Genetic structure of the genera Psorophora (Diptera: Culicidae) in Columbian and north American populations using isoenzymes and ITS2 sequences

Two a priori Psorophora columbiae and one a priori Ps. toltecum populations from Colombia were studied by means of eleven isoenzyme loci. The levels of genetic diversity, Hardy-Weinberg equilibrium, gene flow estimates, isolation by distance and genetic relationships among these three populations were studied and the results were as follows: (1) The gene diversity levels were high as well as very similar among the three populations indicating no differences between them. (2) Within each population and from a hierarchical standpoint several loci were not in Hardy-Weinberg equilibrium simultaneously by excess and defect of heterozygous. This could reflect that several natural selection forces are acting upon these mosquito populations. (3) The gene flow estimate for these populations showed the existence of this event between them. This agrees quite well with the fact that the three populations really belong to a single species. In addition, maximum parsimony analyses with 16 isoenzyme for several individuals from four Colombian and two United States Psorophora populations showed that effectively only one species was present in the Colombian area surveyed, and that this species is Ps. columbiae, which hardly contrast with that previously suggested by other authors. The text was submitted by the authors in English.     

Psorophora columbiae and Psorophora toltecum (Diptera: Culicidae) Colombian populations cannot be differentiated by isoenzymes

Two populations of the mosquito Psorophora columbiae from the central Andean area of Colombia and one population of Ps. toltecum from the Atlantic coast of Colombia were analyzed for 11 isoenzyme markers. Psorophora columbiae and Ps. toltecum are two of the main vectors of Venezuelan equine encephalitis. We found no conspicuous genetic differences between the two species. The relatively high gene flow levels among these populations indicate that these are not two different species or that there has been recent divergence between these taxa. In addition, no global differential selection among the loci was detected, although the alpha-GDH locus showed significantly less genetic heterogeneity than the remaining loci, which could mean that homogenizing natural selection acts at this locus. No isolation by distance was detected among the populations, and a spatial population analysis showed opposite spatial trends among the 31 alleles analyzed. Multiregression analyses showed that both expected heterozygosity and the average number of alleles per locus were totally determined by three variables: altitude, temperature and size of the human population at the locality. Individually, the expected heterozygosity is more related to these three variables than to the average number of alleles.     

Microsatellite analysis of the spectacled bear (Tremarctos ornatus) across its range distribution

DNA samples of the spectacled bear (Tremarctos ornatus) from five Andean countries, Venezuela, Colombia, Ecuador, Peru and Bolivia, were analyzed for nine microsatellite loci. Seven of them were polymorphic, which led us to investigate several population-genetic parameters. Private alleles and significant differences in gene frequencies were found among the populations studied, which demonstrated the extent of genetic differentiation among the spectacled bear populations. The levels of gene diversity measured with these microsatellites were rather modest in this species. Hardy-Weinberg disequilibrium was especially found for the overall and the Ecuadorian samples, and might be due to the Wahl-und effect or consanguinity. Significant genetic heterogeneity was mainly observed among the Colombian and the Ecuadorian populations. Markov chain Monte Carlo simulations clearly showed that two different gene pools were present, one present in the Venezuelan-Colombian bears and other in the Ecuadorian ones.     

Population genetic study of allozyme variation in natural populations of Drosophila antonietae (Insecta, Diptera)

Drosophila antonietae is an endemic South American cactophilic species found in relictual xerophytic vegetation, mostly associated with Cereus hildmaniannus cactus. Low differentiation among populations of this species has been detected using several markers. In this work, we performed an allozyme genetic variability analysis of 11 natural populations of D. antonietae and included a discussion about the possible influences of several evolutionary processes that might be acting to maintain the pattern observed. The genetic variability of 14 isoenzyme loci was analysed and showed a high genetic diversity (average observed heterozygosity = 0.319) and a moderate genetic differentiation among populations ( F statistics = 0.0723). A correlation between genetic and geographical and ecological distances was detected among pairs of populations and the regional equilibrium analysis was thus applied. This analysis resulted in Nm (number of migrants) of approximately 3.21, indicating that moderate levels of both gene flow and genetic drift occur in this species, with gene flow overlapping genetic drift. However, considering ecological features of drosophilids, we propose a hypothesis to explain the moderate differentiation encountered as a result of three different processes, or a combination of them: (1) gene flow; (2) a short period of differentiation, i.e. maintenance of ancestral polymorphism; and (3) action of natural selection. Moreover, if gene flow is present, the high genetic diversity compared with other cactophilic and non-cactophilic species could be due to differential selection in different populations followed by gene exchange among them. These factors are discussed in the light of D. antonietae 's historical and evolutionary association with the host cactus.     

