Phylogeography of Camellia taliensis (Theaceae) inferred from chloroplast and nuclear DNA: insights into evolutionary history and conservation

Abstract

BackgroundAs one of the most important but seriously endangered wild relatives of the cultivated tea, Camellia taliensis harbors valuable gene resources for tea tree improvement in the future. The knowledge of genetic variation and population structure may provide insights into evolutionary history and germplasm conservation of the species.ResultsHere, we sampled 21 natural populations from the species' range in China and performed the phylogeography of C. taliensis by using the nuclear PAL gene fragment and chloroplast rpl32-trnL intergenic spacer. Levels of haplotype diversity and nucleotide diversity detected at rpl32-trnL (h = 0.841; π = 0.00314) were almost as high as at PAL (h = 0.836; π = 0.00417). Significant chloroplast DNA population subdivision was detected (GST = 0.988; NST = 0.989), suggesting fairly high genetic differentiation and low levels of recurrent gene flow through seeds among populations. Nested clade phylogeographic analysis of chlorotypes suggests that population genetic structure in C. taliensis has been affected by habitat fragmentation in the past. However, the detection of a moderate nrDNA population subdivision (GST = 0.222; NST = 0.301) provided the evidence of efficient pollen-mediated gene flow among populations and significant phylogeographical structure (NST > GST; P < 0.01). The analysis of PAL haplotypes indicates that phylogeographical pattern of nrDNA haplotypes might be caused by restricted gene flow with isolation by distance, which was also supported by Mantel’s test of nrDNA haplotypes (r = 0.234, P < 0.001). We found that chlorotype C1 was fixed in seven populations of Lancang River Region, implying that the Lancang River might have provided a corridor for the long-distance dispersal of the species.ConclusionsWe found that C. taliensis showed fairly high genetic differentiation resulting from restricted gene flow and habitat fragmentation. This phylogeographical study gives us deep insights into population structure of the species and conservation strategies for germplasm sampling and developing in situ conservation of natural populations.

Thirteen Camelliachloroplast genome sequences determined by high-throughput sequencing: genome structure and phylogenetic relationships

“…Cp-derived markers, e.g. rpl16 gene , psbA-trnH, trnL-F and rpl32-trnL intergenic spacer (IGS), were employed to study evolutionary relationships between tea plants [8,16]. Repetitive sequences within the cp genomes are also potentially useful for ecological and evolutionary studies of plants [17].…”

Genetic diversity and domestication origin of tea plant Camellia taliensis(Theaceae) as revealed by microsatellite markers

“…However, C. taliensis (W. W. Smith) Melchior, an important plant for use in producing tea, has only been recognized outside of its native areas for a few decades [22,23]. Several studies have investigated the genetic diversity of wild and planted trees of C. taliensis [24-26], and some have detected a reduction in chloroplast DNA (cpDNA) diversity during domestication [25,26]. But none of these studies has given more details on the domestication origin of this plant.…”

“…About a dozen years ago, due to the high price that ‘wild tea’ commanded in the local market, a large number of C. taliensis trees in the natural forest were cut down to collect leaves [24,26]. And the phenomena of directly domesticating wild C. taliensis trees by clearing out the other plants on a parcel of natural forest and keeping only specimens of C. taliensis (Figure 1d) or digging out the wild trees and planting them in gardens (Figure 1e) had been found locally.…”

EPSPS variability, gene expression, and enzymatic activity in glyphosate-resistant biotypes of Digitaria insularis

“…In contrast, the PAL gene and the intergenic spacer gene fragment rpl32-trnL were used to study the population structure and phylogeography of Camellia taliensis (Liu et al, 2012). In the 21 studied natural populations of C. taliensis (Theaceae), moderate genetic differentiation, restricted gene flow through seeds, and historical habitat fragmentation were found (Liu et al, 2012).…”

“…In the 21 studied natural populations of C. taliensis (Theaceae), moderate genetic differentiation, restricted gene flow through seeds, and historical habitat fragmentation were found (Liu et al, 2012). Traditionally, DNA regions such as rbcL, matK, and trnL-F were used to obtain a phylogenetic tree for the Poaceae family (Bouchenak-Khelladi et al, 2008), including the Digitaria, Echinochloa, and Panicum genera.…”