Genetic diversity of Annona crassiflora (Annonaceae) in northern Minas Gerais State

Genetic diversity analyses of tropical tree species are relevant to landscape management, plant genetic resource inventory, and biological conservation of threatened species. Annona crassiflora is an endangered fruit tree native to the Cerrado biome that is threatened by reduction of natural populations and fruit extraction. We examined the intra- and interpopulational genetic diversity of this species in the northern region of Minas Gerais State. Seventy-two individuals from four natural populations were genotyped using RAPD markers. We found moderate genetic diversity among populations, with Shannon's I index varying between 0.31 and 0.44, and Nei's genetic diversity (H(E)) for the population set equal to 0.31. AMOVA indicated a greater genetic variation within (77.38%) rather than among populations (22.62%), tending towards isolation by distance (Mantel's r = 0.914; P = 0.089). Nei's genetic identity estimates among populations revealed a hierarchical pattern of genetic similarity of form [(CA1, CA2), MC], [(GM)], corroborating the high genetic differentiation between spatially isolated populations.     

Development and characterization of microsatellites markers from the macaw

Macaw (Acrocomia aculeata) is a native palm tree from tropical forests, highly abundant in Brazil and cited as one of the principal sources of plant oil, thus presenting a high potential for biodiesel production. We have optimized and utilized a set of eight polymorphic microsatellite markers for A. aculeata from an enriched genomic library. Automatic sequencing and fluorescence detection were employed to analyse 43 individuals from natural populations. In this study, we have obtained an average number of five alleles per locus. These loci will be employed in future studies of population genetics by providing subsidy information for the species conservation and genetic breeding.     

Genetic diversity and structure of natural and managed populations of Cedrus atlantica (Pinaceae) assessed using random amplified polymorphic DNA

Cedrus atlantica (Pinaceae) is a large and exceptionally long-lived conifer native to the Rif and Atlas Mountains of North Africa. To assess levels and patterns of genetic diversity of this species, samples were obtained throughout the natural range in Morocco and from a forest plantation in Arbúcies, Girona (Spain) and analyzed using RAPD markers. Within-population genetic diversity was high and comparable to that revealed by isozymes. Managed populations harbored levels of genetic variation similar to those found in their natural counterparts. Genotypic analyses of molecular variance (AMOVA) found that most variation was within populations, but significant differentiation was also found between populations, particularly in Morocco. Bayesian estimates of F(ST) corroborated the AMOVA partitioning and provided evidence for population differentiation in C. atlantica. Both distance- and Bayesian-based clustering methods revealed that Moroccan populations comprise two genetically distinct groups. Within each group, estimates of population differentiation were close to those previously reported in other gymnosperms. These results are interpreted in the context of the postglacial history of the species and human impact. The high degree of among-group differentiation recorded here highlights the need for additional conservation measures for some Moroccan populations of C. atlantica.     

Genetic characterization of cassava (Manihot esculenta) landraces in Brazil assessed with simple sequence repeats

Based on nine microsatellite loci, the aim of this study was to appraise the genetic diversity of 42 cassava (Manihot esculenta) landraces from selected regions in Brazil, and examine how this variety is distributed according to origin in several municipalities in the states of Minas Gerais, São Paulo, Mato Grosso do Sul, Amazonas and Mato Grosso. High diversity values were found among the five above-mentioned regions, with 3.3 alleles per locus on an average, a high percentage of polymorphic loci varying from 88.8% to 100%, an average of 0.265 for observed heterozygosity and 0.570 for gene diversity. Most genetic diversity was concentrated within the regions themselves (H_S = 0.52). Cluster analysis and principal component based scatter plotting showed greater similarity among landraces from São Paulo, Mato Grosso do Sul and Amazonas, whereas those from Minas Gerais were clustered into a sub-group within this group. The plants from Mato Grosso, mostly collected in the municipality of General Carneiro, provided the highest differentiation. The migration of human populations is one among the possible reasons for this closer resemblance or greater disparity among plants from the various regions.     

