Consistency of population genetics parameters estimated from isozyme and RAPDs dataset in species of genus <Emphasis Type="Italic">Prosopis</Emphasis> (Leguminosae,Mimosoideae)

Genetic variability, population structure and differentiation among 17 populations of 5 species and 2 natural interspecific hybrids of section Algarobia of genus Prosopis were analyzed from data of 23 isozyme and 28 RAPD loci. Both markers indicated that the studied populations are highly variable. P. alba populations in average showed lower values of genetic variability estimates from isozyme data, but this trend was not observed for RAPD markers. The hierarchical analyses of the distribution of genetic variability showed that the highest proportion of variation occurred within populations, the differentiation among species was intermediate and the lowest component was observed among populations within species. The consistency between results from both dataset implies that they are not biased and reflect the actual genetic structure of the populations analyzed. The matrices of Euclidean distances obtained from the two sets of markers were highly correlated according to Mantel test. In both cases the corresponding phenogram and MDS plot tended to cluster conspecific populations while hybrid populations were not intermediate between putative parents. Some disagreements between isozyme and RAPD phenograms were observed mainly in the affinities of hybrid populations. Such inconsistencies might result from reticular rather than dichotomic evolutionary relationships. The phenetic associations retrieved gave no support to the division of the section Algarobia into series.     

Unexpected low genetic differentiation among Allopatric species of section Algarobia of Prosopis (Leguminosae)

The Chaqueña Biogeographic Province, in South America, is the main diversity centre of Prosopis. A group of sympatric species of Section Algarobia in this region constitutes a syngameon, characterised by frequent hybridization and introgression. These processes have been postulated as responsible for the low genetic differentiation observed among species within this group. In this study genetic variability and differentiation among geographically isolated species of the same section was analysed through isoenzyme electrophoresis. Variability parameters and fixation indices were estimated to determine the genetic structure of populations. Two Argentinean, P. ruscifolia (‘vinal’) and P. flexuosa (‘algarrobo amarillo’), and one North American species, P. glandulosa (honey mesquite) were studied. All of them showed, similarly to other species of the same section, high genetic variability and exhibit homozygote excess, probably due to population substructure and low rates of selfing. In contrast to our hypothesis, genetic similarity among species is not related to geographic distance. Genetic distances between P. glandulosa and South American species are similar to those observed among species of this subcontinent. The results obtained suggest that the high genetic similarity among the species of the section Algarobia studied is not due to hybridization.     

RAPD and microsatellite transferability studies in selected species of <Emphasis Type="Italic">Prosopis</Emphasis> (section Algarobia) with emphasis on <Emphasis Type="Italic">Prosopis juliflora</Emphasis> and <Emphasis Type="Italic">P. pallida</Emphasis>

The genus Prosopis (Leguminosae, Mimosoideae), comprises 44 species widely distributed in arid and semi-arid zones. Prosopis pallida (Humb. & Bonpl. ex Willd.) Kunth and P. juliflora (Sw.) DC. are the two species that are truly tropical apart from P. africana, which is native to tropical Africa (Pasiecznik et al. 2004), and they have been introduced widely beyond their native ranges. However, taxonomic confusion within the genus has hampered exploitation and better management of the species. The present study focusses primarily on evaluating the genetic relationship between Prosopis species from the section Algarobia, containing most species of economic importance, though P. tamarugo from section Strombocarpa is also included for comparison. In total, 12 Prosopis species and a putative P. pallida × P. chilensis hybrid were assessed for their genetic relationships based on RAPD markers and microsatellite transferability. The results show that P. pallida and P. juliflora are not closely related despite some morphological similarity. Evidence also agrees with previous studies which suggest that the grouping of series in section Algarobia is artificial.     

Identification of Prosopis juliflora and Prosopis pallida Accessions Using Molecular Markers

There has been much taxonomic confusion over the identification of Prosopis species, especially where introduced. Prosopis juliflora is the most widespread species in the arid and semi-arid tropics, although it has been confused with other species, particularly the closely related Prosopis pallida. In this study, RAPDs markers were used for the first time to distinguish between these species. Eighteen primers were used in amplification reactions, which yielded an average of 120 bands per accession. A dendrogram showing genetic similarities among accessions was constructed using UPGMA cluster analysis and the Nei and Li similarity coefficient. The genetic similarity observed between P. juliflora and P. pallida is similar to the value in sympatric Prosopis species in North America, and reconsideration of the series rank in section Algarobia is suggested. Species-specific markers confirmed that material in Burkina Faso is P. juliflora, but suggested that material collected in Brazil, Cape Verde and Senegal is P. pallida, whereas this has previously been identified as P. juliflora.     

