Morphological variation in British Atherinids, and the status of Atherina presbyter Guvier (Pisces: Atherinidae)

A series of morphometric and meristic analyses conducted on specimens of sand smelt, Atherina , from populations around the British Isles, and including classic A. boyeri and A. presbyter forms, has shown that the characteristics variously used in the past to distinguish these two species are invalid. Multivariate analyses showed no significant splitting of the material into two groups which might correlate to these two species; classic A. boyeri and the very large Atlantic coast A. presbyter individuals represent the tails of a continuum of form. From these and published data, it is concluded that the A. boyeri morphology varies under the influence of conditions of temperature and salinity during embryo development, and the isolation of populations maintains comparative morphological distinctions resulting from local selection and random genetic drift.     

A multivariate morphometric investigation of Atherina boyeri Risso, 1810 and A. presbyter Cuvier, 1829 (Teleostei: Atherinidae): morphometric evidence in support of the two species

Two recently developed morphometric methodologies, multiple group principal components analysis (MGPCA) and the box truss method of body form transformation are used to re-address whether Atherina boyeri Risso, 1810 and A. presbyter Cuvier, 1829 are morphometrically distinct. The results revealed that morphometric differences are present between A. boyeri and A. presbyter , consistent with expectations of the existence of two species.
Females of the two species were clearly discriminated into two separate groups because the within-group covariances of several characters within populations of each species were different between species i.e., the covariances were heteroscedastic. The occurrence of heteroscedasticity within the data, although statistically invalidating the results of canonical variates anslysis, indicated there to be a large amount of morphological variation between females of the two species. Males were differentiated as a result of differences in body 'shape', particularly the relationship between head 'shape' and body 'shape'.
Several probable reasons are given for the failure of a previous study to differentiate the two species. The data rejects the synonymy of the two species in support of the continued use of the taxa A. boyeri Risso, 1810 and A. presbyter Cuvier, 1829.     

Isolation, characterization and cross-species testing of microsatellites obtained from a sand smelt (Atherina boyeri) genomic library

This study reports the isolation and characterization of 11 polymorphic microsatellites from a sand smelt (Atherina boyeri) genomic library. Enrichment was performed with di-, tri- and tetranucleotide motifs following the FIASCO procedure (fast isolation by AFLP of sequences containing repeats). All loci were found to be in linkage and in Hardy-Weinberg equilibrium. This represents the first microsatellite isolation for the family Atherinidae and the isolated loci were accordingly tested on four additional species of the family: two recognized (A. presbyter and A. hepsetus) and two proposed ('punctata' and 'non-punctata' forms). Moreover their cross-species suitability on Menidia menidia, belonging to the same order but to the family Atherinopsidae, was also tested.     

小毛茛居群的遗传分化及其与空间隔离的相关性

采用聚丙烯酰胺凝胶电泳技术,对分布于华中地区的11个小毛茛（Ranunculus ternatus）居群的遗传分化进行了检测。对8个酶系统17个酶位点上的分析结果表明,该种各居群 的各项遗传多样性指标处于一个相对较低的水平：多态位点比率（P）为0～53.0%,平均每位点等位基因数（A）为1～1.647,平均预期杂合度（H_e）和观察杂合度（H_o）分别为0～0.108和0～0.102。居群间遗传一致度甚高（I＝0.9754～0.9991）。根据Nei′s遗传距离所作出的聚类分析表明,豫南信阳地区3个居群与湖北省武汉地区8 个居群之间关系较远。而在武汉地区,长江以北的居群及长江以南的部分居群分别相聚在一 起。用GPS定位方法得到居群间空间距离并据此聚类,结果显示了该种的遗传分化与地理因 素 的相关性,并推测出长江的隔离作用加强了两岸居群间的遗传分化。同时发现一个生于独特 生境的居群在表型和遗传结构上都已与其他邻近居群有了很大分异,由于该居群在所检测的 酶位点上均无特有等位基因出现,作者认为不宜将其作为新种或新变种处理。     

Polymorphic microsatellite markers of freshwater prawn Palaemon paucidens (De Haan, 1844) (Crustacea: Palaemonidae)

We report 11 polymorphic microsatellite loci developed from the freshwater prawn Palaemon paucidens. Their genetic characteristics were assessed in 48 individuals selected from six Korean populations. The number of alleles ranged from two to 21, and the observed and expected heterozygosities were between 0.13 and 0.83, and 0.46 and 0.95, respectively. We examined the cross-specific amplification of each locus in three species of palaemonid prawn and one species of atyid prawn.     