Population genetic analysis of the genes APOE, APOB(3'VNTR) and ACE in some black and Amerindian communities from Colombia

A population genetic study was carried out with the APOE, APOB and ACE loci in 17 Colombian human populations. Ten of them were Amerindian communities coming from the northeastern part of Colombia, Pacific region, Eastern Plains and Amazonia. Six were black populations from Providence Island, Caribbean and Pacific coasts. Finally, the Mestizo population of Bogota was studied as well. The APOE and ACE loci were in Hardy-Weinberg equilibrium, whereas the APOB locus was not studied in all populations. The genetic heterogeneity was substantially greater among the Amerindian populations (G(ST) = 0.059) than in the Afrocolombian populations (G(ST) = 0.009). Also the gene flow population pair estimates were so much higher among the Afrocolombian populations (Nm = 49.08 +/- 43.07) than among Amerindian populations (Nm = 9.66 +/- 18.04). Different phylogenetic and multivariant analyses showed that the Amerindian populations analyzed were clustered in three different arrays: one constituted by the Colombian northeastern and Pacific populations, the second one by the two Amazon populations (Coreguaje and Nukak) and the last one by the Yuco (the unique Caribbe-speaking population among those studied). The latter population was highly divergent from a genetic point of view from the remainder Amerindian populations studied. By using the Mantel test, the existence of a positive and significant correlation between the genetic and geographical distances found among Amerindian populations was demonstrated. This fact was not observed among the Afrocolombian populations. Nevertheless, an isolation-by-distance Slatkin analysis test did not show a significant clear structure of this special pattern among the Indian tribes studied.     

Allozyme diversity in natural populations of Viola palmensis Webb & Berth. (Violaceae) from La Palma (Canary Islands): implications for conservation genetics

Genetic diversity was measured by allozyme electrophoresis in eight natural populations of the threatened Canarian endemic Viola palmensis Webb & Berth. (Violaceae). Nineteen alleles corresponding to 11 gene loci were detected. High levels of genetic diversity were found, ranging from 36.3 to 45.4 % for the percentage of polymorphic loci (P), from 1.45 to 1.60 for the average number of alleles per locus (A) and from 0.128 to 0.200 for the expected heterozygosity (H(e)). Between 85.5 and 96.6 % of genetic variability was apportioned within populations. As a whole, populations were not at Hardy-Weinberg equilibrium, with a deficit of heterozygous individuals attributable to the existence of genetic structuring in the populations analysed. The levels of interpopulation genetic differentiation were low (mean F(ST) = 0.100), while genetic identity pair-wise comparisons were high (mean I = 0.973) suggesting considerable levels of gene flow among populations. No relationship was detected between genetic differentiation and geographical distances between populations. An outcrossing insect-mediated breeding system might contribute to pollen dispersion of this species. For conservation genetics we suggest in situ preservation areas are defined that are free of disturbance and that include populations with the highest genetic diversity.     

Population genetic analysis of Colombian Trypanosoma cruzi isolates revealed by enzyme electrophoretic profiles

Although Colombia presents an enormous biological diversity, few studies have been conducted on the population genetics of Trypanosoma cruzi. This study was carried out with 23 Colombian stocks of this protozoa analyzed for 13 isoenzymatic loci. The Hardy-Weinberg equilibrium, the genetic diversity and heterogeneity, the genetic relationships and the possible spatial structure of these 23 Colombian stocks of T. cruzi were estimated. The majority of results obtained are in agreement with a clonal population structure. Nevertheless, two aspects expected in a clonal structure were not discovered in the Colombian T. cruzi stocks. There was an absence of given zymodemes over-represented from a geographical point of view and the presumed temporal stabilizing selective phenomena was not observed either in the Colombian stocks sampled several times through the years of the study. Some hypotheses are discussed in order to explain the results found.     

