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Species of the red algal genus Mazzaella are widely distributed along the west coast of North America with 11 reported in British Columbia (BC). Like many red algal genera, however, accurate species identification is complicated by phenotypic plasticity and convergent evolution, and considerable taxonomic changes have taken place in recent years. To better understand the diversity of this genus in the BC flora, we variously compared COI-5P, rbcL, and ITS data for 407 collections predominantly from BC (n = 347) and California (n = 59) with other accessions in GenBank. We report the first records of Mazzaella phyllocarpa (Postels & Ruprecht) Perestenko in the BC flora whereas Mazzaella linearis (Setchell & N.L. Gardner) Fredericq is excluded--individuals previously assigned to this name referred to Mazzaella dewreedei sp. nov. Verified records and the distributional range for the poorly documented Mazzaella minima (G.J. Hollenberg) P.W. Gabrielson are greatly extended whereas northern records of Mazzaella rosea (Kylin) Fredericq are established. The presence of Mazzaella flaccida (Setchell & N.L. Gardner) Fredericq and Mazzaella japonica (Mikami) Hommersand (likely introduced) inBC are confirmed whereas resolution of the Mazzaella oregona (Doty) J.R. Hughey, P.C. Silva & Hommersand species complex necessitates description of Mazzaella macrocarpa sp. nov. Two additional cryptic complexes involving M. flaccida and M. oregona were discovered in the Californian flora, but are outside the scope of this study and are in need of further investigation. Key words: COI-5P, DNA barcode, Gigartinaceae, Mazzaella, rbcL. Les especes algacees rouges du genre Mazzaella sont largement distributes le long de la cote ouest de l'Amerique du Nord, dont 11 especes signalees en Colombie-Britannique (CB). Comme c'est le cas pour plusieurs genres d'algaces rouges, l'identification precise des especes est compliquee par la plasticite phenotypique et revolution convergente, et des changements taxonomiques considerables ont recemment eu lieu. Afin de mieux comprendre la diversite de ce genre dans la flore de la CB, nous avons compare la COI-5P, la rbcL et des donnees des ITS de 407 collections provenant de fa^on predominante de CB (n = 347) et de Californie (n = 59) a d'autres donnees de GenBank. Nous rapportons les premiers signalements de la presence de Mazzaella phyllocarpa (Postels & Ruprecht) Perestenko dans la flore de CB alors que Mazzaella linearis (Setchell & N.L. Gardner) Fredericq en est exclue--on refere maintenant a Mazzaella dewreedei sp. nov pour identifier les individus anterieurement designes par ce nom. Les signalements verifies et l'etendue de la distribution de l'espece pauvrement documentee Mazzaella minima (G.J. Hollenberg) P.W. Gabrielson sont grandement elargis alors que des signalements de Mazzaella rosea (Kylin) Fredericq sont etablis au nord. La presence de Mazzaella flaccida (Setchell & N.L. Gardner) Fredericq et de Mazzaella japonica (Mikami) Hommersand (probablement introduite) en CB est confirmee alors que la resolution des especes du complexe Mazzaella oregona (Doty) J.R. Hughey, P.C. Silva & Hommersand necessite la description de Mazzaella macrocarpa sp. nov. Deux complexes cryptiques additionnels qui impliquent M. flaccida et M. oregona ont ete decouverts dans la flore californienne, mais ils se trouvent hors des visees de cette etude et doivent etre etudies de maniere plus approfondie. [Traduit par la Redaction] Mots-cles: COI-5P, code-barres genetique, Gigartinaceae, Mazzaella, rbcL., Introduction The red algal family Gigartinaceae is generally accepted as having nine genera: Chondracanthus Kutzing, Chondrus Stackhouse, Gigartina Stackhouse, Iridaea Bory de Saint-Vincent, Mazzaella G. De Toni f., Ostiophyllum Kraft, [...]

The Precambrian Shield supports a diversity of cryptogams where environmental conditions predict their distribution. Moisture and light are thought to affect secondary metabolite production in lichens, leading to a hypothesis of chemical communities that may be independent of species assemblages. Hypotheses were that habitats will be characterized by lichen secondary metabolites and that lichen and bryophyte species composition will also distinguish among habitats. Lichens and bryophytes were sampled from six quadrats from each of two sites within each of three habitats (rock faces, rock outcrops, and forest floors). This study showed strong relationships among species assemblages, secondary metabolites, and types of habitat. Species abundance, cover, and species richness also differed among habitats. Individual secondary metabolites could differentiate among three habitats, suggesting that certain metabolites such as usnic and squamatic acids would more likely be found in habitats such as dry exposed rock outcrops than in moist shaded habitats. Individual analyses suggested that some secondary metabolites may serve multiple functions in a habitat, such as triterpenes, while others may have more specific functions, such as salazinic acid, where environmental features may be important for secondary metabolite production. Further investigation of specific metabolites is needed to understand their roles in adaptation. Key words: bryophytes, cyanobacterial lichens, fungal secondary metabolites, mosses. Le bouclier precambrien supporte une diversite de cryptogames ou les conditions environnementales permettent de predire leurs distributions. On croit que l'humidite et la lumiere affectent la production de metabolites secondaires chez les lichens conduisant a l'hypothese de 'communautes chimiques' pouvant etre independantes de l'assemblage des especes. Les hypotheses sont que les habitats se caracteriseraient par les metabolites secondaires des lichens et que la composition en especes de lichens et de bryophytes feraint la differences entre les habitats. Les auteurs ont echantillonne les lichens et les bryophytes dans six quadrats de chacun de deux sites dans chacun de trois habitats (crets rocheux, affleurements rocheux et parterres forestiers). Cette etude montre qu'il existe une forte relation entre l'assemblage des especes et leurs metabolites secondaires, avec les types d'habitat. L'abondance des especes, la couverture ainsi que la richesse en especes different egalement entre les differents habitats. Les metabolites secondaires individuels pourraient faire la difference entre les trois habitats, suggerant que certains metabolites comme les acides usniques et squamatiques se retrouveraient plutot dans des habitats comme les crets rocheux secs et exposes, que dans des habitats humides et ombrages. Les analyses individuelles suggerent que certains metabolites secondaires pourraient jouer divers roles dans un habitat, comme les triterpenes, alors que d'autres auraient des fonctions plus specifiques comme l'acide salazinique, ou les caracteristiques environnementales pourraient etre importantes pour la production de metabolites secondaires. De plus, on doit conduire des recherches sur les metabolites secondaires pour comprendre leurs roles dans l'adaptation. [Traduit par la Redaction] Mots-des: bryophytes, lichens cyanobacteriens, metabolites fongiques secondaires, mousses., Introduction Lichens and bryophytes (cryptogams) are known to be effective indicators of environmental conditions because there is no barrier between the ambient environment and the body of the lichen or [...]

