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1.
K. L. Ciborowski S. Consuegra C. García de Leániz J. Wang M. A. Beaumont W. C. Jordan 《Conservation Genetics》2007,8(6):1355-1367
Over the last 50 years, Spanish Atlantic salmon (Salmo salar) populations have been in decline. In order to bolster these populations, rivers were stocked with fish of northern European
origin during the period 1974–1996, probably also introducing the furunculosis-inducing pathogen, Aeromonas salmonicida. Here we assess the relative importance of processes influencing mitochondrial (mt)DNA variability in these populations from
1948 to 2002. Genetic material collected over this period from four rivers in northern Spain (Cantabria) was used to detect
variability at the mtDNA ND1 gene. Before stocking, a single haplotype was found at high frequency (0.980). Following stocking,
haplotype diversity (h) increased in all rivers (mean h before stocking was 0.041, and 0.245 afterwards). These increases were due principally to the dramatic increase in frequency
of a previously very low frequency haplotype, reported at higher frequencies in northern European populations proximate to
those used to stock Cantabrian rivers. Genetic structuring increased after stocking: among-river differentiation was low before
stocking (1950s/1960s Φ
ST = –0.00296–0.00284), increasing considerably at the height of stocking (1980s Φ
ST = 0.18932) and decreasing post-stocking (1990s/2002 Φ
ST = 0.04934–0.03852). Gene flow from stocked fish therefore seems to have had a substantial role in increasing mtDNA variability.
Additionally, we found significant differentiation between individuals that had probably died from infectious disease and
apparently healthy, angled fish, suggesting a possible role for pathogen-driven selection of mtDNA variation. Our results
suggest that stocking with non-native fish may increase genetic diversity in the short term, but may not reverse population
declines. 相似文献
2.
To offset declines in commercial landings of the softshell clam, Mya
arenaria, resource managers are engaged in extensive stocking of seed clams throughout its range in the northwest Atlantic. Because
a mixture of native and introduced stocks can disrupt locally adapted genotypes, we investigated genetic structure in M.
arenaria populations across its current distribution to test for patterns of regional differentiation. We sequenced mitochondrial
cytochrome oxidase I for a total of 212 individuals from 12 sites in the northwest Atlantic (NW Atlantic), as well as two
introduced sites, the northeast Pacific (NE Pacific), and the North Sea Europe (NS Europe). Populations exhibited extremely
low genetic variation, with one haplotype dominating (65–100%) at all sites sampled. Despite being introduced in the last
150–400 years, both NE Pacific and NS Europe populations had higher diversity measures than those in the NW Atlantic and both
contained private haplotypes at frequencies of 10–27% consistent with their geographic isolation. While significant genetic
structure (F
ST = 0.159, P < 0.001) was observed between NW Atlantic and NS Europe, there was no evidence for genetic structure across the pronounced
environmental clines of the NW Atlantic. Reduced genetic diversity in mtDNA combined with previous studies reporting reduced
genetic diversity in nuclear markers strongly suggests a recent population expansion in the NW Atlantic, a pattern that may
result from the retreat of ice sheets during Pleistocene glacial periods. Lack of genetic diversity and regional genetic differentiation
suggests that present management strategies for the commercially important softshell clam are unlikely to have a significant
impact on the regional distribution of genetic variation, although the possibility of disrupting locally adapted stocks cannot
be excluded. 相似文献
3.
Understanding the present-day distribution of molecular variation requires knowledge about the history of the species. Past
colonization routes and locations of refugia of Scots pine (Pinus sylvestris) were inferred from variation in mitochondrial DNA in material collected from 37 populations located in countries within,
and immediately adjacent to the continent of Europe. Two mitochondrial regions, nad1 intron (exon B/C) and nad7 intron 1, were included in the study. Differentiation in maternally inherited mitochondria was high (G
ST′ = 0.824). Two new haplotypes were found at the nad7 intron 1. The occurrence of a 5-bp indel variant was restricted to the Turkish Kalabak population and a 32 bp only found
in Central, Eastern, and Northern Europe. The complete absence of the 32-bp indel from the Mediterranean peninsulas supports
the view that coniferous forests existed outside these areas during the last glacial maximum, and these populations contributed
to the subsequent colonization of the northern parts of Europe. P. sylvestris shares features of its glacial and postglacial history with two other northern, cold-tolerant tree species, Picea abies and Betula sp. These three species differ from many other European trees for which pollen core and molecular evidence indicate colonization
from southern refugia after the last glacial period. 相似文献
4.
