Chloroplast DNA phylogeography ofCunninghamia konishii(Cupressaceae), an endemic conifer of Taiwan

Abstract

In this study, we investigated the genetic structure and phylogeographic pattern of the genus Cunninghamia, a member of the Cupressaceae restricted to mainland China and Taiwan, based on sequences of the trnD-trnT noncoding spacer of the chloroplast DNA. Maternal inheritance of chloroplasts was determined experimentally. No paternal leakage was detected. Both parsimony and neighbor-joining analyses revealed the polyphyly of Cunninghamia konishii, populations of which were nested in clades of C. lanceolata from mainland China. The nucleotide diversity of chloroplast DNA sequences within C. konishii (0.0118) was higher than that between species (0.0104), which agrees with a previous allozyme investigation. Based on mutational differences between sequences, a minimum spanning network consisting of five clades was constructed. Significant genetic differentiation (phiST = 0.130, P < 0.001) was detected between the clades based on AMOVA analyses. We infer several possible refugia in the Yunnan, Zhejiang, and Guangdong provinces of south China, all located in the minimum network as interior nodes. We also infer possible migration routes of Cunninghamia populations. The phylogeographic pattern shown in the reconstructed network suggests that the present-day Cunninghamia populations in Taiwan were derived from six different sources in continental Asia via long-distance seed dispersal. A migrant-pool model explains the heterogeneous composition of the organelle DNA in Taiwan's populations and the low differentiation between populations of Taiwan and China (phiCT = 0.012, P = 0.454). In contrast with the genetic heterogeneity within geographic populations, many local populations have attained coalescence at the trnD-trnT alleles, which has led to significant differentiation at the population level.

Paraphyly of organelle DNAs in Cycas Sect. Asiorientales due to ancient ancestral polymorphisms

“…Nevertheless, multiple colonization and recent isolation can counter forces leading to genetic differentiation between islands and monophyly [20]. Many plants distributed on the island arcs of the western Pacific Rim, including Cunninghamia [40], Michelia [41], Kandelia [42], Trema [43] and Lithocarpus [32,44], show little differentiation. Coalescence in island populations can be a complicated process, determined by counteracting effects of isolation (i.e., historical connection), gene flow, drift, selection and repeated colonization.…”

Spatial and temporal population genetic variation and structure of Nothotsuga longibracteata (Pinaceae), a relic conifer species endemic to subtropical China

“…Although subtropical China has never been covered by ice sheets during the Quaternary, it has been suggested that the development of cooler and drier climates may have influenced the distribution and evolution of many plants in China and further leaded to the extinction or disappearance of some important species (Lu et al , 2001; Shen et al , 2005). The mountain regions including the Nanling and the adjacent Wuyi and Daiyun mountains in southern China have served as the main refugia regions for plant surviving and evolving during climatic oscillations (Ying, 2001; Wang and Ge, 2006).…”

“…The mountain regions including the Nanling and the adjacent Wuyi and Daiyun mountains in southern China have served as the main refugia regions for plant surviving and evolving during climatic oscillations (Ying, 2001; Wang and Ge, 2006). For example, during glacial expansion many previously dominant conifers in the northern part of East Asia were forced to migrate southwards into scattered refugia existing in small patches across mountain regions of southern China (Lu et al , 2001). Ying (2001) localized three regions (the Hengduan range, the Central China and the Lingnan region) with high levels of plant diversity and endemism in China.…”

Species Occurrence, Hybridization and Speciation in Postglacial East and South Asia

“…The ancestral populations of T. radicans were able to migrate across the Bering Straits via a land bridge connection between North America and Asia. After that, the ancestral population separated into two paths: one from Sakhalin to Japan or via the Korean Peninsula to Japan, and one from the north to the south via Siberia which then separated into several paths of scattered refugia in Yunnan, Szechwan, Guizhou, Hunan, Hubai, Fujian and Taiwan (cf Lu et al 2001;Ge et al 2005). The genetic drift effected those isolated populations and promoted the process of speciation in various geographic regions.…”