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1.
In the present study,the genetic diversity of one selected strain(Pujiang No.1),two domesticated populations(GA and HX)and four wild populations(LZ,YN,SS and JL)of blunt snout bream(Megalobrama amblycephala)was analyzed using 17microsatellite markers.The results showed that an average of 4.88-7.65 number of alleles(A);an average of 3.20-5.33 effective alleles(Ne);average observed heterozygosity(Ho)of 0.6985-0.9044;average expected heterozygosity(He)of 0.6501-0.7805;and the average polymorphism information content(PIC)at 0.5706-0.7226.Pairwise FST value between populations ranged from0.0307-0.1451,and Nei’s standard genetic distance between populations was 0.0938-0.4524.The expected heterozygosities in the domesticated populations(GA and HX)were significantly lower than those found in three wild populations(LZ,SS and JL),but no difference was detected when compared with the wild YN population.Likewise,no difference was found between the four wild populations or two domesticated populations.The expected heterozygosity in Pujiang No.1 was higher than the two domesticated populations and lower than the four wild populations.Regarding pairwise FST value between populations,permutation test P-values were significant between the GA,HX and PJ populations,but not between the four wild populations.These results showed that the expected heterozygosity in the selected strain of blunt snout bream,after seven generations of selective breeding,was lower than that of wild populations,but this strain retains higher levels of genetic diversity than domesticated populations.The genetic differences and differentiation amongst wild populations,domesticated populations and the genetically improved strain of blunt snout bream will provide important conservation criteria and guide the utilization of germplasm resources.  相似文献   

2.
山西五台山地区褐马鸡的再引入   总被引:12,自引:0,他引:12  
Brown eared-pheasant Crossoptilon mantchuricum is endemic to China, and mainly occurs in Luliang Mountains of Shanxi, Xiaowntai of Hebei and Huanglong of Shaanxi. Reintroduction of Brown eared pheasant was carried out from April to December in 2000. According to the criterions of release site selection in Guidelines for Reintroductions of IUCN, and habitat selection of Brown eared pheasant, Kuantan forestry in Wutaishan Mountains of Shanxi Province was selected as the release site. Of the 8 released individuals, 5 wild individuals were captured in winter in Luyashan Nature Reserve of Shanxi Province, and 3 were offsprings of captive-reared individuals. Transmitters were attached when the 8 individuals were released. Overall, 6 individuals survived for at least 1 month, and the longest time for survival was 155 days, except that one was confirmed as having been killed by a raptor on the second day and one was lost on the eighth day after release. All moved away from the release site after release and established stable home ranges in different sites after 10 days, respectively. In early May, the individuals again dispersed to establish new home ranges. The wandering distance and days of the captive individuals were longer and the home range size were larger than that of the wild birds,which resulted from the weak adaptability to new habitat for the captive individuals, such as recognizing and fetching food. For wild individuals, the second wandering distance was longer than the first. We believe the difference was related to looking for partners. After wandering, individuals established stable home ranges in different sites [Acta Zoologica Sinica 50 (1): 126-132, 2004].  相似文献   

3.
Leymus chinensis (Trin.) Tzveh is a rhizomatous perennial herbage of Gramineae. Reproduction is mainly by vegetative reproduction. Tillering nodes and rhizomes of L. chinensis serve as organs for both vegetative reproduction and nutrient storage. Water-soluble carbohydrate (WSC) contents were measured in tillering nodes, nodes and Internodes of rhizomes of different age classes of L. chinensis populations at three development stages, namely the dough ripe stage, the vegetative growth stage after full ripeness, and the withering stage, in two habitats: sandy soil and saline-alkaline soil. The results showed that WSC content in tillering nodes of the three age classes of L. chinensis were all markedly decreased with increasing age in both sandy soil and saline-alkaline solh A similar trend of changes In WSC contents was observed in the nodes and internodes of rhizomes in different age classes In both habitats. The highest WSC contents were in 2-age-class nodes and internodes of rhizomes, followed by those In the 1 age class, with the lowest WSC contents found in 3-age-class nodes and internodes of rhizomes at the dough ripe and vegetative growth stages after full ripening. In turn, WSC contents decreased with Increasing age at the withering stage in both habitats. The WSC content in each age class of internode was higher than that in the node of rhizome at three development stages in both habitats.  相似文献   