Guillermo Velo-Antón Mario García-París Adolfo Cordero Rivera 《Conservation Genetics》2008,9(5):1263-1274
The European pond turtle (Emys orbicularis) is threatened and in decline in several regions of its natural range, due to habitat loss combined with population fragmentation.
In this work, we have focused our efforts on studying the genetic diversity and structure of Iberian populations with a fine-scale
sampling (254 turtles in 10 populations) and a representation from North Africa and Balearic island populations. Using both
nuclear and mitochondrial markers (seven microsatellites, ∼1048 bp nDNA and ∼1500 bp mtDNA) we have carried out phylogenetic
and demographic analyses. Our results show low values of genetic diversity at the mitochondrial level although our microsatellite
dataset revealed relatively high levels of genetic variability with a latitudinal genetic trend decreasing from southern to
northern populations. A moderate degree of genetic differentiation was estimated for Iberian populations (genetic distances,
F
ST
values and clusters in the Bayesian analysis). The results in this study combining mtDNA and nDNA, provide the most comprehensive
population genetic data for E. orbicularis in the Iberian Peninsula. Our results suggest that Iberian populations within the Iberian–Moroccan lineage should be considered
as a single subspecies with five management units, and emphasize the importance of habitat management rather than population
reinforcement (i.e. captive breeding and reintroduction) in this long-lived species. 相似文献
5.
Morten E. Allentoft Hans R. Siegismund Lars Briggs Liselotte W. Andersen 《Conservation Genetics》2009,10(1):15-28
The European natterjack toad (Bufo calamita) has declined rapidly in recent years, primarily due to loss of habitat, and in Denmark it is estimated that 50% of the isolated
populations are lost each decade. To efficiently manage and conserve this species and its genetic diversity, knowledge of
the genetic structure is crucial. Based on nine polymorphic microsatellite loci, the genetic diversity, genetic structure
and gene flow were investigated at 12 sites representing 5–10% of the natterjack toad localities presently known in Denmark.
The expected heterozygosity (H
E) within each locality was generally low (range: 0.18–0.43). Further analyses failed to significantly correlate genetic diversity
with population size, degree of isolation and increasing northern latitude, indicating a more complex combination of factors
in determining the present genetic profile. Genetic differentiation was high (overall θ = 0.29) and analyses based on a Bayesian clustering method revealed that the dataset constituted 11 genetic clusters, defining
nearly all sampling sites as distinct populations. Contemporary gene flow among populations was undetectable in nearly all
cases, and the failure to detect a pattern of isolation by distance within major regions supported this apparent lack of a
gene flow continuum. Indications of a genetic bottleneck were found in three populations. The analyses suggest that the remaining
Bufo calamita populations in Denmark are genetically isolated, and represent independent units in a highly fragmented gene pool. Future
conservation management of this species is discussed in light of these results.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
6.
The white-headed duck is a globally threatened species native to the Palaearctic with a range extending from Spain in the
west to the western edge of China in the east. Its populations have become fragmented and undergone major declines in recent
decades. To study genetic differences between populations across the range and change in genetic diversity over time, we sequenced
a portion of the mitochondrial DNA control region from 67 museum specimens (years 1861–1976) as well as 39 contemporary samples
from Spain and seven from Greece (years 1992–2003). In the historical sample, we found a lack of significant genetic structure
between populations in different areas. We found evidence that the species experienced a rapid expansion in the past, perhaps
from glacial refugia centred around the Mediterranean following the last ice age. In Spain, the population went through a
dramatic bottleneck in the 1970s and early 1980s, when only a few dozens individuals remained in the wild. Although population
size has since recovered to a few thousand individuals, we found a highly significant loss of mitochondrial haplotype diversity
between the historical and contemporary samples. Given ongoing declines in other areas, losses in genetic diversity that may
reduce the adaptive potential of white-headed ducks in the future are a continuing concern throughout the geographic range
of this species. 相似文献
7.
