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1.
Invasive crayfish are a worldwide problem for aquatic ecosystems. So far, no control method has proven successful. Field data from invaded streams have suggested that physical structures may hamper the spread rate of invasive crayfish into new areas. However, given the difficulties for carrying out dam construction in natural habitats, data about their effectiveness in incipient invading populations are practically nonexistent. This paper evaluates the effectiveness of small dams to contain the advance of an incipient population of the invasive Procambarus clarkii in a mountain stream harboring the European southernmost population of the endangered Austropotamobius pallipes. The management strategy involved the construction of 3 artificial small (<3 m high) dams that were complemented with specific design solutions to increase their theoretical efficacy. Catch Per Unit Effort (CPUE) obtained during monitoring surveys carried out for 4 years were used as an indicator of containment effectiveness. The dams successfully prevented Procambarus clarkii from extending its range into the area occupied by A. pallipes. In addition, regardless of whether the construction of new dams isolated the leading edge of the invading population between two dams, the CPUE declined to below detectable limits. Therefore, dams are suggested to effectively stop, or at least hinder, the advance of invasive crayfish. Long-term monitoring is recommended to verify the on-going success of the dams in preventing upstream invasion.  相似文献   

2.
In crayfish, one very well-studied circadian rhythm is that of electroretinogram (ERG) amplitude. The cerebroid ganglion has been considered a plausible site for the circadian pacemaker of this rhythm and for the retinular photoreceptors, as the corresponding effectors. The pigment dispersing hormone (PDH) appears to synchronize ERG rhythm, but its characterization as a synchronizer cue remains incomplete. The main purposes of this work were a) to determine whether PDH acts on the cerebroid ganglion, and b) to complete its characterization as a non-photic synchronizer. Here we show that PDH increases the number of the spontaneous potentials of the cerebroid ganglion, reaching 149.92 ± 6.42% of the activity recorded in the controls, and that daily application of PDH for 15 consecutive days adjusts the ERG circadian rhythm period to 24.0 ± 0.2 h and the end of the activity period of the rhythm coincides with the injection of the hormone. In this work, we hypothesized that in crayfish, PDH transmits the “day” signal to the ERG circadian system and acts upon both the presumptive circadian pacemaker and the corresponding effectors to reinforce the synchronization of the system.  相似文献   

3.
Psathyrostachys huashanica Keng., a species endemic to China, is only distributed in Huashan Mountain in Shaanxi Province. It has been listed as “national first-class protected rare species.” In this study, the microsatellites of barley were used to analyze genetic diversity of P. huashanica populations sampled from three valleys (Huangpu, Xian and Huashan Valleys) in Mt. Huashan. A total of 33 alleles of 11 loci were detected from 266 individuals. The observed average number of alleles (A) is 2.75; the effective number of alleles (Ae) is 1.67. The percentage of polymorphic loci (PPB) is 58.33% in Huangpu Valley, 75% in Xian Valley, 83.33% in Huashan Valley, and the total PPB is 83.33%. About 77.6% of (FST = 0.324) genetic diversity was observed within the subpopulations. Genetic differentiation within each subpopulations was higher than that among the subpopulations. Mean genetic distance is 0.17 (range: 0.010–0.401). Correlation analysis detected significant correlation between genetic distance and vertical distance of altitude in Huashan Valley. Differentiation mainly occurred between the higher altitude subpopulations and the lower altitude subpopulations, suggesting that altitude might be the major factor that restricted the gene flow between different altitude subpopulations and resulted in differentiation of subpopulations.  相似文献   

4.
Halophila beccarii (Hydrocharitaceae), a small monoecious seagrass, has been listed as a threatened species. In this study, a total of 106 samples were collected from four Chinese populations located at the northern limit of its distribution range. Using six polymorphic microsatellites, we found low genetic variation in this species, in which the mean number of alleles per locus was 2.8, and 16 multi-locus genotypes were revealed. In the four populations, the mean number of alleles per locus ranged from 1.2 to 2, one to eight genotypes were found, and clonal diversity ranged from 0 to 0.23; observed and expected heterozygosity ranged from 0.17 to 0.40 and from 0.09 to 0.24, respectively. Strong genetic differentiation was found among the populations, and the standardized fixation index (FST) was 0.787. Species traits (i.e., clonal growth) and bottleneck effects due to drastic population fluctuation may contribute to the observed low genetic variation.  相似文献   

