Low genetic diversity and significant pedigree differentiation
characterize the evolutionary history of Camellia drupifera in China
Camellia drupifera is a main tea-oil Camellia species, and understanding
its genetic variation, origin and evolution will facilitate protection
and utilization of its genetic resources. However, the differentiation,
genetic variation, origin and evolution of C. drupifera remains unknown.
Here, SRAP markers and chloroplast sequences of 32 C. drupifera
populations were used to determine genetic variation and differentiation
and infer the origin and evolutionary history of the species. Genetic
diversity is low (H=0.200, Hd=0.861, Pi=0.00238), with obvious pedigree
geographical structure among populations (Nst=0.612, Gst=0.117). Genetic
differentiation is high (Gst=0.400, SRAP; Fst=0.68080, cpDNA), but gene
exchange is low (Nm = 0.749 for nrDNA, Nm = 0.358 for cpDNA). The
phylogenetic tree and PCA showed that this differentiation is mainly due
to separation of the Hainan Island and mainland populations.
Geographical isolation and island effects caused the pedigree structure,
with large genetic differentiation, and reduced genetic diversity.
STRUCTURE analysis revealed that compared with the Hainan Island
population, the mainland population has a single genetic background. The
TCS network showed that H17 was the original haplotype on Hainan Island;
the H41 haplotype was important in the expansion of C. drupifera from
Hainan Island to mainland China. Haplotype historical dynamics revealed
expansion of the Hainan Island populations (Tajima’s D=-2.31467**, Fu’s
Fs=-2.45270*). Comprehensive analysis suggests that C. drupifera
originated on Hainan Island and expanded its range to mainland China.
These results provide a scientific basis for the protection, development
and utilization of C. drupifera resources and a good example of how
geographic isolation and island effects can drive plant lineage