Solanum maglia Schltdl., a wild potato species that has its widest geographical distribution in Chile, is restricted in Argentina to Quebrada La Cumbre (quebrada = gorge), Mendoza province, where no other potato species has been reported. During two collecting expeditions carried out in 2006 and 2007 in this gorge, tubers of two potato populations separated by 500 m (area 1 and 2) were sampled. The morphological and genetic diversity of these two newly sampled populations and of five accessions from the same gorge classified as S. maglia, a plant of Solanum kurtzianum collected outside this gorge, and a Chilean plant of S. maglia were examined by comparing 24 morphological characters and electrophoretic patterns for simple sequence repeat and amplified fragment length polymorphism markers, respectively. Based on the current taxonomic concept, the results support the classification of plants from area 1 as S. kurtzianum and those from area 2 as S. maglia, except for one plant from the former area, which shared electrophoretic bands from both species. This is the first report on the sympatry of populations of the two species in Quebrada La Cumbre. The importance of performing in situ population studies in the same sites over years is discussed. Key words: amplified fragment length polymorphism, genetic resources, introgression, Solanum kurtzianum, Solanum maglia, simple sequence repeat. Le Solanum maglia, une espece de pomme de terre sauvage ayant sa plus importante distribution geographique au Chili, est confine en Argentine a la Quebrada La Cumbre (quebrada = gorge), de la province Mendoza, ou aucune autre espece de pomme de terre n'a ete rapporteee. Au cours de deux expeditions de recortes en 2006 et 2007 dans cette gorge, les auteurs ont pu echantillonner des tubercules de deux populations separees de 500 m (aire 1 et 2). Les auteurs ont examine; la morphologie et la diversite geneetique de ces deux populations nouvellement recoltees, et de cinq accessions de la mieme gorge classifiees comme S. maglia, un plant du Solanum kurtzianum recolte en dehors de cette gorge, et une plante provenant du Chili, en comparant 24 caracteres morphologiques ainsi que les patrons electrophoretiques pour les marqueurs repetition de sequences simples et polymorphisme des longueurs des fragments amplifies respectivement. Sur la base des concepts taxonomiques actuels, les resultats supportent la classification des plantes de l'aire 1 comme S. kurtzianum, et ceux de l'aire 2 comme S. maglia, sauf pour une plante de la premiere aire, partageant des bandes electrophoretiques avec les deux espe:ces. Il s'agit du premier rapport sur la sympatrie des populations des deux espe:ces a Quebrada La Cumbre. Les auteurs discutent l'importance de realiser des etudes de populations in situ sur les meemes sites au cours des anneees. Mots-cles: polymorphisme des longueurs des fragments amplifies, ressources geneetiques, introgression, Solanum kurtzianum, Solanum maglia,repetition de sequences simples. [Traduit par la Redaction], Introduction Potatoes (Solanum L. sect. Petota Durmort, subsec. Potatoe) constitute a significant reservoir of genetic variability for potato improvement, including resistance/tolerance to biotic and abiotic stresses, as well as desirable [...]

ABSTRACT Amplified fragment length polymorphism (AFLP) analysis of the population genetic structure and genetic diversity of Haliotis discus hannai (D), Haliotis gigantea (G), and their reciprocal hybrids D ♀ X [...]

Brachiaria humidicola (Rendle) Schweick. is a warm-season grass commonly used as forage in the tropics. Accessions of this species were collected in eastern Africa and massively introduced into South America in the 1980s. Several of these accessions form a germplasm collection at the Brazilian Agricultural Research Corporation. However, apomixis, ploidy, and limited knowledge of the genetic basis of this germplasm collection have constrained breeding activities. The objectives of this work were to identify genetic variability in the Brazilian B. humidicola germplasm collection using microsatellite markers and to compare the results with information on the following: (1) collection sites of the accessions; (2) reproductive mode and ploidy levels; and (3) genetic diversity revealed by morphological traits. The evaluated germplasm population is highly structured into four major groups. The sole sexual accession did not group with any of the clusters. Genetic dissimilarities did not correlate with either geographic distances or genetic distances inferred from morphological descriptors. Additionally, the genetic structure identified in this collection did not correspond to differences in ploidy level. Alleles exclusive to either sexual or apomictic accessions were identified, suggesting that further evaluation of the association of these loci with apospory should be carried out. Key words: koroniviagrass, Urochloa humidicola, forage grass, variability, molecular markers, aposporous apomixis. Le Brachiaria humidicola (Rendle) Schweick. est une graminee des climats chauds frequemment employee comme plante fourragere dans les tropiques. Des accessions de cette espece ont ete collectes en Afrique de l'Est et massivement introduites dans les Ameriques au cours des annees 1980. Plusieurs de ces accessions sont representees au sein d'une collection de ressources genetiques maintenue par le Brazilian Agricultural Research Corporation. Cependant, l'apomixie, la ploidie et des connaissances limitees des bases genetiques des accessions de cette collection ont restreint les efforts de selection. Les objectifs de ce travail etaient d'identifier la variabilite genetique au sein de la collection bresilienne du B. humidicola au moyen de microsatellites et de comparer les resultats avec les informations suivantes : 1) le lieu de collection des accessions ; 2) le mode de reproduction et le niveau de ploidie ; et 3) la diversite genetique mesuree sur la base des caracteres morphologiques. La collection de ressources genetiques examinee forme quatre groupes majeurs tres distincts. La seule accession a reproduction sexuee se distinguait des quatre autres groupes. Le degree de differentiation genetique n'etait correle ni avec la distance geeographique ni avec la distance genetique mesuree sur la base des caracteres morphologiques. De plus, la structure genetique identifiee au sein de la collection ne correspond pas a des differences quant aux niveaux de ploidie. Les alleles presents uniquement au sein d'accessions sexuees ou apomictiques ont ete identifies et une evaluation ulterieure de l'association entre ces locus et l'aposporie serait utile. Mots-cles: koroniviagrass, Urochloa humidicola, graminee fourragere, variabilite, marqueurs moleculaires, apomixie gametophytique (aposporie). [Traduit par la Redaction], Introduction Koroniviagrass is one of the vernacular names adopted in the New World for a grass species that is characterized as a perennial stoloniferous plant possessing narrow, wiry stems and [...]

Camelina (Camelina sativa (L.) Crantz) is an oilseed known for its potential as a low-input biofuel feedstock and its high levels of beneficial fatty acids. We investigated the role of geographical origin in genetic variation and fatty acid content, expecting to find significant variability among 53 accessions and a link between ecogeography and both origin and key oil traits. Amplified fragment length polymorphism (AFLP) fingerprinting revealed high levels of diversity within the 53 accessions. Even though sampling was relatively biased towards the Russian-Ukrainian area, this region was identified as a genetic diversity hotspot and possible centre of origin for camelina. The accessions were categorized by principal coordinate analysis using molecular marker data, enabling identification of links between geographical distribution and these categories. The influence of geographic location on four canola oil quality measures in camelina was evaluated using a geographic information system. These measures were (1) more than 30% α-linolenic acid, (2) less than 3% erucic acid, (3) less than 10% saturated fatty acids, and (4) a ratio of α-linolenic to linoleic acid greater than 1. The results clearly confirm that camelina oil quality characteristics are strongly influenced by environmental factors. The unprecedented high genetic diversity in this group of accessions offers an excellent opportunity to investigate valuable genes for successful adaptation of camelina to specific ecogeographical conditions such as drought. Key words: AFLP, GIS, false flax, oilseed, genetic diversity, cluster analysis. La cameline (Camelina sativa (L.) Crantz) est une oleagineuse reconnue comme source de matiere premiere pour la production de biocarburants qui demande peu d'intrants et offre de hauts niveaux d'acides gras beenefiques. Les auteurs ont etudie le lien entre l'origine geographique et la diversite genetique ainsi que la teneur en acides gras. Ils s'attendaient a trouver une variabilite significative entre les 53 accessions et un lien entre l'ecogeographie et l'origine ainsi que les caracteristiques de l'huile. Une analyse AFLP (<< amplified fragment length polymorphism >>) a revete une grande diversite; au sein des 53 accessions. Bien que l'echantillonnage ait ete relativement biaise en faveur de la Russie et de l'Ukraine, cette region s'est averee riche en diversite genetique et un possible centre d'origine pour la cameline. Les accessions ont ete classeees au moyen d'une analyse en coordonnes principales sur la base des donnees moleculaires. Cela a permis de trouver des liens entre la distribution geographique et ces categories. L'influence de l'origine geographique sur quatre caracteristiques qualitatives employees dans revaluation de l'huile de canola a ete evahtee chez la cameline au moyen d'un systeme d'information geographique. Ces mesures etaient : (1) une teneur en acide alpha-linotenique superieure a 30 %, (2) une teneur en acide erucique inferieure a 3 %, (3) moins de 10 % d'acides gras satures et (4) un ratio entre les acides alpha-linotenique et linoteique superieur a 1. Les resultats ont montre clairement que la qualite de l'huile de cameline etait fortement influencee par ces facteurs environnementaux. La diversite genetique exceptionnelle au sein de ce groupe d'accessions offre une excellente opportunite de puiser des genes utiles pour l'adaptation de la cameline a des conditions ecogeographiques specifiques comme la seecheresse. Mots-cles: AFLP, GIS, faux lin, oteagineux, diversite genetique, analyse de groupement. [Traduit par la Redaction], Introduction Camelina (Camelina sativa (L.) Crantz), commonly known as false flax, is a diploid, herbaceous oilseed plant in the family Brassicaceae. The earliest records of camelina in eastern and central [...]

