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1.
The Sumatran rhinoceros (Dicerorhinus sumatrensis) is the smallest and one of the most endangered rhinoceros species, with less than 100 individuals estimated to live in the wild. It was originally divided into three subspecies but only two have survived, D. sumatrensis sumatrensis (Sumatran subspecies), and D. s. harrissoni (Bornean). Questions regarding whether populations of the Sumatran rhinoceros should be treated as different management units to preserve genetic diversity have been raised, particularly in light of its severe decline in the wild and low breeding success in captivity. This work aims to characterize genetic differentiation between Sumatran rhinoceros subspecies using complete mitochondrial genomes, in order to unravel their maternal evolutionary history and evaluate their status as separate management units. We identified three major phylogenetic groups with moderate genetic differentiation: two distinct haplogroups comprising individuals from both the Malay Peninsula and Sumatra, and a third group from Borneo. Estimates of divergence time indicate that the most recent common ancestor of the Sumatran rhinoceros occurred approximately 360,000 years ago. The three mitochondrial haplogroups showed a common divergence time about 80,000 years ago corresponding with a major biogeographic event in the Sundaland region. Patterns of mitochondrial genetic differentiation may suggest considering Sumatran rhinoceros subspecies as different conservation units. However, the management of subspecies as part of a metapopulation may appear as the last resource to save this species from extinction, imposing a conservation dilemma.  相似文献   

2.
Abstract

Brassica rupestris Raf. is a chasmophyte species that includes two subspecies, both endemic to Central-Western Sicily (Italy). Inter-Simple Sequence Repeat (ISSR) markers were used to detect genetic diversity within and among eight populations representative of the species' distribution range. High levels of genetic diversity were revealed both at the population (PPB = 53.88%, H S = 0.212, Sh = 0.309) and at the species level (PPB = 96.55%, H T = 0.307, Sh = 0.464). The correlation between genetic and geographical distances was negative (Mantel test, r = ?0.06, P < 0.95). The two subspecies of B. rupestris, subsp. rupestris and subsp. hispida, showed remarkable genetic similarity and molecular data did not unequivocally support their distinctness. The pattern of genetic variation revealed by our study bears important consequences for conservation management: It is desirable to preserve B. rupestris populations in situ with a “dynamic” strategy, while, ex situ conservation programmes might be improved to safeguard maximum genetic diversity.  相似文献   

3.
For species that are habitat specialists or sedentary, population fragmentation may lead to genetic divergence between populations and reduced genetic diversity within populations, with frequent inbreeding. Hundreds of kilometres separate three geographical regions in which small populations of the endangered Eastern Bristlebird, Dasyornis brachypterus, a small, ground-dwelling passerine that occurs in fire-prone bushland in eastern Australia, are currently found. Here, we use mitochondrial and microsatellite DNA markers to: (i) assess the sub-specific taxonomy designated to northern range-edge, and central and southern range-edge D. brachypterus, respectively, and (ii) assess levels of standing genetic variation and the degree of genetic subdivision of remnant populations. The phylogenetic relationship among mtDNA haplotypes and their spatial distribution did not support the recognised subspecies boundaries. Populations in different regions were highly genetically differentiated, but in addition, the two largest, neighboring populations (located within the central region and separated by ~50 km) were moderately differentiated, and thus are likely closed to migration (microsatellites, F ST = 0.06; mtDNA, F ST = 0.12, ?? ST = 0.08). Birds within these two populations were genotypically diverse and apparently randomly mating. A long-term plan for the conservation of D. brachypterus??s genetic diversity should consider individual populations as separate management units. Moreover, managers should avoid actively mixing birds from different populations or regions, to conserve the genetic integrity of local populations and avoid outbreeding depression, should further translocations be used as a recovery tool for this species.  相似文献   

