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1.
Dai-Chang Kuo Chia-Chia Lin Kuo-Chieh Ho Yu-Pin Cheng Shih-Ying Hwang Tsan-Piao Lin 《Conservation Genetics》2010,11(3):803-812
Cinnamomum kanehirae Hayata (Lauraceae), the most valuable subtropical and temperate broadleaf timber tree in Taiwan, is rapidly disappearing
from the wild. Taking advantage of a scion garden established by the Taiwan Forestry Research Institute, we examined patterns
of chloroplast DNA (cpDNA) variations in 19 populations including 94 individuals. By sequencing two cpDNA fragments using
universal primers (the trnL-trnF and petG-trnP intergenic spacers), we found eight polymorphic sites, six haplotypes, and extremely low nucleotide diversity (π = 0.00016) from 792 bp aligned sequences. The ancestral haplotype is widely distributed. Among the populations studied, three
separated populations, at Yungfeng, Fuli, and Tahu have high nucleotide diversity. No phylogeographical structures of haplotypes
were revealed because the tests of N
ST−G
ST for populations did not differ from zero in any situations; a ‘star-like’ genealogy is characteristic when all haplotypes
rapidly coalesce and is a general outcome of population expansion. The neutrality test also suggested demographic expansion.
The genetic divergence and diversity analyses suggested that two potential refugia existed during the last glaciation with
a major one located in southeastern Taiwan and a minor one located in Tahu in north-central Taiwan in the Hsuehshan Range,
west of the Central Mountain Range. 相似文献
2.
Xun Gong Shan-Shan Luan Kuo-Hsiang Hung Chi-Chuan Hwang Chung-Jean Lin Yu-Chung Chiang Tzen-Yuh Chiang 《Journal of plant research》2011,124(2):221-230
Nouelia insignis, an endangered species, is distributed in the Jinsha and Nanpan drainage areas in southwestern China. In this study, we examined
the genetic diversity and population structure based on the sequences of the cpDNA rpL 16 intron. Low levels of genetic variation were detected within all populations of the endemic species. A gene genealogy
of 11 haplotypes recovered two major lineages I and II, with haplotypes H1 and H6 nested as interior nodes, respectively.
Haplotype H1 was widespread in all populations, while haplotype H6 was restricted to populations southern of the Jinsha River.
Low levels of genetic differentiation were detected, as most F
st values between populations were zero. This result, however, contradicts previous studies based on allozymes and fingerprinting.
Genetic analyses suggested that coancestry due to low evolutionary rates resulted in the lack of geographical subdivision.
Molecular dating estimated that the two lineages split about 3.224 MYA (95% CI 1.070–6.089 MYA). Maintenance of ancestral
polymorphisms was possibly attributable to a long-standing large effective population size until recently. Postglacial demographic
expansion was supported by a unimodal mismatch distribution and star-like phylogenies. 相似文献
3.
Elena V. Artyukova Marina M. Kozyrenko Peter G. Gorovoy Yury N. Zhuravlev 《Genetica》2009,137(2):201-212
Microbiota decussata Kom. (Cupressaceae) is a subalpine species endemic to the Sikhote Alin Mountains with populations scattered throughout the
range. We used sequence data for four noncoding regions of chloroplast DNA to characterize the genetic diversity in populations
sampled from different parts of M. decussata natural range. No variation was observed in the trnT–trnF region, whereas the trnH–psbA, trnS–trnfM, and trnS–trnG regions showed polymorphisms. At the species level, we found a low nucleotide diversity (π = 0.0009) and high haplotype diversity
(h = 0.981) as well as high differentiation (ΦST = 0.420). N
ST and G
ST values suggested the existence of a phylogeographic structure in M. decussata. The observed patterns of diversity could be explained in part by ecological features of the species and its long-term persistence
throughout the range with population expansion, successive fragmentation and isolation. 相似文献
4.