Geographically distributed genetic variation is expected in species that have wide latitudinal and habitat ranges, like Eucalyptus pilularis Sm. Coastal and inland ecotypes of this tall forest tree have been distinguished in genecological studies, but patterns of regionally distributed quantitative variation are weak. At the coarsest level, variation of 12 microsatellite markers divided a rangewide sample of 424 E. pilularis trees into two zones: the region to the south of Sydney forming one zone and regions to the north forming another. Genetic structuring did not correspond with ecotypes but rather with a biogeographic division, suggesting an imprint of historical isolation. Typical and uniform levels of genetic diversity ([H.sub.e] = 0.78 ± 0.02 (mean ± SE)) were found across 10 geographic regions. Genetic structuring by regions (PhiRT = 3%), by localities within regions (PhiPT = 2%), between coastal and inland provenances (PhiPT = 2%), or due to isolation by distance was subtle. These observations, along with the lack of evidence for bottlenecks, suggested genetic cohesion within zones due to gene flow and historically large population sizes. The low levels of diversity and poor growth performance of the Fraser Island ecotype were better explained by recent colonization and adaptation than by genetic isolation, since there was no evidence of inbreeding. Resume: On s'attend a ce que la diversite genetique soit distribuee selon la geographie pour les especes a grand deploiement latitudinal et a large spectre d'habitats comme Eucalyptus pilularis Sm. Des ecotypes de la cote et de l'interieur ont ete reconnus chez cette espece d'arbre de grande taille a partir d'etudes genecologiques. Cependant, les patrons de variation quantitative distribuee selon les regions apparaissent faibles. A la plus grande echelle, la variation de 12 marqueurs de microsatellites a permis de diviser en deux zones un echantillon de 424 tiges representatif de l'ensemble de l'aire de repartition d'E. pilularis. La region situee au sud de Sydney formait une zone distincte des regions situees au nord. La structure genetique ne correspondait pas aux ecotypes mais plutot a une division biogeographique impliquant une empreinte d'isolement historique. Les auteurs ont note des niveaux de diversite genetique typiques et uniformes ([H.sub.e] = 0,78 [+ or -] 0,02 (moyenne ± erreur standard)) dans les 10 regions geographiques etudiees. La structure genetique par regions (PhiRT = 3 %), par localites au sein des regions (PhiPT = 2 %), entre les provenances de la cote et celles de l'interieur (PhiPT = 2 %), ou due a l'isolement par la distance etait faible. Ces observations, de meme que l'absence d'indices pointant vers des goulots d'etranglement, indiquent que chaque zone est genetiquement cohesive en raison du flux genique et de la grande taille historique des populations. La diversite genetique et la performance en croissance de l'ecotype de l'ile de Fraser etaient faibles. Ce patron s'expliquait mieux par la colonisation recente et l'adaptation que par un effet d'isolement genetique puisqu'il n'y avait pas de signes d'endogamie. [Traduit par la Redaction], Introduction Genetic variation in forest trees often has a geographic basis because the evolutionary forces of adaptation, gene flow, and genetic drift act differentially across landscapes. There is a long [...]

In this study we characterize the genetic diversity and relationships between the Shia and Sunni Muslim populations of North India and geographically targeted neighboring and global populations. We examined a number of parameters of population genetic and forensic interest based on the allele frequencies from 15 autosomal STR loci (D8S1179, D21S11, D7S820, CSF1PO, D19S433, VWA, TPOX, D18S51, D3S1358, THO1, D13S317, D16S539, D2S1338, D5S818, and FGA). All the studied loci were consistent with Hardy-Weinberg equilibrium, except loci D18S51 and FGA for both Muslim populations, even after applying the Bonferroni correction. The combined power of exclusion and combined power of discrimination values for all 15 STR loci were 0.9999 and >0.99999, respectively, in both Muslim populations. Gene diversity values ranged from 0.6784 (TPOX) to 0.9027 (FGA) for Shia Muslims and from 0.7152 (CSF1PO) to 0.9120 (D18S51) for Sunni Muslims. The observed heterozygosity ([H.sub.o]) ranged from 0.5833 (D18S51) to 0.8595 (VWA) in Shia Muslims and from 0.6818 (CSF1PO) to 0.8333 (D21S11) in Sunni Muslims and was lower than the expected heterozygosity ([H.sub.e]) for 11 out of the 15 STRs typed. We analyzed the genetic affinities of the Shia and Sunni Muslim populations with their geographically closest neighboring North Indian, Middle Eastern, East Asian, and European populations using distance-based methods, including neighbor-joining trees and multidimensional scaling. In addition, we estimated the genetic contribution of the putative parental populations included in the analysis to the Shia and Sunni Muslim gene pool using admixture analysis. Although we observed a certain degree of genetic contribution from Iran to both Muslim populations, the results of the phylogenetic analyses based on autosomal STRs suggest genetic relatedness with some of the geographically closest neighboring Hindu religious populations. KEY WORDS: POPULATION GENETICS, AMPFLSTR IDENTIFILER, SHORT TANDEM REPEATS (STRS), SHIA MUSLIMS, SUNNI MUSLIMS, GENETIC AFFINITIES, D8S1179, D21S11, D7S820, CSF1PO, D19S433, VWA, TPOX, D18S51, D3S1358, THO1, D13S317, D16S539, D2S1338, D5S818, FGA, AMELOGENIN., India is the largest secular country with a polygenetic population, and it is said to be the melting pot of various ethnic groups. Among the various known religions found in [...]

Natural selection, drift, and gene flow are the three major evolutionary forces at the origin of genetic diversity among human populations. To further explore these mechanisms, we present an innovative approach using various medical genetic markers and focusing on the Basque population. From this study we can confirm the important role of drift in this endogamous human group and can report some disorders related to founder effects. Most important, the peculiar distribution of various polymorphisms, such as blood group O, factor V Leiden, DF508, C282Y, and CCR5 D32 mutations, which are implicated in resistance to infection, hemostasis, or iron conservation, could be interpreted as an adaptive profile. Multidisciplinary data have shown that the Neolithic period arrived significantly later in this southwestern corner of Europe. We hypothesize that the long-lasting Paleolithic mode of life, especially regarding nutrition and microbial exposure, was at the origin of this selective pressure within this population of ancient local ancestry. This approach could open new avenues in the field of population genetics. KEY WORDS: POPULATION GENETICS, MEDICAL GENETICS, NATURAL SELECTION, FOUNDER EFFECT, DRIFT, GENE FLOW, BASQUES, ABO, RH, DUFFY, HLA, MTDNA HAPLOGROUPS, CFTR GENE, DF508 MUTATION, CCR5 GENE, FACTOR V LEIDEN, HFE GENE, FACTOR XI DEFICIENCY, NEUROMUSCULAR DISEASES., Over the past two decades biological anthropologists have commonly used molecular genetic techniques for reconstructing human population history. Thus a major scenario for early colonization of Europe was established by [...]