雌雄异株稀有植物伞花木(Eurycorymbus caraleriei)自然居群的等位酶遗传多样性研究

伞花木（Eurycorymbus caraleriei）为中国特有的第三纪孑遗单种属植物,雌雄异株。采用超薄平板微型聚丙烯酰胺等电聚焦电泳方法对其5个自然居群和1个人工迁地保护居群的等位酶变异进行了初步研究。对7个酶系统中14个位点的等位酶居群遗传多样性及遗传结构分析结果表明：伞花木具有较高水平的遗传多样性,其每位点平均等位基因数A=1．6,平均多态位点比率P=42．9％,平均预期遗传杂合度Hr=0．216;各居群的遗传多样性无显著性差异,但都表现为严重偏离Hardy-Weinberg平衡的杂合子过量;其遗传变异主要发生在居群内（93．1％）,居群间分化较小（Gst=0．069）,居群问遗传一致度较高（I=0．965～1．000）。推断这可能是由于其古老孑遗性、雌雄异株、混和传粉方式的生物学特性以及其长寿命的生活史等原因所导致;同时,居群间的较高基因流（Nm=3．128）也可能起到很大的作用。还使用UPGMA聚类方法推断了武汉植物园迁地保护的野外居群来源,在对迁地保护居群的评价中发现迁地保护居群仅保存了该物种基因型多样性的16％,在此基础上提出了今后进一步的保育策略。     

DNA microsatellite characterization of the jaguar (Panthera onca) in Colombia

The Colombian jaguar population is thought to contain two different subspecies, Panthera onca centralis and Panthera onca onca. The genetic structure of this population was evaluated using 12 microsatellite loci (n = 62 samples). In addition, 22 jaguar DNA samples from Guatemala, Paraguay, Perú, Bolivia, Venezuela and Brazil were analyzed for these microsatellite loci (n = 84 samples). The results of this study indicate six primary themes. First, the levels of gene diversity were very high. Second, the majority of the loci analyzed showed an absence of Hardy-Weinberg equilibrium, probably due to the Wahlund effect (= population subdivision). Third, several microsatellite loci showed significant heterogeneity between the two supposed subspecies in the country. Nevertheless, gene flow was present between them, and heterogeneity was relatively low, although the assignment analyses showed good classification of the jaguars studied into their respective subspecies. Fourth, the long-term historical effective population sizes were calculated through a maximum likelihood procedure for single and multi-step mutation models. Fifth, seven out of twelve DNA microsatellites studied significantly deviated from a single-step mutation model. However, the overall mean multi-step mutation percentage for these 12 DNA microsatellites was only 6%. Therefore, 94% of mutations were uni-step. Sixth, no bottleneck events were detected in the Colombian jaguar population overall.     

Microsatellite variation reveals high levels of genetic variability and population structure in the gorgonian coral Pseudopterogorgia elisabethae across the Bahamas

The primary mechanism of gene flow in marine sessile invertebrates is larval dispersal. In Pseudopterogorgia elisabethae, a commercially important Caribbean gorgonian coral, a proportion of the larvae drop to the substratum within close proximity to the maternal colony, and most matings occur between individuals in close proximity to each other. Such limited dispersal of reproductive propagules suggests that gene flow is limited in this gorgonian. In this study, we characterized the population genetic structure of P. elisabethae across the Bahamas using six microsatellite loci. P. elisabethae was collected from 18 sites across the Bahamas. Significant deviations from Hardy-Weinberg equilibrium due to deficits of heterozygotes within populations were detected for all 18 populations in at least one of the six screened loci. Levels of genetic structure among populations of P. elisabethae were high and significant. A distance analysis placed populations within three groups, one formed by populations located within Exuma Sound, a semi-isolated basin, another consisting of populations located outside the basin and a third group comprising two populations from San Salvador Island. The patterns of genetic variation found in this study are concordant with the life-history traits of the species and in part with the geography of the Bahamas. Conservation and management plans developed for P. elisabethae should considered the high degree of genetic structure observed among populations of the species, as well as the high genetic diversity found in the San Salvador and the Exuma Sound populations.     

