An AFLP-based survey of genetic diversity among accessions of sea oats (Uniola paniculata, Poaceae) from the southeastern Atlantic and Gulf coast states of the United States

Uniola paniculata, commonly known as sea oats, is a C₄ perennial grass capable of stabilizing sand dunes. It is most abundant along the Gulf of Mexico and southeastern Atlantic coastal regions of the United States. The species exhibits low seed set and low rates of germination and seedling emergence, and so extensive clonal reproduction is achieved through production of rhizomes, which may contribute to a decline in genetic diversity. To date, there has been no systematic assessment of genetic variability and population structure in naturally occurring stands in the USA. This study was conducted to assess the genetic relationship and diversity among nineteen U. paniculata accessions representing eight states: Texas, Louisiana, Mississippi, Alabama, Florida, South Carolina, North Carolina, and Virginia, using amplified fragment length polymorphism (AFLP). Twelve AFLP EcoRI+MseI primer combinations generated a wide range of polymorphisms (42–81%) with a mean of 59%. Overall, the sea oats plants exhibited a low range of genetic similarity. Florida accessions, FL-33 and FL-39, were most genetically diverse and the accessions from both Carolinas and Virginia (NC-1, NC-11, SC-15, and VA-53) harbored less genetic variability. Cluster analysis using the UPGMA approach separated U. paniculata plants into four major clusters which were also confirmed by principal coordinate analysis (PCO). Further examination of the different components of genetic variation by analysis of molecular variance (AMOVA) indicated the largest proportion of variability at the state level (47.8%) followed by the variation due to the differences among the genotypes within an accession (34.4%), and the differences among the accessions within a state (17.8%). The relationship between genetic diversity and geographic source of sea oats populations of the United States as revealed through this comprehensive study will be helpful to resource managers and commercial nurseries in identifying suitable plant materials for restoration of new areas without compromising the adaptation and genetic diversity.     

Construction of Texas coastal foredunes with sea oats (Uniola paniculata) and bitter panicum (Panicum amarum)

Studies were conducted on Padre Island, Texas since 1968 to provide specifications for how to use vegetation to reconstruct destroyed portions of foredunes of Gulf Coast barrier islands. The area has a subtropical, semi-arid climate, moderated by maritime tropical air from the Gulf of Mexico. Annual precipitation averages 670 mm for the island. We established experimental foredunes in broad overwash areas, 1.5 m M.S.L. where foredunes were eroded by hurricanes or destroyed by blowouts and across hurricane overwash channels of lower elevation behind the berm and more susceptible to surges. Most successful establishment of a vegetated dune was by transplanting directly onto the level backbeach to reestablish the original duneline about 125 meters inland. Sea oats and bitter panicum proved best of all species tested. Bitter panicum was the more desirable because of higher transplant survival, a longer planting season, and ease of harvest. Transplant survival was influenced more by soil salinity, soil moisture, and plant vigor, than by planting season as successful plantings occurred during all seasons. December through February plantings were best for sea oats, but survival of bitter panicum transplants different little from November through May. Both species are capable of growth year round during periods of favorable climatic conditions, although little growth occurs from mid-December to mid-February. Transplants placed 0.6 m apart with total planting width of 15 m produced foredunes nearly 6 m high in 6 years. Such plantings trapped sand at the rate of 12.5 m³/m of beach. In hurricane overwash channels, we used 0.6 m high sand fence placed 3 m apart to produce a flat topped dune free of salt for a planting surface. Without this site preparation, no transplants survived due to high soil salinity. Dune width was effectively widened by planting a strip 15 m wide immediately beachward of a previously established 4-year old dune.Presented at the Seventh International Biometeorological Congress, 17–23 August 1975, College Park, Maryland, USA.     

Micropropagation of Uniola paniculata L.

