首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
    
The rummy‐nose tetra, Hemigrammus bleheri, is a small fish found in forest streams of the Rio Negro floodplain, central Amazonia. This species is popular in aquaria and used as an ornamental fishery resource by the riverine people from middle Rio Negro. Here we describe eight microsatellite DNA loci for rummy‐nose tetras. Number of alleles and heterozygosity per locus in a sample of 30 fish ranged from five to 22 and from 0.52 to 0.96, respectively. These highly variable genetic markers provide important tools for investigating population history and identifying conservation units in rummy‐nose tetras.  相似文献   

2.
    
The one‐lined pencilfish Nannostomus unifasciatus is a small fish from the flooded forests of the Amazon basin. Pencilfish are popular in aquaria and are used as ornamental fishery resource by riverine communities from central Amazonia. Here we report a set of nine microsatellite loci for N. unifasciatus. Number of alleles and heterozygosity per locus in a sample of 30 pencilfish ranged from 4 to 19 and from 0.39 to 0.86, respectively. These markers will prove useful to investigate population genetic structure, identify conservation units, and to conduct phylogeographical reconstructions in pencilfish from the flooded forests of Amazonia.  相似文献   

3.
The blackwing hatchetfish, Carnegiella marthae, is a small characin species distributed in forest streams of the Negro and upper Orinoco River basins in Amazonia. Freshwater hatchetfish are popular in the aquarium trade and represent an economic resource for the riverine people from middle Rio Negro, in Brazil. We isolated and characterized seven microsatellite DNA loci for the blackwing hatchetfish. Number of alleles and heterozygosity per locus in a sample of 30 fish ranged from three to 17 and from 0.19 to 0.87, respectively. These microsatellite loci provide powerful markers for studies on taxonomy, management and phylogeographic history of Amazonian hatchetfish.  相似文献   

4.
    
Accurately describing biodiversity in tropical regions such as Amazonia is difficult because of insufficient morphological inventories and the lack of studies on the distribution of genetic diversity. Aquatic organisms from Amazonian flooded forests are generally expected to move laterally along the forests during the annual inundation cycle, a behaviour that should promote admixture of populations and reduce within‐drainage speciation. We used an unprecedented fine‐scale sampling effort and multiple DNA markers to quantify region‐wide population differentiation in an Amazonian floodplain forest specialist, the black‐wing hatchet fish Carnegiella marthae ( Myers, 1927 ). Our study revealed three previously unsuspected and ancient cryptic species of black‐wing hatchet fish in the Rio Negro floodplain (RNF), in central Amazonia. Two species produce occasional first‐generation hybrids. The third and rarer species, although found in extreme sympatry with another species, appears to be reproductively isolated, and also differs in external morphology and dentition. Our findings have important implications for guiding conservation management because C. marthae is harvested commercially in the RNF ornamental fishery. They also suggest that the diversity of Amazonian ichthyofauna is vastly underestimated, including that found in landscapes lacking contemporary barriers to account for population divergence and speciation. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102 , 391–403.  相似文献   

5.
    
We describe seven microsatellite loci, including tetra‐, tri‐ and dinucleotides, isolated from Brycon hilarii, which is a migratory fish inhabiting the Paraguay River basin (Brazil) and is highly valued for its meat quality. Three to eight alleles per locus were detected and the expected heterozygosity ranged from 0.31 to 0.81. Positive results were obtained with cross‐amplification in five other species of Brycon. These microsatellites provide a potential tool for wild population and aquaculture studies of B. hilarii and other species of the genus.  相似文献   

