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1.
The genetic structure of sweet chestnut ( Castanea sativa Mill.) across Europe was assessed using 73 inter-simple sequence repeat markers to screen 1,768 individuals from 68 stands
distributed across 29 sites in five European countries (Italy, France, Spain, Greece, and UK). At each site, trees were sampled
from three distinct management types (domestication levels): naturalized stands, managed coppice, and grafted fruit orchards.
In more than a third of the orchards, nonlocal genetic material (grafted clones) were evident, showing (as predicted) large
differences from the other two domestication levels for most of the within-population genetic diversity parameters estimated.
Randomly generated linkage disequilibrium analysis revealed weak though significant differences in two-locus allelic correlations
between naturalized stands and coppice, suggesting that long-term management techniques may influence the genetic makeup of
the populations. Multivariate analysis revealed the existence of five distinct gene pools across the study area; three were
located in Greece, one on the northwestern coast of the Iberian peninsula and a large gene pool covering the rest of the Mediterranean
basin. The implications of the results are discussed in relation to developing conservation strategies for chestnut genetic
resources in Europe. 相似文献
2.
Michelia maudiae Dunn. is a Magnoliaceae species threatened by habitat destruction and over-exploitation. Genetic diversity and differentiation, population contribution to total diversity and allelic/haplotypic richness, and the relative importance of pollen- and seed-mediated gene flow were investigated in nine populations (192 individuals) of M. maudiae using nuclear and chloroplast microsatellites to further our understanding of the genetic structure and evolutionary history of this tree species and to provide a genetic perspective for its conservation. The species had strong pollen mediated gene flow in the past. The ratio of pollen to seed gene flow was 25.4. Three clusters from the western, central, and eastern China were identified by both chloroplast and nuclear microsatellites. Western populations at Xiaodanjiang and Daoxian were phylogenetically divergent from the remaining populations and might be particularly important for the conservation of this species. The populations of Xiaodanjiang, Daoxian, and Minjiangyuan made positive contribution to the total diversity and allelic/haplotypic richness, and were worthy of being conserved with priority. In the central cluster, population at Laopengding should be protected since it harbored the greatest genetic diversity. 相似文献
3.
Endangered species worldwide exist in remnant populations, often within fragmented landscapes. Although assessment of genetic
diversity in fragmented habitats is very important for conservation purposes, it is usually impossible to evaluate the amount
of diversity that has actually been lost. Here, we compared population structure and levels of genetic diversity within populations
of spotted suslik Spermophilus suslicus, inhabiting two different parts of the species range characterized by different levels of habitat connectivity. We used microsatellites
to analyze 10 critically endangered populations located at the western part of the range, where suslik habitat have been severely
devastated due to agriculture industrialization. Their genetic composition was compared with four populations from the eastern
part of the range where the species still occupies habitat with reasonable levels of connectivity. In the western region,
we detected extreme population structure ( F
ST = 0.20) and levels of genetic diversity (Allelic richness ranged from 1.45 to 3.07) characteristic for highly endangered
populations. Alternatively, in the eastern region we found significantly higher allelic richness (from 5.09 to 5.81) and insignificant
population structure ( F
ST = 0.03). As we identified a strong correlation between genetic and geographic distance and a lack of private alleles in the
western region, we conclude that extreme population structure and lower genetic diversity is due to recent habitat loss. Results
from this study provide guidelines for conservation and management of this highly endangered species. 相似文献
4.
The Stone-curlew Burhinus oedicnemus, a steppe bird species, is mainly distributed in the Mediterranean and Macaronesian regions, which are considered hotspots of biodiversity with priority for animal and plant species richness conservation. In this study, we investigated the genetic diversity of the Stone-curlew in the Mediterranean basin and in the Canary Islands by applying a multilocus approach. We analysed mitochondrial and nuclear markers in order to evaluate the genetic structure and the congruence between morphological subspecies and geographic samples. We found a significant level of genetic differentiation between Mediterranean and Canary Island populations with all markers. Both in the Mediterranean basin and in the Canary Islands, we found a significant level of genetic diversity with nuclear markers only. We identified seven population groups, including insular populations. The four subspecies described for the Western Palaearctic were confirmed with some changes in distribution range. In spite of habitat fragmentation and negative population trend, the Stone-curlew showed a significant level of genetic diversity and gene flow among continental populations. However, islands constitute important reservoirs of genetic diversity and a potential for the evolution of the species. 相似文献
5.