Population genetic structure of Nantucket pine tip moth

Summary Variation at polymorphic isozyme loci was analyzed in Nantucket pine tip moth (NPTM) populations from 5 geographic locations. At the North Carolina location, populations representing 3 generations at 3 local sites were also studied. Four of the loci investigated (LAP, MDH, -GPDH and AK), although variable, had few alleles per locus (3–5) and few differences among populations in allele frequencies. At each locus, all populations had the same allele at a high frequency.At the PGM locus, fifteen alleles were identified and allelic frequencies varied among populations. At least eight alleles were present within a population and, in most populations, two or more alleles had high frequencies that differed among populations. An excess of homozygotes over Hardy-Weinberg expectations was found for 7 out of the 10 populations studied, indicating the probable existence of some form of inbreeding structure or populational subdivision within sampled stands.Joint consideration of the results observed for PGM and the other four loci is counterindicative of neutrality at all loci and strongly indicative of genetic differentiation among locally disjunct populations.Published as Paper No. 6751 of the Journal Series of the North Carolina Agricultural Research Service     

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.     

广西区西南桦天然居群遗传多样性的研究

 以采自广西区11个西南桦(Betula alnoides)天然居群的种子培育出的幼苗为材料,取其嫩叶开展21种酶系统的水平切片淀粉凝胶电泳实验,运用作者改进的Tris-马来酸提取缓冲液 (含30%PVP 40 000和1%2-巯基乙醇),筛选出AMP(氨基肽酶Aminopeptidase)、FBA(果糖二磷酸酶Fructose-bisphosphate aldolase)、GDH(谷氨酸脱氢酶Glutamate dehydrogenase)、G6PD(6-磷酸葡萄糖脱氢酶Glucose-6-phosphate dehydrogenase)、IDH(异柠檬酸脱氢酶Isocitrate dehydrogenase)、MDH(苹果酸脱氢酶Malate dehydrogenase)、PGD(6-磷酸葡萄糖酸脱氢酶Phosphogluconate dehydrogenase)、PGI(磷酸葡萄糖异构酶Phosphoglucoisomerase)、PGM(磷酸葡萄糖变位酶Phosphoglucomutase)和SKD(莽草酸脱氢酶Shikimate dehydrogenase)等10种酶,获得了清晰且可重复的酶谱。通过谱带遗传分析确定了15个位点,其中有6个单态位点,9个多态位点 (0.95标准),具40个等位基因。在居群水平上,西南桦的多态位点百分数 (P) 为55.2%,平均每个位点的等位基因数 (A) 为2.00,平均预期杂合度 (He) 为0.204。均超过Hamrick (1992)等提出的远交风媒木本植物的平均值(53.0%,184%和0154),表明西南桦的遗传变异水平高。在11个西南桦居群内,实际杂合度 (Ho)均高于预期杂合度,出现杂合子过量,可能存在利于杂合子的自然选择。西南桦遗传多样性与地理位置相关不显著。居群2 (靖西地州)、5 (平果海城)、9 (田林者苗) 包含绝大部分的等位基因,而且具较高的遗传多样性,应加以保护和管理,作为其基因资源就地保存的基地。本研究解决了以西南桦嫩叶为材料进行等位酶分析的关键技术,为进一步开展西南桦乃至桦木属树种的遗传结构和遗传多样性等提供了技术基础;同时掌握了西南桦天然居群的遗传多样性现状,为其有效保护和合理经营以及西南桦的遗传改良提供了理论依据。     

Genetic diversity of six populations of Atractomorpha sinensis and Atractomorpha peregrina in Shanxi Province, China