The Muslim population of India is known for its historical and socioreligious significance. Literature on the genetic structure of this segment of India's population is scanty. Therefore we have investigated the allele frequency distribution of haptoglobin (HP) and transferrin (TF) phenotypes among the Muslims to explore the genetic diversity of the Muslim immigrant populations of Aligarh. Aligarh is a city in Uttar Pradesh, India (latitude 27°54' N, longitude 78°5' E), situated 130 km southeast of Delhi. The population is mainly represented by Muslim immigrants from the eastern, northern, southern, and western regions of India and from abroad. Differences in allele frequencies of both HP and TF were statistically significant for the population of immigrants from western India and insignificant for others. The alleles HP*2 and TF*C2 show maximum frequencies in the southern population (0.882 and 0.822, respectively) followed by the eastern population (0.862 and 0.807) and the northern population (0.806 and 0.650). In the northern population a third allele, TF*C3, is also detected, with a mean frequency of 0.044. The average heterozygosity (HL) values for HP and TF are 0.273 and 0.361, respectively, and the pooled values for gene diversity parameters for both loci are [H.sub.T] = 0.4294 ± 0.0351, [H.sub.S] = 0.4225 ± 0.0271, and [D.sub.ST] = 0.0069 ± 0.0051. The pooled [G.sub.ST] value is 0.0153 ± 0.0108. The magnitude of these values indicates genetic similarity among the investigated populations. Our AMOVA results also demonstrate similarity among populations of the same geographic region. However, we note substantial differentiation among different regions ([Φ.sub.CT] = 0.221). The UPGMA dendrogram shows a cluster between the eastern and southern populations, to which the northern population joins. Our results reveal genetic similarity among different immigrant populations, with the western population being the most distant. Therefore the present study on culturally, geographically, and linguistically different endogamous groups of Muslims may have significance in understanding their genetic relationship. KEY WORDS: GENETIC MARKER LOCI, HETEROZYGOSITY, GENE DIVERSITY PARAMETERS, HAPTOGLOBIN (HP), TRANSFERRIN (TF), MUSLIM POPULATION, INDIA., The population structure of different regions of India has been shaped by historical events that include tribalism, origin and arrival of new faiths and ethnic groups, episodes of isolation, and [...]

Abstract: The northern leopard frog (Rana pipiers Schreber, 1782) underwent a large decline in the western portion of its range and only occurs in 20%i of historically occupied sites in [...]

Abstract: We collected data from 20 biparentally inherited microsatellite loci, and nucleotide sequence from the maternally inherited mitochondrial DNA (mtDNA) control region, to determine levels of genetic variation of the [...]

Abstract: We test predictions of the Morton and James hypothesis, which states that high termite diversity promotes high lizard diversity. We explore consumption of termites by lizards in the Brazilian [...]

Agalinis auriculata (Orobanchaceae) is a state-listed species in Illinois and is rare throughout its range in the midwestern United States. In recent years, research has been conducted on the biology of this hemiparasitic plant in order to understand better what factors should be included in the development of sound preservation practices. Our objective in this study was to assess genetic variation using allozyme and RAPD markers for Illinois populations of A. auriculata and two of its more common congeners, A. purpurea and A. tenuifolia. A total of 13 allozyme loci and 112 RAPD markers were scored for the studied species. Overall, lower percent polymorphic loci/markers were observed in A. auriculata than in its congeners. Analyses of molecular variance on RAPD markers showed that most of the genetic variation was within populations. In addition, the allozyme and RAPD UPGMA and RAPD principle coordinates analyses separated the three species of Agalinis. The genetic results of this study in conjunction with ecological studies of A. auriculata in Illinois serve as a springboard for the conservation of the species, not only in Illinois but also throughout its range., INTRODUCTION Rare species are often categorized by different characteristics of their range and habitat (e.g., Rabinowitz, 1981). Stereotypically, rare species are thought to exist as small populations and have very [...]

ABSTRACT A single population of Pediomelum piedmontanum (Fabaceae) occurs in Columbia County, Georgia. We examined allozyme variation in this population for 20 loci in eleven enzyme systems. Genetic diversity was [...]

Isolated populations that recently have been derived from small homogeneous groups of founders should have low genetic diversity and high levels of linkage disequilibrium and should be ideal for mapping ancestral polymorphisms that influence complex genetic disease susceptibility. Populations that fulfill these criteria have been difficult to identify. We have been looking for Polynesian populations with these characteristics, because Polynesians have high rates of complex genetic diseases. In Niue Islanders all ancestral female (mitochondrial HSV1 sequence) and 90.4% of ancestral male (Y-chromosome haplogroup) lineages are of Southeast Asian origin. The frequency of European Y-chromosome haplogroups is 7.2%. The diversities of mitochondrial HSV1 sequences (h = 0.18 ± 0.05) and Y-chromosome haplogroups (h = 0.18 ± 0.05) are lower than values published for any other population. Ten autosomal microsatellites spaced over 5.8 cM show low allele numbers in Niue Islanders relative to Europeans (55 vs. 88 total alleles, respectively) and a modest reduction in heterozygous loci (0.71 ± 0.02 vs. 0.78 ± 0.02, p = 0.04). The higher linkage disequilibrium ([d.sup.2]) between these loci in Niue Islanders relative to Europeans (p = 0.001) is negatively correlated (r = -0.47, p = 0.01) with genetic distance. In summary, Niue Islanders are genetically isolated and have a homogeneous Southeast Asian ancestry. They have reduced autosomal genetic diversity and high levels of linkage disequilibrium that are consistent with the influence of genetic drift mechanisms, such as a founder effect or bottlenecks. High-powered linkage disequilibrium studies designed to map ancestral polymorphisms that influence complex genetic disease susceptibility may be feasible in this population. KEY WORDS: NIUE ISLAND, TONGA, POLYNESIA, GENETIC DIVERSITY, HAPLOGROUP, MITOCHONDRIAL DNA, HSV1, HLA, Y CHROMOSOME, LINKAGE DISEQUILIBRIUM, MICROSATELLITE., Identification of the ancestral genetic polymorphisms that influence susceptibility to complex genetic diseases should increase our understanding of disease mechanisms and lead to new strategies for prevention and treatment. Because [...]

Characterization of genetic diversity of maize (Zea mays L.) germplasm is of great importance in hybrid maize breeding. The objectives of this study were to (i) investigate genetic diversity in CIMMYT subtropical, tropical midaltitude and highland inbreds with simple sequence repeat (SSR) markers, (ii) identify appropriate testers for the development of new inbred lines, (iii) compare this sample to U.S. and European elite maize lines and CIMMYT tropical lowland inbreds, and (iv) use the marker and pedigree information as a guide to understanding the heterotic relationship among the CIMMYT maize lines (CMLs) and their potential practical use in maize breeding programs worldwide. Inbreds included in the study were assayed with 79 SSR markers. The CIMMYT inbred lines originated from 35 mostly broad-based populations and pools with mixed origins. A total of 566 alleles were scored, (averaging 7.2 and ranging from 2 to 16 alleles per locus). The modified Roger's distance (MRD) between pairs of inbreds averaged 0.78, with a range of 0.45 to 0.93. Unweighted paired group method using arithmetic averages (UPGMA) cluster analysis revealed no clear clustering. This reflects a mixed composition of CIMMYT subtropical, tropical midaltitude and highland maize populations and pools, and indicates that large amounts of variation have been incorporated into CIMMYT germplasm. Temperate heterotic groups were separated based on the markers, and nontemperate CIMMYT maize was genetically distinct from temperate lines. Discrete clusters were difficult to identify within and often between megaenvironments. Specific recommendations for nontemperate hybrid maize breeding are made., THE DEFINITION OF HETEROTIC GROUPS and heterotic patterns is an empirical task in hybrid maize breeding that has, in temperate maize germplasm, contributed to large increases in yield. Reciprocal recurrent [...]