5.
Masu salmon, Oncorhynchus masou masou, is an economically important fish species in the Far East and occurs in two life history forms: sea-run migratory (anadromous) and freshwater resident (non-anadromous). The non-anadromous form has recently become a popular freshwater food and game fish during a well-known Korean winter festival. However, the genetic background of this species remains largely unknown, partly due to a lack of molecular genetic markers. In this study, we developed new polymorphic microsatellite markers for masu salmon using next-generation sequencing technology. From 40 primer sets, 11 primer sets (27.5% of the primer sets selected) were successfully amplified with 106 alleles (range 2–9) in 64 individuals from different populations: two wild and one hatchery. Observed and expected heterozygosities ranged from 0.304 to 0.947 and 0.278 to 0.865, respectively. Significant departures from the Hardy–Weinberg equilibrium were detected for four markers (OMM11, OMM17, OMM28, and OMM33) in a single population. All pair-wise FST values were highly significant between the wild and hatchery populations (range 0.084–0.183, P < 0.0001). We identified a set of robust microsatellite markers that worked well even in formalin-fixed samples, which will be suitable for biogeographical and population structure analyses of the masu salmon.  相似文献   

6.
The West Himalayan yew, Taxus fuana Nan Li & R.R. Mill (Taxaceae), is an endangered species endemic to the Western Himalayas. An investigation of the genetic diversity of wild populations of T. fuana in Pakistan was undertaken. The genetic diversity and genetic structure was quantified using random amplified polymorphic DNA (RAPD) variation in 219 individuals of the 10 populations. Of the 32 universal primers screened 16 produced highly reproducible, clear RAPD bands. Using these primers, 193 discernible DNA fragments were generated, of which 164 (84.97%) were polymorphic. The statistical results indicated that there was a relatively low genetic diversity within populations (with percentages of polymorphic bands, PPB, ranging from 29.53 to 50.26%, with an average of 38.34% and a Nei's genetic diversity index (HE) of 0.1165), and a high genetic differentiation among populations (GST = 0.5842, ΦST = 0.5685) within these populations. The gene flow (Nm) was low with only 0.3558.  相似文献   

7.
The perennial herb Primula cicutariifolia Pax is an endangered and endemic species with narrow distribution in eastern Anhui and Zhejiang provinces of China. In this study, the levels of genetic variation and the pattern of genetic structure in five natural populations of P. cicutariifolia were assessed by inter-simple sequence repeats (ISSR) and simple sequence repeat (SSR) markers. Both markers revealed that there was remarkably low genetic variation within populations (e.g., He = 0.19 and 0.18, for ISSR and SSR respectively) and high differentiation among populations (GST = 0.714 and 0.611; ΦST = 0.698 and 0.599, for ISSR and SSR respectively). The level of population genetic diversity was correlated to population size only detected by ISSR markers. The genetic structure of P. cicutariifolia may be explained by limited gene flow that was caused by habitat fragmentation and limited seeds and pollen dispersal ability, self breeding system and biennial life form. To protect and avoid disappearance of P. cicutariifolia, much more attentions should be paid to protect all the remnant populations and their habitats, and three management units, i.e. Tianmushan, Damodao, and Panan units, were proposed.  相似文献   

8.
Genetic diversity and population structure of 15 wild emmer wheat (Triticum dicoccoides) populations from Israel were detected by 30 sequence-related amplified polymorphism (SRAP) primer pairs. Two hundred and forty four fragments out of 438 were polymorphic. The proportion of polymorphic loci (P), the genetic diversity (He), and Shannon's information index were 0.557, 0.198, and 0.295, respectively. The population Amirim had the highest genetic variation, whereas the population of Tabigha had the lowest genetic variation. The hierarchical analysis of molecular variance (AMOVA) revealed that most of the variation was presented within populations. The value of genetic distance (D) between the populations varied from 0.027 to 0.165 with an average of 0.079, and the estimates of genetic distance were geographically independent based on the Mantel test (r = 0.105, P = 0.168). A total of 30 significant (P < 0.05) correlations were detected between 14 SRAP loci and 12 ecogeographic factors.  相似文献   