4.
Hucho taimen are listed as endangered in China. The population size has declined recently, prompting an increase in the level of listing from grade three in 2002 to grade five in 2006. We analyzed the genetic diversity of wild populations using 17 microsatellite markers to establish a scientific basis for conservation of this species. We collected tissue samples from four populations in the Heilongjiang River basin: Huma River (HM), Hutou (HT), Haiqing (HQ), and Zhuaji (ZJ). A total of 21 loci were amplified, 18 of which were polymorphic. The number of alleles per locus ranged from 2 to 9 (mean: 4.1905). There were 13 highly polymorphic loci and 5 moderately polymorphic loci. Analysis of five genetic diversity parameters (Na, Ne, Ho, He, and PIC) suggested moderate levels of diversity within the populations. The populations were ranked HT > HQ > ZJ > HM, but the differences in diversity were not statistically significant (P > 0.05). A comparison of variation among all four populations suggested Hardy–Weinberg disequilibrium at 20% of the loci. Genetic differentiation (Fst) was 0.0644 and the gene flow among populations was estimated at 3.36 individuals per generation. The majority of diversity (93.88%) occurred among individuals within a population. In contrast, relatively little (6.12%) of the genetic diversity was distributed between the populations. An analysis of genetic differentiation and genetic distance between pairs of populations revealed that both parameters were higher in comparisons of the HM population to the HT, HQ, and ZJ populations than among the three latter populations. This suggests that the HM population has a distinct genetic structure. We hypothesize that habitat degradation and excessive fishing, not low genetic diversity, has caused the decline in H. taimen populations. However, this species should be protected from further declines in genetic diversity.  相似文献   

5.
The Chinese alligator Alligator sinensis is one of the most endangered crocodilian species, and typically exhibits temperature-dependent sex determination. It is extremely important to clarify the sex structure of Chinese alligators to implement recovery projects successfully. However, the sex ratio of wild Chinese alligators remains unknown. In this study, we collected 28 years of sex ratio data from Chinese alligators residing in the natural and artificial habitats of Changxing Nature Reserve, China, and examined the differences in the sex ratio dynamics between these two populations. We observed that the sex ratio of wild Chinese alligators is 1 male to 4.507 females, which was significantly lower compared to that of the captive population (1 to 2.040; P 〈 0.001), and is significantly different to previously documented sex ratios for this species (all P 〈 0.01). Furthermore, we documented an annually stable (P = 1.000) female-biased sex ratio for wild alligators at hatching [1 male to 4.747 females; 0.174 (0.167~).182)], in contrast to a dramatically fluctuating sex ratio (P 〈 0.001) in captivity [1 male to 1.674 females; 0.374 (0.246-0.593)], showing a potential mechanism for adjusting the sex structure. Finally, we found that the hatchling sex ratios were similar to that of the population sex ratio (P = 0.748), with little correlation to air temperature values in the 60-70 day incubation period during the breeding season (July and August; both P 〉 0.05). Overall, this study indicates that the stabilized female-biased sex ratio of Changxing Chinese alligators might result from selection pressure caused by local mate competition and major inbreeding .  相似文献   

6.
The Chinese tree shrew (Tupaia belangeri chinensis) is a small experimental animal with a close affinity to primates. This species has long been proposed to be an alternative experimental animal to primates in biomedical research. Despite decades of study, there is no pure breed for this animal, and the overall genetic diversity of wild tree shrews remains largely unknown. In order to obtain a set of genetic markers for evaluating the genetic diversity of tree shrew wild populations and tracing the lineages in inbreeding populations, we developed 12 polymorphic microsatellite markers from the genomic DNA of the tree shrew. An analysis of a wild population of 117 individuals collected from the suburb of Kunming, China, showed that these loci exhibited a highly expected heterozygosity (0.616). These 12 microsatellites were sufficient for individual identification and parentage analysis. The microsatellite markers developed in this study will be of use in evaluating genetic diversity and lineage tracing for the tree shrew.  相似文献   