Sweet chestnut ( Castanea sativa Mill.) is a multipurpose species of great ecological and economic importance in southwest Bulgaria. Bulgarian chestnut forests are severely degraded, however, due to the intensive exploitation and bad management that have occurred over the last 2000 years. Given the urgent need to define conservation strategies to preserve the biodiversity of Bulgarian chestnut, we estimated its genetic variability. A set of eight microsatellite primers were used to analyze the genetic diversity and structure of six C. sativa populations distributed throughout the range of species in Bulgaria. Results showed a generally high level of genetic diversity but little divergence among populations. A significant, positive, within-population inbreeding coefficient (Fis) was observed in four populations. A STRUCTURE analysis revealed three genetic clusters. Using a landscape approach, significant genetic barriers among populations were found by integrating genetics with geographical distance. We hypothesize that one population is a relict from a glacial refugium; the structure of the remaining populations is probably the result of a combination of natural events and human impacts. For the purposes of conservation planning, we have identified populations that are particularly rich in diversity and private alleles that are good candidates for preservation. 相似文献
6.
Given the large extent of hybrid cultivation, the importance of conserving the diversity of crop genetic resources has given birth to numerous collections of old races. In the present paper, we conduct a molecular characterisation of a large collection of 488 European maize populations using the bulk RFLP analysis. The analysis of 23 RFLP loci showed a high allelic richness of 11.5 alleles per locus. Populations from eastern Europe (Poland, Austria, Germany, etc.) showed the lowest genetic diversity, a lower number of unique alleles and a higher percentage of fixed loci than populations from southern Europe. In fact, genetic diversity appeared higher in Southern regions where the first maize populations are thought to have been introduced. Molecular classification based on Rogers' distance (i.e. alleles frequencies) allowed us to distinguish three main clusters which were highly consistent with geographic origins. A Northeastern cluster grouped together early or intermediate populations from Northeastern countries and the Balkans, a southeastern cluster joined late and partially dent populations from Greece and Italy, and, a southwestern cluster was made up of early flint populations from northern Spain, Portugal and the Pyrenees. A correlation between allelic frequencies at some loci and latitude and/or longitude was observed. Such tendencies may reflect the direction of gene flow between different races of maize: for instance, North American (Northern flint) and Caribbean populations were introduced, respectively, to northern and southern Europe, in the past. 相似文献
7.
We studied microsatellite genetic variation in 14 different geographic populations of black grouse ( Tetrao tetrix) across the European range. Populations were grouped in three different fragmentation categories: isolated, contiguous and
continuous, respectively. Genetic diversity, measured as observed heterozygosity ( H
O), expected heterozygosity ( H
E) and allelic richness, were lower in isolated populations as compared to the other two categories that did not differ amongst
one another. These results imply that lowered genetic variability in black grouse populations is negatively affected by population
isolation. Our results suggest that the connectivity of small and isolated populations in Western Europe should be improved
or else these face an increased risk of extinction due to genetic and demographic stochasticity. 相似文献
8.
We investigated the impact of past changes in habitat suitability on the current patterns of genetic diversity of two southern beeches ( Nothofagus nervosa and Nothofagus obliqua) in their eastern fragmented range in Patagonian Argentina, and model likely future threats to their population genetic structure. Our goal was to develop a spatially-explicit strategy for guiding conservation and management interventions in light of climate change. We combined suitability modelling under current, past (Last Glacial Maximum ~ 21,000 bp), and future (2050s) climatic conditions with genetic characterization data based on chloroplast DNA, isozymes, and microsatellites. We show the complementary usefulness of the distribution of chloroplast haplotypes and locally common allelic richness calculated from microsatellite data for identifying the locations of putative glacial refugia. Our findings suggest that contemporary hotspots of genetic diversity correspond to convergence zones of different expansion routes, most likely as a consequence of admixture processes. Future suitability predictions suggest that climate change might differentially affect both species. All genetically most diverse populations of N. nervosa and several of N. obliqua are located in areas that may be most severely impacted by climate change, calling for forward-looking conservation interventions. We propose a practical spatially- explicit strategy to target conservation interventions distinguishing priority populations for (1) in situ conservation (hotspots of genetic diversity likely to remain suitable under climate change), (2) ex situ conservation in areas where high genetic diversity overlaps with high likelihood of drastic climate change, (3) vulnerable populations (areas expected to be negatively affected by climate change), and (4) potential expansion areas under climate change. 相似文献
9.