Discovery of a life history shift: precocious flowering in an introduced population of Prosopis

The genus Prosopis contains many valuable, long-lived, multi-purpose legume trees, some of which are also invasive species. The time of first flowering is important for increasing production of sweet, protein-rich pods in plantations, especially under short rotations, and affects the rate of spread as a weed. Trees generally begin flowering at 3–5 years of age. However, seedlings from a small seedlot collected from an introduced population in southern Mauritania were observed to begin flowering at 3–4 months after germination. This is unknown in the native range of any Prosopis species, and appears to represent a major evolutionary event triggered after naturalization. This paper reports a detailed investigation with seed collected from Aleg, Brakna region, Mauritania, in 1998 (Prosopis sp. ‘Aleg’). Two experiments were established, in glasshouses at Cirad, Montpellier, France, and Coventry University, UK. Flowering began at the two sites 104 and 169 days after sowing, respectively, and 97.5% of plants had flowered at Coventry after 306 days. Flowers produced abundant pollen with 50–60% viability indicated by FDA staining and 40–50% germination on an artificial medium. No pods were formed. All plants analysed were diploid. Morphologically, these juvenile plants were similar to American species of section Algarobia, and exhibited leaf characters typical of P. pallida. However, due to the large variation in morphology within this section of the genus, further studies are required to confirm the actual species. This is the first record of precocious flowering in Prosopis, and has been found only in a single, introduced population. Implications for genetic improvement of tropical Prosopis, and particularly the spread of these species as invasive weeds, are discussed. Such a life history shift in the increased reproductive ability of a species following introduction, with potentially significant environmental effects, may not be restricted to Prosopis and merits further detailed investigation.     

Genetic divergence among species of the section Strombocarpa,genusProsopis (Leguminosae)

We studied degree of variability and relationships among populations belonging to five species of the section Strombocarpa of the family Leguminosae, namelyProsopis ferox, P. torquata, P. pubescens, P. strombulifera andP. reptans, by isozyme electrophoresis. The genetic similarity betweenP. reptans andP. strombulifera is high enough for the two to be considered subspecies or geographic races ofP. strombulifera instead of good taxonomic species. As expected these species cluster withP. pubescens, all belonging to series Strombocarpae. This group is different isoenzymatically from the remaining species,P. torquata andP. ferox. Comparison of our results with those obtained earlier for species of the section Algarobia showed that genetic variability in the section Strombocarpa is lower than in the section Algarobia, while the species divergence is much higher. These results suggest different adaptive strategies between these sections.     

Isozyme variation and species relationships in peanut and its wild relatives (Arachis L. — Leguminosae)

Summary Arachis hypogaea (peanut or groundnut) is an AABB allotetraploid whose precise ancestry is not yet clear. Its closest diploid relatives are the annual and perennial wild species included with it in the section Arachis. Variation in these species for 11 different enzymes was studied by starch-gel electrophoresis. Differences attributed to at least 13 genetic loci were found among eight enzymes, while three enzymes appeared uniform throughout the section. Values for Nei's genetic distance were calculated for all pairs of species and were used to estimate relationships. All diploid species, apart from two whose validity had previously been questioned, could be distinguished by their overall zymotypes, but few contained unique alleles. When species were grouped by their mean genetic distances, they formed two clusters, which agreed reasonably well with the division of the section into annual versus perennial species. The single B-genome species was an outlier within the annual group. A. hypogaea showed fixed heterozygosity at four loci (in ssp. hypogaea) or six loci (in ssp. fastigiata), which agrees with previous conclusions that the peanut is an allotetraploid. None of the diploids included in this survey could be conclusively identified as donors of either the A or the B genome to the tetraploids. The two subspecies of A. hypogaea differed consistently in two of the thirteen putative loci studied. This may call into question the simple hypothesis that A. hypogaea originated from just two diploid species.     