Switchgrass (Panicum virgatum L.) has potential as feedstock for a cellulose-based biofuels industry in temperate steppe regions of the northern Great Plains. Therefore, our objectives were to determine: (i) patterns of biomass accumulation and optimum harvest times for an early maturing cultivar, Dacotah (origin 46° N, 100° W), and a later maturing cultivar, Cave-In-Rock (origin 37° N, 88° W), in central South Dakota (44° N, 100° W) and (ii) if variation in patterns of biomass accumulation were associated with variation in patterns of precipitation. Dacotah and Cave-In-Rock were no-till planted near Pierre, SD, on 6 Dec. 1999. Harvest dates were once per year during July, August, September, or October 2001 through 2004. Morphological development was determined in early, mid, and late summer 2004. Maximum biomass yields for Dacotah were obtained during July or August. Optimum harvest time for Cave-In-Rock was as late as September depending amount of summer precipitation. Biomass production of both cultivars was highly plastic, fluctuating > fivefoid over a 4-yr period. Maximum annual biomass yields were from >9 Mg [ha.sup.-1] to 90% of variation in maximum annual biomass production. The superior biomass yield potential of the putatively unadapted Cave-In-Rock compared with the putatively adapted Dacotah was only expressed during years when precipitation was >75% of average., SWITCHGRASS, a native, perennial, warm-season grass, is important for forage and conservation in the USA and southern Canada, primarily east of the 100th meridian. The use of switchgrass as a [...]

The New Mexico cotton breeding program was established in 1926 and has been led by five generations of breeders and geneticists. The program has released more than 30 Acala 1517 cotton (Gossypium hirsutum L.) cultivars and numerous germplasm lines known for high fiber quality and Verticilliam wilt (caused by Verticillium dahliae Kleb.) tolerance that have made substantial contributions to cotton breeding in the USA. The present project was initiated in 2003 to evaluate the genetic improvement of Acala 1517 cultivars and lines released over the past 75 yr in yield, boll size, seed index, lint percentage, fiber length, fiber strength, and micronaire. Their genetic divergence was also estimated by simple sequence repeat (SSR) markers. On the basis of the data available from annual yield trials, lint yield and lint percentage in Acala 1517 cotton have steadily increased since the 1930s, while boll size and seed index have gradually decreased since the 1960s. Fiber strength has been enhanced since the 1960s, which has been accompanied by steady increase in micronaire. However, fiber length in Acala 1517 cultivars tended to shorten from 31.0 to 30.0 mm from 1960 to 1990, whereas newly released Acala 1517 cultivars (Acala 1517-95,1517-99,1517-02, 1517-03, and 1517-04) have fiber greater than 30.5 mm. Genetic distance among Acala 1517 genotypes ranged from 0.06 to 0.38 with an average of 0.18 on the basis of 189 SSR marker alleles, indicating a substantial genetic diversity among Acala 1517 cotton germplasm. Divergent germplasm introgression in the program has contributed to genetic diversity of Acala cotton germplasm and continuous genetic gain in Acala cotton cultivar improvement. Abbreviations: JC, Jaccard coefficient; SSR, simple sequence repeats., COTTON, primarily G. hirsutum, is the leading fiber crop and the second most important oilseed crop in the USA. Profitability in growing cotton crop is affected by yields, quality, and [...]

Thorough assessment of modern genetic diversity and interpopulation affinities within the African continent is essential for understanding the processes that have been at work during the course of worldwide human evolution. Regardless of whether autosomal, Y-chromosome, or mtDNA markers are used, allele- or haplotype-frequency data from African populations are necessary in setting the framework for the construction of global population phylogenies. In the present study we analyze genetic differentiation and population structure in a data set of nine African populations using 12 polymorphic Alu insertions (PAIs). Furthermore, to place our findings within a global context, we also examined an equal number of non-African groups. Frequency data from 456 individuals presented for the first time in this work plus additional data obtained from the literature indicate an overall pattern of higher intrapopulation diversity in sub-Saharan populations than in northern Africa, a prominent differentiation between these two locations, an appreciably high degree of transcontinental admixture in Egypt, and significant discontinuity between Morocco and the Iberian peninsula. Moreover, the topologies of our phylogenetic analyses suggest that out of the studied sub-Saharan groups, the southern Bantu population of Sotho/Tswana presents the highest level of antiquity, perhaps as a result of ancestral or acquired Khoisan genetic signals. Close affinities of eastern sub-Saharan populations with Egypt in the phylogenetic trees may indicate the existence of gene flow along the Nile River. KEY WORDS: POLYMORPHIC ALU INSERTIONS, GENETIC DIVERSITY, HUMAN POPULATIONS, MOROCCO, EGYPT, SUDAN, KENYA, RWANDA, BENIN, CAMEROON, MADRAS, BRAHMINS, FORMOSA, GALICIA, IBERIAN PENINSULA, SOUTH AFRICA, ZAIRE, BANTU, CHINA, JAPAN, FRANCE, POLAND, INDIA, APO. B65, COL3A1, HS2, HS4, PV92, SB19, TPA25., The genetic landscape of Africa has been the focal point of numerous molecular investigations (Chen et al. 1995; Poloni et al. 1997; Watson et al. 1997; Scozzari et al. 1999; [...]

Buffalograss [Buchloe dactyloides (Nutt.) Engelm.] is a perennial, warm-season turfgrass that is native to the shortgrass prairie of North America. It offers potential benefits as a turfgrass because of its drought resistance, low incidence of pest problems, and relatively low nutrient requirements. This study was initiated to evaluate the level of organelle DNA diversity among buffalograss genotypes and to determine the mode of inheritance of the chloroplast organelle by cpDNA and mtDNA PCR-RFLPs. The 56 genotypes studied included diploids, triploid, tetraploids, pentaploids, and hexaploids. These genotypes represented 273 buffalograsses collected during 1994 and 1995 from diverse locations in the North American Great Plains. Six cpDNA and three mtDNA noncoding regions were amplified by polymerase chain reaction, using universal chloroplast anti mitochondrial printer pairs. Each amplified fragment was digested with two to six different restriction enzymes. On the basis of the use of cpDNA primers, psbC-trnS, and restriction enzyme HaeIII, cpDNA was determined to be maternally inherited in buffalograss. Of the 225 scored fragments, 189 were polymorphic (84%), which included the outgroups, perennial ryegrass (Lolium perenne L.) and blue grama [Bouteloua gracilis (H.B.K.) Lag. Ex Steud.]. Similarities among all genotypes ranged from 0.41 to 1.0, with a mean of 0.70. The UPGMA-generated dendrogram clustered all buffalograsses together with the similarity value of 0.95. Out of the 56 genotypes studied, nine (16%) were discriminated from the other buffalograsses. The remaining 47 genotypes did not differ for cpDNA and mtDNA PCR-RFLPs even though they represented diverse geographic origins and five ploidy levels. These results suggest that low levels of organelle DNA PCR-RFLP are present in naturally occurring buffalograss populations., BUFFALOGRASS is a perennial, warm-season turfgrass hat is native to the shortgrass prairie of North America (Wenger, 1943). It is distributed from Canada to Mexico and from the eastern slope [...]