Uniola paniculata L. is a major sand-dune stabilizing grass which is being utilized to prevent shoreline erosion. In vitro cultured caryopses of U. paniculata produced callus on MS medium supplemented with 22.5 M 2,4-D, 4.4 M BA and 87.6 mM sucrose. Shoot induction occurred after these calli were inoculated onto the same medium without 2,4-D. Rooting of in vitro-derived shoots occurred when transferred to a one-half strength MS medium containing 43.8 mM sucrose and 14.7 M IBA. Plantlets were planted after the roots reached a length greater than 20 mm.Abbreviations BA N-(phenyl-methyl)-lH-purine-6-amine - IBA lH-indole-3-butanoic acid - MS Murashige and Skoog (1962) - 2,4-D (2,4-dichlorophenoxy) acetic acid - TC agar tissue culture agar, (K.C. Biologicals, Lenexa, KS) - Subdue methaxyl:N-(2,6-dimethylphenyl)-N-(methyoxyacetyl) alanine methyl ester (CIBA- GEIGY)     

Water relations and growth responses of Uniola paniculata (sea oats) to soil moisture and water-table depth

Summary This study examined the water relations and growth responses of Uniola paniculata (sea oats) to (1) three watering regimes and (2) four controlled water-table depths. Uniola paniculata is frequently the dominant foredune grass along much of the southeastern Atlantic and Gulf coasts of the United States, but its distribution is limited in Louisiana. Throughout most of its range, U. paniculata tends to dominate and be well adapted to the most exposed areas of the dune where soil moisture is low. Dune elevations in Louisiana, however, rarely exceed 2 m, and as a result the depth to the water table is generally shallow. We hypothesized that if U. paniculata grows very near the water-table, as it may in Louisiana, it will display signs of water-logging stress. This study demonstrated that excessive soil moisture resulting from inundation or shallow water-table depth has a greater negative effect on plant growth than do low soil moisture conditions. Uniola paniculata's initial response to either drought or inundation was a reduction of leaf (stomatal) conductance and a concomitant decrease in leaf elongation. However, plants could recover from drought-induced leaf xylem pressures of less than-3.3 MPa, but prolonged inundation killed the plants. Waterlogging stress (manifested in significantly reduced leaf stomatal conductances and reduced biomass production) was observed in plants grown at 0.3 m above the water table. This stress was relieved, however, at an elevation of 0.9 m above the water table. As the elevation was increased from 0.9 to 2.7 m, there were no signs of drought stress nor a stimulation in growth due to lower soil moisture. We concluded that although U. paniculata's moisture-conserving traits adapt it well to the dune environment, this species can grow very well at an elevation of only 0.9 m above the water table. Field measurements of water-table depth in three Louisiana populations averaged about 1.3 m. Therefore, the observed limited distribution of U. paniculata along the Louisiana coast apparently cannot be explained by water-logging stress induced by the low dune elevations and the corresponding shallow water-table depth.     

Photosynthetic and carbohydrate status of easy-and difficult-to-acclimatize sea oats (Uniola paniculata L.) genotypes during In vitro culture and Ex vitro acclimatization

Summary The photosynthetic and carbohydrate status of an easy-to-acclimatize (EK 16-3) and a difficult-to-acclimatize (EK 11-1) genotype of Uniola paniculata L. (sea oats), a native dune species of the southeastern US, were evaluated during in vitro culture and ex vitro acclimatization. Net photosynthetic rate was eight times greater for EK 16-3 than EK 11-1 plantlets after ex vitro transfer. In vitro-produced leaves were morphologically similar to ex vitro-produced leaves and exhibited similar photosynthetic competence. EK 11-1 plantlets exhibited greater transpiration rates at the time of ex vitro transfer than EK 16-3 plantlets. However, the small magnitude of this difference, although significant, indicated that control of water loss was probably not the main cause for poor acclimatization of EK 11-1 plantlets. Carbohydrate analysis in vitro revealed that EK 16-3 plantlets utilized leaf starch reserves more rapidly than EK 11-1 plantlets. Starch utilization correlated with the development of leaves with expanded leaf blades during in vitro rooting in EK 16-3 plantlets. After ex vitro transfer, both genotypes exhibited significant decreases of starch and soluble sugar content in shoots and roots. However, the higher photosynthetic ability of shoots in EK 16-3 resulted in greater accumulation of shoot soluble sugars than EK 11-1 after 2-wk ex vitro culture. After 6-wk in vitro rooting, there were significantly higher chlorophyll and soluble protein contents, ribulose 1,5-bisphosphate carboxylase (rubisco) and phosphoenolpyruvate carboxylase activities in EK 16-3 than EK 11-1 shoots. These differences also correlated with the development of anatomical and morphological leaf features in EK 16-3 similar to those of greenhouse-produced leaves.     