Genetic diversity within and among 11 juvenile populations of green alder (Alnus crispa) in Canada

Germinated seeds from 11 populations of green alder [ Alnus crispa (Ait.) Pursh] sampled in four Canadian provinces were analysed for electrophoretically demonstrable diversity of 10 enzymes encoded by 15 structural loci. Of these, nine were polymorphic, and on average, 52% of the loci per population were polymorphic. Assuming a diploid model of expression, average level of expected heterozygosity was 0.11 with nearly all populations in Hardy-Weinberg equilibrium for the set of polymorphic loci analysed. No significant inbreeding and associated subpopulation structuring were noted. Rates of gene flow appeared high within and among populations. Although little divergence was observed among populations, genetic and geographical distances between populations were related. Discriminant and cluster analyses revealed a pattern of genetic variation associated with geography. Populations from northern Quebec were poorly differentiated, whereas western populations from Alberta exhibited a larger degree of genetic differentiation. Introgresive hybridization with the sympatric species Alnus sinuata (Regel) Rydberg and partial isolation in the West are suggested as an explanation for this larger differentiation. The occurrence and significance of rare alleles is discussed in relation to the importance of geographical distance in the process of population differentiation in this species.     

Genetic diversity and gene flow in the endangered dwarf bear poppy, Arctomecon humilis (Papaveraceae)

Arctomecon humilis is a critically endangered species endemic to the Moenkopi shale of Washington County, Utah. Recovery plans for the species would be improved by an understanding of genetic diversity and gene flow among its remaining populations. Ten variable isozyme loci were used to calculate genetic diversity statistics for study populations. Westerly populations possessed higher levels of genetic variability than other populations at the same isozyme loci. Three of the populations exhibited significant deviations from Hardy-Weinberg expectations. No correlation existed between genetic distance and geographic distance. Most of the genetic diversity was distributed among populations with little gene flow between populations, suggesting that observed genetic differences may arise from genetic drift. For the westerly populations, similar genotypes were observed in the seedling and old age classes, while intermediate age classes typically possessed an alternate set of genotypes at Pgi-2. Mean heterozygosity increased with age class across populations. Westerly populations of A. humilis shared more alleles with the nearest geographic population of A. californica than other populations. Since the westerly populations contained more genetic variability and more alleles in common with a near relative, they may be relictual. Other populations may contain less genetic diversity due to founder effects and/or genetic drift.     

云南金钱槭 等位酶 遗传多样性 生境片段化 保育策略

云南金钱槭（Dipteronia dyeriana）是我国特有的国家Ⅱ级重点保护珍稀濒危植物,仅分布于云南的文山、屏边和蒙自三县交界地区。采用水平切片淀粉凝胶电泳等位酶分析方法,对采自三个县的天然居群的63个样品进行了遗传多样性检测。8个酶系统的13个等位基因位点分析表明,云南金钱槭的遗传多样性水平低,其平均多态位点百分率P=15.4%,每位点平均等位基因数A=1.2,平均预期杂合度He=0.064,各居群都偏离Hardy-Weinberg平衡,杂合子过量,居群间的基因分化系数GST=0.099,遗传变异主要发生在居群内（90.1%）,居群间分化较小,居群间遗传一致度较高（I=0.985～1）,具有一定的基因流（Nm=2.669）。不加权对平均法（UPGMA）聚类可将4个居群分为两支,水头箐居群和马家寨居群亲缘关系最近,聚类后与黑洞居群形成一支再和中槽子居群聚类,这与其地理分布格局大致吻合。据此提出了关于云南金钱槭保育策略的建议。     

Allozyme Variation and the Genetic Structure of Populations of the Rare Sedge Carex misera (Cyperaceae)