9.
Genetic diversity within and among six natural populations of Nypa fruticans from China, Vietnam, and Thailand was assessed using SSR and ISSR analysis. Our results showed an extremely low level of genetic diversity of N. fruticans (at the species level, P = 11.76% and 2.88%, He = 0.0279 and 0.0113, I = 0.0470 and 0.0167 by SSRs and ISSRs, respectively) across a total of 183 individuals. No genetic variation was detected within any population except for the Thailand population by SSRs (P = 11.76%, He = 0.0417; I = 0.0622). The bottlenecks during glacial epochs, founder effects, and propagation pattern may be responsible for the extremely low level of genetic diversity of N. fruticans.  相似文献   

10.
Few studies have investigated the genetic diversity of populations of common and widespread lichenized fungi using microsatellite markers, especially the relationships between different measures of genetic diversity and environmental heterogeneity. The main aim of our study was to investigate the population genetics of a widespread and mainly clonally reproducing Usnea subfloridana at the landscape scale, focusing on the comparison of lichen populations within hemiboreal forest stands. Particular attention has been paid to the genetic differentiation of lichen populations in two geographically distinct regions in Estonia and the relationships between forest characteristics and measures of genetic diversity. We genotyped 578 Usnea thalli from eleven lichen populations using seven specific fungal microsatellite markers. Measures of genetic diversity (allelic richness, Shannon's information index, Nei's unbiased genetic diversity, clonal diversity, the number of multilocus genotypes, the number of private alleles, and the minimum number of colonization events) were calculated and compared between Usnea populations. Shared haplotypes, gene flow and AMOVA analyses suggest that unconstrained gene flow and exchange of multilocus genotypes exist between the two geographically remote regions in Estonia. Stand age, mean circumference of the host tree, size of forest site and tree species composition did not show any significant influence on allelic richness, Shannon's information index, Nei's unbiased genetic diversity, clonal diversity, the number of private alleles, and the minimum number of colonization events of U. subfloridana populations. Therefore it was concluded that other factors of habitat heterogeneity could probably have a more significant effect on population genetics of U. subfloridana populations.  相似文献   

11.
European foulbrood (EFB) persists in England and Wales despite current treatment methods, all of which include feeding honey bee colonies with the antibiotic oxytetracycline (OTC). A large-scale field experiment was conducted to monitor a husbandry-based method, using comb replacement (known as Shook swarm), as a drug free EFB control option. The understanding of EFB epidemiology is limited, with little information on the presence of Melissococcus plutonius in disease free colonies. Additional samples were collected from diseased and disease free apiaries to identify symptomless infection. EFB reoccurrence was not significantly different between OTC and husbandry methods and real-time PCR data demonstrated that fewer Shook swarm treated colonies contained M. plutonius carryover to the Spring following treatment. Asymptomatic colonies from diseased apiaries showed an increased risk of testing positive for M. plutonius compared to asymptomatic colonies from disease free apiaries. The probability of a sample being symptomatic increased when a greater quantity of M. plutonius was detected in adult bees and larvae. The possibility of treating EFB as an apiary disease rather than a colony disease and the implications of a control strategy without antibiotics are discussed.  相似文献   

12.
Amblyospora infections in Aedes stimulans are transovarially transmitted by females infected in the previous year. Pathogen development in progeny is dimorphic and host sex dependent. In males, the pathogen invades fat body tissue and undergoes an extensive developmental sequence which kills the host and results in the formation of eight haploid spores enclosed in an accessory membrane that are not infectious to other larvae. In females, the pathogen invades host oenocytes and undergoes a simple developmental sequence which has no detrimental affect on longevity, fecundity, oviposition, or egg hatch, and results in the formation of binucleated spores that infect the ovaries and ensure transmission to the next generation. Transovarial transmission is continuous and is the major way in which these microsporidia are maintained from year to year, but is incapable of maintaining infections in breeding populations because of low transmission rates and is not sufficient to account for the types and levels of infection observed in the field. Horizontal transmission is reported for the first time. It occurs sporadically during the early stages of larval subsequently disseminated to oenocytes of adult hosts and are transovarially transmitted by females to filial host generations. This pathway of transmission provides the necessary mechanism whereby these microsporidia can reenter the mosquito population and thus perpetuate themselves.  相似文献   