7.
Many aphid species exhibit a variation in reproductive mode which is influenced by winter climate regimes,with cyclical parthenogenetic (CP)lines dominating in cold winter areas (because they produce cold-resistant eggs)and obligate parthenogenetic (OP) ones in mild winter regions (because of their parthenogenetic overwintering).Genetic studies on several aphid species have shown that the OP trait can be transmitted during sexual events involving the 2 types of lines.This genetic system could be considered as a local safeguarding mechanism for OP alleles in case severe frost would have killed all parthenogenetically overwintering individuals.However,this strategy would only be efficient in restoring local polymorphism in breeding systems if the newly hatched OP recombinants remain competitive over their CP counterparts.In this study we compared egg hatching sequences of CP and OP F1 clones from several crosses obtained for 2 cereal aphid species,Sitobion avenae (constant 5℃,8 h of light)and Rhopalosiphum padi (winter outdoor conditions).For S.avenae,we obtained F1 offspring from 6 crosses, involving 4 clones while in R.padi F1 were obtained from 11 crosses involving 14 clones. We showed that in both species proportions of OP clones were higher in the first half of the progeny relative to the second half.In addition,F1 OP clones hatched in the mean about a week earlier than their CP sibs,which gives them a demographic advantage at the start of the growth season.We then discussed the consequences of this fitness advantage for the maintenance and spread of the OP trait in aphid populations.  相似文献   

8.
Knowledge of sex ratio and spatial distribution of males and females of dioecious species is both of evolutionary interest and of crucial importance for biological conservation. Eurycorymbus cavaleriei, the only species in the genus Eurycorymbus (Sapindaceae), is a dioecious tree endemic to subtropical montane forest in South China. Sex ratios were investigated in 15 natural populations for the two defined ages (young and old). Spatial distribution of males and females was further studied in six large populations occurring in different habitats (fragmented and continuous). The study revealed a slight trend of male- biased sex ratio in both ages of E. cavaleriei, but sex ratio of most populations (13 out of 15) did not display statistically significant deviation from equality. All of the four significantly male-biased populations in the young class shifted to equality or even female-biased, The Ripley's K analysis of the distribution of males with respect to females suggested that individuals of the opposite sexes were more randomly distributed rather than spatially structured. These results suggest that the male-biased sex ratio in E. cavaleriei may result from the precocity of males and habitat heterogeneity. The sex ratio and the sex spatial distribution pattern are unlikely to constitute a serious threat to the survival of the species.  相似文献   

9.
Gong MH  Song YL  Yang ZS  Lin C 《动物学研究》2012,33(3):e18-e24
Population viability analysis(PVA) is a tool to evaluate the risk of extinction for endangered species and aid conservation decision-making.The quality of PVA output is dependent on parameters related to population dynamics and life-history;however,it has been difficult to collect this information for the giant panda(Aliuropoda melanoleuca),a rare and endangered mammal native to China,confined to some 30 fragmented habitat patches.Since giant pandas are long-lived,mature late,have lower reproductive rates,and show little sexual dimorphism,obtaining data to perform adequate PVA has been difficult.Here,we develop a parameter sensitivity index by modeling the dynamics of six giant panda populations in the Minshan Mountains,in order to determine the parameters most influential to giant panda populations.Our data shows that the giant panda populations are most sensitive to changes in four female parameters:initial breeding age,reproductive rate,mortality rate between age 0 and 1,and mortality rate of adults.The parameter sensitivity index strongly correlated with initial population size,as smaller populations were more sensitive to changes in these four variables.This model suggests that demographic parameters of females have more influence on the results of PVA,indicating that females may play a more important role in giant panda population dynamics than males.Consequently,reintroduction of female individuals to a small giant panda population should be a high priority for conservation efforts.Our findings form a technical basis for the coming program of giant panda reintroduction,and inform which parameters are crucial to successfully and feasibly monitoring wild giant panda populations.  相似文献   