Multi-scale genetic analysis of Uniola paniculata (Poaceae): a coastal species with a linear, fragmented distribution

Geographic and fine-scale population genetic structures of Uniola paniculata, the dominant coastal dune grass in the southeastern USA, were examined. The linear, naturally fragmented distribution of this native perennial was hypothesized to lead to high genetic structure and lower genetic diversity at the margin of the species range. The extensive ramet production and low seed germination of this species were also expected to cause populations to be dominated by a few large clones. At 20 sites throughout the range of the species, leaf tissue was collected from 48 individuals. Clonal structure was examined using leaf tissue collected from an additional 60 individuals, each in four patches at two sites. Starch gel electrophoresis was used to resolve 27 allozyme loci. The results indicated that Uniola had greater genetic structure (G(ST) = 0.304) than most other outcrossing species, indicating moderate barriers to gene flow. There was a weak but significant positive relationship between genetic distance and geographic distance, supporting an isolation-by-distance model of gene flow. There were no obvious disjunctions between regions. Genetic diversity (H(e)) was relatively uniform throughout most of the range of the species but was lower in all western Gulf of Mexico populations. Clonal diversity varied both within and among sites, but clones were often small, suggesting that sexual reproduction and recruitment from seeds are important factors maintaining genetic diversity.     

Selection from parasites favours immunogenetic diversity but not divergence among locally adapted host populations

The unprecedented polymorphism in the major histocompatibility complex (MHC) genes is thought to be maintained by balancing selection from parasites. However, do parasites also drive divergence at MHC loci between host populations, or do the effects of balancing selection maintain similarities among populations? We examined MHC variation in populations of the livebearing fish Poecilia mexicana and characterized their parasite communities. Poecilia mexicana populations in the Cueva del Azufre system are locally adapted to darkness and the presence of toxic hydrogen sulphide, representing highly divergent ecotypes or incipient species. Parasite communities differed significantly across populations, and populations with higher parasite loads had higher levels of diversity at class II MHC genes. However, despite different parasite communities, marked divergence in adaptive traits and in neutral genetic markers, we found MHC alleles to be remarkably similar among host populations. Our findings indicate that balancing selection from parasites maintains immunogenetic diversity of hosts, but this process does not promote MHC divergence in this system. On the contrary, we suggest that balancing selection on immunogenetic loci may outweigh divergent selection causing divergence, thereby hindering host divergence and speciation. Our findings support the hypothesis that balancing selection maintains MHC similarities among lineages during and after speciation (trans‐species evolution).     

Three new species of Muhlenbergia and Uniola (Poaceae) from Northern Peru

Three new grass species, Muhlenbergia coxamarcensis, M. maxima and Uniola peruviana are described from Northern Peru. Their affinities and geographical distribution are briefly discussed.     

Genome accumulation in eastern gamagrass,Tripsacum dactyloides (L.) L. (Poaceae)

Intermatings between sexual diploids (2n=36) and facultative apomictic tetraploids (2n=4n=72) of Tripsacum dactyloides var. dactyloides, (L.), L., have been generated. Subsequent exchange and addition of genetic material between the two cytotypes, via a backcrossing program, provides one method for the manipulation of genetic elements involved in apomictic reproduction (diplospory) of this species.Identification and development of fertile triploids, and their innate tendency to exhibit a high frequency of unreduced egg cells which remain receptive to fertilization by a sperm nucleus, allows for the unique development of B _III (2n=3x+n) tetraploids by genome accumulation. The resultant B _III progeny provide new breeding stock for investigating the inheritance and generation of such materials also allows for the occurrence of genetic recombination between sexual diploids and apomictic tetraploids. Potential use of fertile triploids, their tendency for genome accumulation and their use in exploiting apomictic tetraploid germplasm resources are also discussed.All programs and services of the U.S. Department of Agriculture are offered on a nondiscriminatory basis without regard to race, color, national origin, religion, sex, age, marital status, or handicap.     