6.
  总被引:1,自引:0,他引:1  
In species of great conservation concern, special attention must be paid to their phylogeography, in particular the origin of animals for captive breeding and reintroduction. The endangered European mink lives now in at least three well-separated populations in northeast, southeast and west Europe. Our aim is to assess the genetic structure of these populations to identify 'distinct population segments' (DPS) and advise captive breeding programmes. First, the mtDNA control region was completely sequenced in 176 minks and 10 polecats. The analysis revealed that the western population is characterized by a single mtDNA haplotype that is closely related to those in eastern regions but nevertheless, not found there to date. The northeast European animals are much more variable (pi = 0.012, h = 0.939), with the southeast samples intermediate (pi = 0.0012, h = 0.469). Second, 155 European mink were genotyped using six microsatellites. The latter display the same trends of genetic diversity among regions as mtDNA [gene diversity and allelic richness highest in northeast Europe (H(E) = 0.539, R(S) = 3.76), lowest in west Europe (H(E) = 0.379, R(S) = 2.12)], and provide evidences that the southeast and possibly the west populations have undergone a recent bottleneck. Our results indicate that the western population derives from a few animals which recently colonized this region, possibly after a human introduction. Microsatellite data also reveal that isolation by distance occurs in the western population, causing some inbreeding because related individuals mate. As genetic data indicate that the three populations have not undergone independent evolutionary histories for long (no phylogeographical structure), they should not be considered as distinct DPS. In conclusion, the captive breeding programme should use animals from different parts of the species' present distribution area.  相似文献   

7.
8.
    
Arapaima gigas is a CITES II listed species, but it is also one of the most important food fish of the Amazon basin with a historically very large commercial and subsistence fishery. By the 1980s it became commercially extinct in many areas, and in early 2001 the Brazilian government banned all fishing, although this has not prevented illegal fishing. Therefore we developed 14 variable microsatellite markers for A. gigas to gain a knowledge of its population structure, which is needed to implement a sound management policy, and also to provide us with the forensic tools to manage and monitor this over‐exploited fish.  相似文献   

9.
颜海飞  王凤英  郝刚 《广西植物》2009,29(6):751-757
现存物种的分布格局、遗传结构是当前因素和历史因素共同作用的结果。人类的过度开发、全球变暖等当前因素造成的生境片段化是目前许多报春花属植物濒危的一大原因。该文总结了近年来报春花属内的保育遗传学研究进展,期望以此为更好地保护报春花属植物提供一定的理论基础。应用亲缘地理学研究方法可以弥补古生物学难以研究报春花植物历史成因的不足,因此也总结该方法在报春花属内的研究进展,并初步整理不同地区间的报春花属植物的分化式样,同时期望这些研究成果能为为研究报春花属植物在应对全球气候变化的响应机制方面提供一些参考。  相似文献   

10.
    
With advances in sequencing technology, research in the field of landscape genetics can now be conducted at unprecedented spatial and genomic scales. This has been especially evident when using sequence data to visualize patterns of genetic differentiation across a landscape due to demographic history, including changes in migration. Two recent model‐based visualization methods that can highlight unusual patterns of genetic differentiation across a landscape, SpaceMix and EEMS, are increasingly used. While SpaceMix's model can infer long‐distance migration, EEMS’ model is more sensitive to short‐distance changes in genetic differentiation, and it is unclear how these differences may affect their results in various situations. Here, we compare SpaceMix and EEMS side by side using landscape genetics simulations representing different migration scenarios. While both methods excel when patterns of simulated migration closely match their underlying models, they can produce either un‐intuitive or misleading results when the simulated migration patterns match their models less well, and this may be difficult to assess in empirical data sets. We also introduce unbundled principal components (un‐PC), a fast, model‐free method to visualize patterns of genetic differentiation by combining principal components analysis (PCA), which is already used in many landscape genetics studies, with the locations of sampled individuals. Un‐PC has characteristics of both SpaceMix and EEMS and works well with simulated and empirical data. Finally, we introduce msLandscape, a collection of tools that streamline the creation of customizable landscape‐scale simulations using the popular coalescent simulator ms and conversion of the simulated data for use with un‐PC, SpaceMix and EEMS.  相似文献   

11.
    
