Abstract
Genetic diversity is vital to the sustainable utilization and conservation of plant species. Rhododendron rex subsp. rex Lévl. is an endangered species endemic to the southwest of China. Although the natural populations of this species are facing continuous decline due to the high frequency of anthropogenic disturbance, the genetic information of R. rex subsp. rex is not yet elucidated. In the present study, 10 pairs of microsatellite markers (nSSRs) and three pairs of chloroplast DNA (cpDNAs) were used in the elucidation of the genetic diversity, population structure, and demographic history of 11 R. rex subsp. rex populations. A total of 236 alleles and 12 haplotypes were found. A moderate genetic diversity within populations (HE = 0.540 for nSSRs, Hd = 0.788 for cpDNA markers), high historical and low contemporary gene flows, and moderate genetic differentiation (nSSR: FST = 0.165***; cpDNA: FST = 0.841***) were detected among the R. rex subsp. rex populations. Genetic and geographic distances showed significant correlation (p < 0.05) determined by the Mantel test. The species exhibited a conspicuous phylogeographical structure among the populations. Using the Bayesian skyline plot and species distribution models, we found that R. rex subsp. rex underwent a population demography contraction approximately 50,000–100,000 years ago. However, the species did not experience a recent population expansion event. Thus, habitat loss and destruction, which result in a population decline and species inbreeding depression, should be considered in the management and conservation of R. rex subsp. rex.
Highlights
Rhododendron is the largest woody plant genus in Ericaceae, containing more than 1000 recognized species, of which 567 species representing six subgenera are known from China [1]
We identified 169 alleles at polymorphic loci among R. rex subsp. rex populations, ranging from eight (R-40, R-49) to 30 (R-30), with an average of 16.9 alleles per locus ()
Sequences showed that three reciprocally lineages were detected. This species possessed unique genetic lineages and endemic Chloroplast DNA (cpDNA) haplotypes in its separate refuge populations
Summary
Rhododendron is the largest woody plant genus in Ericaceae, containing more than 1000 recognized species, of which 567 species representing six subgenera are known from China [1]. Wild Rhododendron species are the major components of alpine and subalpine vegetation and widely distributed in America, Europe, and Asia, which have tropical to polar climates [2,3]. These species are Plants 2020, 9, 338; doi:10.3390/plants9030338 www.mdpi.com/journal/plants. Plants in the genus Rhododendron L. produce numerous chemical constituents and are recognized as an important source of bioactive phytochemicals [5]. Research on the population genetic information of Rhododendron species is undoubtedly beneficial for germplasm protection and sustainable utilization [6,7,8,9]
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