Ten enzymes (AAT,CK,G3PDH,HEX,IDH,LDH,MDH,ME,PGI,PGM)were examined using horizontal starch gel electrophoresis to estimate the levels of genetic variation within and among six natural populations of two grasshopper species Atractomorpha sinensis and A.peregrina from Shanxi,China.The collecting sites were geographically distant from each other from south to north:Quwo district,Linfen city;Xiangyuan county,Changzhi;Jinyuan district,Taiyuan city;Yuanping county,Xinzhou city and Fanshi county of Xinzhou.A.sinensis showed 43 alleles at 16 loci but A.peregrine showed 39 alleles at 15 loci (ldh-1 was deficient).The zymograms showed that some common alleles were shared at several loci in these two species (Aat-1-b,Aat-2-b,G3pdh-a,Ck-1-b and Ldh-b).However,Hex-1-a,Hex-2-a,Hex-3-a,Idh-2-b,Mdh-2-b,Mdh-1-f Pgi-b,Pgm-b had common alleles in A.sinensis and Hex-1-b,Hex-2-b,Hex-3-b,Idh-2-a,Mdh-2-a,Mdh-1-d,Pgi-a,Pgm-c were of high frequency in A.peregrine instead.Most of the observed genotype frequencies were found to significantly deviate from the Hardy-Weinberg expectations in both species.A tendency of clinal distribution of allele frequency was observed at three loci.The frequency of the moderately migrating allele Me-c (0.318-0.740)in A.peregrina,Hex-1-a (0.800-1.000)and Ldh-b (0.487-0.750)in A.sinensis demonstrated increased frequency from north to south.Such tendency suggests that the allele frequency in these three loci may be correlated with the species'geographic distributions.A.sinensis showed higher genetic diversity than A.peregrina as indicated by higher mean number of alleles per locus (A=1.9-2.3 in A.sinensis and 1.7-2.2 in A.peregrina),percentage of polymorphic loci (56.3%-68.8%in A.sinensis and 43.8%-56.3%in A.peregrina),and the observed heterozygosities (Ho=0.072-0.096 in A.sinensis and 0.070-0.107 in A.peregrina).The observed heterozygosities of the six populations were all noticeably lower than the Hardy-Weinberg expectations,mostly due to heterozygote deficiency in the populations of both species.The overall mean Fsr were small (FST=0.045,P＞0.05 in A.sinensis populations and 0.087,P＞0.05 in A.peregrina populations).Nei's genetic identity (I)estimates indicate low intraspecific (＞0.95)but higher interspecific (0.377-0.447)genetic diversity.The cluster analysis based on modified Roger's genetic distance (D)showed that the two species were divided into two branches.Both species are of limited dispersal capacity and a moderate geographical barrier might significantly restrict the gene exchange among populations,resulting in accumulation of local genetic differentiations.The A.sinensis populations used in this study were separated from each other by 155.2 to 271.4 km and the A.peregrina populations were separated from each other by 78.8 to 174.9 km with observable physical barriers.The aUozyme data showed only minimal genetic differentiation at population level,most likely as a result of gene exchange.It is reasoned that natural factors and human agricultural activities might have facilitated migration and dispersal for the two species.     

Isolation and characterization of the first microsatellite loci from the order Psocoptera in the economically important pest insect Liposcelis decolor (Pearman) and cross‐species amplification

A total of 11 microsatellite loci from the invasive insect pest Liposcelis decolor were isolated and characterized of which six loci were polymorphic. A population survey involving a total of 30–192 individuals per locus from five populations revealed a range of four to seven alleles per locus and moderate observed heterozygosities (0.183–0.565), highlighting the utility of these loci in further population genetic studies. Cross‐species amplifications were successful for two to 11 loci in five other Liposcelis species also of international economic importance.     

Multilocus phylogenetic analysis of the genus Atherina (Pisces: Atherinidae)

Sand-smelts are small fishes inhabiting inshore, brackish and freshwater environments and with a distribution in the eastern Atlantic and Mediterranean Sea, extending south into the Indian Ocean. Here, we present a broad phylogenetic analysis of the genus Atherina using three mitochondrial (control region, 12S and 16S) and two nuclear markers (rhodopsin and 2nd intron of S7). Phylogenetic analyses fully support the monophyly of the genus. Two anti-tropical clades were identified, separating the South African Atherina breviceps from the north-eastern Atlantic and Mediterranean Atherina' species. In European waters, two groups were found. The first clade formed by a well supported species-pair: Atherina presbyter (eastern Atlantic) and Atherina hepsetus (Mediterranean), both living in marine waters; a second clade included Atherina boyeri (brackish and freshwater environments) and two independent lineages of marine punctated and non-punctated fishes, recently proposed as separate species. Sequence divergence values strongly suggest multiple species within the A. boyeri complex.     