To explore natural biodiversity we developed and examined introgression lines (ILs) containing chromosome segments of wild species (Solanum pennellii) in the background of the cultivated tomato (S. lycopersicum). We identified Brix9-2-5, which is a S. pennellii quantitative trait locus (QTL) that increases sugar yield of tomatoes and was mapped within a flower- and fruit-specific invertase (LIN5). QTL analysis representing five different tomato species delimited the functional polymorphism of Brix9-2-5 to an amino acid near the catalytic site of the invertase crystal, affecting enzyme kinetics and fruit sink strength. These results underline the power of diverse ILs for high-resolution perspectives on complex phenotypes., The genetic basis of many natural phenotypes takes the form of a continuous range rather than discrete classes. The complexity of traits showing continuous distribution often results from the segregation [...]

For the first time, sufficient numbers of molecular markers that reveal polymorphism in cultivated peanut (Arachis hypogaea L.) have become available for diversity assessments. In this study, the amount and distribution of genetic variation within and among six peanut botanical varieties, as well as its partitioning among three continents of origin, was assessed at 12 simple sequence repeat (SSR) loci by means of 10 sequence-tagged microsatellite site (STMS) primers. Eighty-nine alleles were revealed, varying from 2 to 17 per locus with an average of 7.4 alleles per locus. Greater differentiation was observed between varieties (Fst = 0.33), compared with between continents (Fst = 0.016). However, maximum differentiation was observed among continents within varieties (Fst = 0.366) for three varieties. Rogers' modified distance among varieties revealed the similarity of three varieties of subspecies fastigiata Waldron, namely fastigiata, vulgaris C. Harz, and aequatoriana Krapov. & W.C. Gregory. It did not support the inclusion of var. peruvlana Krapov. & W.C. Gregory in this grouping. In addition, the results suggest that subsp. hypogaea var. hypogaea and var. hirsuta Kohler are not closely related and therefore should not hold the same subspecific ranking. Discriminant function analysis reveals a high degree of accordance between variety delimitation on the basis of morphological and molecular characters. Landraces from Africa and Asia were more closely related to each other than to those from South America. Nei's unbiased estimate of gene diversity revealed very similar levels of diversity within botanical varieties. Landraces from South America had the highest diversity, and possessed 90% of alleles, compared with Africa (63%) and Asia (67%)., AN UNDERSTANDING of the distribution of genetic variation among peanut botanical varieties in relation to the geographical origin will enhance the efficiency of the conservation and utilization of diverse genetic [...]

The autosomal AmpFLSTR markers validated and widely used for forensic applications are used in this study to examine the extent of diversity and genetic relationships among nine Meghalaya populations. Altogether, 932 chromosomes from 9 populations were analyzed using 9 tetrameric AmpFLSTR loci. The included populations were all seven subtribes of the Austro-Asiatic Mon-Khmer-speaking Khasi and the neighboring Tibeto-Burman Garo. The Lyngngam, which are linguistically closer to the Khasi but are culturally intermediate between the Khasi and the Garo, are also included in the study. Although most of the microsatellite loci are highly polymorphic in each of these populations, the allele distributions are fairly uniform across the Meghalaya populations, suggesting relative homogeneity among them. Concurrent with this, the coefficient of gene differentiation ([G.sub.ST]) is observed to be low (0.026 ± 0.002). This is naturally reflected in the lack of clear differentiation and clustering pattern of the Meghalaya tribes based on either geographic proximity or the historical or current affiliations of these tribes. Analysis of molecular variance (AMOVA) suggests no significant population structure. The structure analysis further suggests that, barring War-Khasi and Pnar, no other population shows any semblance of genetic identity. Even the position of the linguistically distinct Garo is not portrayed as separate from the Khasi. However, when comparable data from other Indian, Southeast Asian, and other continental populations were analyzed, the Meghalaya populations formed a compact cluster clearly separated from other populations, suggesting genetic identity of the Meghalaya populations as a whole. These results are concurrent with the hypothesis of a common and recent origin of these Meghalaya populations, whose genetic differentiation is overwhelmed by the homogenizing effect of continuous gene flow. KEY WORDS: KHASI SUBTRIBES, GARO POPULATION, LYNGNGAM POPULATION, MEGHALAYA POPULATIONS, INDIA, AMPFLSTR LOCI, D3S1358, D8S1179, D5S181, VWA, D21S11, D13S317, FGA, D7S820, D18S5, GENE FLOW, GENETIC HOMOGENIZATION., The northeastern part of India is referred to as a melting pot of Mongoloid, Australoid, and Caucasoid populations, which is exhibited in the unique sociocultural diversity of the region. It [...]

One-hundred three individuals from two Mongolian, two Siberian, and ten native American populations were studied in relation to a 340bp sequence from an Alu insertion located in the 3' untranslated region of the LDLR gene. Seven haplotypes have been determined, and haplotype B1 was the most common, accounting for about half the sequences found. In general, diversity values are quite high, about 2.5 times higher than those found in other autosomal Alu sequences. Almost all (93%) of the variability occurs at the intrapopulation level, but the greatest among-group differentiation (6-8%) was found when we grouped in a single population all Native Americans plus Siberian Eskimos and Chukchi and compared them with Mongolians. This result is compatible with earlier mtDNA and Y-chromosome suggestions of a single origin for the first colonizers of the American continent. With this nuclear locus it was not possible to broadly distinguish between Central and South American natives. No evidence of selection or marked demographic changes was obtained with these data. KEY WORDS: LOW-DENSITY LIPOPROTEIN RECEPTOR GENE, LDLR, AMERINDIANS, MONGOLIANS, SIBERIANS., Genetic diversity is influenced by a large number of factors, and these factors generally interact among themselves, making interpretations difficult. Intrinsic factors are mutation rates and the constraints imposed on [...]

The GM polymorphism of human immunoglobulins is analyzed in three Berber populations of southern Tunisia and compared to other GM data. Genetic diversity among Tunisian populations is higher than that among Europeans but does not exhibit any significant geographic or linguistic structure. This result suggests a complex pattern of genetic differentiation. KEY WORDS: ARABS, BERBERS, GM, HUMAN GENETIC DIVERSITY, IMMUNOGLOBULINS, NORTH AFRICA, TUNISIA., Berber populations from North Africa are commonly considered in situ descendants of local Mesolithic populations, namely, Capsian populations who settled in the area around the 10th millennium B.P. but who [...]

Two Y-chromosome DNA polymorphisms, the DYS19 microsatellite and the YAP (at locus DYS287), were tested in males from two autochthonous Basque populations from France and northern Navarre (Spain). The results are compared to those obtained for the same genetic markers in 32 populations from Europe, northern Africa, and western Asia. The high predominance of the DYSJ9*11 (190-base-pair) allele in Basques indicates that their genetic diversity for microsatellite DYSJ9 is around half that observed in Europeans, North Africans, and western Asians. The Y-Alu insertion ([YAP.sup.+]) was not detected in the Basque samples. This study attempts to throw some light on the importance of historically recent migratory movements, the main corridors of gene flow, and demographic sizes and their variations in shaping gene frequency patterns in contemporary human populations, particularly in the Mediterranean region. Historical processes may have had more significant effects on the genetic make-up of current human populations than those of prehistoric times. KEY WORDS: FRENCH AND SPANISH BASQUES, Y-CHROMOSOME STRS. GENETIC DIvERSITY, MEDITERRANEAN REGION, The analysis of the human Y-chromosome DNA variation is proving to be a useful genetic tool for the reconstruction of recent human population history through paternal lineages (Spurdle and Jenkins [...]