Xiao-Li Peng Chang-Ming Zhao Gui-Li Wu Jian-Quan Liu 《Trees - Structure and Function》2007,21(4):457-464
Repeated cycles of retreat and recolonization during the Quaternary ice ages are thought to have greatly influenced current
species distributions and their genetic diversity. It remains unclear how this climatic oscillation has affected the distribution
of genetic diversity between populations of wind-pollinated conifers in the Qinghai-Tibetan region. In this study, we investigated
the within-species genetic diversity and phylogenetic relationships of Picea likiangensis, a dominant forest species in this region using polymorphic DNA (RAPD) markers. Our results suggest that this species has
high overall genetic diversity, with 85.42% of loci being polymorphic and an average expected heterozygosity (H
E) of 0.239. However, there were relatively low levels of polymorphism at population levels and the differences between populations
were not significant, with percentages of polymorphic bands (PPB) ranging from 46.88 to 69.76%, Nei’s gene diversity (H
E) from 0.179 to 0.289 and Shannon’s indices (Hpop) from 0.267 to 0.421. In accordance with our proposed hypothesis, a high level of genetic differentiation among populations
was detected based on Nei’s genetic diversity (G
ST = 0.256) and AMOVA analysis (Phi
st = 0.236). Gene flow between populations was found to be limited (Nm = 1.4532) and far lower than reported for other conifer species with wide distribution ranges from other regions. No clusters
corresponding to three morphological varieties found in the south, north and west, respectively, were detected in either UPGMA
or PCO analyses. Our results suggest that this species may have had different refugia during the glacial stages in the southern
region and that the northern variety may have multiple origins from these different refugia. 相似文献
8.
The intraspecific genetic diversity of the kelp Undaria pinnatifida (Harvey) Suringar (Laminariales, Phaeophyceae) was investigated using DNA sequences of the mitochondrial cytochrome oxidase
subunit 3 (cox3) gene and internal transcribed spacer 1 (ITS1) of nuclear ribosomal DNA in plants collected from 21 localities along the
Japanese coast between 2001 and 2003. Morphological variation was also examined and compared with the genetic diversity. Cox3 analyses of 106 plants revealed 9 haplotypes (I–IX) that differed from each other by 1–7 bp (all synonymous substitutions).
Haplotype I was distributed in Hokkaido and the northern Pacific coast of Honshu, while haplotype III was found along the
Sea of Japan coast of Honshu. Other types were found along the central and southern coast of Honshu. ITS1 analyses of 42 plants
revealed 0–1.7% nucleotide differences, but plants from the Sea of Japan coast and northern Japan had similar sequences. The
lower genetic differentiation along the Sea of Japan and northern coasts might be due to the recent establishment (after the
middle of the last glacial period) of the Sea of Japan flora. The cox3 haplotype of cultivated plants was found in natural populations occurring close to cultivation sites (Naruto, Tokushima
Pref., and Hokutan, Hyogo Pref.). This suggests that cultivated plants possibly escaped and spread or crossed with plants
of natural populations. Morphological analyses of variation in 10 characters were conducted using 66 plants. The results showed
no significant local variation owing to the wide variation in each population and did not support any forma previously described.
No correlations between the morphological characters and cox3 haplotypes were detected. 相似文献
9.
Fungi have been only rarely isolated from glacial ice in extremely cold polar regions and were in these cases considered as random, long-term preserved Aeolian deposits. Fungal presence has so far not been investigated in polar subglacial ice, a recently discovered extreme habitat reported to be inhabited exclusively by heterotrophic bacteria. In this study we report on the very high occurrence (up to 9000 CFU L−1) and diversity of filamentous Penicillium spp. in the sediment-rich subglacial ice of three different polythermal Arctic glaciers (Svalbard, Norway). The dominant species was P. crustosum, representing on the average half of all isolated strains from all three glaciers. The other most frequently isolated species were P. bialowiezense, P. chrysogenum, P. thomii, P. solitum, P. palitans, P. echinulatum, P. polonicum, P. commune, P. discolor, P. expansum, and new Penicillium species (sp. 1). Twelve more Penicillium species were occasionally isolated. The fungi isolated produced consistent profiles of secondary metabolites, not different from the same Penicillium species from other habitats. This is the first report on the presence of large populations of Penicillium spp. in subglacial sediment-rich ice. 相似文献
10.