A thorough understanding of the levels and partitioning of genetic variation across populations and geographical regions of endangered species is a prerequisite to ensure effective conservation and/or restoration activities. Here, we examined chloroplast DNA (cpDNA) trnH-psbA intergenic spacer sequences variation within Notopterygium forbesii, an endangered and endemic perennial herb in China. Sequence data obtained from 141 individuals in 14 populations revealed twenty-two haplotypes. A high level of haplotype diversity (Hd = 0.81) and low level of nucleotide diversity (Pi = 0.0047) were detected. Low genetic differentiation among populations and also among regions was consistently indicated by both hierarchical analyses of molecular variance (AMOVA) and the structure of a neighbor-joining tree. Low level of population differentiation between populations or between regions in cpDNA sequences may be due to effects of the abundance of ancestral haplotype sharing and the high number of private haplotypes fixed for each population. Based on our results, we proposed some conservation strategies. 相似文献
5.
Yoshinari Moriguchi Kyu-Suk Kang Kab-Yeon Lee Seok-Woo Lee Yong-Yul Kim 《Journal of plant research》2009,122(2):153-160
Genetic variation associated with Picea jezoensis populations of South Korea was investigated using chloroplast (cp), mitochondrial (mt) and nuclear DNA markers. In South
Korea, P. jezoensis is distributed across a very restricted area, being found on the summits of three mountains: Mts. Jiri, Dokyu and Gyebang.
Examination of five region restriction enzyme combinations for mtDNA and four for cpDNA revealed haplotypes endemic to South
Korea. The Gyebang population, the most northerly and most isolated, was genetically distinct from the other populations.
Nuclear microsatellite markers indicated, overall, a low level of genetic diversity (H
e = 0.406) in South Korea; this could be attributed to genetic drift and/or founder effects associated with historical events.
The Wilcoxon sign-rank test did not indicate a recent bottleneck in any of the populations irrespective of the model considered
(infinite allele model, two-phased model of mutation, and stepwise mutation model). Microsatellite markers also demonstrated
that the Gyebang population was distinct from the others. The results of this study could be used as the basis for conservation
guidelines for the management of this species in South Korea. 相似文献
6.
A. Mohanty J. P. Martín I. Aguinagalde 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2000,100(8):1304-1310
High chloroplast DNA (cpDNA) diversity was found within and among populations of Prunus spinosa sampled from seven European deciduous forests. A study of 12% of the total chloroplast genome detected 44 mutations, which
were distributed over 24 haplotypes; four were common to two or more populations and the rest were unique haplotypes. The
most-abundant and widely distributed haplotype was H2 (frequency = 41% approximately). Six of the seven populations were polymorphic.
All of the six polymorphic populations had ”private” haplotypes (frequency < 5%) in addition to common haplotypes. The UPGMA
dendrogram demonstrated a correlation between populations and their geographical locations. The total diversity was high (hT = 0.824) and a major portion of it was within populations (hs = 0.663). The level of population subdivision for unordered alleles was low (GST = 19.5%) and for ordered alleles was lower (NST = 13.6%). No phylogeographic structure could be demonstrated in the present geographical scale. High polymorphism in the cpDNA
of P. spinosa has to be considered carefully when planning phylogenetic studies involving this species.
Received: 20 September 1999 / Accepted: 10 November 1999 相似文献
7.