Restriction fragment length polymorphism evaluation of six peanut species within the Avachis section

Summary Restriction fragment length polymorphisms (RFLP) were assessed among accessions within six peanut species of the Arachis section: tetraploid cultivated species, A. hypogaea; tetraploid wild species, A. monticola; and four diploid wild species, A. batizocoi,A. cardenasii, A. duranensis and A. glandulifera. While the two tetraploid species did not show polymorphism with 16 PstI-generated random genomic probes, two of seven seed cDNA probes detected polymorphisms. The RFLP variation detected by two seed cDNA probes appeared to be related to structural changes occurring within tetraploid species. The botanical var. fastigiata (Valencia market type) of A. hypogaea subspecies fastigiata was shown to be the most variable. Arachis monticola was found to be more closely related to A. hypogaea subspecies hypogaea than to subspecies fastigiata. Diploid species A. cardenasii, A. duranensis, and A. glandulifera showed considerable intraspecific genetic diversity, but A. batizocoi showed little polymorphism. The genetic distance between the cultivated peanut and wild diploid species was found to be closest for A. duranensis.Florida Agricultural Experiment Station, Journal Series No. R-01493     

Sequence analyses of the ITS regions and the matK gene for determining phylogenetic relationships of Diospyros kaki (persimmon) with other wild Diospyros (Ebenaceae) species

To elucidate the relationships among Diospyros kaki and species closely related in previous studies, the nuclear ribosomal internal transcribed spacer (ITS) DNA sequence and the chloroplast matK gene were sequenced and compared with those of nine Diospyros species from Thailand, four species from temperate regions, and one species of southern Africa, D. lycioides. Maximum parsimony, maximum likelihood, and neighbor joining analyses of the matK and ITS data sets revealed that D. kaki is closely related to two diploid species, D. oleifera and D. glandulosa. D. kaki, D. glandulosa, and D. oleifera were placed differently in the trees obtained from ITS and matK data sets, suggesting that hybridization and/or introgression may have occurred during the development of these species. D. kaki was not found to be closely related to D. ehretioides, a diploid species from Thailand. These results differed from a prior analysis of this genus performed with chloroplast DNA (cpDNA) restriction site mutations in 3.2- and 2.1-kb amplified sequences. The results supported Ng’s hypothesis that D. glandulosa and D. kaki may share a common ancestor. D. oleifera was also closely associated with D. kaki.     

Noncoding chloroplast DNA variation in Mexican pines

Universal primers were used for PCR amplification of three noncoding regions of chloroplast DNA in order to study restriction site variation in 12 Mexican pine species. Two length mutations were identified that are of diagnostic value for two subgenera or sections of the genus. Phylogenetic analysis of the restriction site and length variation showed patterns of variation largely consistent with previous arrangements of these pines, except for the position of Pinus nelsonii, indicating that Pinus section Parraya Mayr, as circumscribed by Little and Critchfield (1969) and later authors, is not a monophyletic group.     

The impact of species-specific traits and phylogenetic relatedness on allozyme diversity inCarex sect.Phyllostachys (Cyperaceae)

Allozyme variation was examined inCarex sect.Phyllostachys (Cyperaceae) to study the effects of species-specific traits and phylogenetic relatedness on genetic structure. In contrast to the findings of similar studies, genetic variability in thePhyllostachys is poorly correlated with geographic range and putative differences in breeding systems (as inferred from morphology). This suggests that other patterns of evolution, colonization, and gene flow characterize the species found in this section. Fixation indices are negative for all populations suggesting that mechanisms such as disassortative mating and selection are maintaining heterozygous excess within populations. Closely related taxa often exhibit different genetic variability statistics. In some instances, however, clades (e.g.C. jamesii andC. juniperorum) display very similar levels of genetic variability despite marked differences in species-specific traits. Recent speciation coupled with the ability to maintain historical levels of variation within populations may be factors accounting for this phenomenon. Contrary to similar studies, species restricted to known glacial refugia have lower genetic diversity than those species that underwent mass migrations in response to deglaciation. Narrowly endemic species were found to partition their genetic diversity within, as opposed to between populations. The opposite trend was evident in wider ranging congeners.     

Molecular phylogeny of genus Vigna subgenus Ceratotropis based on rDNA ITS and atpB-rbcL intergenic spacer of cpDNA sequences

The genetic diversity and phylogenetic relationships among species in the genus Vigna subgenus Ceratotropis were investigated using sequence data from the ribosomal DNA ITS and atpB-rbcL intergenic spacer of chloroplast DNA regions. While both sets of sequences were of similar lengths about 700bp the rDNA-ITS was more informative than atpB-rbcL having 170% more polymorphic sites and five times as many parsimony-informative sites. The atpB-rbcL spacer may be appropriate for analysis of taxa above the species level in the genus Vigna. Results of analyzing rDNA-ITS revealed, with low level of statistical bias, separation of the subgenus into three groups that correspond to the three sections Aconitifoliae, Angulares, and Ceratotropis. The ancestral section is Aconitifoliae based on comparison with the outgroup species cowpea, Vigna unguiculata. The V. minima complex, V. minima, V. riukiuensis, and V. nakashimae, has a distinct evolutionary path within section Angulares. Other species in section Angulares are very closely related except V. trinervia. Vigna trinervia has an intermediate position between sections. Sequence data suggests one genome donor to V. reflexo-pilosa came from a lineage within section Angulares close to V. exilis, V. hirtella, and V. umbellata. Data presented supports the view that section Angulares is the most recently diversified section in the subgenus, as inferred by short terminal branch lengths among the species of this section.     