13.
Thirteen wild species of Passiflora were analyzed using conventional and CMA/DA/DAPI staining to evaluate the karyotype diversity between and within the subgenus Decaloba and Passiflora. The karyotypic features indicate that both subgenera have a conserved chromosome number, as reported before for several species. Submetacentric (sm) chromosomes were found in species from both subgenera, suggesting that sm chromosomes are not restricted to a particular subgenus. The analysis of the karyotypic heterogeneity enabled to distribute the species in three groups, but with no support to phylogenetic and taxonomic levels. The application of fluorochromes allowed for the visualization of CMA+/DAPI blocks, which in our studies always correlated with the occurrence of satellites, showing that occurrence of two chromosome pairs with satellites per cell is a characteristic shared by some species from both subgenera. This feature does not always have relationship with the basic chromosome number. The data found in this study will help to understand the phylogeny, cytotaxonomy, and evolution of the genus Passiflora showing that karyotypic variation can be seen between and within the subgenus Decaloba and Passiflora.  相似文献   

14.
Rare plant species can be divided into naturally, ‘old rare’ species and anthropogenically, ‘new rare’ species. Many recent studies explored genetic diversity of ‘new rare’ species. Less is, however, known about genetic diversity of ‘old rare’ species. We examined isozyme genetic variability of 20 populations of an ‘old rare’ plant species, Ligularia sibirica (Asteraceae) in the Czech and Slovak Republic. It is a long-lived perennial herb with mixed-mating breeding system, widely distributed from East Asia to European Russia, with few isolated relict populations in the remaining part of Europe.The results showed high genetic diversity within populations (80.8%) and a low level of genetic differentiation (FST = 0.179). Genetic distance between populations correlated significantly with geographic distance. There was also a significant positive correlation between genetic diversity and population size. This is probably caused by destruction of habitats in last centuries and subsequent decrease of population size. Patterns of genetic diversity suggest that the recent distribution is a result of stepwise postglacial migration of the species and subsequent natural fragmentation.We conclude that L. sibirica populations preserve high levels of genetic diversity and are not yet threatened by genetic factors. However, this may change if changes in habitat conditions continue.  相似文献   

15.
To elucidate the relationships among Diospyros kaki and species closely related in previous studies, the nuclear ribosomal internal transcribed spacer (ITS) DNA sequence and the chloroplast matK gene were sequenced and compared with those of nine Diospyros species from Thailand, four species from temperate regions, and one species of southern Africa, D. lycioides. Maximum parsimony, maximum likelihood, and neighbor joining analyses of the matK and ITS data sets revealed that D. kaki is closely related to two diploid species, D. oleifera and D. glandulosa. D. kaki, D. glandulosa, and D. oleifera were placed differently in the trees obtained from ITS and matK data sets, suggesting that hybridization and/or introgression may have occurred during the development of these species. D. kaki was not found to be closely related to D. ehretioides, a diploid species from Thailand. These results differed from a prior analysis of this genus performed with chloroplast DNA (cpDNA) restriction site mutations in 3.2- and 2.1-kb amplified sequences. The results supported Ng’s hypothesis that D. glandulosa and D. kaki may share a common ancestor. D. oleifera was also closely associated with D. kaki.  相似文献   

16.
The genetic diversity of silver pomfret (Pampus argenteus) from the Bohai, East China, and South China Seas was investigated using mitochondrial DNA (mtDNA) control region sequence data. We found high levels of variation with 17 haplotypes among the 45 individuals (h = 0.88, π = 0.006). AMOVA analysis detected significant structuring among China Sea silver pomfret (P < 0.05, FST = 0.050), which indicates significant genetic differentiation. No significant differentiation between Bohai Sea and East China Sea samples was detected (P > 0.05). Whether silver pomfret from the South China Sea exhibit a different demographic history than those from the Bohai and East China Seas remains to be determined.  相似文献   