Laura J. Pollock Michael J. Bayly Paul G. Nevill Peter A. Vesk 《Journal of Biogeography》2013,40(1):155-167
Aim To relate genetic diversity to topographic features and to investigate genetic interactions between Eucalyptus species in a local centre of endemism and diversity in south‐eastern Australia. Location Grampian Ranges, Victoria, Australia. Methods We documented chloroplast DNA (cpDNA) variation for a group of endemic Eucalyptus species (E. serraensis, E. verrucata and E. victoriana) that dominate rocky, high‐elevation ridgelines of the Grampian Ranges and for one closely‐related, widespread species (E. baxteri) occupying flanking slopes and valleys. We documented genetic patterns across the landscape using cpDNA microsatellites, and related them to topographic features (exposed west‐facing versus protected east‐facing slopes and valleys). We also determined the extent of local haplotype sharing between populations of endemic species and neighbouring E. baxteri downslope with cpDNA microsatellites, and haplotype sharing between the endemic group and more distantly related species (E. obliqua, E. pauciflora and E. willisii) with sequences of the JLA+ chloroplast region. Results We detected 26 cpDNA microsatellite haplotypes in a relatively small area of c. 20 km × 50 km. Populations of E. baxteri on east‐facing slopes and valleys had greater cpDNA microsatellite diversity than E. baxteri and endemic species on exposed west‐facing slopes. Endemic species frequently shared chloroplast haplotypes with E. baxteri downslope. Sharing of JLA+ haplotypes with species outside the endemic group was mostly restricted to E. victoriana, which had cpDNA more similar to the species from other sections of Eucalyptus (E. obliqua, E. willisii and E. pauciflora). Main conclusions Intensive sampling of related species on small isolated mountain ranges allowed us to relate genetic diversity to fine‐scale habitats and to document extensive local haplotype sharing between species. This study contributes to a general understanding of the environmental conditions that enable plant population persistence by linking concentrations of genetic diversity to particular habitats. 相似文献
8.
Berchemiella wilsonii var. pubipetiolata (Rhamnaceae) is an endangered tree in eastern China. Habitat destruction has resulted in fragmentation of remnant populations
and extinction of local populations. AFLP and cpDNA markers were used to determine the population structure of remnant populations
of B. wilsonii var. pubipetiolata. Moderate nuclear genomic diversity was found within each of the four remnant populations (H
S = 0.141–0.172), while the cpDNA haplotype diversity in each population ranged from 0.356 to 0.681. Six haplotypes were identified
by a combined cpRFLP and cpSSR analysis in a total of 89 individuals. AMOVA revealed significantly AFLP genetic differentiation
within and between regions (ΦSC = 0.196, ΦCT = 0.396, respectively), and a high cpDNA haplotype differentiation between regions (ΦCT = 0.849). The results suggest low gene flow between populations of B. wilsonii var. pubipetiolata. Strong genetic divergence between two regional populations as revealed by both AFLP and cpDNA markers provided convincing
evidence that two distinct evolutionary lineages existed, and should be recognized as ‘evolutionary significant units’ (ESUs)
for conservation concerns. 相似文献
9.
The population genetic variation of the tetraploid species Oxytropis chankaensis Jurtz. (Fabaceae), a local endemic of the western coast of Khanka Lake (Primorye), was examined. Five populations were analyzed using 28 isozyme loci encoding 16 enzyme systems. Significant allelic heterogeneity among the populations was found for six out of twelve polymorphic loci. The heterozygosity of the samples (total sample size 294 plants) H e = 0.301 was considerable higher than the mean values in populations of endemic species (0.076). Based on the results of this study, we identified two groups of O. chankaensis populations (southern and northern), in spite of the absence of marked hiatus between them. Of special interest is the population from Przhewalski Spit, which is a natural reserve of genetic diversity of the species and the putative center of formation of the autotetraploid O. chankaensis. 相似文献
10.