10.
Variations in the trnK region of chloroplast DNA were investigated in the present study using polymerase chain reactionrestriction fragment length polymorphism to detect the genetic structure and to infer the possible glacial refugia of Ginkgo biloba L. in China. In total, 220 individuals from 12 populations in China and three populations outside China were analyzed, representing the largest number of populations studied by molecular markers to date. Nineteen haplotypes were produced and haplotype A was found in all populations. Populations in south-western China, including WC, JF, PX, and SP, contained 14 of the 19 haplotypes and their genetic diversity ranged from 0.771 4 to 0.867 6. The TM population from China also showed a high genetic diversity (H = 0.848 5). Most of the genetic variation existed within populations and the differentiation among populations was low (GsT = 0.2). According to haplotype distribution and the historical record, we suggest that populations of G. biloba have been subjected to extensive human impact, which has compounded our attempt to infer glacial refugia for Ginkgo. Nevertheless, the present results suggest that the center of genetic diversity of Ginkgo is mainly in south-western China and in situ conservation is needed to protect and preserve the genetic resources.  相似文献   

11.
Longevity and age at sexual maturity were estimated in two anurans from the arid Isalo Massif (southern-central Madagascar), the blue-legged frog (Mantella expectata) and the rainbow frog (Scaphiophryne gottlebei). Phalanges from 69 individuals of M. expectata and 38 individuals of S. gottlebei were analyzed, using the skeletochronological method, in samples collected during two periods: January-February and November-December 2004. The male gonads of both species were also analyzed in order to better correlate reproductive activity with phenology. The phalangeal diaphysis in adults of both species was composed of two concentric bone layers: an innermost endosteal bone, which was less developed or sometimes lacking in S. gottlebei, and an outermost and broader layer of periosteal bone. Lines of arrested growth (LAGs) were observed in both species, although their recognition was more problematic and their distinctiveness much less evident in S. gottlebei. The results presented here indicate that M. expectata and S. gottlebei have a short life span and attain sexual maturity within the first active season after metamorphosis. Maximum longevity was 3 years in M. expectata and 2 years in S. gottlebei. In S. gottlebei the adult body size is likely attained during the same season in which metamorphosis occurs, but then breeding occurs only after the first latency period. Thus, mature individuals have only one LAG, corresponding to 1 year. The low number of individuals with two LAGs suggests that most animals die before the second latency period.  相似文献   

12.
The age and growth of individuals in a population of the water frog Rana epeirotica, from northwestern Greece, were studied in 1998 and 1999 using skeletochronology. Analysis of the age structure was based on the enumeration of Lines of Arrested Growth (LAGs) in phalanges. Ages ranged from 1-5 years among 145 males and from 1-5 years among 173 females. The mean snout-vent length was 72.74 +/- 7.96 mm in males and 83.63 +/- 11.73 mm in females. The difference between the sexes in age and size was significant. Endosteal resorption may have eroded away the first LAG in only 9% of the studied individuals and was more frequent in females. Growth of adults was fitted by the Bertalanffy model. The growth coefficient (K) was 0.88 in males and 0.49 in females, reflecting faster male growth between metamorphosis and maturation.  相似文献   

13.
Hundreds of genes, when manipulated, affect the lifespan of model organisms (yeast, worm, fruit fly, and mouse) and thus can be defined as longevity‐associated genes (LAGs). A major challenge is to determine whether these LAGs are model‐specific or may play a universal role as longevity regulators across diverse taxa. A wide‐scale comparative analysis of the 1805 known LAGs across 205 species revealed that (i) LAG orthologs are substantially overrepresented, from bacteria to mammals, compared to the entire genomes or interactomes, and this was especially noted for essential LAGs; (ii) the effects on lifespan, when manipulating orthologous LAGs in different model organisms, were mostly concordant, despite a high evolutionary distance between them; (iii) LAGs that have orthologs across a high number of phyla were enriched in translational processes, energy metabolism, and DNA repair genes; (iv) LAGs that have no orthologs out of the taxa in which they were discovered were enriched in autophagy (Ascomycota/Fungi), G proteins (Nematodes), and neuroactive ligand–receptor interactions (Chordata). The results also suggest that antagonistic pleiotropy might be a conserved principle of aging and highlight the importance of overexpression studies in the search for longevity regulators.  相似文献   

