Abstract
The genus Dendrobium was used as a case study to elucidate the evolutionary history of Orchidaceae in the Sino-Japanese Floristic Region (SJFR) and Southeast Asia region. These evolutionary histories remain largely unknown, including the temporal and spatial distribution of the evolutionary events. The present study used nuclear and plastid DNA to determine the phylogeography of Dendrobium officinale and four closely related taxa. Plastid DNA haplotype and nuclear data were shown to be discordant, suggesting reticulate evolution drove the species’ diversification. Rapid radiation and genetic drift appeared to drive the evolution of D. tosaense and D. flexicaule, whereas introgression or hybridization might have been involved in the evolution of D. scoriarum and D. shixingense. The phylogeographical structure of D. officinale revealed that core natural distribution regions might have served as its glacial refuges. In recent years, human disturbances caused its artificial migration and population extinction. The five taxa may have originated from the Nanling Mountains and the Yungui Plateau and then migrated northward or eastward. After the initial iteration expansion, D. officinale populations appeared to experience the regional evolutionary patterns in different regions and follow the sequential or rapid decline in gene exchange.
Highlights
Flowering plants provide superb cases for investigating evolutionary processes, and orchids are useful examples because of their extraordinary diversity[1]
The phylogenetic trees inferred from Maximum likelihood (ML) and Bayesian inference (BI) analyses were nearly identical with high support values and included two outgroup taxa (Fig. 2)
A significantly larger NST than GST value was estimated across all populations for the cpDNA datasets, which indicated that the genetic variation of D. officinale was geographically structured across its distributional regions (Table 1)
Summary
Dendrobium species are the important economic plant and distributed widely in the SJFR and Southeast Asia region, we used the genus Dendrobium as a case study to elucidate the evolutionary history of Orchidaceae in these two regions. We sought to elucidate the evolutionary and population demographic history of D. officinale, D. tosaense, D. flexicaule, D. scoriarum and D. shixingense. To determine the evolutionary history and expansion patterns of Orchidaceae in the SJFR and Southeast Asia region, the study had three specific objectives: 1) to illustrate the expansion model of D. officinale and infer the influence of the glacial period, 2) to determine the phylogeographical structure of D. officinale and explain the cause of its endangered status, and 3) to clarify the relationship between Dendrobium and its four relatives and elucidate the evolutionary history of five Dendrobium species
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