The sweet chestnut ( Castanea sativa Mill.) is a widely spread and important multipurpose tree species in the Mediterranean area, which has played an important role in human history. Natural events, such as glaciations, and human influence played significant roles in the distribution and genetic makeup of the sweet chestnut. In order to better understand how natural and human-mediated past events affected the current genetic diversity and structure of the sweet chestnut, we analysed populations from Central Europe and the western part of the Balkan Peninsula, utilizing ten polymorphic nuclear microsatellite markers. The study revealed the existence of three genetically and, to a large extent, geographically distinct and well-defined groups of sweet chestnut populations. Two not entirely separated groups of populations were detected in the northern part of the studied area and one in the southern. Our results indicate that the genetic structure of sweet chestnut populations in Central Europe and the western part of the Balkan Peninsula is the result of both natural colonization events and significant and lengthy human impact. Furthermore, it has been proven that the gene flow between cultivated/grafted trees’ and wild chestnut stands can influence their genetic structure. However, our results reveal that cultivated-to-wild introgression in the sweet chestnut is dependent on the close proximity of chestnut orchards and naturally occurring populations. 相似文献
10.
According to a recent demographic survey, the population structure of Pectinaria koreni might fit a source–sink metapopulation model at least at a regional scale. Spatial and temporal genetic structure of the populations
present in the Baie de Seine (eastern Baie de Seine and Baie des Veys) was assessed using four highly polymorphic microsatellite
loci which have revealed strong intra-locality genetic diversity. In the eastern Baie de Seine, both temporal (1994–1996)
and spatial (1994) genetic differentiation were relatively low but significantly different from zero despite a 15-day dispersing
larval stage. Such structures may be explained by the settlement of larvae from different gene pools and differing recruitment
histories among sites within the eastern Baie de Seine. At a larger scale, similar levels of spatial differentiation were
observed in 1999 between the eastern Baie de Seine and the Baie des Veys. The lack of any significant differences in gene
diversity and allelic richness rules out a source–sink functioning at the scale of our study. The present paper provides further
knowledge on the population dynamics of a univoltine species and its persistence in a highly dispersive environment via a
shifting spatial mosaic.
Electronic Publication 相似文献
11.
Summary This study demonstrates the impact of natural factors and human activities on biodiversity at gene level on a keystone Mediterranean
forest ecosystem species. We monitored the within and among population gene diversity of Cedrus libani, a forest tree species of the Eastern Mediterranean mountains. We used paternally inherited chloroplast microsatellites (57
haplotypes) and bi-parentally inherited isozymes (12 loci) to estimate allelic richness, heterozygosity, and differentiation
in 18 natural and 1 planted populations from Turkey and Lebanon. We showed that there is a phylogeographic structure in C. libani, and that forests from Lebanon and Turkey constitute two genetically isolated groups which probably arose from distinct refugia
after the last Quaternary glacial cycle. We found extensive gene flow and relatively low differentiation in Turkey, as well
as little evidence of genetic drift within populations. However, one population we analyzed, which was planted more than 20
centuries ago, and is isolated from core populations in Turkey, demonstrated extremely low genetic diversity and deserves
high conservation priority. In contrast, we found low gene flow, high differentiation and severe cases of genetic drift in
Lebanon. As forests there are the remnants of millennia-long extensive deforestation, all deserve high conservation priority. 相似文献
12.
The current need for forest conservation and management has driven a rapid expansion of landscape genetics approach. This
discipline combines tools from molecular genetics, landscape ecology and spatial statistics and is decisive for improving
not only ecological knowledge but also for properly managing population genetic resources. This approach could be appropriate
to sweet chestnut ( Castanea sativa Mill.), a multipurpose species of great economic importance in the Mediterranean basin and a species considered to be a good
model of integration between natural and human-driven distribution of diversity. Sixteen chestnut populations, covering the
distribution range of the species in Spain, were analysed using seven microsatellite markers. Results revealed a high level
of genetic diversity in Spanish chestnut populations, which in part followed a geographical pattern, although distribution
was not homogeneous. Likewise, areas particularly rich in diversity were detected, facilitating the development of a hypothesis
about the history of chestnut in Spain. In conclusion, these results provide valuable baseline data for more in-depth studies
on chestnut landscape genetics that can contribute to its conservation. 相似文献
13.