Phylogeny of Caragana (Fabaceae) based on DNA sequence data from rbcL, trnS–trnG, and ITS

Phylogenetic relationships of 48 species of Caragana (Fabaceae: tribe Hedysareae) and one representative each of Astragalus, Calophaca, Halimodendron, and Hedysarum are estimated from DNA sequences of the rbcL gene, trnS–trnG intron and spacer, and ITS region. At least one representative of all five sections and 12 series within Caragana are included. Analyses yielded strongly supported clades corresponding to sections Caragana, Bracteolatae, and Frutescentes. The species of section Jubatae are distributed among three strongly supported clades, i.e., one with the species of section Bracteolatae, another with two species of section Spinosae, and a third as sister to section Frutescentes. All but the last of these six clades are corroborated by at least one unambiguously traced morphological character. The placement of the other four species of section Spinosae are not well supported and lack unambiguous morphological synapomorphies, and the samples of Calophaca and Halimodendron nest within Caragana with weak support.     

Effect of a gap on gene flow between otherwise adjacent transgenic <Emphasis Type="Italic">Brassica napus</Emphasis> crops

The chloroplast DNA diversity of 33 accessions belonging to 16 species of five sections in Allium subgenus Rhizirideum was studied by analysing the sequence of three fragments: the trnL-F intergenic spacer, the rps 16 intron and rbcL (rubisco large subunit). The three sections Cepa, Schoenoprasum and Rhizirideum, representing the majority of the included species, each possess a separate clade after phylogenetic analysis. Exceptions to this general rule are the placement of Allium pskemense (section Cepa) connected to Allium senescens (section Rhizirideum) and Alium roylei, taking an intermediate position between sections Cepa and Schoenoprasum. Both species were located in their own section after nuclear DNA analysis. A range of crossing experiments has been carried out. The different position of A. roylei when comparing cpDNA and nDNA diversity was not confirmed with the production of hybrid seeds after crossing A. roylei with species other than those of section Cepa. The different position of A. pskemense in the cpDNA and the nDNA tree can not be compared to its crossability, since only a few crossing experiments are reported for this species. The hypothesis that a shorter distance between two species in a cpDNA tree compared to their distance in a nDNA tree will indicate interfertility at a certain level, is neither confirmed nor rejected by the currently available results.Communicated by R. Hagemann     

Karyotype relationships among four South American species of Urvillea (Sapindaceae: Paullinieae)

A cytogenetic study was conducted on four species of the genus Urvillea (Sapindaceae, Paullinieae): U. chacoensis Hunz., U. filipes Radlk. and U. ulmacea Kunth of the Urvillea section and U. laevis Radlk. of the Stenelytron section. The chromosome numbers in U. chacoensis (2n = 22) and U. laevis (2n = 24) were confirmed, and new chromosome numbers are reported for U. filipes with 2n = 22 and U. ulmacea with 2n = 88. Additionally, data on interphase nuclear structure, chromosome banding patterns (C-Giemsa and C-CMA₃/DAPI) and FISH with rDNA probes are also presented. The distribution of AT- and GC-rich regions and the physical mapping of ribosomal genes (45S and 5S rDNA sites) were established for the first time in these Urvillea species. Sections of Urvillea are cytogenetically differentiated according to basic chromosome number, where x = 11 in the section Urvillea and x = 12 in the section Stenelytron. This first section displayed an important karyotypic feature, the occurrence of large AT- and GC-rich bands at terminal chromosomal regions. The Urvillea section showed polyploidy and its species were differentiated by their banding patterns. Urvillea chacoensis showed several terminal AT-rich bands, while terminal AT- and GC-rich bands were both found in U. ulmacea. However, the section Stenelytron did not exhibit this banding pattern. The 45S rDNA sites appeared always associated with GC-rich regions and they were numerically variable among species, being located or not the same chromosome 5S rDNA sites. Variation in the repetitive DNA distribution and their role in karyotype differentiation among these Urvillea species are discussed.     