14.
Skeletochronological estimation of age, longevity, age at sexual maturity and breeding of Microhyla ornata was done. Frogs (n=62) were collected locally in August (rainy season) 1997 and brought to the laboratory. Body mass and snout-vent-length (SVL) of each frog was recorded; the 4th toe of both the hind limbs was clipped under anaesthesia, fixed in 10% formalin, demineralized in 5% nitric acid and processed for histology. Limb bones (femur, humerus, tibiofibula and radioulna) of 6 large sized frogs were also processed for skeletochronology in order to study the rate of resorption. Gonads of 25 frogs (belonging to different body size ranges) were processed for histology in order to ascertain the gametogenic status of individual frogs. One to four growth rings consisting of growth zones and lines of arrested growth (LAGs) were noticed in frogs of different body sizes; the number of LAGs remained identical in all the limb bones and phalanges in 5 out of 6 frogs. Back calculation indicated that the resorption rate is very low in this frog. Male frogs possessed sperm bundles in seminiferous tubules in the 1st year, while females showed yolky follicles in the ovary in the 2nd year. Frogs found in amplexus were 3 5 years old. The results suggest that this frog may live for a maximum of 5 years in the natural population.  相似文献   

15.
Somatic growth rate data for wild sea turtles can provide insight into life‐stage durations, time to maturation, and total lifespan. When appropriately validated, the technique of skeletochronology allows prior growth rates of sea turtles to be calculated with considerably less time and labor than required by mark‐–recapture studies. We applied skeletochronology to 10 dead, stranded green turtles Chelonia mydas that had previously been measured, tagged, and injected with OTC (oxytetracycline) during mark–recapture studies in Hawaii for validating skeletochronological analysis. We tested the validity of back‐calculating carapace lengths (CLs) from diameters of LAGs (lines of arrested growth), which mark the outer boundaries of individual skeletal growth increments. This validation was achieved by comparing CLs estimated from measurements of the LAG proposed to have been deposited closest to the time of tagging to actual CLs measured at the time of tagging. Measureable OTC‐mark diameters in five turtles also allowed us to investigate the time of year when LAGs are deposited. We found no significant difference between CLs measured at tagging and those estimated through skeletochronology, which supports calculation of somatic growth rates by taking the difference between CLs estimated from successive LAG diameters in humerus bones for this species. Back‐calculated CLs associated with the OTC mark and growth mark deposited closest to tagging indicated that annual LAGs are deposited in the spring. The results of this validation study increase confidence in utilization of skeletochronology to rapidly obtain accurate age and growth data for green turtles.  相似文献   

16.
SUMMARY. 1. To investigate the contribution of hatchlings from lake- Daphnia resting eggs (ephippia) to population and community structure, hatching was monitored in situ from April to November 1986 in two north German lakes. Hatching traps were placed on the sediments and the incidence, genetic and species composition of ephippial hatchlings determined twice-weekly.
2. Hatching began in April after the thawing of ice. and continued for 3–4 weeks until the lakes stratified. There was no obvious relationship between the onset and duration of hatching and the environmental variables recorded, namely Secchi depth, surface temperature, temperature and oxygen concentration at the sediment-water interface.
3. Among the hatchlings were D. galeata, D. hyalina and their interspecific hybrid.
4. In the lake which contained overwintering animals the number of ephippial hatchlings was approximately one third of the total number of juveniles present in the lake.
5. In the second lake, no adults were recorded during winter and the population was probably founded by ephippial hatchlings alone. There was good agreement, in the short term, between the proportion of each species represented among hatchlings and the subsequent species composition in the lake.
6. The hatchlings were genetically diverse, and alleles were representative of those alleles present in contemporary populations.  相似文献   