Ren‐Bin Zhu Qing Wang Wen‐Bin Guan Yanjia Mao Bin Tian Ji‐Min Cheng Yousry A. El‐Kassaby 《Ecology and evolution》2019,9(6):3251-3263
Genetic structure and major climate factors may contribute to the distribution of genetic diversity of a highly valued oil tree species Xanthoceras sorbifolium (yellowhorn). Long‐term over utilization along with climate change is affecting the viability of yellowhorn wild populations. To preserve the species known and unknown valuable gene pools, the identification of genetic diversity “hotspots” is a prerequisite for their consideration as in situ conservation high priority. Chloroplast DNA (cpDNA) diversity was high among 38 natural populations (Hd = 0.717, K = 4.616, Tajmas’ D = ?0.22) and characterized by high genetic divergence (FST = 0.765) and relatively low gene flow (Nm = 0.03), indicating populations isolation reflecting the species’ habitat fragmentation and inbreeding depression. Six out of the studied 38 populations are defined as genetic diversity “hotspots.” The number and geographic direction of cpDNA mutation steps supported the species southwest to northeast migration history. Climatic factors such as extreme minimum temperature over 30 years indicated that the identified genetic “hotspots” are expected to experience 5°C temperature increase in next following 50 years. The results identified vulnerable genetic diversity “hotspots” and provided fundamental information for the species’ future conservation and breeding activities under the anticipated climate change. More specifically, the role of breeding as a component of a gene resource management strategy aimed at fulfilling both utilization and conservation goals. 相似文献
11.
Zhou HF Zheng XM Wei RX Second G Vaughan DA Ge S 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2008,117(7):1181-1189
The cross compatible wild relatives of crops have furnished valuable genes for crop improvement. Understanding the genetics
of these wild species may enhance their further use in breeding. In this study, sequence variation of the nuclear Lhs1 gene was used to investigate the population genetic structure and gene flow of Oryza rufipogon and O. nivara, two wild species most closely related to O. sativa. The two species diverge markedly in life history and mating system, with O. rufipogon being perennial and outcrossing and O. nivara being annual and predominantly inbreeding. Based on sequence data from 105 plants representing 11 wild populations covering
the entire geographic range of these wild species, we detected significantly higher nucleotide variation in O. rufipogon than in O. nivara at both the population and species levels. At the population level the diversity in O. rufipogon (Hd = 0.712; θ
sil = 0.0017) is 2–3 folds higher than that in O. nivara (Hd = 0.306; θ
sil = 0.0005). AMOVA partitioning indicated that genetic differentiation among O. nivara populations (78.2%) was much higher than that among O. rufipogon populations (52.3%). The different level of genetic diversity and contrasting population genetic structure between O. rufipogon and O. nivara might be explained by their distinct life histories and mating systems. Our simulation using IM models demonstrated significant
gene flow from O. nivara to O. rufipogon, indicating a directional introgression from the annual and selfing species into the perennial and outcrossing species. The
ongoing introgression has played an important role in shaping current patterns of genetic diversity of these two wild species.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
12.
Commiphora wightii is a medicinally important endangered species endemic to the Thar Desert of Rajasthan, India and adjoining areas of Pakistan.
The populations of this species are declining sharply because of its extensive use as a natural herb. Random amplified polymorphic
DNA analysis was conducted to find the genetic variation among 7 populations of C. wightii. Of the 100 random primers screened, 44 primers yielded 220 loci. Statistical analysis indicated low genetic diversity (H
pop = 0.0958; I = 0.1498; mean polymorphic loci = 14.28%), and high genetic differentiation among the populations (G
ST = 0.3990; AMOVA Φ
ST of 0.3390; Bayesian θ
(II) = 0.3002). The low genetic diversity may be due to geographic isolation and restricted gene flow (N
m = 0.7533) between the fragmented populations. Unsustainable utilization of the plant has fragmented the population continuum
which served the purpose of genetic exchange between populations. Mantel’s test was performed which revealed a highly significant
positive correlation between genetic and geographic distance (r
2 = 0.614, P = 0.023) among the populations studied. Low variation can also be attributed to poor seed setting and the slow growth pattern
of the species, which is also an apomict. In UPGMA dendrogram the Commiphora wightii samples were divided into two major and one minor cluster. These findings can serve as a guide to preserving the genetic
resources of this medicinal plant species. 相似文献
13.