禾本科燕麦属植物的地理分布

为探讨燕麦属(Avena L.)植物的地理分布,通过野外调查及查阅标本和文献资料,对燕麦属植物的地理分布进行整理和研究。结果表明,燕麦属植物约有29种,主要分布在欧洲、地中海地区、北非、西亚、东亚和美洲。中国有4种,分布于华北、西北、西南各省(区)的高海拔地区。燕麦属下分7个组,分别是多年生燕麦组[sect.Avenotrichon(Holub)Baum]、偏凸燕麦组(sect.Ventricosa Baum)、耕地燕麦组(sect.Agraria Baum)、软果燕麦组(sect.Tenuicarpa Baum)、埃塞俄比亚燕麦组(sect.Ethiopica Baum)、厚果燕麦组(sect.Pachycarpa Baum)和真燕麦组(sect.Avena)。其中,埃塞俄比亚燕麦组分布在埃塞俄比亚、沙特阿拉伯、也门,其他6个组分布在欧洲、地中海、西北非洲、西亚、东亚和美洲地区。地中海、西北非洲、西亚地区分布有除埃塞俄比亚燕麦组之外的所有6个组,因此推断该地区可能是燕麦属的现代分布中心和多样性中心,而燕麦属的起源地尚需确证。     

Genetic differentiation among sea trout, Salmo trutta L., populations from western Norway

Samples of sea trout, Salmo trutta L., were collected by electrofishing in eight rivers of western Norway. The samples consisted mainly of presmolt, but also contained some spawners. Muscle, eye and liver tissue were sampled and analysed for allozyme polymorphism by standard starch gel electrophoresis. Nine polymorphic loci were found. The genotype as well as the allele distributions was significantly different in all but six pair‐wise comparisons, showing the high degree of population differentiation in this anadromous species. Even some nearby rivers displayed very different allele frequencies. The correlation between genetic and geographic distances was nearly significant.     

The typification of Lolium perenne L. and Loliutn temulentum L. (Poaceae)

LOOS, B. P. & JARVIS, C. E., 1992. The typification of Lolium perenne and Lolium temulentum (Poaceae). The typification of the Linnaean species Lolium perenne and Lolium temulentum has been studied. Lolium perenne is typified by material in LINN, as proposed by Terrell, but it has been necessary to select a lectotype for L. temulentum , and material in the Burser herbarium (UPS) has been chosen for this purpose. The study shows that although Linnaeus used awns as a diagnostic character to distinguish the two species, he was aware of the intraspecific variability in this character.     

Genetic divergence does not predict change in ornament expression among populations of stalk-eyed flies

Stalk-eyed flies (Diptera: Diopsidae) possess eyes at the ends of elongated peduncles, and exhibit dramatic variation in eye span, relative to body length, among species. In some sexually dimorphic species, evidence indicates that eye span is under both intra- and intersexual selection. Theory predicts that isolated populations should evolve differences in sexually selected traits due to drift. To determine if eye span changes as a function of divergence time, 1370 flies from 10 populations of the sexually dimorphic species, Cyrtodiopsis dalmanni and Cyrtodiopsis whitei, and one population of the sexually monomorphic congener, Cyrtodiopsis quinqueguttata, were collected from Southeast Asia and measured. Genetic differentiation was used to assess divergence time by comparing mitochondrial (cytochrome oxidase II and 16S ribosomal RNA gene fragments) and nuclear (wingless gene fragment) DNA sequences for c. five individuals per population. Phylogenetic analyses indicate that most populations cluster as monophyletic units with up to 9% nucleotide substitutions between populations within a species. Analyses of molecular variance suggest a high degree of genetic structure within and among the populations; > 97% of the genetic variance occurs between populations and species while < 3% is distributed within populations, indicating that most populations have been isolated for thousands of years. Nevertheless, significant change in the allometric slope of male eye span on body length was detected for only one population of either dimorphic species. These results are not consistent with genetic drift. Rather, relative eye span appears to be under net stabilizing selection in most populations of stalk-eyed flies. Given that one population exhibited dramatic evolutionary change, selection, rather than genetic variation, appears to constrain eye span evolution.     