On the evolutionary consequences of increasing litter size with multiple paternity in wild boar (Sus scrofa scrofa)

Understanding how some species may be able to evolve quickly enough to deal with anthropogenic pressure is of prime interest in evolutionary biology, conservation, and management. Wild boar (Sus scrofa scrofa) populations keep growing all over Europe despite increasing hunting pressure. In wild boar populations subject to male‐selective harvesting, the initially described polygynous mating system may switch to a promiscuous/polyandrous one. Such a change in the mating system, where potentially more males sire a litter at one reproductive event, may be associated with the retention of high genetic diversity and an increase of litter size. We tested these hypotheses by estimating the number of sires per litter based on a six‐year long monitoring of a wild boar population subject to particularly high harvesting pressure. Our results show a high and stable genetic diversity and high rates of multiple paternity compared to other populations, thus depicting a promiscuous/polyandrous mating system in this population. We also show that litter size is positively linked to the number of sires, suggesting that multiple paternity increases fecundity. We finally discuss that multiple paternity may be one of the factors allowing rapid evolution of this population by maintaining both genetic and phenotypic diversity.     

Regional patterns of genetic diversity in Pinus flexilis (Pinaceae) reveal complex species history

Pinus flexilis (limber pine) is patchily distributed within its large geographic range; it is mainly restricted to high elevations in the Rocky Mountains and the Basin and Range region of western North America. We examined patterns of allozyme diversity in 30 populations from throughout the species' range. Overall genetic diversity (H(e) = 0.186) was high compared with that of most other pine species but was similar to that of other pines widespread in western North America. The proportion of genetic diversity occurring among populations (G(ST) = 0.101) was also high relative to that for other pines. Observed heterozygosity was less than expected in 28 of the 30 populations. When populations were grouped by region, there were notable differences. Those in the Basin and Range region had more genetic diversity within populations, a higher proportion of genetic diversity among populations, and higher levels of inbreeding within populations than populations from either the Northern or Utah Rocky Mountain regions. Patterns of genetic diversity in P. flexilis have likely resulted from a complex distribution of Pleistocene populations and subsequent gene flow via pollen and seed dispersal.     

Genetic Diversity and Structure of Populations of Annona crassiflora Mart. of Brazilian Savanna and Its Association with Chemical Variability

Annona crassiflora Mart . is a native tree from Brazilian savanna. Isoquinoline alkaloids are characteristic of species of Annonaceae. This work aimed to assess the magnitude of genetic diversity among different populations of A. crassiflora using AFLP markers, and verify the existence of any correlation between the AFLP data and previous reported alkaloid composition. A. crassiflora from eight populations in the states of São Paulo, Goiás, Minas Gerais, and Distrito Federal were analyzed. The data suggest a low, moderate, and high level of genetic diversity from different populations of A. crassiflora. Concentration of alkaloids was significantly correlated with AFLP data, suggesting interaction between chemical and molecular markers in A. crassiflora. The data of association between the chemical and genetic differentiation of A. crassiflora may be useful to establish cultivation areas allowing the definition of strategies to preserve their genetic diversity with an interest in specific chemotypes for genetic improvement programs focused on sustainable utilization of this specie.     

Phylogeography of Plathymenia reticulata (Leguminosae) reveals patterns of recent range expansion towards northeastern Brazil and southern Cerrados in Eastern Tropical South America

Little is known about past vegetation dynamics in Eastern Tropical South America (ETSA). Here we describe patterns of chloroplast (cp) DNA variation in Plathymenia reticulata, a widespread tree in the ETSA Atlantic Forest and Cerrado biomes, but not found in the xeromorphic Caatinga. Forty one populations, comprising 220 individuals, were analysed by sequencing the trnS‐trnG and trnL‐trnL‐trnF cpDNA regions. Combined, they resulted in 18 geographically structured haplotypes. The central region of the sampling area, comprising Minas Gerais and Goiás Brazilian states, is a centre of genetic diversity and probably the most longstanding area of the distribution range of the species. In contrast, populations from northeastern Brazil and the southern Cerrados showed very low diversity levels, almost exclusively with common haplotypes which are also found in the central region. Coupled with a long‐branched star‐like network, these patterns suggest a recent range expansion of P. reticulata to those regions from central region sources. The recent origin of the species (in the early Pleistocene) or the extinction of some populations due to drier and cooler climate during the last glacial maximum could have been responsible for that phylogeographic pattern. The populations from northeastern Brazil originated from two colonization routes, one eastern (Atlantic) and one western (inland). Due to its high diversity and complex landscape, the central region, especially central‐north Minas Gerais (between 15°–18° S and 42°–46° W), should be given the highest priority for conservation.     