? Premise of the study: Geographically peripheral (marginal) populations are expected to have lower genetic diversity and higher genetic differentiation than geographically core (central) populations as a result of supposedly lower effective population size (N(e)) and higher genetic drift, founder effect, fragmentation, and isolation in peripheral than in core populations. Here we address this issue for a long-lived plant species, eastern white cedar (Thuja occidentalis). ? Methods: Genetic diversity and population structure of 13 natural populations of eastern white cedar from its Canadian eastern peripheral and core natural ranges in New Brunswick, Nova Scotia, and Prince Edward Island were studied using six nuclear microsatellite DNA markers. ? Key results: The core populations of eastern white cedar had significantly higher allelic diversity (mean A = 8.83, A(r) = 8.13, A(e) = 4.03) and N(e) (428) than the peripheral populations (A = 6.64, A(r) = 6.15, A(e) = 3.12, N(e) = 198). However, expected heterozygosity was similar in the core (H(e) = 0.64) and peripheral (H(e) = 0.60) populations. Genetic differentiation was significantly higher among the peripheral (F(ST) = 0.089) than among the core (F(ST) = 0.032) populations. No genetic differentiation (F(ST)/Φ(RT) = 0.000) was detected between core and peripheral regions. ? Conclusions: Peripheral populations have significantly lower N(e) and genetic diversity in terms of allelic diversity (richness) and significantly higher genetic differentiation than the core populations of eastern white cedar in its Canadian eastern range. However, core and peripheral populations have similar levels of expected heterozygosity. Implications for conservation of eastern white cedar genetic resources are discussed. 相似文献
14.
To determine extant patterns of population genetic structure in common ash and gain insight into postglacial recolonization processes, we applied multilocus-based Bayesian approaches to data from 36 European populations genotyped at five nuclear microsatellite loci. We identified two contrasting patterns in terms of population genetic structure: (1) a large area from the British Isles to Lithuania throughout central Europe constituted effectively a single deme, whereas (2) strong genetic differentiation occurred over short distances in Sweden and southeastern Europe. Concomitant geographical variation was observed in estimates of allelic richness and genetic diversity, which were lowest in populations from southeastern Europe, that is, in regions close to putative ice age refuges, but high in western and central Europe, that is, in more recently recolonized areas. We suggest that in southeastern Europe, restricted postglacial gene flow caused by a rapid expansion of refuge populations in a mountainous topography is responsible for the observed strong genetic structure. In contrast, admixture of previously differentiated gene pools and high gene flow at the onset of postglacial recolonization of western and central Europe would have homogenized the genetic structure and raised the levels of genetic diversity above values in the refuges. 相似文献
15.
The aims of this study were to assess the genetic diversity of 17 populations of Vietnamese local chickens (VNN) and one Red Jungle Fowl population, together with six chicken populations of Chinese origin (CNO), and to provide priorities supporting the conservation of genetic resources using 20 microsatellites. Consequently, the VNN populations exhibited a higher diversity than did CNO populations in terms of number of alleles but showed a slightly lower observed heterozygosity. The VNN populations showed in total seven private alleles, whereas no CNO private alleles were found. The expected heterozygosity of 0.576 in the VNN populations was higher than the observed heterozygosity of 0.490, leading to heterozygote deficiency within populations. This issue could be partly explained by the Wahlund effect due to fragmentation of several populations between chicken flocks. Molecular analysis of variance showed that most of genetic variation was found within VNN populations. The Bayesian clustering analysis showed that VNN and CNO chickens were separated into two distinct groups with little evidence for gene flow between them. Among the 24 populations, 13 were successfully assigned to their own cluster, whereas the structuring was not clear for the remaining 11 chicken populations. The contributions of 24 populations to the total genetic diversity were mostly consistent across two approaches, taking into account the within‐ and between‐populations genetic diversity and allelic richness. The black H'mong, Lien Minh, Luong Phuong and Red Jungle Fowl were ranked with the highest priorities for conservation according to Caballero and Toro's and Petit's approaches. In conclusion, a national strategy needs to be set up for Vietnamese chicken populations, with three main components: conservation of high‐priority breeds, within‐breed management with animal exchanges between flocks to avoid Wahlund effect and monitoring of inbreeding rate. 相似文献
16.
Species introductions often coincide with loss of genetic diversity and natural enemies. Anthropogenic translocation of the North-American pumpkinseed Lepomis gibbosus (L., 1758) (Centrarchidae) and its further spread have resulted in recent species establishment in most European countries. This study determines genetic differentiation of non-native European pumpkinseed populations and identifies how their genetic structure relates to the distribution and abundance of parasite species. Microsatellite analysis indicated presence of three genetic lineages, which were well supported by discriminant analysis based on parasite abundance data. The first lineage clustered pumpkinseed populations from northern and southern France and showed high allelic richness, heterozygosity and parasite richness. The second included populations along the “Southern invasion corridor” connecting the rivers Rhine, Main and Danube. The fish exhibited low to high genetic and parasite diversity and generally high parasite abundance. The third lineage clustered populations with low genetic and parasite diversity, located in Portuguese reservoirs and water bodies along the upper Elbe. Parasite species richness was significantly associated with host microsatellite heterozygosity and allelic richness, a trend partially affected by richness of North-American parasites. Furthermore, our results indicate that parasite community composition may serve as a useful biological tool to discriminate non-native fish populations and their inter-relationships. 相似文献
17.