Genetic diversity is low in southern United States elite soybean [Glycine max (L.) Merr.] cultivars. Multiple sources of diversity will be required to effectively diversify this gene pool. The objective in this study was to evaluate the genetic diversity and yield of familiess derived from crosses between northern elite (NE) by southern elite (SE) parents. Lines were derived from 10 crosses of NE x SE parents. Molecular markers were used to estimate genetic distance between each line and its SE parent. Yield and agronomic traits were measured in field trials from 1997 to 1999 in six of the crosses. The association of diversity with line yield, expressed relative to yield of the SE parent was determined with regression. On average, the use of NE parents reduced yield, relative to using other SE parents. Some crosses and NE parents were better than others and produced families with yield that exceeded that of their SE parent, indicating that some genes from the NE parents were superior to the genes in the SE parent. At least one line with yield either superior or similar to their SE parent was found in each cross. The finding of positive transgressive segregants in some crosses and the results of the regression analyses indicate that most of the NE parents posses some yield genes that are likely to be superior to those of the SE parents. Our approach to selecting for diversity and yield may be applicable to large introgression programs where diversity from many sources is desired., SUCCESSFUL CROP IMPROVEMENT depends on genetic variability that arises from genetic diversity. The predominant use of selected elite parents in soybean cultivar breeding has lead to a narrow genetic base [...]

Knowledge, access, and use of diversity available in cultivated and wild relatives are essential for broadening the genetic base of cultivars to sustain improvement. My objectives are to review briefly the origin, domestication, and organization of genetic diversity in Phaseolus beans, highlight production problems and traits deficient in the common bean (P. vulgaris L.) cultivars, cite sources of useful gemplasm, and review progress achieved in broadening the genetic base of cultivars. Phaseolus beans originated in the Americas. Only five species, P. acutifolius A. Gray, P. coccineus L., P. lunatus L., P. polyanthus Greenman, and P. vulgaris L. were domesticated. The interspecies diversity in relation to common bean is organized in primary, secondary, tertiary, and quaternary gene pools. Intraspecies diversity in common bean is separated into two major gene pools (Andean and Middle American). Cultivars are further divided into races, each with their distinguishing characteristics. Also, cultivars of dry seed and snap bean exist. Abiotic and biotic stresses limit common bean production. The genetic base of cultivars within market classes is narrow and inadequate level of resistance to common bacterial blight [caused by Xanthomonas campestris pv. phaseoli (Smith) Dye] and white mold [caused by Sclerotinia sclerotiorum (Lib) de Bary] exist in cultivars. High levels of resistance to these and other desirable traits exist in the relatives and gene pools of P. vulgaris. Early maturity, adaptation to higher latitude, upright plant type, high pod quality and seed yield, and resistance to Bean common mosaic virus (a potyvirus) and/or rust [caused by Uromyces appendiculatus (Pers.:Pers.) Unger] have been bred into cultivars. However, most of the genetic variability available in the common bean races, gene pools, and wild relatives remains to be utilized. To maximize and sustain bean production, high yielding, high quality cultivars that are less dependent on water, fertilizer, pesticides, and manual labor should be developed. This need warrants sustained, comprehensive, and integrated genetic improvement, in which favorable alleles from cultivated and wild relatives are accumulated in superior cultivars. A three-tiered breeding approach involving: (i) gene introgression from alien germplasm, (ii) pyramiding favorable alleles from different sources, and (iii) simultaneous improvement of multiple traits for common bean cultivars would be the most appropriate strategies to meet theses needs., THE GENETIC BASE of most common bean cultivars within a market class is narrow (Adams, 1977; McClean et al., 1993; Voysest et al., 1994; Zaumeyer, 1972). This is because only [...]

Geographic isolation, first recognized by Darwin (1859) as playing an important role in promoting evolutionary diversification, is the foundation upon which the theory of allopatric speciation rests (Mayr 1942). Differentiated [...]

A broad genetic base for a crop species such as wheat (Triticum spp.) may be important to reduce genetic vulnerability and assure long-term potential for genetic gun. The number and diversity of original ancestors can provide insight into relative genetic diversity within and among gene pools. Based on the coefficient of parentage values between cultivars and ancestral Kan, the relative genetic contributions of ancestral lines to spring wheat (Triticum aestivum L.) cultivars were computed for successive 25-yr time periods. The cultivars were from Canada (47), the USA (133), and Mexico (90). Genetic backgrounds were studied for important changes in the ancestral base over time and to determine trends that continue today. About 124 ancestors, tracing to 32 countries on five continents, were found to have contributed to the North American spring wheat gene PoolCanadian western red spring cultivars released before 19M had an intermediate level of ancestral diversity. Their post-1975 cultivars have narrow ancestral diversities probably due to strict quality regulations. They consist primarily of `Thatcher' germplasm modified by a set of pest resistance genes carefully managed in backcross schemes. Before 1950, the U.S. hard red spring wheat cultivars traced to the same Matcher ancestors but also to `Kota' and `Yaroslav'. Many more ancestors were added to this base after 1950 and especially after 1975. This was a side effect of the incorporation of pest resistance, most notably from sources `Gabo-Timstein', `Frontana', and `Kenya Sr, and reduced height sources, most notably CIMMYT cultivars with new ancestry from `Kenya 324' and Turkey. CIMMYT cultivars have also expanded their genetic base over time, with the systematic incorporation of new ancestry from various sources including winter wheats. Introduction of novel alleles from wild ancestors or other sources should contribute to future broadening of the genetic base, maximizing genetic gains, and reducing genetic vulnerability of the gene pools., Concern about a perceived lack of genetic diversity and the resulting genetic vulnerability of our food plants has lead researchers to assess the situation in different crops. In wheat, the [...]

Genetic diversity constitutes the raw material for plant improvement, and it can provide protection aping genetic vulnerability to biotic and abiotic stream. Our objectives were to determine patterns of relatedness using the coefficient of parentage (COP) matrix among 270 spring wheat (Triticum aestivum L.) cultivars and to compote mean COP values for major regional breeding programs. The collection included most important cultivars released during this century from Canada (47), the USA (133), and Mexico (90). Cluster analysis, based on the COP matrix, resulted in 20 major clusters of few or more entries and six small dusters of two cultivars each. The first three axes from a principle coordinate analysis of the intercluster COP matrix showed (i) a group of seven clusters including most hard red spring cultivars (HRS) from the USA, and Canada (CWRS), based mainly on a `Marquis' background, (ii) a group of nine interrelated clusters including most cultivars from CIMMYT (Mexico), (iii) two interrelated dusters including mostly white wheats, and (iv) two small clusters including mostly old Canadian cultivars. Mean COP values were computed among cultivars released during three successive tune periods for major regional breeding programs. The CWRS cultivars have become progressively more interrelated based on a Thatcher background. Average COP values (0.58 among modern cultivars) for this class were higher than values reported for winter wheat, barley (Hordeum vulgare L.), and oat (Avena sativa L.) gene pools. The HRS wheats showed a fairly high but slowly decreasing interrelatedness (COP = 0.22) among modem cultivars, with some regional differences. CIMMYT cultivars were less interrelated (COP = 0.15-0.20) and comparable to levels reported for soft red winter wheat and barley. Quality requirements and kernel type have probably been major factors in maintaining relatively high COP in the CWRS bud somewhat less in the HRS in the USA. CIMMYT cultivars, in general, do not have quality restrictions, allowing the introduction of more diversity., Bread wheat (Triticum aestivum L.), as a crop, has a history of several thousand years with many parts of the world having developed locally adapted landraces. In the Western hemisphere, [...]

Studies of differentiation among closely related populations or species often center on phenotypes involved in reproduction (e.g., Ahearn and Templeton 1989; Barret 1989; Eberhard 1992; Littlejohn 1965; Ryan 1990; Coyne [...]

