Relict Species: Phylogeography and Conservation Biology
When geographic groups were tested separately, mismatch distribution of the populations in southwestern China produced a unimodal value Fig 3D , which showed that populations in this region experienced range expansion. A Total China. B South of Mt. C North of Mt.
D Southwestern China. We proposed that these seven populations could be designated as the priority protected units of B. There are two possible explanations for this phenomenon.
On one hand, relict plant species with a long evolutionary history may have accumulated a large amount of genetic variation [ 50 , 51 ]. On the other hand, the wide geographic range of B. In contrast, high diversity of B. A similar result was produced by AMOVA analysis, which showed that almost all of the variation existed among, rather than within, populations. Low genetic diversity within populations, combined with strong population differentiation, revealed that the B.stamnodedi.tk
Relict Species : Phylogeography and Conservation Biology
The 23 natural populations investigated in our field survey occurred in isolated and fragmented locations. Range fragmentation may have reduced effective population size and gene flow, and consequently led to low genetic diversity within populations and strong genetic differentiation across the species.
Population differentiation resulted from urbanization-caused range fragmentation has been documented for several other relict species with a geographic range similar to B. Short-distance dispersal in B. The seeds of B. We did not observe animals feeding on the B. Population differentiation of the chloroplast genome was found to be strongly influenced by the mode of seed dispersal in different ways, and species with seeds dispersed by gravity showed higher genetic differentiation than those with wind-dispersed seeds [ 26 ], consistent with the strong genetic differentiation observed in B.
There are several criteria for the recognition of glacial refugia: they must have harbored both ancestral and endemic haplotypes [ 56 ]; they must possess high levels of genetic diversity; and they must have had comparatively stable ecological conditions during periods of environmental fluctuation, which made the accumulation of genetic diversity possible [ 29 , 57 ].
Coalescent theory maintains that older alleles occupy interior nodes of a haplotype network [ 58 ].
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In our network of 13 haplotypes, D, E, and F were the most interior and can be considered as ancestral Fig 1B. To solve such a problem, a better sampling for B. Populations in this area possess high levels of both nucleotide and haplotype diversity. In addition, all of the haplotypes found in this area C, D, and E, of which D and E are ancestral are endemic in the East Yungui Plateau Fig 1B , which is located in the southeast of Qinghai-Tibet Plateau, south of Qinling Mountains, suggesting that the East Yungui Plateau may have been less influenced by the Neogene and Quaternary glaciations than other geographic areas in China.
The Yungui Plateau and its adjacent regions have long been considered an important center of origin for other members of the East Asiatic flora [ 59 ]. These species include Eurycorymbus cavaleriei [ 19 ], Ginkgo biloba [ 29 ], and Cunninghamia konishii [ 62 ], etc. The East Yungui Plateau is also a refugium for several taxa of Sapindaceae, a family that is closely related to Akaniaceae, as represented by Handeliodendron bodinieri and Eurycorymbus cavaleriei [ 19 ].
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Furthermore, we discovered that the southeastern part of Yunnan Province and its adjacent regions, where the PB population is found, is another glacial refugium of B. Although we did not detect particularly high nucleotide or haplotype diversity in this area, haplotype F, one of the most ancestral, occurred here.
This area, with its historically temperate and humid climate, which is conducive to the preservation of ancient plants, may be another center of relict species [ 63 ]. Whereas PB is the only population being collected in Yunnan, a scenario of multi-refugia in this province may be implied. For example, Hengduan Mtn. The Nanling Mountains and adjacent regions, where six populations of B. This area does, however, harbor high levels of nucleotide and haplotype diversity. Four haplotypes G, H, I, J occur in this area and all are endemic. One possible explanation the high genetic diversity observed in this region may have resulted from genetic admixture after dispersal from adjacent regions.
According to the abovementioned inference, Bretschneidera sinensis may have the following history of population dynamics see Fig 4. The East Yungui Plateau refugium may be the source of populations from southeastern Hunan and Hubei provinces. After last glacial period in Quaternary, evergreen broadleaf forest in South China reached its flourish. Mismatch distribution analysis in southwestern China shows that populations in the East Yungui Plateau refugium had undergone range expansion under the circumstances.