4.
The demographic history and population genetic structure of the blackfin flounder (Glyptocephalus stelleri) along coastal regions of Japan were investigated. Genetic variation in DNA sequences was examined from the first hypervariable region of the mitochondrial DNA control region. A high level of haplotypic diversity (h = 0.99 ± 0.004) was detected, indicating a high level of intrapopulation genetic diversity. The starburst structure of the minimum spanning tree suggested a very recent origin for most haplotypes. The demographic history of G. stelleri was examined using neutrality tests and mismatch distribution analysis, which also indicated a Pleistocene population expansion at about 124,100–413,400 years ago. Hierarchical molecular variance analysis and conventional population Fst comparisons revealed no significant genetic differentiation throughout the range examined.  相似文献   

5.
Genetic diversity provides populations with the possibility to persist in ever-changing environments, where selective regimes change over time. Therefore, the long-term survival of a population may be affected by its level of genetic diversity. The Mexican howler monkey (Alouatta palliata mexicana) is a critically endangered primate restricted to southeast Mexico. Here, we evaluate the genetic diversity and population structure of this subspecies based on 83 individuals from 31 groups sampled across the distribution range of the subspecies, using 29 microsatellite loci. Our results revealed extremely low genetic diversity (HO = 0.21, HE = 0.29) compared to studies of other A. palliata populations and to other Alouatta species. Principal component analysis, a Bayesian clustering method, and analyses of molecular variance did not detect strong signatures of genetic differentiation among geographic populations of this subspecies. Although we detect small but significant FST values between populations, they can be explained by a pattern of isolation by distance. These results and the presence of unique alleles in different populations highlight the importance of implementing conservation efforts in multiple populations across the distribution range of A. p. mexicana to preserve its already low genetic diversity. This is especially important given current levels of population isolation due to the extreme habitat fragmentation across the distribution range of this primate.  相似文献   

6.
Melampyrum sylvaticum is an endangered annual hemiparasitic plant that is found in only 19 small and isolated populations in the United Kingdom (UK). To evaluate the genetic consequences of this patchy distribution we compared levels of diversity, inbreeding and differentiation from ten populations from the UK with eight relatively large populations from Sweden and Norway where the species is more continuously distributed. We demonstrate that in both the UK and Scandinavia, the species is highly inbreeding (global F IS = 0.899). Levels of population differentiation were high (FST = 0.892) and significantly higher amongst UK populations (FST = 0.949) than Scandinavian populations (FST = 0.762; P < 0.01). The isolated populations in the UK have, on average, lower genetic diversity (allelic richness, proportion of loci that are polymorphic, gene diversity) than Scandinavian populations, and this diversity difference is associated with the smaller census size and population area of UK populations. From a conservation perspective, the naturally inbreeding nature of the species may buffer the species against immediate effects of inbreeding depression, but the markedly lower levels of genetic diversity in UK populations may represent a genetic constraint to evolutionary change. In addition, the high levels of population differentiation suggest that gene flow among populations will not be effective at replenishing lost variation. We thus recommend supporting in situ conservation management with ex situ populations and human-mediated seed dispersal among selected populations in the UK.  相似文献   

7.
The accurate diagnosis of conservation units now typically includes recognition of genetic diversity and unique evolutionary lineages and is necessary to inform the conservation management of endangered species. We evaluated whether the two currently recognized subspecies of the endangered Central American squirrel monkey (Saimiri oerstedii) in Costa Rica are evolutionarily significant units (ESUs) that should be managed separately in conservation efforts. We used previously published sequences of 50 individuals of Saimiri oerstedii for 880 bp of the mtDNA d-loop and genotypes of 244 individuals for 16 microsatellites and conducted novel analyses to characterize genetic differentiation between subspecies of Saimiri oerstedii. We measured sequence differentiation and inferred an intraspecific molecular phylogeny and a haplotype network, and found consistent results supporting statistically significant divergence and reciprocal monophyly between subspecies. A population aggregation analysis also supported Saimiri oerstedii citrinellus and S. o. oerstedii as diagnosably distinct units. These results confirm previous genetic studies with smaller sample sizes and are consistent with other factors including differences in pelage and morphology and divergence at nuclear markers. Conservation managers should manage these subspecies separately to prevent the loss of genetic diversity via artificially induced outbreeding. High levels of genetic diversity may buffer populations against outside extinction pressures, to which Saimiri oerstedii are vulnerable because of their dwindling habitat and small population size.  相似文献   