Joëlle Goüy de Bellocq Franz Suchentrunk Stuart J. E. Baird Helmut Schaschl 《Immunogenetics》2009,61(2):131-144
We surveyed the genetic diversity of the expressed major histocompatibility complex class II DQA locus in natural populations
of European brown hares, Lepus europaeus, from Austria and Belgium (267 individuals in total). Based on cDNA sequences, we designed hare-specific primers to amplify
the highly variable second exon of the DQA gene. Using cloning–sequencing methodology and capillary electrophoresis single-strand
conformation polymorphism, we found ten alleles of the DQA exon 2 locus across these two European regions, of which eight
are described for the first time. To search for signals of selection and recombination in the evolution of the DQA gene within
the leporids, we augmented our sample with orthologous DQA alleles from the European rabbit, Oryctolagus cuniculus, in order to carry out a species level, species pairwise comparison. We found evidence of recombination in the history of
the DQA sequences in leporids with some recombinant alleles bridging the species divide. In both species, selection on peptide
binding site codons can be detected, though stronger for the rabbit. This result suggests that there may be a differential
selection pressure in the deeper evolutionary history of these two species due to differences in several demographic and ecological
traits likely subjecting them to differential selection by parasites. Finally, evolutionary relationships show a widespread
and statistically significant intermingling of alleles from the two species. The many macroparasites shared between hares
and rabbits may explain this pattern of trans-species polymorphism.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
The nucleotide sequence data reported in this paper have been submitted to Genbank and have been assigned the accession numbers
FJ225335–FJ225346. 相似文献
11.
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
12.
Ten enzymes (AAT, CK, G3PDH, HEX, IDH, LDH, MDH, ME, PGI, PGM) were examined using horizontal starch gel electrophoresis to
estimate the levels of genetic variation within and among six natural populations of two grasshopper species Atractomorpha sinensis and A. peregrina from Shanxi, China. The collecting sites were geographically distant from each other from south to north: Quwo district,
Linfen city; Xiangyuan county, Changzhi; Jinyuan district, Taiyuan city; Yuanping county, Xinzhou city and Fanshi county of
Xinzhou.A. sinensis showed 43 alleles at 16 loci but A. peregrine showed 39 alleles at 15 loci (Idh-1 was deficient). The zymograms showed that some common alleles were shared at several loci in these two species (Aat-1-b, Aat-2-b, G3pdh-a, Ck-1-b and Ldh-b). However, Hex-1-a, Hex-2-a, Hex-3-a, Idh-2-b, Mdh-2-b, Mdh-1-f, Pgi-b, Pgm-b had common alles in A. sinensis and Hex-1-b, Hex-2-b, Hex-3-b, Idh-2-a, Mdh-2-a, Mdh-1-d, Pgi-a, Pgm-c were of high frequency in A. peregrine instead. Most of the observed genotype frequencies were found to significantly deviate from the Hardy-Weinberg expectations
in both species. A tendency of clinal distribution of allele frequency was observed at three loci. The frequency of the moderately
migrating allele Me-c (0.318–0.740) in A. peregrina, Hex-1-a (0.800–1.000) and Ldh-b (0.487–0.750) in A. sinensis demonstrated increased frequency from north to south. Such tendency suggests that the allele frequency in these three loci
may be correlated with the species’ geographic distributions. A. sinensis showed higher genetic diversity than A. peregrina as indicated by higher mean number of alleles per locus (A = 1.9–2.3 in A. sinensis and 1.7–2.2 in A. peregrina), percentage of polymorphic loci (56.3%–68.8% in A. sinensis and 43.8%–56.3% in A. peregrina), and the observed heterozygosities (H
o
= 0.072–0.096 in A. sinensis and 0.70–0.107 in A. peregrina). The observed heterozygosities of the six populations were all noticeably lower than the Hardy-Weinberg expectations, mostly
due to heterozygote deficiency in the populations of both species. The overall mean F
ST
were small (F
ST
= 0.045, P > 0.05 in A. sinensis populations and 0.087, P > 0.05 in A. peregrina populations). Nei’s genetic identity (I) estimates indicate low intraspecific (>0.95) but higher interspecific (0.377–0.447) genetic diversity. The cluster analysis
based on modified Roger’s genetic distance (D) showed that the two species were divided into two branches.