The tropical and subtropical estuarine fish Rivulus marmoratus is known for its synchronous, self-fertilizing hermaphroditism. It matures within 3 mo and can produce eggs throughout the year. These features would allow a particular strain to quickly colonize refuge such as crab holes in the high intertidal zone habitat. However, a high strain diversity has been found in the field. In order to explain this observation, we examined the phenotypic responses of R. marmoratus to variation in biotic and abiotic environmental factors over two consecutive generations and employed a modified Euler-Lotka equation to estimate and compare the net reproductive rate, R, among strains. We included five strains of R. marmoratus and manipulated levels of temperature, salinity, and food for the parental generation and levels of food only for the second generation. Low temperature (19 ° C) inhibited sexual maturity, precluding any egg production during the entire 6-mo study. For individuals kept at high temperature (26 ° C), salinity and food had an interactive effect on time to maturity, body size at maturity, and number of eggs produced. Using multivariate analysis of variance, we found a significant two-way interactive effect (food levels for the parental and the second generations) on the five reproductive traits studied in the second generation. When each trait was analyzed separately, we found significant three-way interactions for time to maturity and total length at maturity. We found that the fitness values for each strain varied in different environmental combinations (3 salinities X 3 incubation salinities for eggs X 2 food levels). However, four of five strains had similar overall fitness. Despite a lack of genetic variation within each strain, R. marmoratus demonstrates considerable phenotypic variation in response to environmental changes. This feature and genetic variation among strains may explain how this species can survive and even prosper in an extremely variable and stressful environment. Key words: environmental factors; fitness; life history traits; maternal effect; net reproductive rate; phenotypic plasticity; reproduction; Rivulus marmoratus., INTRODUCTION Genetic variation is the raw material of evolution. Phenotypic plasticity within genotypes has been considered as the most important mechanism of 'adaptation' to the environments encountered by a population [...]

The patterns of cytoplasmic diversity, as revealed by chloroplast and mitochondrial DNA (mtDNA) sequence variation within and among populations, can be different from that of nuclear DNA variation (Avise et [...]

The study of temporal variation in the genetic constitution of populations has the potential for documenting evolutionary processes and for revealing the agents responsible for microevolutionary change. Accordingly, the subject [...]

The continuing debate about the role of gene flow as a cause of intraspecific genetic cohesion (e.g., Mayr 1963, 1970; Ehrlich and Raven 1969; Endler 1973, 1977; Jackson and Pounds [...]

This paper examines the link between passage of the Plant Variety Protection Act (PVPA), private R&D, public R&D, and genetic diversity in farmers' fields. PVPA did have a limited positive impact on private wheat breeding but did not lead to a decrease in public wheat research. Instead, public wheat research increased rapidly after PVPA passed. The trends in wheat diversity over time for the entire United States suggest that private research has undergone minor increases in diversity. Regression analysis of genetic diversity in Kansas, Nebraska, and Montana indicates that public sector research has increased diversity in farmers' wheat fields and that PVPA has had a small positive impact on diversity., I. INTRODUCTION Genetic diversity in the major U.S. field crops is an important defense against pest or disease epidemics. If most crop varieties have common characteristics due to common ancestors, [...]

Author(s): Andrea Manica (corresponding author) [1]; William Amos [1]; François Balloux [2]; Tsunehiko Hanihara [3] The origin and patterns of dispersal of anatomically modern humans are the focus of considerable [...]

Author(s): Heidi Ledford [illus. 2] [illus. 3] Researchers have used a DNA sequence to distinguish between more than 1,600 botanical samples from two biodiversity hotspots, providing the largest test yet [...]

Elephants from the tropical forests of Africa are morphologically distinct from savannah or bush elephants. Dart-biopsy samples from 195 free-ranging African elephants in 21 populations were examined for DNA sequence variation in four nuclear genes (1732 base pairs). Phylogenetic distinctions between African forest elephant and savannah elephant populations corresponded to 58% of the difference in the same genes between elephant genera Loxodonta (African) and Elephas (Asian). Large genetic distance, multiple genetically fixed nucleotide site differences, morphological and habitat distinctions, and extremely limited hybridization of gene flow between forest and savannah elephants support the recognition and conservation management of two African species: Loxodonta africana and Loxodonta cyclotis., Conservation strategies for African elephants have consistently been based on the consensus that all belong to the single species Loxodonta africana (1-3). Yet relative to African savannah elephants, the elephants [...]

Soybean [Glycine max (L.) Merr.] was domesticated in China but has a long history of cultivation on the Korean peninsula and in Japan. All three areas are considered important sources of soybean germplasm. The objectives of this study were to evaluate the genetic variation in soybean within and among China, S. Korea, and Japan by means of 120 accessions from eight Chinese and three S. Korean provinces, and three Japanese districts; and to relate genetic diversity patterns to geographical regions. Genetic relationships were estimated by 115 random amplified polymorphic DNA (RAPD) markers with simple matching coefficients expressed as Euclidean distances. Hierarchical and nonhierarchical cluster analyses as well as principal component analysis were used to define relationships among the genotypes. The results indicate that the mean genetic distance within China is much larger than that within Japan or S. Korea, but smaller than that between China and Japan or S. Korea. Cluster and principal component analyses almost completely separated the accessions from China from those of Japan and S. Korea, but could not distinguish between the accessions from Japan and S. Korea. These results are consistent with previous research using enzymes and morphological data to classify soybean germplasm from Asia. The groups formed by cluster analysis were mainly based on the frequencies of RAPD fragments among accessions and generally reflected the geographical regions of origin. No clear relationship was found between latitude and genetic diversity among accessions from these countries. Although the soybean accessions from Japan and S. Korea originally came from China, these data indicate that current accessions from Japan and S. Korea are genetically very distinct from those from China and more similar to each other., THE USE OF PLANT INTRODUCTIONS for the development of soybean cultivars will be an important approach to create diversity in soybean breeding in the future (Sneller et al., 1997). Selecting [...]

MICHAEL N. DAWSON [1],[2],[*] DAVID K. JACOBS [1] Morphological taxonomy suggests that marine faunas are species poor compared to terrestrial and freshwater faunas (1). This dichotomy has been attributed to [...]

The genetic base of soybean [Glycine max (L.) Merr.] cultivars developed for North America is very narrow. This may threaten the ability of breeders to sustain improvement and increase vulnerability of the crop to pests. The objective of this research was to assess the relationship of 18 major ancestors of North American soybean germplasm with 87 plant introductions (PIs) that are potential new sources of genetic variation for soybean breeding programs. Genetic distances (GD) among the 105 genotypes analyzed were calculated from 109 polymorphic DNA fragments amplified with random oligonucleotide primers and simple sequence repeat (SSR) primer pairs. Two hierarchical clustering algorithms were combined with data resampling and multidimensional scaling (MDS) to evaluate relationships among the genotypes. Genetic distances ranged from 0.08 to 0.76, with a mean of 0.52. Genotypes were placed in 11 clusters on the basis of a consensus of the different methods utilized. Co-occurrence values calculated from the resampling iterations showed that the stability of clusters varied. The most stable grouping was among ancestors that corresponded with known relationships based on pedigree and maturity. Several groups of PIs are distinct from the majority of the ancestors. These genotypes may be useful to breeders wanting to utilize genetically diverse introductions in soybean improvement., SOYBEAN BREEDING PROGRAMS in the USA have successfully developed hundreds of improved cultivars through hybridization of elite cultivars and breeding lines that trace back to a small number of original [...]

In 2006, a white bear with patches of brown fur was shot by hunters in the Arctic. DNA tests confirmed what many Suspected--it was a hybrid of a polar bear [...]