Mahogany (Swietenia macrophylla, Meliaceae) is the most valuable and intensively exploited Neotropical tree. No information is available regarding the genetic structure of mahogany in South America, yet the region harbours most of the unlogged populations of this prized hardwood. Here we report on the genetic diversity within and the differentiation among seven natural populations separated by up to 2100 km along the southern arc of the Brazilian Amazon basin. We analysed the variation at eight microsatellite loci for 194 adult individuals. All loci were highly variable, with the number of alleles per locus ranging from 13 to 27 (mean = 18.4). High levels of genetic diversity were found for all populations at the eight loci (mean HE = 0.781, range 0.754-0.812). We found moderate but statistically significant genetic differentiation among populations considering both estimators of FST and RST, theta = 0.097 and rho = 0.147, respectively. Estimates of theta and rho were significantly greater than zero for all pairwise population comparisons. Pairwise rho-values were positively and significantly correlated with geographical distance under the isolation-by-distance model. Furthermore, four of the populations exhibited a significant inbreeding coefficient. The finding of local differentiation among Amazonian mahogany populations underscores the need for in situ conservation of multiple populations of S. macrophylla across its distribution in the Brazilian Amazon. In addition, the occurrence of microgeographical genetic differentiation at a local scale indicates the importance of maintaining populations in their diverse habitats, especially in areas with mosaics of topography and soil.  相似文献   

12.
    
In the early 1800s, the European roe deer (Capreolus capreolus) was probably extirpated from Switzerland, due to overhunting and deforestation. After a federal law was enacted in 1875 to protect lactating females and young, and limiting the hunting season, the roe deer successfully recovered and recolonized Switzerland. In this study, we use mitochondrial DNA and nuclear DNA markers to investigate the recolonization and assess contemporary genetic structure in relation to broad topographic features, in order to understand underlying ecological processes, inform future roe deer management strategies, and explore the opportunity for development of forensic traceability tools. The results concerning the recolonization origin support natural, multidirectional immigration from neighboring countries. We further demonstrate that there is evidence of weak genetic differentiation within Switzerland among topographic regions. Finally, we conclude that the genetic data support the recognition of a single roe deer management unit within Switzerland, within which there is a potential for broad‐scale geographic origin assignment using nuclear markers to support law enforcement.  相似文献   

13.
    
The past processes that have shaped geographic patterns of genetic diversity may be difficult to infer from current patterns. However, in species with sex differences in dispersal, differing phylogeographic patterns between mitochondrial (mt) and nuclear (nu) DNA may provide contrasting insights into past events. Forest elephants (Loxodonta cyclotis) were impacted by climate and habitat change during the Pleistocene, which likely shaped phylogeographic patterns in mitochondrial (mt) DNA that have persisted due to limited female dispersal. By contrast, the nuclear (nu) DNA phylogeography of forest elephants in Central Africa has not been determined. We therefore examined the population structure of Central African forest elephants by genotyping 94 individuals from six localities at 21 microsatellite loci. Between forest elephants in western and eastern Congolian forests, there was only modest genetic differentiation, a pattern highly discordant with that of mtDNA. Nuclear genetic patterns are consistent with isolation by distance. Alternatively, male‐mediated gene flow may have reduced the previous regional differentiation in Central Africa suggested by mtDNA patterns, which likely reflect forest fragmentation during the Pleistocene. In species like elephants, male‐mediated gene flow erases the nuclear genetic signatures of past climate and habitat changes, but these continue to persist as patterns in mtDNA because females do not disperse. Conservation implications of these results are discussed.  相似文献   