8.
9.
A decreasing population size is often causing species extinction, however, relict species persisting in small-sized populations counter this. We analysed spatial genetic variation and past changes in population size at the maternally-inherited mitochondrial DNA level to clarify the origin of all recently known isolated populations of Pholidoptera frivaldskyi occurring in the range of Carpathian Mountains. Along with that we analysed also morphological variation as some phenotypic traits can retain useful information on population genetic structure. We found a relatively low genetic diversity within isolated populations as 778 bp COI gene sequences revealed only 13 unique haplotypes (n = 173 individuals from 10 populations). The spatial analysis of molecular variance identified three geographically homogenous genetic clusters (one in Slovakia and two in Romania) with a high level of differentiation among them, suggesting restricted gene flow, whilst Bayesian skyline simulation reconstructed a negative demographic change through evolutionary time. Inferred genetic pattern clearly coincides with differences in males’ colour phenotype as the extent of pigmentation on the lateral pronotum varied significantly among genetic lineages. We suggest that geographical variation in the species populations has relict-like character and their isolated occurrence is not a result of recent introduction events. Identification of ‘evolutionary units’ may help in the conservation and management of this rare insect species.  相似文献   

10.
Litsea szemaois (Lauraceae) is an endemic and endangered species from the tropical rain forests of Xishuangbanna, southern Yunnan, SW China, but habitat fragmentation, especially exacerbated by rubber planting, has caused a decline in population size of the species. AFLP and ISSR were used to investigate the genetic diversity and population structure of eight populations from across its known distribution. Three AFLP and ten ISSR primer combinations produced a total of 203 and 77 unambiguous and repeatable bands respectively, of which 164 (80.8%) and 67 (87.0%) were polymorphic for the two markers. These two markers showed that Litsea szemaois exhibits comparatively high genetic diversity at species level (heterozygosity (hs) = 0.2109) relative to some other Lauraceae. Most of the genetic variation was partitioned within populations, but genetic differentiation between populations was significant and relatively high (Φ st = 0.2420, θ= 0.1986) compared with other tropical plants. The genetic characteristics of L. szemaois may be related to its outbreeding system, insect pollination and fragmented distribution. Because L. szemaois is dioecious and slow to mature, ex situ conservation across its genetic diversity is unlikely to succeed, although seedlings grow well under cultivation. Thus, in situ conservation is very important for this endangered species, especially as only 133 adult individuals are known in the wild. In particular, the Nabanhe and Mandian populations should be given a high conservation priority due to their higher genetic diversity, larger population size and better field condition, but wider sampling is required across all populations to determine additional areas with significant genetic conservation value.  相似文献   

11.
Limonium sinense is a halobiotic herb endemic to China that has been traditionally used for hundreds of years for its good restorative function. Genetic variation and population structure of this species were investigated by using amplified fragment length polymorphisms (AFLPs) and inter simple sequence repeats (ISSRs). A high level of genetic diversity was detected [AFLP: H E = 0.284, percentage of polymorphic loci (PPL) = 92.68 %; ISSR: H E = 0.257, PPL = 85.71 %] at the species level with POPGENE. Based on analysis of molecular variation (AMOVA), the among-population component accounted for 29.03 % (AFLP) and 28.81 % (ISSR) of the genetic variation, indicating that most of the genetic variation was between individuals within populations. The Shannon diversity index (I) was higher for AFLP (0.432) than for ISSR (0.395). Five main clusters were shown in the unweighted pair-group method with arithmetic mean (UPGMA) dendrogram created using TFPGA, consistent with the result of principal coordinate analysis using NTSYS. In situ conservation is advocated first. Keeping a stable environment for this halobiotic herb is necessary. For ex situ conservation, it is important to establish a germplasm bank. AFLP and ISSR markers were proved to be efficient tools in assessing the genetic variation among populations of L. sinense. The patterns of variation appeared to be consistent for these two marker systems, and they can be used for management of genetic structure, protection of the halobiotic plant, and conservation of germplasm.  相似文献   

