the divergence because vicariance events and IMa suggesting low level of gene flow (2.7-8.7 ∗ 10-8) among group. The divergence time estimates c. 3.3-0.5 mya, a timescale with recent uplift of Qinghai-Tibet Plateau and the formation Hengduan Mountains. Pleistocene glaciation in Hengduan Mountains is relatively warm and rainy, became a refuge of DE group. FP group associated with the extinctive species of North America, and the refugia of glaciation located in Guizhou and Guangxi that have high genetic diversity of species. The RASP analysis inferred species expansion from west to east and north to south in southeast China.
Keteleeria davidiana var. formosana in Taiwan and K. hainanensis in Hainan have unique genotype in assignment test respectively. Two species suggesting low level of gene flow (1.55-9.3 ∗ 10-10, 26-1.6 ∗ 10-10), small effective population size (70-270 k, 12-6 k), diverged c. 70 and 18 ka with FP group by IMa and the vicariance events inferred by RASP. The period of continental shelf was almost free of marine influence, these islands provided refugia for northern species that migrated south during glacial periods. Keteleeria revealed species evolving through glacial cycles and caused separation, migration, and extinction as well as accelerating speciation.
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