Abstract Carex misera is a rare sedge, endemic to rocky outcrops and mountain summits within the southern Appalachian Mountains from northern Georgia to northern North Carolina. We assessed allozyme diversity for 406 individuals from nine populations over most of the geographic range. Twenty-seven putative loci were assayed and eight (30%) were found to be polymorphic. Nei's gene diversity statistics ( H _T =0.043, H _S =0.019, G _ST =0.551) indicated low levels of variation but relatively highly differentiated populations, suggesting little gene flow. Significant deviations from genotypic expectations under Hardy-Weinberg equilibrium, high positive fixation indices, and the existence of small genetic neighborhoods within populations suggest that at least some inbreeding occurs. Cluster analysis of Nei's genetic identity statistics and principal component analysis of allele frequency data showed high similarity among the six southern populations with the two northern populations more differentiated from them and from each other. These results suggest that preservation of the northern populations is necessary to conserve the already low levels of genetic diversity within the species.     

Isolation and characterization of 15 nuclear microsatellite markers for Baillonella toxisperma Pierre (Sapotaceae), a low-density tree species of Central Africa

Baillonella toxisperma is a scattered endemic species of the Guineo-Congolian forest. We developed 15 nuclear microsatellite markers specifically for B. toxisperma to analyse the genetic diversity of 188 individuals distributed in two natural populations in Gabon. On average, 8.3 alleles per locus were identified; observed heterozygosity ranged from 0.056 to 0.872 and expected heterozygosity from 0.282 to 0.823 among populations. Only three loci showed a significant departure to Hardy-Weinberg equilibrium, but no linkage disequilibrium was observed for any pair of loci.     

雌雄异株稀有植物伞花木(Eurycorymbus caraleriei)自然居群的等位酶遗传多样性研究

伞花木(Eurycorymbuscaraleriei)为中国特有的第三纪孑遗单种属植物,雌雄异株。采用超薄平板微型聚丙烯酰胺等电聚焦电泳方法对其5个自然居群和1个人工迁地保护居群的等位酶变异进行了初步研究。对7个酶系统中14个位点的等位酶居群遗传多样性及遗传结构分析结果表明:伞花木具有较高水平的遗传多样性,其每位点平均等位基因数A=1.6,平均多态位点比率P=42.9%,平均预期遗传杂合度He=0.216;各居群的遗传多样性无显著性差异,但都表现为严重偏离Hardy-Weinberg平衡的杂合子过量;其遗传变异主要发生在居群内(93.1%),居群间分化较小(Gst=0.069),居群间遗传一致度较高(I=0.965~1.000)。推断这可能是由于其古老孑遗性、雌雄异株、混和传粉方式的生物学特性以及其长寿命的生活史等原因所导致;同时,居群间的较高基因流(N_m=3.128)也可能起到很大的作用。还使用UPGMA聚类方法推断了武汉植物园迁地保护的野外居群来源,在对迁地保护居群的评价中发现迁地保护居群仅保存了该物种基因型多样性的16%,在此基础上提出了今后进一步的保育策略。     

Low levels of genetic variation within and high levels of genetic differentiation among populations of species of Abies from southern Mexico and Guatemala

Populations of Abies in southern Mexico and Guatemala (A. flinckii, A. guatemalensis, A. hickeli, and A. religiosa) have a patchy distribution. This pattern is particularly clear in A. guatemalensis. Genetic diversity within populations, measured by average heterozygosity at 16 isozyme loci, is lower than the range reported for most conifers (mean H(o) ranging from 0.069 in A. guatemalensis to 0.113 in A. flinckii), while differentiation among populations is higher than that observed in most conifer species studied (θ = F(st) ranging from 0.073 in A. hickeli to 0.271 in A. flinckii). Estimated levels of gene flow are low (ranging from 0.672 in A. flinckii to 3.17 in A. hickeli). Populations in most cases had an excess of homozygosity over that expected under Hardy-Weinberg equilibrium, suggesting some inbreeding (F(is) ranging from 0.074 in A. flinckii to 0.235 in A. guatemalensis). A significant relationship between gene flow and geographic distance was observed in A. religiosa, but not in the other three taxa studied. The patterns of genetic variation appear to have been influenced by the distributions and histories of these species. Paleoclimatic evidence suggests that the ranges of these species retreated upwards during the Pleistocene glaciation and became fragmented during the warming period that followed. The populations could have passed through genetic bottlenecks that reduced genetic variation and led to interpopulation differentiation.     