12.
Monitoring levels of genetic diversity in wildlife species is important for understanding population status and trajectory. Knowledge of the distribution and level of genetic diversity in a population is essential to inform conservation management, and help alleviate detrimental genetic impacts associated with recent population bottlenecking. Mitochondrial DNA (mtDNA) markers such as the control region have become a common means of surveying for within-population genetic diversity and detecting signatures of recent population decline. Nevertheless, little attention has been given to examining the mtDNA control region’s sensitivity and performance at detecting instances of population decline. We review genetic studies of bird populations published since 1993 that have used the mtDNA control region and reported haplotype diversity, number of haplotypes and nucleotide diversity as measures of within-population variability. We examined the extent to which these measures reflect differences in known demographic parameters such as current population size, severity of any recent bottleneck and IUCN Red List status. Overall, significant relationships were observed between two measures of genetic diversity (haplotype diversity and the number of haplotypes), and population size across a number of comparisons. Both measures gave a more accurate reflection of recent population history in comparison to nucleotide diversity, for which no significant associations were found. Importantly, levels of diversity only correlated with demographic declines where population sizes were known to have fallen below 500 individuals. This finding suggests that measures of mtDNA control region diversity should be used with a degree of caution when inferring demographic history, particularly bottleneck events at population sizes above N = 500.  相似文献   

13.
Population genetics has been recognized as a key component of policy development for fisheries and conservation management. In this study, natural sea bass (Lateolabrax japonicus) populations in three ocean basins in Korea were assessed using multiplex assays with 12 highly polymorphic microsatellite loci; 203 alleles and similarly high levels of genetic diversity [mean number of alleles (NA) = 14.43, mean expected heterozygosity (He) = 0.84] were detected. All populations showed significant heterozygote deficiency at four loci, which could be explained by the presence of null alleles. The genetic population subdivision was low and was significantly different according to F-statistics (overall F ST = 0.003, R ST = 0.005). However, this substructure was not supported by an analysis of molecular variance test, analyses of isolation by distance or Bayesian analysis. The passive dispersal of eggs/larvae via the main currents appears to facilitate gene flow. The possibility of a recent genetic bottleneck was observed in all three populations of L. japonicus, indicating that overfishing and degradation of the environment in recent years has led to a decline in the sea bass populations in Korea. Our study demonstrates that sea bass in Korea do not appear to be genetically partitioned and should be managed as a single unit; however, the potential for a rapid loss of genetic diversity remains. Information regarding the genetic characteristics of Korean sea bass populations has important implications for fishery management and conservation efforts and will aid in the sustainable exploitation of fishing resources and the preservation of biodiversity.  相似文献   

14.
Understanding patterns of genetic diversity and population structure for rare, narrowly endemic plant species, such as Pinguicula ionantha (Godfrey’s butterwort; Lentibulariaceae), informs conservation goals and can directly affect management decisions. Pinguicula ionantha is a federally listed species endemic to the Florida Panhandle in the southeastern USA. The main goal of our study was to assess patterns of genetic diversity and structure in 17 P. ionantha populations, and to determine if diversity is associated with geographic location or population characteristics. We scored 240 individuals at a total of 899 AFLP markers (893 polymorphic markers). We found no relationship between the estimated population size with either of two measures of diversity (proportion of loci polymorphic, P = 0.37; Nei’s gene diversity, P = 0.50). We also found low levels of population genetic structure; there was no clear relationship of genetic isolation by distance (P = 0.23) and only a small (but significant) proportion of genetic variation was partitioned amongst regions (2.4 %, P = 0.02) or populations (20.8 %, P < 0.001). STRUCTURE analysis found that the model with two inferred clusters (K = 2) best described the AFLP data; the dominant cluster at each site corresponded to the results from PCoA and Nei’s genetic distance analyses. The observed patterns of genetic diversity suggest that although P. ionantha populations are isolated spatially by distance and both natural and anthropogenic barriers, some gene flow occurs among them or isolation has been too recent to leave a genetic signature. The relatively low level of genetic diversity associated with this species is a concern as it may impair fitness and evolutionary capability in a changing environment. The results of this study provide the foundation for the development of management practices that will assist in the protection of this rare carnivorous plant.  相似文献   