17.
Several investigators have generated long-lived nematode worms (Caenorhabditis elegans) in the past decade by mutation of genes in the organism in order to study the genetics of aging and longevity. Dozens of longevity assurance genes (LAG) that dramatically increase the longevity of this organism have been identified. All long-lived mutants of C. elegans are also resistant to environmental stress, such as high temperature, reactive oxygen species (ROS), and ultraviolet irradiation. Double mutations of some LAGs further extended life span up to 400%, providing more insight into cellular mechanisms that put limits on the life span of organisms. With the availability of the LAG mutants and the combined DNA microarray and RNAi technology, the understanding of actual biochemical processes that determine life span is within reach: the downstream signal transduction pathway may regulate life span by up-regulating pro-longevity genes such as those that encode antioxidant enzymes and/or stress-response proteins, and down-regulating specific life-shortening genes. Furthermore, longevity could be modified through chemical manipulation. Results from these studies further support the free radical theory of aging, suggest that the molecular mechanism of aging process may be shared in all organisms, and provide insight for therapeutic intervention in age-related diseases.  相似文献   

18.
19.
Abstract Ecological specialization, such as major dependence upon a single‐prey species, can render a predator taxon vulnerable to extinction. In such cases, understanding the population dynamics of that prey type is important for conserving the predator that relies upon it. In eastern Australia, the endangered broad‐headed snake Hoplocephalus bungaroides feeds largely on velvet geckos (Oedura lesueurii). We studied growth, longevity and reproduction in a population of velvet geckos in Morton National Park in south‐eastern Australia. We marked 458 individual geckos over a 3‐year period (1992–1995) and made yearly visits to field sites from 1995–2006 to recapture marked individuals. Female geckos grew larger than males, and produced their first clutch at age 4 years. Males can mature at 2 years, but male–male combat for females probably forces males to delay reproduction until age 3 years. Females lay a single clutch of two eggs in communal nests in November, and up to 22 females deposited eggs in a single nest. Egg hatching success was high (100%), and juveniles had high survival (76%) during their first 6 months of life. Velvet geckos are long‐lived, and the mean age of marked animals recaptured after 1995 was 6.1 years (males) and 8.4 years (females). Older females (7.5–9.5 years) were all gravid when last recaptured. Like other temperate‐climate gekkonids, O. lesueurii has a ‘slow’ life history, and population viability could be threatened by any factors that increase egg or adult mortality. Two such factors – the removal of ‘bush rocks’ for urban gardens, and the overgrowth of rock outcrops by vegetation – could render small gecko populations vulnerable to extinction. In turn, the reliance of predatory broad‐headed snakes on this slow‐growing lizard species may increase its vulnerability to extinction.  相似文献   

20.
The knowledge of the life histories of wild mammals is of crucial importance in the field of conservation management. The endangered status of many species calls for faster data collection that can be used in risk assessment and, ultimately, for designing conservation policies. This study is pioneering the potential of bone histology to provide data on life history traits crucial for conservation biology in long-lived mammals. Long bone cross-sections show pronounced annual cycles of growth arrest allowing application of skeletochronology (counts of lines of arrested growth ‘LAGs’). Consequently, the number of LAGs within the primary fast-growing bone tissue up to the outer cortical slow-growing bone tissue corresponds to the age at first reproduction; whereas the age at death can be estimated by the total number of rest lines throughout the whole of bone cross-section. Furthermore, the diameters of successive growth rings as well as the osteocyte lacuna density may shed light on growth rates. We use the endangered desert dwelling antelope Addax nasomaculatus as a case study. By analyzing different ontogenetic stages in five Addax individuals (three captive and two wild specimens) from a museum collection, we show that bone histology may be a reliable tool for determining certain key life history traits. In our sample, the wild Addax female attained reproductive maturity at three years, whereas the male specimens, both the captive and the wild ones, reached maturity at four years. This is congruent with data from other large antelopes with male-biased size dimorphism, but differs slightly from data on sexual maturity previously published for wild Addax. Moreover, quantification of osteocyte lacunae in both adult males provides a higher cell density in the captive one than in the wild one suggesting the strong effect of constant resources supply in individuals from zoos on growth rates. While age at first reproduction and longevity are essentials parameters to carry out demographic models, growth rates may allow evaluation of the health status of wild populations. This approach may provide useful data on life history traits when applied to bones collected in the wild.  相似文献   

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