Disposition of ribosomal DNAs in the chromosomes of perennial oats (Poaceae: Aveneae)

The chromosomal loci of 5S and 45S ribosomal DNAs (rDNAs) and the activity of nucleolar‐organizing regions (NORs) were analysed in perennial oats of the genera Ammophila, Amphibromus, Arrhenatherum, Avena, Deschampsia, and Helictotrichon s.l. (Poaceae: Aveneae) using fluorescence in situ hybridization, staining with chromomycin/4′,6‐diamidino‐2‐phenylindole (DAPI), and silver impregnation. All chromosomes with a secondary constriction were nucleolar active. In chromosomes without a secondary constriction, NORs corresponded exclusively to broad bands of 45S rDNA with chromomycin‐positive, DAPI‐negative, and silver‐positive stainability. Additional minor bands of 45S rDNA showed no nucleolar activity. 5S rDNA was localized mostly in loci different from the nucleolar‐active 45S rDNA. If both rDNAs occurred within the same chromosome, they were at largely corresponding distances from the centromere, irrespective of their particular localization in either the same chromosome arm or in opposite arms. In the latter case, 5S rDNA was never more distal to the centromere than 45S rDNA. A new model was devised to explain this non‐random distribution of both rDNAs in nucleolar‐organizing chromosomes, which identified the Rabl orientation of chromosomes as ensuring a spatial proximity of 5S to 45S rDNA in interphase nuclei, even if they were localized in opposite arms. The possible role of the Rabl orientation in determining the spread and accumulation of 5S rDNA sequences in further chromosomes of the genome was discussed. B chromosomes were devoid of 5S rDNA, but most contained 45S rDNA and were nucleolar active. In some large groups of species, the number and arrangement of 5S and 45S rDNA sites in the chromosomes were remarkably uniform, especially in Helictotrichon subgenus Helictotrichon and Helictotrichon subgenus Pratavenastrum. Such distribution patterns have survived many speciation processes and have also remained widely unchanged in polyploids. © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society, 2007, 155 , 193–210.     

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

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

Thyroxine affects behavioral thermoregulation but not growth rate among populations of the western fence lizard (Sceloporus occidentalis)

We investigated whether thyroxine influences hatchling growth rate of the western fence lizard (Sceloporus occidentalis) throught its effects on thermoregulatory behaviors. We reared control and thyroxine-injected hatchlings from three populations of S. occidentalis that differ in growth rate in a thermal gradient. We also measured the daily changes in body temperature and activity level (proportion of time spent out of retreat sites) of control and thyroxine-injected lizards. Previous studies have shown that within and among population differences in growth rate of the western fence lizard are correlated with the maintenance of high activity levels (proportion of time spent outside of retreat sites) and high body temperatures throughout the day. Growth rate was not influenced by injections of thyroxine. However, injections of thyroxine did elevate average daily body temperature and daily activity. Although administration of thyroxine uniformly increased the probability of activity throughout the day, it did not appear to alter the daily changes in activity. Previous studies have shown that the slower-growing hatchlings from northern populations exhibit a decline in activity during the later part of the thermal cycle, whereas the faster growing southern hatchlings maintain the same level of high activity throughout the thermal cycle. The decline in activity of northern populations was not prevented by thyroxine injection used in our current study. Northern lizards receiving exogenous thyroxine were still less active later in the day compared to early in the day, even though activity level throughout the day was elevated. Thus, the effects of thyroxine on temperature regulation observed in our study (general increase in activity level) appear to be unrelated to those aspects of temperature regulation (e.g., daily changes in behavioral thermoregulation) that are correlated with among population differences in growth rate. We also raised hatchlings in a cycling thermal regime (forced thermal cycle of 34°C:15°C, 12L:12D) where behavioral thermoregulation is not possible. The growth rate of lizards forced to cycle between 34°C:15°C on a daily basis was significantly lower than those lizards allowed to behaviorally thermoregulate, further underscoring the importance of the circadian pattern of thermoregulation for growth.Abbreviations GR growth rate - MR metabolic rate - SMR standard metabolic rate - SVL snout-vent length - T₄ thyroxine - T _b body temperature - T _e environmental temperature     

Intraspecific taxonomy and ecology characterize morphological divergence among cutthroat trout (Oncorhynchus clarkii ssp. Richardson) populations