15.
Malacobdella arrokeana is an entocommensal nemertean exclusively found in the bivalve geoduck Panopea abbreviata, and it is the only representative of the genus in the southern hemisphere. To characterize its genetic diversity, population structure and recent demographic history, we conducted the first genetic survey on this species, using sequence data for the cytochrome oxidase I gene (COI), 16S rRNA (16S) and the internal transcribed spacer (ITS2). Only four different ITS2 genotypes were found in the whole sample, and the two main haplotypes identified in the mitochondrial dataset were present among all localities with a diversity ranging from 0.583 to 0.939. Nucleotide diversity was low (π = 0.001–0.002). No significant genetic structure was detected between populations, and mismatch distribution patterns and neutrality tests results are consistent with a population in expansion or under selection. Analysis of molecular variance (AMOVA) revealed that the largest level of variance observed was due to intrapopulation variation (100, 100 and 94.39 % for 16S, COI and ITS2, respectively). F st values were also non-significant. The observed lack of population structure is likely due to high levels of genetic connectivity in combination with the lack or permeability of biogeographic barriers and episodes of habitat modification.  相似文献   

16.
To establish a management plan for endangered and rare species, genetic assessment must first be conducted. The genetic characteristics of plant species are affected by demographic history, reproductive strategy, and distributional range as well as anthropological effects. Abies koreana E. H. Wilson (Pinaceae), Korean fir, is endemic to Korea and found only in sub-alpine areas of the southern Korean Peninsula and Jejudo Island. This species has been designated as critically endangered by the International Union for Conservation of Nature due to a continuous decline in its range and population fragmentation. We genotyped 176 individuals from seven natural populations and two afforested populations on the Korean Peninsula using 19 microsatellite loci. STRUCTURE analysis revealed two genetic clusters in natural populations (F st  = 0.040 and R st  = 0.040) despite low differentiation. We did not detect a significant reduction in genetic diversity or the signature of a genetic bottleneck despite population fragmentation and small population size. We deduced that this species exhibits a metapopulation structure, with the population on Jirisan Mountain acting as a source of genetic diversity for other local small populations on the Korean Peninsula, through contemporary asymmetric gene flow. However, the majority of afforested individuals on the Korean Peninsula originated from a different gene cluster. Thus, we recommend a conservation strategy that maintains two genetically unique clusters.  相似文献   

17.
The Diamondback terrapin (Malaclemys terrapin) is a brackish-water turtle species whose populations have been fragmented due to anthropogenic activity such as development of coastal habitat and entrapment in commercial blue crab (Callinectes sapidus) fishing gear. Genetic analyses can improve conservation efforts for the long-term protection of the species. We used microsatellite DNA analysis to investigate levels of gene flow among and genetic variability within 21 geographically separate collections of the species distributed from Massachusetts to Texas. Quantified levels of genetic variability (allelic diversity, genotypic frequencies, and heterozygosity) revealed three zones of genetic discontinuity, resulting in four discrete populations: Northeast Atlantic, Coastal Mid-Atlantic, Florida and Texas/Louisiana. The average number of alleles and expected heterozygosity for the four genetic clusters were NA = 6.54 and HE = 0.050, respectively. However, the geographic boundaries of the populations did not correspond to accepted terrapin subspecies limits. Our results illuminate not only the need to sample terrapins in additional sites, specifically in the southeast, but also the necessity for allowing uninterrupted gene flow among population groupings to preserve current levels of genetic diversity.  相似文献   