Phylogenetic relationships of Atherina hepsetus and Atherina boyeri (Pisces: Atherinidae) populations from Greece, based on mtDNA sequences

The genetic divergence and the phylogenetic relationships of six Atherina boyeri (freshwater and marine origin) and five Atherina hepsetus populations from Greece were investigated using partial sequence analysis of 12s rRNA, 16s rRNA and control region mtDNA segments. Three different well divergent groups were revealed; the first one includes A. boyeri populations living in the sea, the second includes A. boyeri populations living in the lakes and lagoons whereas the third one includes all A. hepsetus populations. Fifty-seven different haplotypes were detected among the populations studied. In all three mtDNA segments examined, sequence analysis revealed the existence of fixed haplotypic differences discriminating A. boyeri populations inhabiting the lagoon and the lakes from both the coastal A. boyeri and the A. hepsetus populations. The genetic divergence values estimated between coastal (marine) A. boyeri populations and those living in the lagoon and the lakes are of the same order of magnitude as those observed among coastal A. boyeri and A. hepsetus populations. The results obtained by different phylogenetic methods were identical. The deep sequence divergence with the fixed different haplotypes observed suggests the occurrence of a cryptic or sibling species within A. boyeri complex.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 92 , 151–161.     

High genetic variability in an ecologically variable vertebrate,Bufo viridis

Allozymic variation in proteins encoded by 26 loci was analyzed electrophoretically in 517 specimens of green toads from 11 populations from Israel and one population from Vis Island in the Adriatic Sea. Genetic variation in this toad is the highest yet reported in any vertebrate. All three genetic parameters, mean number of alleles per locus (A), mean proportion of loci polymorphic per population (P), and mean number of heterozygous loci per individual (H), are very high (A = 1.65, range 1.38-2.04; P = 0.423, range 0.346-0.615; H = 0.133, range 0.108-0.159). Central and marginal mainland populations are only slightly more variable than desert isolates, but much more variable than the Vis Island population. Genetic similarity is very high between mainland populations (S = 0.951, range 0.93-0.97). Frequencies of two alleles (Icd-lc and Tfa) are correlated with an ecological gradient of increasing aridity. Regulatory enzymes appeared to contribute more to overall polymorphism than non-regulatory enzymes. The genetic variation observed suggests that selection for heterozygosity as an adaptive strategy is operating in the ecologically variable environment in which green toads live.     

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。     

Colour polymorphism and genetic strains in Avion intermedins from Flores, Azores (Mollusca: Pulmonata)

Thirty specimens of Arion intermedins from Flores (and Corvo) were electrophoretically (PAGE) assayed for 11 enzymes, yielding information about 14 putative loci in two colour morphs of this species. One of these colour variants was tentatively identified as A. pascalianus (P morph). Except for the Mdh locus, all loci in A. intermedins sensu lato from Flores were monomorphic. Mdh , however, was diallelic for Mdh₁₀₀ and Mdh₁₂₂. This latter electromorph was absent in A. intermedins sensu stricto from Flores, but present in the P morph and A. intermedins from Belgium. As a consequence A. intermedins sensu lato from Flores consists of two genetic strains defined by the Mdh alleles. The genetic identity between these strains (7) is 0.929. The genetic identity between the P morph and A. intermedins sensu stricto in Flores is 0.951, while between the P morph and Belgian A. intermedins it is 0.973. These values suggest that the supposed A. pascalianus from Flores is only a colour morph of A. intermedins. This paper also provides the first published record of this species from the island of Corvo.     