We compared the proportion of morphological variation accounted for by subspecies categories with the proportion encompassed by ecologically based categories in cutthroat trout ( Oncorhynchus clarkii ssp.), as a means of assessing the relative importance of each approach in identifying intraspecific diversity. We used linear and geometric morphometrics to compare measures of body shape, fin length, and head features between and within subspecies of cutthroat trout. Both categories accounted for a significant proportion of the variation between and within the subspecies; however, the larger proportion was explained by subspecific differences, with the greatest morphological divergence between coastal cutthroat trout ( Oncorhynchus clarkii clarkii ) and interior subspecies. Ecotypic categories within each subspecies also explained significant morphological differences: stream populations had longer fins and deeper, more robust bodies than lake populations. The largest ecotypic differences occurred between stream and lake populations of Yellowstone cutthroat trout ( Oncorhynchus clarkii bouvieri ). Given that many cutthroat trout subspecies are of conservation concern, our study offers a better understanding of intraspecific variation existing within the species, providing precautionary evidence of incipient speciation, and a framework of describing phenotypic diversity that is correlated with ecological conditions.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 96 , 266–281.     

Genetic and morphological divergence between populations of the flatfish Platichthys flesus (L.) (Pleuronectidae)

Populations of the flounder, Platichthys flesus , were screened for electrophoretically detectable protein variation at up to 37 loci. Atlantic and North Sea populations (subspecies flesus ) were genetically very similar to one another ( I >0.99) but different from Adriatic (subspecies italicus ) and Black Sea (subspecies luscus ) populations. The values for genetic identity between subspecies were around 0.9. Diagnostic loci enabled specimens of flesus, italicus and luscus to be differentiated from one another. Samples of flesus showed two to three times the heterozygosity levels of italicus or luscus , consistent with the greater population size of flesus . Morphological comparisons enabled populations to be categorized to subspecies. Platichthys flesus italicus and luscus are valid subspecies: the terms are not synonyms. The genetic distance data provide an estimate of divergence time of the three subspecies at about 2 My ago, an estimate that seems reasonable in the light of present knowledge concerning the recent geological histories of the Mediterranean and Black Sea basins.     

Morphometric and genetic divergence among populations ofNeotinea ustulata (Orchidaceae) with different flowering phenologies

The terrestrial orchid speciesNeotinea ustulata has recently been split into two subspecies, differing remarkably in their flowering time, but only slightly in morphological characteristics, which makes their taxonomic status uncertain. We have analyzed morphometric and genetic differences between the early- and late-flowering populations in Central Europe. Our results on morphology are ambiguous. Indirect gradient analysis has not shown a distinct separation of early- and late-flowering individuals in the ordination space. However, according to MANOVA, populations of early- and late-flowering plants can be distinguished by plant height, leaf length, numbers of basal (rosette) and stem leaves and even better by certain ratios of these numbers. All genetic analyses, on the other hand, are definite and consistently distinguish two groups. Random amplified polymorphic DNA (RAPD) markers have shown that the early- and late-flowering populations differ significantly from one another. Principal coordinate analysis (PCoA) based on presence/absence matrix of RAPD bands separated the two groups, implying that the difference in flowering phenology could form an effective barrier to gene exchange. Partitioning of genetic diversity in analysis of molecular variance (AMOVA) has shown that the genetic divergence between the two groups, early- and late-flowering populations, is somewhat greater (33%) than the genetic variability among populations within particular group (23%). Using the Mantel test, we found that genetic differentiation coefficients between populations closely correspond to their geographic distribution. After elimination of the effect of sample origin from the model, direct gradient analysis (RDA) has shown that the early- and late-flowering groups differ significantly in their RAPD spectra. To conclude, our results indicate the presence of two genetically and phenologically distinct taxa, but the weak morphological differentiation supports the taxonomic rank of variety rather than subspecies.     

Comparative Analysis of Triticum aestivum L. (Poaceae,Poales) and Pisum sativum L. (Fabaceae,Fabales) Resistance to Heavy Metals

Biology Bulletin - Abstract—Heavy metals are widespread soil pollutants frequently identified in agricultural lands. In many cases, their pollution levels significantly exceed the maximum...