P. Abellán J. Gómez-Zurita A. Millán D. Sánchez-Fernández J. Velasco J. Galián I. Ribera 《Conservation Genetics》2007,8(1):79-88
Saline inland waters are globally threatened habitats harbouring many specialised endemic species, which often have restricted
geographic ranges, and occur as highly isolated populations. We studied the genetic variation and phylogeography of Ochthebius glaber Montes and Soler, a rare and endangered water beetle endemic to hypersaline streams in the South and Southeast of the Iberian
Peninsula. We used a 633 bp fragment of cytochrome oxidase subunit 1 gene to determine the genetic diversity and phylogeographic
structure within this species, and interpret this in the light of the speciesȁ9 conservation requirements. Thirteen populations
were sampled across the speciesȁ9 geographic range, and genetic diversity found to be very high, with 37 haplotypes across
the 71 specimens examined (p-distance 0.2–7.3%, average 3.1±0.4). Phylogeographic analyses revealed a surprisingly high degree of geographical structure,
detectable among populations separated by relatively short geographical distances, with three main groups of haplotypes which
have apparently been isolated for significant periods of time. Past fragmentation and contiguous range expansion events were
inferred as the main causes of the detected geographical associations of haplotypes. The establishment of independent evolutionary
lineages as conservation units is particularly important for species inhabiting saline habitats such as O. glaber, which is endangered by habitat loss across most of its distribution. However, given the natural instability of hypersaline
environments, the conservation of a network of populations and potential habitats would be necessary to enable the preservation
of the process generating and maintaining the diversity of the species. 相似文献
14.
In this paper we addressed the phylogeographical genetic structure of the economically important red shrimp, Aristeus
antennatus (Crustacea, Aristeidae) in the Western Mediterranean. Partial mitochondrial regions of the cytochrome c oxidase subunit I
(514 bp) and ribosomal 16S subunit (547 bp) were sequenced in 137 individuals collected at three localities: Catalan Sea,
Ligurian Sea and the southern Tyrrhenian Sea. Values of haplotypic diversity were h = 0.552–0.724, whereas those for nucleotide diversity were π = 0.0012–0.0026. Among-sample genetic diversity was not significant and no geographical patterns in the distribution of haplotypes
were apparent. Results of the present study are consistent with a past population expansion that occurred <2,000 years ago.
Despite the current fishing pressure, genetic variability appears to be sufficiently high to keep A. antennatus populations stable over time. Dispersal-related life history traits may account for the shallow genetic structure. Our results
are not in contrast with the hypothesis of sustainability of Western Mediterranean red shrimp fisheries predicted on the basis
of previously obtained biological results. 相似文献
15.
Ling‐Xiao Ying Ting‐Ting Zhang Ching‐An Chiu Tze‐Ying Chen Shu‐Jin Luo Xiao‐Yong Chen Ze‐Hao Shen 《Ecology and evolution》2016,6(9):2805-2816
The beech species Fagus hayatae is an important relict tree species in subtropical China, whose biogeographical patterns may reflect floral responses to climate change in this region during the Quaternary. Previous studies have revealed phylogeography for three of the four Fagus species in China, but study on F. hayatae, the most sparsely distributed of these species, is still lacking. Here, molecular methods based on eight simple sequence repeat (SSR) loci of nuclear DNA (nDNA) and three chloroplast DNA (cpDNA) sequences were applied for analyses of genetic diversity and structure in 375 samples from 14 F. hayatae populations across its whole range. Both nDNA and cpDNA indicated a high level of genetic diversity in this species. Significant fixation indexes and departures from the Hardy–Weinberg equilibrium, with a genetic differentiation parameter of Rst of 0.233, were detected in nDNA SSR loci among populations, especially those on Taiwan Island, indicating strong geographic partitioning. The populations were classified into two clusters, without a prominent signal of isolation‐by‐distance. For the 15 haplotypes detected in the cpDNA sequence fragments, there was a high genetic differentiation parameter (Gst = 0.712) among populations. A high Gst of 0.829 was also detected outside but not within the Sichuan Basin. Consistent with other Fagus species in China, no recent population expansion was detected from tests of neutrality and mismatch distribution analysis. Overall, genetic isolation with limited gene flow was prominent for this species and significant phylogeographic structures existed across its range except for those inside the Sichuan Basin. Our study suggested long‐term geographic isolation in F. hayatae with limited population admixture and the existence of multiple refugia in the mountainous regions of the Sichuan Basin and southeast China during the Quaternary. These results may provide useful information critical for the conservation of F. hayatae and other Chinese beech species. 相似文献
16.