17.
The identification of the conventionally accepted species of Clavulina (Cantharellales, Basidiomycota) in Europe (Clavulina amethystina, Clavulina cinerea, Clavulina cristata, and Clavulina rugosa) is often difficult and many specimens are not straightforwardly assignable to any of those four species, which is why some authors have questioned their identity. In order to assess the status of those species, a morphological examination was combined with the molecular analysis of the ITS region. The same six major clades were obtained in the Bayesian and parsimony phylogenetic analyses, and all six clades were well-supported at least by one of the analyses. Morphological characters, such as the overall branching pattern, the presence and intensity of grey colour, the cristation of the apices, and basidiospore size and shape were to various extents correlated with the phylogenetic signal obtained from the ITS region. The congruence between the molecular analyses and morphology, rather than geographical origin, suggests the existence of several species that can be delimited using a combined phylogenetic and morphological species recognition. The analyses revealed that C. cristata and C. rugosa are well-delimited species. In contrast, more than one taxa could be subsumed under the names C. amethystina and C. cinerea, the taxonomical complexity of which is discussed. The ITS region is proved to be adequate to separate phylogenetic species of Clavulina.  相似文献   

18.
Halacsya and Paramoltkia are two monotypic genera of the Balkan ultramafic outcrops, both classified as paleoendemics. They show close phylogenetic relationship, similar ecology and partially sympatric range, but contrasting life-history traits, patterns of distribution and chromosomal features. We performed a study to compare their infraspecific genetic structure using AFLP fingerprinting. Within-population heterozygosity (HS) and total heterozygosity (HT) were lower in diploid H. sendtneri than in polyploid P. doerfleri (0.121 and 0.142 vs. 0.165 and 0.178, respectively). Number of polymorphic loci was also higher in the latter species. Halacsya showed significant levels of among-population variation (14.5%) and population differentiation (FST = 0.145), as well as a structuring in four main geographic groups connected by low gene flow. Combined with inability for long-distance dispersal, these data suggest that present-day range fragmentation in this species is the result of historical losses of intervening populations and support its status of paleoendemic surviving in refugial serpentine “islands”. Populations of P. doerfleri were instead genetically very close (FST = 0.049), and variation was partitioned almost exclusively among individuals (95.1%). Lack of population groupings and higher levels of gene flow suggested a single, panmictic group, fitting more a metapopulation than a “classical” paleoendemic model.  相似文献   

19.
The genetic structure of populations of the Sigmodontinae rodent Calomys laucha was studied by means of allozyme electrophoresis. This highly opportunistic species is found preferably in periodically perturbed habitats of crop fields in central Argentina, where it can attain very high densities. A total of 17 enzymatic proteins assayed gave information on 25 loci; only four were monomorphic in the seven populations studied. Levels of genetic variability (Ho from 0.144 to 0.171; P95% from 44% to 56%) were higher than mean values reported for mammals and rodents. These high levels of heterozygosity could be maintained by large populations that do not experience great fluctuations in size, or by a social structure consistent in many small breeding groups that are formed and dissappear every breeding season. Genetic differentiation at a macrogeographical scale (θ=0.018) was low but statistically significant, and showed no correlation with geographic distance between pairs of populations. The pattern of population differentiation found is compatible with a relatively recent range expansion.  相似文献   

20.
In an attempt to delineate the area of origin and migratory expansion of the highly successful invasive weedy species Hypochaeris radicata, we analysed amplified fragment length polymorphisms from samples taken from 44 populations. Population sampling focused on the central and western Mediterranean area, but also included sites from Northern Spain, Western and Central Europe, Southeast Asia and South America. The six primer combinations applied to 213 individuals generated a total of 517 fragments of which 513 (99.2%) were polymorphic. The neighbour-joining tree presented five clusters and these divisions were supported by the results of Bayesian analyses: plants in the Moroccan, Betic Sierras (Southern Spain), and central Mediterranean clusters are all heterocarpic. The north and central Spanish, southwestern Sierra Morena, and Central European, Asian and South American cluster contain both heterocarpic (southwestern Sierra Morena) and homocarpic populations (all other populations). The Doñana cluster includes two homocarpic populations. Analyses of fragment parameters indicate that the oldest populations of H. radicata are located in Morocco and that the species expanded from this area in the Late Quaternary via at least three migratory routes, the earliest of which seems to have been to the southwestern Iberian Peninsula, with subsequent colonizations to the central Mediterranean area and the Betic Sierras. Homocarpic populations originated in the southwestern Iberian Peninsula and subsequently spread across north and central Spain, Central Europe and worldwide, where they became a highly successful weed.  相似文献   

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