Both species are of limited dispersal capacity and a moderate geographical barrier might significantly restrict the gene exchange
among populations, resulting in accumulation of local genetic differentiations. The A. sinensis populations used in this study were separated from each other by 155.2 to 271.4 km and the A. peregrina populations were separated from each other by 78.8 to 174.9 km with observable physical barriers. The allozyme data showed
only minimal genetic differentiation at population level, most likely as a result of gene exchange. It is reasoned that natural
factors and human agricultural activities might have facilitated migration and dispersal for the two species.
__________
Translated from Acta Ecologica Sinica, 2005, 25(10): 2574–2481 [译自: 生态学报] 相似文献
13.
Ungava Bay is ice covered 6–7 months of the year and evidence of ice scouring of seaweeds is extensive in the intertidal and
shallow subtidal. Maximum tidal amplitudes of 16 m, among the highest in Canadian waters, compound this impact. Despite this
level of annual perturbation, very extensive and dense beds of fucoids in the intertidal and laminarians in the subtidal are
common on the western shores of Ungava Bay. Ground surveys of 24 intertidal stations combined with satellite images delineated
82,000 tons standing crop of Fucus vesiculosus and Fucus evanescens in Payne Bay, of which 36,000 tons were considered harvestable. Subtidally, kelp cover reached peak biomass at 5–10 m consisting
of three primary species, Saccharina longicruris, Laminaria digitata, and Laminaria solidungula. In the area of Payne Bay, kelp beds of 100 ha were common, averaging 9–12 kg m−2 wet weight. The productivity of brown algae at these latitudes has been assumed to be low relative to southern latitudes.
Direct measurement of lineal growth indicates productivity is intermediate between arctic and temperate populations. The potential
for medium level industrial harvest exists under conservative management strategies within the constraints of subarctic logistics. 相似文献
14.
Abies ziyuanensis is a highly endangered fir species endemic to South China. Unlike other Abies species that are distributed in areas with cold climates, A. ziyuanensis is restricted to several isolated island-like localities at subtropical mountains. In this study, we used dominant amplified
fragment length polymorphism (AFLP) and co-dominant simple sequence repeats (SSR) markers to infer the genetic structure of
A. ziyuanensis. Seven populations consisting of 139 individuals were sampled across their whole distribution. A. ziyuanenesis has a relatively low level of genetic variation, with a mean genetic diversity per population (He) of 0.136 (AFLP) and 0.337 (SSR), which is lower than that of other reported endemic species based on the same kind of marker.
We observed high population differentiation, with Gst = 0.482 (AFLP) and Fst = 0.250 (SSR), among the seven populations. AMOVA also detected significant differentiation among populations (Φst (AFLP) = 0.550
and Φst (SSR) = 0.289) and among regions (Φct (AFLP) = 0.139 and Φct (SSR) = 0.135) in both marker types. Both ongoing evolutionary
forces (e.g., genetic drift resulting from small population size) and historical events (e.g., population contraction and
fragmentation during and after the Quaternary glacial cycles) may have contributed to the genetic structure in A. ziyuanensis. 相似文献
15.
Genetic variability among 122 Rhynchosporium secalis isolates collected from barley in three regions of Tunisia was investigated using host differentials, amplified fragment
length polymorphism (AFLP), and microsatellite markers. The isolates were collected from a widely grown scald-susceptible
barley cultivar Rihane and a range of local landrace cultivars in geographically distinct regions with different agroclimatic
conditions. Pathotypic diversity (the proportion of unique pathotypes) was high in R. secalis populations from the high (100% diversity), moderate (95%), and low (100%) rainfall areas of Tunisia, and from both Rihane
(which is the sole variety grown in the high rainfall region) and local landraces (which predominate in the low rainfall area).
This may reflect a general adaptability for aggressiveness and suggests that the widely grown cultivar Rihane has exerted
little or no selection pressure on the pathogen population since its release in 1983. Genotypic diversity (GD), defined as
the probability that two individuals taken at random had different genotypes, was high for populations from Rihane, local
landraces, and different agro-ecological zones (GD = 0.96–0.99). There was low genetic differentiation among pathogen populations
from different host populations (G
ST ≤ 0.08, θ ≤ 0.12) and agro-ecological zones (G
ST ≤ 0.05, θ ≤ 0.04), which may be partly explained by gene flow due to the movement of infected stubble around the country.