Evonnildo C. Gon?alves Stephen F. Ferrari Tibério César T. Burlamaqui Leonardo Miranda Marcelo S. Santos Artur Silva Maria Paula C. Schneider 《Journal of Ornithology》2010,151(4):797-803
The possible origin of the Scarlet ibis population of Cubat?o in southern Brazil, and its levels of genetic diversity and
differentiation in relation to populations from the country’s northern coast were investigated through the sequences of 980
base pairs of β-fibrinogen intron 7 from a sample of 37 specimens. A total of 19 haplotypes were recorded in the three populations.
Despite observed discrepancies in the levels of genetic diversity (π = 0.0017–0.0033; h = 0.60–0.95), AMOVA, K*st and Fst values all indicated that genetic differentiation among the populations was relatively low. This suggests that the Cubat?o
population was isolated recently from the panmictic population that was once distributed all along the Brazilian coast, although
it does not totally refute its possible derivation from a specific population on the north coast. Given our results, genetic
management should focus on the minimization of inbreeding, especially in the smaller populations, such as Cubat?o. However,
a more definitive study, including markers with higher evolutionary rates (e.g. microsatellites) and a much larger sample,
would be required before any such actions can be taken. 相似文献
17.
Elongate loach (Leptobotia elongata (Bleeker)), an endemic fish species to China, is a famous ornamental freshwater fish. Here, a comparative study of mtDNA
control region (D-loop) (835 bp) sequences was performed to analyze its wild population structure and evaluate the genetic
diversity for 110 individuals from five locations in the upper reaches of the Yangtze River, China. A total of 49 polymorphic
sites and 45 haplotypes yielded high haplotype diversity (h = 0.952), but low nucleotide diversity (π = 0.00454) as that of many fish species. Sequence divergences between haplotypes ranged from 0.0033 ± 0.0011 to 0.0050 ± 0.0012
in intra-groups, and from 0.0037 ± 0.0.0011 to 0.0050 ± 0.0012 between groups. Significant values of Tajima’s D (−1.86383, P < 0.01) and Fu’s F
S (−25.93, P < 0.01), together with uni-modal mismatch distribution, indicated a recent genetic bottleneck or population expansion of
the species. Analysis of molecular variance (AMOVA) indicated a small amount of differentiation among groups (1.7%); most
of the total variation occurred within groups (98.3%). Also, there was no significant population structure (F
ST = 0.017, P > 0.05), and estimates of gene flows among groups were extremely high (Nm = 28.88), suggesting low genetic divergence between populations in the species. The lack of genetic differentiation among
groups is most likely due to the combined gene flow from the downstream movement of eggs and larvae with currents and the
upstream or downstream migration of adults throughout the distribution. These groups of L. elongata distributed in upper reaches of the Yangtze River should be considered as a single management unit. 相似文献
18.