14.
Subalpine larch (Larix lyallii Parl.) and western larch (Larix occidentalis Nutt.) represent two closely related species with contrasting abundance and distribution patterns in Western North America. Genetic diversity at seven informative microsatellite loci was determined for 19 populations of subalpine larch and nine populations of western larch. Contrasting genetic diversity and patterns of population differentiation were observed between the two species. The overall within-population genetic diversity parameters were lower in subalpine larch (A = 3.2; A(P) = 3.6; H(E) = 0.418) than in western larch (A(P) = 5.51; H(E) = 0.580), a pattern that is likely related to historical or demographic factors. No evidence of interspecific hybridization was observed. Significantly more population differentiation (theta = 0.15; R(ST) = 0.07), consistent with more restricted gene flow, was observed for subalpine larch as compared to western larch (theta = 0.05; R(ST) = 0.04). Under the assumption of an infinite allele mutation model, 12 of the 19 subalpine larch populations showed signs of deviation from the mutation-drift equilibrium, which suggests Holocene population bottlenecks and fluctuations in effective population size for this species. None of the western larch populations deviated significantly from the mutation-drift equilibrium. For both species, Mantel's test revealed a significant positive relationship between geographical and genetic distances indicative of isolation by distance. A similar geographical structure was detected in both species, suggesting at least two genetically distinct glacial populations in each species. The various implications for gene conservation are discussed.  相似文献   

15.
    
Analyzing genetic variation through time and space is important to identify key evolutionary and ecological processes in populations. However, using contemporary genetic data to infer the dynamics of genetic diversity may be at risk of a bias, as inferences are performed from a set of extant populations, setting aside unavailable, rare, or now extinct lineages. Here, we took advantage of new developments in next‐generation sequencing to analyze the spatial and temporal genetic dynamics of the grasshopper Oedaleus decorus, a steppic Southwestern‐Palearctic species. We applied a recently developed hybridization capture (hyRAD) protocol that allows retrieving orthologous sequences even from degraded DNA characteristic of museum specimens. We identified single nucleotide polymorphisms in 68 historical and 51 modern samples in order to (i) unravel the spatial genetic structure across part of the species distribution and (ii) assess the loss of genetic diversity over the past century in Swiss populations. Our results revealed (i) the presence of three potential glacial refugia spread across the European continent and converging spatially in the Alpine area. In addition, and despite a limited population sample size, our results indicate (ii) a loss of allelic richness in contemporary Swiss populations compared to historical populations, whereas levels of expected heterozygosities were not significantly different. This observation is compatible with an increase in the bottleneck magnitude experienced by central European populations of O. decorus following human‐mediated land‐use change impacting steppic habitats. Our results confirm that application of hyRAD to museum samples produces valuable information to study genetic processes across time and space.  相似文献   

16.
    
Madagascar's ring‐tailed lemurs (Lemur catta) are experiencing rapid population declines due to ongoing habitat loss and fragmentation, as well as increasing exploitation for bushmeat and the illegal pet trade. Despite being the focus of extensive and ongoing behavioral studies, there is comparatively little known about the genetic population structuring of the species. Here, we present the most comprehensive population genetic analysis of ring‐tailed lemurs to date from across their likely remaining geographic range. We assessed levels of genetic diversity and population genetic structure using multilocus genotypes for 106 adult individuals from nine geographically representative localities. Population structure and FST analyses revealed moderate genetic differentiation with localities being geographically partitioned into northern, southern, western and also potentially central clusters. Overall genetic diversity, in terms of allelic richness and observed heterozygosity, was high in the species (AR = 4.74, HO = 0.811). In fact, it is the highest among all published lemur estimates to date. While these results are encouraging, ring‐tailed lemurs are currently affected by ongoing habitat fragmentation and occur at lower densities in poorer quality habitats. The effects of continued isolation and fragmentation, coupled with climate‐driven environmental instability, will therefore likely impede the long‐term viability of the species.  相似文献   

17.
18.
    