Mitochondrial genetic variability of Didelphis albiventris (Didelphimorphia, Didelphidae) in Brazilian localities

Didelphis albiventris is a well-known and common marsupial. Due to its high adaptability, this very widespread generalist species occurs under various environmental conditions, this even including protected regions and disturbed urban areas. We studied a 653 bp fragment of cytochrome oxidase c (COI) from 93 biological samples from seven Brazilian localities, with linear distances ranging between 58 and about 1800 km to analyze the effects of geographic distances on variability and genetic differentiation. The haplotype network presented nine haplotypes and two genetic clusters compatible with the two most distant geographic areas of the states of Minas Gerais, in the southeast, and Rio Grande do Sul, in the extreme south. As each cluster was characterized by low nucleotide and high haplotype diversities, their populations were obviously composed of closely related haplotypes. Surprisingly, moderate to high F(ST) differentiation values and a very weak phylogeographic signal characterizes interpopulation comparisons within Minas Gerais interdemes, these being correlated with the presence of privative haplotypes. On a large rgeographic scale, a comparison between demes from Minas Gerais and Rio Grande do Sul presented high F(ST) values and a robust phylogeographic pattern. This unexpected scenario implies that mtDNA gene flow was insufficient to maintain population cohesion, reflected by the observed high differentiation.     

PERMANENT GENETIC RESOURCES: Characterization of eight microsatellite loci in the woolly mouse opossum, Micoureus paraguayanus, isolated from Micoureus demerarae

Eight novel microsatellite markers were isolated from the woolly mouse opossum from the Amazon Forest in Peru, Micoureus demerarae, using a partial genomic DNA library and an enrichment protocol. These loci were polymorphic in M. demerarae and Micoureus paraguayanus populations from the Atlantic Forest in Brazil with the number of alleles ranging from two to 23. Those eight loci plus another five already described for M. paraguayanus will allow for the evaluation of genetic diversity of populations from the 'Rio Doce' Park, one of the last Atlantic Forest fragments in Minas Gerais state, Brazil.     

Population Genetic Diversity of Bombax malabaricum(Bombacaceae) in China

In order to discuss the level of genetic diversity of Bombax malabaricum, we surveyed the genetic diversity of 4 populations (YJ, YM, QJ, DJ) from dry-hot valleys of Yunnan province, 2 populations (GX, HN) from dry-hot regionsand 1 population (BN) from wet-hot region of Yunnan using ISSR molecular markers . Based on 10 selected primers, 142 clear and reproducible DNA fragments were generated. The percentage of polymorphic loci PPB was 90.14%, Nei′s ( 1973) gene diversity H was 0. 2530 and Shannon′s Information index I was 0. 3864 . The coefficient of genetic differentiation( G_ST ) was 0. 1870 and the Фst was 0. 177 estimated by AMOVA. The results showed high level of genetic diversity within population and low level of genetic differentiation among populations. We inferred that the high level of genetic diversity and effective gene flow of B. malabaricum may play an important role in its better adaptability. Considering the introduction of B. malabaricum in dry-hot regions, we suggest to sample abundantly within populations and involve different populations .     

Genetic divergence among invasive and native populations of Plagioscion squamosissimus (Perciformes, Sciaenidae) in Neotropical regions

The genetic divergence among invasive and native populations of Plagioscion squamosissimus from four Neotropical hydrographic basins was assessed using the hypervariable domain of the mitochondrial DNA (mtDNA) control region. Plagioscion squamosissimus is native to the neighbouring hydrographic basins of the Parnaíba and Amazon Rivers, and the latter includes the Araguaia-Tocantins drainage, but it is invasive in other basins due to introductions. The mtDNA nucleotide polymorphism supported the hypothesis that the Amazon and Parnaíba populations constitute the same species and are separated into two independent evolutionary lineages. Absence of nucleotide polymorphism was observed within and among P. squamosissimus populations invasive to the uppper and middle Paraná River basins. Nucleotide divergence was null or low comparing the Paraná invasive populations with the populations native to the Parnaíba River basin, whereas it was significantly high compared to Tocantins populations. These results ascertain that P. squamosissimus populations invasive to the upper Paraná River basin and to the middle Paraná River basin downstream of the Itaipu dam are derived from the Parnaíba River basin. The genetic data presented are potentially useful to assist further studies on P. squamosissimus taxonomic and geographic distribution, development of ecological guidelines for managing populations invasive to the upper Paraná River basin and for preservation of native fish diversity.     