利用叶绿体基因(rbcL和trnS-G)及核糖体DNA内转录间隔区(ITS),对祁连山区狭域分布的特有物种黑虎耳草8个居群(115个个体)进行遗传多样性研究,旨在揭示黑虎耳草的居群遗传结构及其历史进化过程。结果表明:(1)所有取样个体共检测到4个cpDNA单倍型和9个ITS单倍型,其中祁连山东南部的居群固定较多的单倍型和特有单倍型,而西北部居群只固定少数几个广泛分布的单倍型,且遗传多样性普遍较低。(2)基于cpDNA数据和ITS数据的分子变异分析(AMOVA)显示,遗传变异主要来源于居群内。(3)基于cpDNA数据的中性检验表明,Tajima’s D(-1.012 30,P 0.05)和FuLi’s D*(-2.066 77,P 0.05)均为负值,均不显著;歧点分布分析结果显示,黑虎耳草居群经历过近期的扩张事件。根据物种现有遗传分布格局推测,黑虎耳草在第四纪冰期时退缩到祁连山东南部的边缘避难所,间冰期或冰期后回迁到祁连山西北部地区,在回迁过程中由于奠基者效应导致祁连山西北部的居群仅固定少数广泛分布的单倍型,并呈现出较低的遗传多样性;由于居群较小且相互隔离,该物种经历了严重的瓶颈效应和遗传漂变,导致该物种总遗传多样性(H_T)和居群平均遗传多样性(H_S)远低于虎耳草属其他青藏高原-喜马拉雅广域分布的物种。 相似文献
19.
We assessed genetic variation in a total of 22 populations of the tree species Cordia africana Lam. in Ethiopia and analyzed the country-wide impact of population history, forest disturbance and alteration of land use
on extant intraspecific diversity. Amplified Fragment Length Polymorphisms (AFLPs) and chloroplast microsatellite markers
were investigated. The analyses of the AFLP data revealed high diversity in all investigated populations: the percentage of
polymorphic loci (PPL) ranged from 62.2% to 92.2% and Nei's gene diversity from 0.220 to 0.320 within the populations. The
mean PPL and the mean diversity within populations were 85.7% and 0.287, respectively. The analysis of molecular variance
revealed a moderate level of differentiation (ΦST = 0.07, p < 0.001) among the populations. The Mantel test proved a significant but low correlation (r = 0.31, p < 0.001) between the geographic distance and the genetic differentiation matrices. Only three different cpDNA haplotypes
were observed; no more than two haplotypes were found in any population. The dominant haplotype with an overall frequency
of 81% was observed in all populations. The level of differentiation among the populations was comparatively low at chloroplast
DNA (G
ST = 0.18, R
ST, N
ST = 0.22). The observed patterns and levels of genetic variation within and among the populations indicate that efficient gene
flow via pollen and seed is likely to be the main factor contributing to the maintenance of genetic diversity in natural and
disturbed conditions. 相似文献
20.
In this study we evaluated the influence of recent landscape fragmentation on the dynamics of remnant fragments from the Brazilian
Atlantic Forest. This biome is one of the richest in the world and has been extensively deforested and fragmented. We sampled
five populations of the threatened Dalbergia nigra, a tree endemic to the Brazilian Atlantic Forest, two located in a large reserve of continuous forest and three in fragments
of different sizes and levels of disturbance. In order to assess historical changes, considering the longevity of the analyzed
species, 119 adults and 116 saplings were genotyped for six microsatellite loci. Lower levels of genetic diversity were found
in the most impacted fragments when compared to the most preserved population located inside the reserve, and there was significant
genetic structure among the populations studied (pairwise F
ST = 0.031–0.152; pairwise D
EST = 0.039–0.301). However, genetic structure among saplings (F
ST = 0.056; D
EST = 0.231) was significantly lower than among adults (F
ST = 0.088; D
EST = 0.275). Estimates of contemporary gene flow based on assignment tests corroborated this result, suggesting that fragmentation
led to an increase in gene flow. This connectivity among remnant fragments could mitigate the loss of genetic diversity through
a metapopulation dynamic, but the high rate of habitat loss and the unknown long-term genetic effects add uncertainty. These
results, taken together with the presence of private alleles in disturbed populations, highlight the importance of preserving
the extant fragments. 相似文献