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 differentiation of theErigeron species (Asteraceae) in the Alps: A case of unusual allozymic uniformity

Allozyme variation was studied in all nine diploidErigeron species known from the Alps:E. alpinus, E. neglectus, E. polymorphus, E. candidus, E. uniflorus, E. atticus, E. gaudinii, E. acer, andE. angulosus. A total of 248 individuals from 24 natural populations was investigated using starch gel electrophoresis. Seven enzymes and 13 loci were assessed. Genetic variation within populations was low with the proportion of polymorphic loci ranging from 0.0–0.385, and average number of alleles per polymorphic locus from 2.0–2.5. In general, 70–100% of the genetic variation was attributed to between population differences. Mean genetic identities for pair-wise comparisons of populations averaged 0.893 within species, and 0.890 among species. Interspecific genetic variation of populations usually did not exceed intraspecific variation. It was concluded that theErigeron species from the Alps may have arisen by recent speciation probably during the epoches of glaciation. Morphological and ecological differences between species seem to be based on few gene loci.     

Assessing the allozyme variation in cultivars and Swedish landraces of rye (Secale cereale L.)

Genetic interpretation and diversity of 9 isozyme loci have been estimated in 7 improved varieties and 19 landraces from Sweden by means of starch gel electrophoresis. The isozyme systems were ACO, DIA, GPI, MDH, PGD and PGM. For the statistic analysis we used the following measures: average number of alleles per locus, percentage of polymorphic loci, average heterozygosity direct count and average heterozygosity Hardy-Weinberg expected unbiased estimate. The measures were made on species and population levels. The distribution of the total genetic diversity among populations was also calculated. To illustrate the genetic relationships among populations, genetic distances were measured and principal component analysis performed. As expected in a cross-pollinated crop we found high genetic diversity and a larger variation within than among the populations. Somewhat unexpectedly, however, we found that the currently used varieties have the same high level of heterozygosity as the landraces but in the dendrogram the two groups are separated. The dendrogram showed three main clusters. The large cluster included 21 populations and the two small clusters were clearly distinguishable from the rest. The landrace spring-type could not be separated from the landraces winter-type, but we did detect a difference between different spring types. A few populations had unique alleles for certain loci.     

Allozyme variation among biotypes of the brown planthopperNilaparvata lugens in the Philippines

Allozyme variation was studied in threeNilaparvata lugens biotypes infesting specific rice varieties and a biotype infesting a weed grass,Leersia hexandra. Of the 20 enzymes inN. lugens for which activity was noted, 9 were polymorphic. Eleven enzyme loci were monomorphic for the same allele in all biotype populations; the rest were polymorphic for two or more alleles. The mean number of alleles per polymorphic locus was 2.3, while the mean number of alleles per locus was 1.5; heterozygosity ranged from 0.02 to 0.06 (biotype 1 > biotype 3 >Leersia-infesting biotype > biotype 2). Allelic frequency differences were observed in five loci among the four biotypes. However, the coefficient of genetic identity (I) of 0.99+ showed that the four biotype populations were genetically close relatives or merely populations ofN. lugens undergoing genetic differentiation. This work was partly supported by a financial grant received from the Directorate for Technical Cooperation and Humanitarian Aid, Switzerland.     

Discriminating coho salmon (Oncorhynchus kisutch) populations within the Fraser River, British Columbia, using microsatellite DNA markers

Three microsatellite loci were used to examine genetic variation among 16 coho salmon ( Oncorhynchus kisutch ) populations within the Fraser River drainage system, in British Columbia, Canada. Each locus was highly polymorphic with 30 alleles at the Ots 101 locus, 15 alleles at the Ots 3 locus and 38 alleles at the Ots 103 locus. Average observed heterozygosities were 86.1%, 70%, and 56.1%, respectively. With the exception of the Dunn and Lemieux River populations, Chi-square tests and F _ST values indicated that all populations had significantly different allele frequencies. Two distinct population groups within the Fraser River drainage were observed. Lower Fraser River populations were strongly differentiated from populations spawning in the upper Fraser River, which includes the Thompson River (a tributary flowing into the upper Fraser) and the portion of the Fraser River beyond the precipitous Fraser River canyon. This regional population structure may have resulted from colonization of the upper and lower Fraser River regions by different founder populations following Pleistocene glaciation, and be maintained by adaptive differences between the two groups of coho salmon. Coho salmon populations in the upper Fraser and Thompson River drainages form an evolutionarily significant unit (ESU) of importance for conservation of biodiversity in coho salmon. Microsatellite DNA loci show promise as technically simple and highly informative genetic markers for coho salmon population management.