18.
The silky shark, Carcharhinus falciformis, is a large-bodied, oceanic-coastal, epipelagic species found worldwide in tropical and subtropical waters. Despite its commercial importance, concerns about overexploitation, and likely ecological significance of this shark as an upper trophic-level predator, understanding of its population dynamics remains unclear for large parts of its distribution. We investigated the genetic diversity, population structure and demographic history of the silky shark along the western Atlantic Ocean based on the use of 707 bp of the mitochondrial DNA control region (mtCR). A total of 211 silky sharks were sampled, originating from five areas along the western Atlantic Ocean. The mitochondrial sequences revealed 40 haplotypes, with overall haplotype and nucleotide diversities of 0.88 (± 0.012) and 0.005 (± 0.003), respectively. The overall population structure was significantly different among the five western Atlantic Ocean regions. Phylogenetic analysis of mtCR sequences from globally sourced silky shark samples revealed two lineages, comprising a western Atlantic lineage and western Atlantic—Indo-Pacific lineage that diverged during the Pleistocene Epoch. In general, tests for the demographic history of silky sharks supported a population expansion for both the global sample set and the two lineages. Although our results showed that silky sharks have high genetic diversity, the current high level of overexploitation of this species requires long-term, scientifically informed management efforts. We recommend that fishery management and conservation plans be done separately for the two western Atlantic matrilineal populations revealed here.  相似文献   

19.
The goal of this study was to investigate the phylogeny, invasion history and genetic structure of the global invader Megabalanus coccopoma. First, we created a Bayesian phylogeny using cytochrome oxidase I and 16S mitochondrial genes of samples we collected and sequences available on GenBank for all species in the genus Megabalanus. Second, we compared the genetic differences within and between native and invasive populations verified as M. coccopoma by constructing a haplotype network of the COI sequences and estimating gene diversity (h) and nucleotide diversity (π). Finally, we ran an analysis of molecular variance and calculated pairwise Φ ST to evaluate the similarity among populations. We identified several lineages that correspond to putatively different species of Megabalanus and uncovered nomenclature discrepancies among GenBank samples and undocumented lineages from our own collections. However, we found that the majority of samples were indeed M. coccopoma. Among populations of M. coccopoma, levels of within-population genetic diversity were not significantly different (p h  = 0.131, p π  = 0.129) between native (h = 0.970, π = 0.00708) and non-native populations (h = 0.950, π = 0.00605) and analysis of molecular variance analyses revealed that 98.34 % of the genetic variation was partitioned within populations with a significant global Φ ST  = 0.017. Our results revealed that invasions in at least the southeastern United States and Brazil are composed of multiple lineages; however, we found that most of the global invasion occurred from a single lineage, M. coccopoma, and that no significant genetic differentiation exists between native and non-native populations of this species.  相似文献   

20.
The endemic Samango monkey subspecies (Cercopithecus albogularis labiatus) inhabits small discontinuous Afromontane forest patches in the Eastern Cape, KwaZulu-Natal midlands and southern Mpumalanga Provinces in South Africa. The subspecies is affected by restricted migration between forest patches which may impact on gene flow resulting in inbreeding and possible localized extinction. Current consensus, based on habitat quality, is that C. a. labiatus can be considered as endangered as the small forest patches they inhabit may not be large enough to sustain them. The aim of this study was to conduct a molecular genetic investigation to determine if the observed isolation has affected the genetic variability of the subspecies. A total of 65 Samango monkeys (including juveniles, subadults and adults) were sampled from two localities within the Hogsback area in the Amathole Mountains. Nuclear and mitochondrial DNA variation was assessed using 17 microsatellite markers and by sequencing the hypervariable 1 region (HVR1). Microsatellite data generated was used to determine population structure, genetic diversity and the extent of inbreeding. Sequences of the HVR1 were used to infer individual origins, haplotype sharing and haplotype diversity. No negative genetic factors associated with isolation such as inbreeding were detected in the two groups and gene flow between groups can be regarded as fairly high primarily as a result of male migration. This was in contrast to the low nuclear genetic diversity observed (H o = 0.45). A further reduction in heterozygosity may lead to inbreeding and reduced offspring fitness. Translocations and establishment of habitat corridors between forest patches are some of the recommendations that have emerged from this study which will increase long-term population viability of the subspecies.  相似文献   

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