The aim of this study was to estimate genetic diversity and assess its importance for plant fitness in a species belonging
to the most endangered species in Europe, Dracocephalum austriacum L., and to select the most valuable populations for conservation of genetic diversity within the species in the studied regions.
We analyzed allozyme variation of 12 populations in three distinct regions (Czech Karst, Moravia and Slovak Karst) in Central
Europe. The results showed high genetic diversity within populations (80.14%) and relatively low differentiation among populations
within regions (9.42%) and between regions (10.45%). Seed production was significantly higher in larger, genetically more
diverse and less inbred populations. The results suggest that genetic diversity has important effect on seed production in
this species and thus can be expected to have strong direct consequences for plant fitness and vitality of the whole populations.
They also show large variation in genetic diversity between populations and indicate which populations should get a priority
in attempts to conserve all the genetic diversity within the region. 相似文献
18.
In previous studies we reported that while core populations of Sitka spruce [ Picea sitchensis (Bong.) Carr] have little within-population genetic structure, peripheral populations are strongly spatially structured at
distances up to 500 m. Here we explore the implications of this difference in structure on ex situ gene conservation collections
and estimates of genetic diversity from research collections. We test the effects of varying the number of individuals sampled
and the total area they are sampled across on capture of neutral genetic variation in collections from core, continuous versus
peripheral, disjunct populations. Bivariate response surface analysis of genetic marker data for eight sequence tagged site
loci from core and peripheral populations suggest that a population sample from 150 trees covering at least 225 ha would be
adequate for capturing 95% of the genetic diversity (as measured by allelic richness or expected heterozygosity) in core populations.
However, a larger sample of 180 individuals from an area of at least 324 ha is needed in peripheral populations to capture
the same proportion of standing variation because of stronger within-population spatial genetic structure. Standard population
sampling protocols for estimating among and within-population genetic diversity would significantly underestimate the within-population
allelic richness and expected heterozygosity of peripheral but not core populations, potentially leading to poor representation
of genetic variation in peripheral populations as well as erroneous conclusions about their genetic impoverishment. 相似文献
19.
Mielichhoferia elongata, one of the so-called “copper mosses,” has a broad but highly disjunctive geographic distribution and is rare throughout its range. A genetic analysis of 30 populations based on a survey of 21 allozyme loci reveals the following. 1) Total gene diversity at the specific level is high (0.41). 2) Within-population diversity is low, and over 90% of all genetic variation is among rather than within populations (mean G ST = 0.93). 3) There is little differentiation in allele frequencies between North American and European populations. 4) Populations consist of one to six multilocus genotypes; 13 of the populations appear to consist of a single clone. 5) Colorado populations contain a tremendous reservoir of genetic variation (88% of all alleles found in the species in North America and Europe occur in one or more Colorado populations). 6) Populations in the eastern and western United States, and in Europe, contain subsets of the allelic diversity found in Colorado. The genetic structure of M. elongata suggests repeated dispersal and founding of populations. 相似文献
20.
Genetic diversity is the raw material for evolutionary change, so a species’ capacity to maintain its genetic diversity is a major concern in conservation genetics. Although genetic diversity within a population is reduced through time by genetic drift, gene flow among populations can act to recover or add new genetic variants. The goal of this study was to infer potential connectivity among isolated-by-sea populations of the vulnerable freshwater blenny ( Salaria fluviatilis) and to determine if gene flow could contribute to maintaining genetic diversity in connected populations. Four genetic clusters (one small at the North, one large at the South for both East and West coasts) were detected with different clustering methods (FLOCK, STUCTURE, UPGMA, AMOVA). The two larger genetic clusters with higher migration-rate estimates among localities had higher genetic diversity and allelic richness and lower relatedness between individuals, compared to isolated localities found in smaller clusters. Our results also suggest that sea currents may facilitate fish movements among neighbouring rivers. Overall, gene flow among isolated-by-sea but close rivers could maintain the evolutionary potential of freshwater blenny populations. This finding should be considered when elaborating a conservation program for this species. 相似文献
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