Contrarily, populations from the Mt. Nanling and mountains in Taiwan may be derived from the other refugium, southeastern Yunnan, after its initial eastern colonization of B. Letters below the colorful circles in the map stand for the population names; different colorful circles are to distinguish the haplotypes see Legend ; Three larger circles stands for refugia; arrows indicate possible migration directions.
Haplotype A, which is not an ancient haplotype, occurs throughout most populations from the Mt. Nanling and Mt. Wuyi, providing strong support for a postglacial range expansion from a single refugium to its present range. The network of haplotypes shows that haplotype A is closely related to haplotype K, which is closely related to the ancestral haplotype F found in eastern Yunnan Province.
Thus, eastern Yunnan is likely a source for the colonization of B. Postglacial dispersal and range expansion also occurred in other relict plants in China, such as Cercidiphyllum [ 64 ], Davidia [ 65 , 66 ], Euptelea [ 67 ] and Tetracentron [ 68 ]. Thus, we recommend these populations to be the priority conservation units for this species. These seven populations exhibit the following characteristics.
Table of Contents: Relict species : phylogeography and conservation biology
If these populations become extinct, the diversity of B. Thirdly, several populations HZ and CY exhibit high genetic diversity. Protection of these populations could best preserve the diversity of this species to the maximum extent possible. Fortunately, most populations of B. Finally, the seven priority populations can be used for ex situ conservation. Given the high degree of among-population differences in genotype, it is likely that genetic diversity will increase substantially by the exchange of genetic materials that takes place among those populations.
We are grateful to the various organizations and individuals who provided information, suggestions, and help in field and lab work. We would like to give special thanks Dr. Jun Wen, Dr. Li-ping Gao, and Dr.
Ren-chao Zhou for their useful comments and English corrections to this manuscript, Miao-fang Lin and Xiao-qing Tang for embellishing the figues. Browse Subject Areas? Click through the PLOS taxonomy to find articles in your field. Abstract Bretschneidera sinensis , a class-I protected wild plant in China, is a relic of the ancient Tertiary tropical flora endemic to Asia. Introduction Bretschneidera sinensis Hemsl. Download: PPT. Table 1.
PCR amplification and direct sequencing An initial screen for DNA sequence variability of various chloroplast markers using universal primers was conducted on four individuals from geographically disjunct populations [ 32 — 40 ]. Table 2.
The data analyses included the following four aspects: Genetic diversity and genetic structure analysis. Haplotype genealogy reconstruction. Population history dynamic analysis. Evaluation of priority protection units. Results cpDNA sequences and haplotypes of B. Genetic diversity and spatial patterns of cpDNA variation The haplotype diversity h of all populations, excluding sites with gaps, was 0.
Table 3. Geographic distribution of cpDNA haplotypes The geographic distribution of the 13 haplotypes identified in the 23 populations is shown in Fig 1A. Phylogenetic relationships among haplotypes of B. Fig 2. Neighbor-joining tree for haplotypes of Bretschneidera sinensis in China. Table 4. Neutral tests of all Bretschneidera sinensis populations and geographic regions.
Fig 3. Mismatch distribution analysis of Bretschneidera sinensis among different biogeogrphical groups. Table 5. H values for Bretschneidera sinensis. Discussion Genetic diversity and population differentiation in B. Refugia, demographic history and phylogeographic implications There are several criteria for the recognition of glacial refugia: they must have harbored both ancestral and endemic haplotypes [ 56 ]; they must possess high levels of genetic diversity; and they must have had comparatively stable ecological conditions during periods of environmental fluctuation, which made the accumulation of genetic diversity possible [ 29 , 57 ].
Possible migration and expansion routes of Bretschneidera sinensis in China. Acknowledgments We are grateful to the various organizations and individuals who provided information, suggestions, and help in field and lab work. References 1. Lu AM. The geography of spermatophytic families and genera.
Beijing: Science Press; The families and genera of Angiosperms in China: A comprehensive analysis. Parasitology Research , 8 , — Plant ecology 5: AoB Plants 8: plw; doi International Journal for Parasitology , doi. Biological journal of the Linnean Society, 2 , Book of abstracts.