There was no correlation (r = 0.06, P = 0.39) between virulence phenotype and AFLP haplotype. A phenetic tree revealed groups with low bootstrap values that did
not reflect the grouping of isolates based on host, pathotype, or agro-ecological region. The implications of these findings
for R. secalis evolutionary potential and scald-resistance breeding in Tunisia are discussed. 相似文献
16.
Northern and mountainous ice sheets have expanded and contracted many times due to ice ages. Consequently, temperate species have been confined to refugia during the glacial periods wherefrom they have recolonized warming northern habitats between ice ages. In this study, we compare the gene CYP405A2 between different populations of the common burnet moth Zygaena filipendulae from across the Western Palearctic region to illuminate the colonization history of this species. These data show two major clusters of Z. filipendulae populations possibly reflecting two different refugial populations during the last ice age. The two types of Z. filipendulae only co‐occur in Denmark, Sweden, and Scotland indicating that Northern Europe comprise the hybridization zone where individuals from two different refugia met after the last ice age. Bayesian phylogeographic and ecological clustering analyses show that one cluster probably derives from an Alpe Maritime refugium in Southern France with ancestral expansive tendencies to the British Isles in the west, touching Northern Europe up to Denmark and Sweden, and extending throughout Central Europe into the Balkans, the Peleponnes, and South East Europe. The second cluster encompasses East Anatolia as the source area, from where multiple independent dispersal events to Armenia, to the Alborz mountains in north‐western Iran, and to the Zagros mountains in western Iran are suggested. Consequently, the classical theory of refugia for European temperate species in the Iberian, Italian, and Balkan peninsulas does not fit with the data from Z. filipendulae populations, which instead support more Northerly, mountainous refugia. 相似文献
17.
Rimgaudas Treinys Asko L?hmus Darius Stonius Saulis Skuja Eugenijus Drobelis Bronius ableviius Saulius Rumbutis Deivis Dementaviius Vladas Narueviius Antanas Petraka Danas Augutis 《Journal of Ornithology》2008,149(1):75-81
Recent trends in the European Black Stork Ciconia nigra population are geographically distinct: range expansion and adaptation to human activity dominate in western and central
Europe, while declines—probably induced by landscape change—are reported in the east. We studied the large Lithuanian Black
Stork population in the transition zone to explore whether, and how, the detrimental influences of recent Baltic landscape
changes are balanced by the West European tendency of behavioural adaptation to human activity. Based on monitoring in sample
plots, the current population was estimated at 650–950 pairs, indicating a significant decrease (possibly over 20%) during
the last two decades. In comparison to the Latvian and Estonian populations, however, this decline is smaller, and the reproductive
success remains at a high level [66% breeding success and 2.99 ± 0.97 (SD) fledglings per successful attempt, 2000–2006];
this north–south gradient suggests a climate-mediated impact of habitat degradation in the Baltic countries. The storks are
also nesting closer to forest edges and in younger stands than 15–30 years ago, which has probably reduced the nest-tree limitation,
as indicated by an increased use of large oaks. Thus, habitat degradation and adaptation seem to be taking place simultaneously
in the Lithuanian Black Stork population, as was expected from its geographical location. In general, our study supports the
view that, whenever possible, species conservation strategies and the use of indicator species should be geographically explicit. 相似文献
18.
M. G. Giacobbe A. Penna E. Gangemi M. Masò E. Garcés S. Fraga I. Bravo F. Azzaro N. Penna 《Hydrobiologia》2007,580(1):125-133
Summer outbreaks of the dinoflagellate Alexandrium taylorii Balech are recurrent events in nearshore waters of Sicily (Italy)—a central region in the Mediterranean Sea—producing dense
yellowish–green patches. Beyond the local phenomenon, the problem covers a broader geographic scale, involving also other
European localities, mostly in Spain.
Biological, environmental, and molecular data are reported here from a semi-closed bay of Sicily (Vulcano Island, Tyrrhenian
Sea, 2000–2003), showing in summer the recurrence of high-biomass blooms and events of water discolouration. Without underestimating
the setbacks to the tourism industry, the ecological impact of A. taylorii blooms may be important considering the high levels of biomass produced (West Bay, Vulcano: up to a magnitude order of 107 cells l−1, 50–180 μg-Chla l−1, June 2002 and 2003) and coincident conditions of oxygen supersaturation of the waters (130–170%). Trophic trends in the
Tyrrhenian site indicate high amounts of nutrients linked to the increased anthropogenic activity in summer, although recently
there has been an apparent shift of the marked eutrophic conditions towards a slighter eutrophy.