鄂尔多斯高原不同降雨量梯度中间锦鸡儿(Caragana davazamcii Sancz)种群的遗传结构

为了阐明环境条件对中间锦鸡儿适应状况的影响,在鄂尔多斯高原从东向西按照降雨逐渐减少的梯度选取了5个生境,从遗传多样性的角度出发,应用简单重复间序列（ISSR）方法,对各生境的中间锦鸡儿种群进行了分子生态学研究．结果表明随着生境由东向西的变化,多年平均降雨量的减少,中间锦鸡儿种群遗传多样性有所增加,大部分变异发生在种群内（79．95％）,属异交类型,中间锦鸡儿群体间遗传距离缓慢增加,遗传一致度降低,说明生境条件的变化特别是长期形成的水分条件对中间锦鸡儿的遗传多样性有一定的影响。     

附子野生资源群体遗传多样性的RAPD分析

应用RAPD标记分析了分布在附子主栽区四川、重庆、陕西及湖北16个野生乌头种群的遗传变异。24个引物共检测到643个RAPD位点,多态位点602个,总的多态位点百分率达93．5％。Shannon多样性和Nei遗传分化结果一致显示重庆酉阳种群和重庆城口种群遗传多样性最高,四川盐源种群和陕西勉县种群的遗传多样性最低。Shannon指数测出的种群内的遗传变异（57．6％）略占优势,群体间的遗传分化达到42．4％;Nei基因分化系数（GST）达40．0％;分子方差分析（AMOVA）发现群体间遗传变异仅为25．37％;种群每代迁移数Nm为0．756。Nei相似性系数的UPGMA分析结果显示该地区的野生乌头分布上有一定的地域性,特别是同为附子道地产地江油供种的北川、安县和青川种群间遗传关系密切,说明种质资源在道地药材形成中具有重要作用。研究结果表明,附子主要栽培地区的乌头野生种群之间存在较大的遗传分化,遗传多样性较高,遗传种质资源较丰富,存在一定的特异性资源,为进一步开发利用乌头（川乌、附子）提供了丰富的种质资源。     

Selection of high heterozygosity popcorn varieties in Brazil based on SSR markers

We analyzed genetic structure and diversity among eight populations of popcorn, using SSR loci as genetic markers. Our objectives were to select SSR loci that could be used to estimate genetic diversity within popcorn populations, and to analyze the genetic structure of promising populations with high levels of heterozygosity that could be used in breeding programs. Fifty-seven alleles (3.7 alleles per locus) were detected; the highest effective number of alleles (4.21) and the highest gene diversity (0.763) were found for the Umc2226 locus. A very high level of population differentiation was found (F(ST) = 0.3664), with F(ST) for each locus ranging from 0.1029 (Umc1664) to 0.6010 (Umc2350). This analysis allowed us to identify SSR loci with high levels of heterozygosity and heterozygous varieties, which could be selected for production of inbred lines and for developing new cultivars.     