Genetic diversity in Mediterranean diploid and tetraploid Bromus L. (section Bromus Sm.) populations.

The levels of genetic diversity assessed from allozyme data were investigated in 25 populations of Mediterranean Bromus intermedius, B. squarrosus, B. lanceolatus, and B. hordeaceus from Algeria. The geographically restricted diploids B. intermedius and B. squarrosus displayed less genetic diversity (the mean population gene diversity of Nei (Hu) ranged from 0.03 to 0.12) than the widespread tetraploid colonizers B. lanceolatus and B. hordeaceus (Hu = 0.07-0.27). Deviations from Hardy-Weinberg expectations in diploid populations of B. intermedius and B. squarrosus were observed owing to heterozygote excess at several loci and suggested that these self-fertilizing species may have substantial amounts of allogamy. Tetraploid populations of B. lanceolatus and B. hordeaceus were largely homozygous at homologous loci and frequently exhibited intergenomic fixed heterozygosity in accordance with their alloploid origin. Genetic variation at the infraspecific level was mostly distributed within populations in the four species, B. hordeaceus showing the lowest level of interpopulation differentiation (Gst = 0.06) and the highest level of gene flow (Nm = 3.75). Consistent gene flows are in agreement with the strongest intercontinental invasive behaviour of B. hordeaceus. Less differentiation was reported in the literature among later introduced B. hordeaceus populations from England and Australia, indicating reduced differentiation under the process of colonization. Moderate divergence occured among the four taxa, with interspecific genetic identities ranging from 0.87 to 0.93. In spite of substantial genetic similarity, species were clearly differentiated, with each tetraploid being more closely related to a diploid: B. hordeaceus to B. squarrosus and B. lanceolatus to B. intermedius.     

太湖日本沼虾野生群体遗传结构的微卫星分析

利用8个高度多态性的微卫星位点分析了太湖日本沼虾野生群体的遗传结构.结果表明:在15个群体中至少有3个位点经Bonferroni校正后显示杂合不足,显著偏离了HardyWeinberg平衡;15个群体中观测杂合度均大于0.683,显示出较高的遗传多样性水平,但其波动明显,如太湖东、南部的渡口和陆巷等群体的遗传多样性高于西、北部的华庄和洋渚等群体;突变-漂移平衡分析结果显示,15个群体中部分位点杂合显著过剩,偏离了突变-漂移平衡,且近期曾经历过瓶颈效应,群体数量曾经下降;群体间AMOVA分析表明,太湖日本沼虾群体间遗传分化程度较低(FST=0.011),98.9%的遗传变异来自群体内,1.1%来自群体间,并没有形成显著的遗传结构,在种质资源保护和管理上可视作一个单元;华庄与吴塘门群体间DA遗传距离达到0.206,已接近种间分类界限,故太湖日本沼虾种质资源可持续利用工作仍须深入的研究.     

云南金钱槭天然居群等位酶遗传多样性研究

云南金钱槭(Dipteronia dyeriana)是我国特有的国家Ⅱ级重点保护珍稀濒危植物,仅分布于云南的文山、屏边和蒙自三县交界地区。采用水平切片淀粉凝胶电泳等位酶分析方法,对采自三个县的天然居群的63个样品进行了遗传多样性检测。8个酶系统的13个等位基因位点分析表明,云南金钱槭的遗传多样性水平低,其平均多态位点百分率P=15.4%,每位点平均等位基因数A=1.2,平均预期杂合度H_e=0.064,各居群都偏离Hardy-Weinberg平衡,杂合子过量,居群间的基因分化系数G_ST=0.099,遗传变异主要发生在居群内(90.1%),居群间分化较小,居群间遗传一致度较高(I=0.985~1),具有一定的基因流(Nm=2.669)。不加权对平均法(UPGMA)聚类可将4个居群分为两支,水头箐居群和马家寨居群亲缘关系最近,聚类后与黑洞居群形成一支再和中槽子居群聚类,这与其地理分布格局大致吻合。据此提出了关于云南金钱槭保育策略的建议。