Genetic data on isolates of A. taylorii from the Mediterranean Sea are also discussed. Molecular analyses implied the sequencing of target rDNA regions (5.8S rDNA
and ITS regions) of several isolates from different Mediterranean localities, as well as the application of species-specific
PCR assays for rapid species identification in preserved field samples. The confirmation of the specific identity provided
new insights into the biogeography of this species and further evidence of the occurrence of A. taylorii in a number of Mediterranean localities, both in the western side (the Catalan coast of Spain) and the eastern area (Greece).
Analyses of the molecular diversity of geographically distinct isolates of A. taylorii from Italy, Spain, and Greece based on the 5.8S rDNA-ITS region sequences showed a high level of similarity, indicating the
existence of an unique Mediterranean population. 相似文献
19.
Dipteronia is an endemic genus to China and includes only two species, Dipteronia sinensis and D. dyeriana. Based on random amplified polymorphic DNA (RAPD) markers, a comparative study of the genetic diversity and genetic structure
of Dipteronia was performed. In total, 128 and 103 loci were detected in 17 D. sinensis populations and 4 D. dyeriana populations, respectively, using 18 random primers. These results showed that the proportions of polymorphic loci for the
two species were 92.97% and 81.55%, respectively, indicating that the genetic diversity of D. sinensis was higher than that of D. dyeriana. Analysis, based on similarity coefficients, Shannon diversity index and Nei gene diversity index, also confirmed this result. AMOVA analysis demonstrated that the genetic variation of D. sinensis within and among populations accounted for 56.89% and 43.11% of the total variation, respectively, and that of D. dyeriana was 57.86% and 42.14%, respectively. The Shannon diversity index and Nei gene diversity index showed similar results. The abovementioned characteristics indicated that the genetic diversity levels
of these two species were extremely similar and that the interpopulational genetic differentiation within both species was
relatively high. Analysis of the genetic distance among populations also supported this conclusion. Low levels of interpopulational
gene flow within both species were believed to be among the leading causes for the above-mentioned phenomenon. The correlation
analysis between genetic and geographical distances showed the existence of a remarkably significant correlation between the
genetic distance and the longitudinal difference among populations of D. sinensis (p < 0.01), while no significant correlation was found between genetic and geographical distances among populations of D. dyeriana. This indicated that genetic distance was correlated with geographical distances on a large scale rather than on a small
scale. This result may be related to differences in the selection pressure on species by their habitats with different distribution
ranges. We suggest that in situ conservation efforts should focus on establishing more sites to protect the natural populations and their habitats. Ex situ conservation efforts should focus on enhancing the exchange of seeds and seedlings among populations to facilitate gene exchange
and recombination, and to help conserve genetic diversity.
__________
Translated from Acta Phytoecologica Sinica, 2005, 29(5): 785–792 [译自: 植物生态学报, 2005, 29(5): 785–792] 相似文献
20.
Anastasia Imsiridou Alexandros Triantafyllidis Athanasios D. Baxevanis Costas Triantaphyllidis 《Biologia》2009,64(4):781-785
Wild common carp from two lakes and two rivers in Greece were genetically characterized with sequencing analysis of two mitochondrial
DNA segments: cytochrome b (1119 bp) and D-loop (646 bp). A total of 9 variable singleton sites and 7 unique haplotypes were detected. A common haplotype was found in three
out of the four populations examined, which seems to be the ancestral one and represents the European origin of common carp
from Greece. This haplotype could be also justified by the introductions reported with individuals belonging to the Central
European race, into many natural habitats in Greece. Limited genetic variation — in Evros and Aliakmonas populations — could
be due to bottleneck effects and small effective population sizes, whereas the different haplotypes found in Lake Volvi could
represent different common carp stocks. Values of sequence divergence among Greek haplotypes ranged from 0.0006 to 0.0023.
The Neighbour-Joining (NJ) phylogenetic tree constructed based on the combined sequences, reveals that the populations of
common carp from Greece belong to the European group of populations — which is highly divergent from the South East-Asia cluster
— and to the subspecies Cyprinus carpio carpio. 相似文献