Temporal change in genetic structure and effective population size in steelhead trout (Oncorhynchus mykiss)

There is a wealth of published molecular population genetic studies, however, most do not include historic samples and thus implicitly assume temporal genetic stability. We tested for changes in genetic diversity and structure in three populations of steelhead trout (Oncorhynchus mykiss) from a northern British Columbia watershed using seven microsatellite loci over 40 years. We found little change in genetic diversity (mean allele numbers and observed and expected heterozygosity), despite large variation in the estimated numbers of steelhead returning to the watershed over the same time period. However, the temporal stability in genetic diversity is not reflected in population structure, which appears to be high among populations, yet significantly variable over time. The neighbour-joining tree showed that, overall, two of the populations (Zymoetz and Kispiox) clustered separately from the third (Babine); a finding which was not consistent with their geographical separation. The clustering pattern was also not temporally consistent. We used the temporal method to estimate the effective number of breeders (Nb ) for the three populations; our values (Nb = 17-102) were low for the large and presumed vigorous populations of steelhead trout sampled. The low Nb values were also not consistent with the generally high genetic diversity estimates, suggesting the possibility of intermittent gene flow among the three populations. The use of temporal analyses in population genetic samples should be a priority; first, to verify observed patterns in contemporary data, and second, to build a dataset of temporal analyses to allow generalizations to be made concerning temporal genetic stability and effective population size in natural populations.     

RAPD Profiling in Detecting Genetic Variation in Endemic Coelonema (Brassicaceae) of Qinghai-Tibet Plateau of China

Random amplified polymorphic DNA (RAPD) markers were used to measure genetic diversity of Coelonema draboides (Brassicaceae), a genus endemic to the Qilian Mountains of the Qinghai-Tibet Plateau. We sampled 90 individuals in 30 populations of Coelonema draboides from Datong and Huzhu counties of Qinghai Province in P.R. China. A total of 186 amplified bands were scored from the 14 RAPD primers, with a mean of 13.3 amplified bands per primer, and 87% (161 bands) polymorphic bands (PPB) was found. Analysis of molecular variance (AMOVA) shows that a large proportion of genetic variation (84.2%) resides among individuals within populations, while only 15.8% resides among populations. The species shows higher genetic diversity between individuals than other endemic and endangered plants. The RAPDs provide a useful tool for assessing genetic diversity of rare, endemic species and for resolving relationships among populations. The results show that the genetic diversity of this species is high, possibly allowing it to adapt more easily to environmental variations. The main factor responsible for the high level of differentiation within populations and the low level of diversity among populations is probably the outcrossing and long-lived nature of this species. Some long-distance dispersal, even among far separated populations, is also a crucial determinant for the pattern of genetic variation in the species. This distributive pattern of genetic variation of C. draboides populations provides important baseline data for conservation and collection strategies for the species. It is suggested that only populations in different habitats should be studied and protected, not all populations, so as to retain as much genetic diversity as possible.     

Genetic structure and diversity of the Chilean flat oyster Ostrea chilensis (Bivalvia: Ostreidae) along its natural distribution from natural beds subject to different fishing histories

Ostrea chilensis (Küster, 1844), the flat oyster, is native to Chile and New Zealand. In Chile, it occurs in a few natural beds, from the northern part of Chiloé Island (41 ºS) to the Guaitecas Archipelago (45 ºS). This bivalve is slow growing, broods its young, and has very limited dispersal potential. The Ostrea chilensis fishery has been over-exploited for a number of decades such that in some locations oysters no longer exist. The aim of this study was to study the genetic diversity of the Chilean flat oyster along its natural distribution to quantify the possible impact of the dredge fishery on wild populations. The genetic structure and diversity of Ostrea chilensis from six natural beds with different histories of fishing activity were estimated. Based on mitochondrial (Cytb) and nuclear (ITS1) DNA sequence variation, our results provide evidence that genetic diversity is different among populations with recent history of wild dredge fishery efforts. We discuss the possible causes of these results. Ultimately, such new information may be used to develop and apply new management measures to promote the sustainable use of this valuable marine resource.     

Genetic diversity in Brazilian populations of Aedes albopictus

Random amplified polymorphic DNA (RAPD) analysis technique was undertaken in Aedes albopictus populations from three states in Brazil, Rio de Janeiro (RJ), Minas Gerais (MG) and Pernambuco (PE), to estimate the level of genetic variability and levels of genetic exchange between populations. Allele and genotype frequencies were measured on 47 RAPD loci. Average observed heterozigosity (Ho) ranged from 0.282 in MG to 0.355 in Casa Forte (PE) population. Genetic distances estimates indicated that RJ and MG were more genetically similar than populations from PE. Genetic variation observed in local Brazilian populations was attributed to genetic drift associated with restricted gene flow in recently established populations.