Microsatellite variation from eight loci was studied in five populations of Drosophila teissieri, a fruit-fly found only in the rain forests of sub-Saharan Africa. Five noncontiguous rain forest sites (from Tanzania, Gabon and Ivory Coast) were sampled to measure the effects of historical forest fragmentation on population structure in an obligatory forest-dwelling species. The Ivory Coast and Gabon populations showed a wider range of alleles, different modal alleles and had a higher genetic diversity than the three East African populations. As could be expected, genetic differentiation (FST) was significantly correlated with physical distance, but the westernmost population (Ivory Coast) showed values that were intermediate between the central (Gabon) and Eastern (Tanzania) populations. A migration-drift equilibrium in a stable continuum of populations did not appear adequate to describe the observed distribution. It seems probable that the species has undergone abrupt changes involving isolation, merging and migration of populations, as a consequence of repeated waves of forest fragmentation and coalescence.  相似文献   

19.
In order to properly manage and conserve exploited shark species, detailed analyses of their population structure is needed. Global populations of Galeorhinus galeus are in decline due to the exploitation of the fishery over the past 80 years. Currently, the genetic structure of eastern Pacific populations of G. galeus is not known and recent observations in the northeastern Pacific suggest an increase in numbers. To evaluate gene flow among populations of G. galeus , 116 samples were collected and analysed from six geographically dispersed locations: Australia, North America, South Africa, South America (Argentina and Peru), and the UK. Analysis of 968 to 1006 bp of the 1068-bp mitochondrial control region revealed 38 unique haplotypes that were largely restricted to their collecting locality. Significant genetic structure was detected among populations (ΦST = 0.84; P  < 0.000001) and migration estimates were low ( Nm  = 0.05–0.97). Due to an apparent lack of migration, populations of G. galeus appear to be isolated from each other with little to no gene flow occurring among them. As a consequence of this isolation, increasing numbers of G. galeus in the northeastern Pacific can be best explained by local recruitment and not by input from geographically distant populations.  相似文献   

20.
Abstract Aim To examine how the genetic diversity of selected taxa of forest‐dwelling small mammals is distributed between and within the major rain forest domains of Amazonia and Atlantic Forest and the intervening interior forests of Brazil, as inferred by the relationships between gene genealogies and geography. I also addressed the historical importance of the central Brazilian forests in connecting Amazon and Atlantic Forest populations of rodents and marsupials. Methods I evaluated variation in the mitochondrial cytochrome b gene to estimate the levels of sequence divergence between those taxa occurring throughout the Amazon, Atlantic Forest, and forests in the Cerrado and Caatinga regions. I inferred the hierarchical relationships between haplotypes, populations and formal taxa using the cladistic approach of maximum parsimony. I compared areas and the clades identified by superimposing cladograms on the geographical distribution of samples. The degree of concordance both in phylogeny and the depth of the nodes in these phylogenies, in addition to patterns of geographical distribution of clades, permitted me to make inferences on how, when and where the taxa differentiated. Results Sequence similarity is often greater between samples from the Atlantic Forest and either Amazon or central Brazilian forests than it is within each of the two rain forest domains. The Atlantic Forest clades are either not reciprocally monophyletic or are the sister group to all the other clades. There is some indication of northern and southern components in the Atlantic Forest. Given the geographical distribution of clades and the relatively deep levels of divergence, the central Brazilian area does not behave as a separate region but is complementary to either Amazon or Atlantic Forest. Patterns of area relationships differ across taxa, suggesting that different processes and/or historic events affected the diversification within each lineage. Main conclusions The Amazon and the Atlantic forests are not exclusive in terms of their small mammal faunas; both overlap broadly with taxa occurring in gallery forests and dry forests in central Brazil. Central Brazilian forests are an integral part of the evolutionary scenario of lowland small mammals, playing an important role as present and past habitats for rain forest species. Therefore, representatives from this area should always be included in analyses of the evolutionary history of lowland rain forest faunas. The incongruence of branching patterns among areas is in agreement with recent results presented for Neotropical passerine birds and indicates that a single hypothesis of Neotropical area relationships is unlikely. These findings reinforce the idea that speciation in the Neotropics will not be explained by any single model of vicariance or climatic changes.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号