中国丝瓜藓属直蒴组的分类学研究

采用经典分类学研究方法,对河北师范大学植物标本馆(HBNU)等国内多个标本馆保存的中国丝瓜藓属直蒴组(Pohlia Hedw.section Cacodon Lindb.ex Broth.)及其近缘类群植物标本共计130余号进行了分类学分析鉴定,并对所确定的中国产直蒴组物种的芽胞大小、形状及叶原基数量和长度等形态学特征进行比较分析,以期为中国丝瓜藓属直蒴组的分类学研究提供理论依据。结果表明:(1)经鉴定中国丝瓜藓属直蒴组植物共有8种——夭命丝瓜藓[Pohlia annotina(Hedw.)Lindb.]、糙枝丝瓜藓[P.camptotrachela(Ren.Card.)Broth.]、林地丝瓜藓[P.drummondii(Müll.Hal.)Andr.]、疣齿丝瓜藓[P.flexuosa Harv.]、纤毛丝瓜藓[P.hisae T.J.Kop.et J.X.Luo]、异芽丝瓜藓[P.leucostoma(BoschSande Lac.)M.Fleisch.]、念珠丝瓜藓[P.lutescens(Limpr.)H.Lindb.]和卵蒴丝瓜藓[P.proligera(Kindb.ex Breidl.)Lindb.ex Arnell]。(2)中国丝瓜藓属直蒴组植物的重要鉴别特征是在假根或叶腋处生有芽胞,而且芽胞形状以及叶原基形状和数量在直蒴组中存在差异,如念珠丝瓜藓具有假根生芽胞,而疣齿丝瓜藓具有两型芽胞。(3)对所鉴定的中国丝瓜藓属直蒴组8种植物的识别特征、生境及其与相近种的关系进行了详细描述,并绘制了形态特征墨线图。     

Physical mapping of rDNA sites in possible diploid progenitors of polyploid Festuca species

Festuca species form a polyploid series but only two of the diploid species have been firmly proposed as progenitors of any polyploid. The number and distribution of rDNA sites on the chromosomes of F. scariosa (section Scariosae) and the four diploid species that comprise section Montanae are presented with their relative DNA amounts and key morphological features. Comparisons of the results with those of some polyploid Festuca species from section Bovinae published previously indicate that F. scariosa and F. altissima could be diploid progenitors of the polyploids. It is unlikely that any one of the other three Montanae species is a progenitor of these polyploids.     

The distribution of submerged aquatic macrophyte biomass in a eutrophic stream,Badfish Creek: the effect of environment

The distribution of biomass of the macrophyte community in Badfish Creek was examined in three sections (A–C) totaling ten kilometers. Biomass samples were taken in a stratified-random manner, with sediment characteristics, depth, current velocity and incident light measured at each site to correlate individual biomass samples with environmental factors. Total community biomass decreased in the downstream section (C), with the biomass ofElodea canadensis decreasing abruptly below section A. The only environmental factors which were correlated with the decrease in macrophyte community biomass, especially that ofPotamogeton pectinatus, in section C was the increase in substrate heterogeneity and sand substrates which lacked surface gravel. The change in substrate was related to channelization. Considering the stream as a whole, the biomass of the dominant species,Potamogeton pectinatus, was correlated with incident light. Other species present wereCeratophyllum demersum andCladophora glomerata. Analysis of riparian vegetation type indicates that tree cover significantly reduced macrophyte biomass by incident light reduction.     

Pollen morphology of the genera Polygonum s. str. and Polygonella (Polygoneae: Polygonaceae)

The pollen of 30 taxa (27 species, one subspecies and two varieties) in two genera, viz Polygonum s. str. and Polygonella was investigated with LM and SEM, and some selected taxa with TEM. In all genera investigated the pollen is prolate to spheroidal, and the aperture is mostly tricolporate, rarely panto-hexacolporate (especially Polygonum section Polygonum). The exine sculpturing pattern is the most variable feature. Three types of exine can be recognized. Type 1 (Avicularia-Type, sensu Hedberg) - All species of section Polygonum and section Tephis share the smooth tectate exine with spinules, sometimes the surface is more or less rough (Polygonum afromontanum in section Tephis). Type 2 (Pseudomollia-Type, sensu Hong) - Pollen of Polygonum molliaeforme (section Pseudomollia) has the exine, which is verrucose on both poles and nearby the mesocolpium, and mostly psilate around the ectoaperture. Type 3 (Duravia-Type, sensu Hedberg) - Pollen grains of Polygonum section Duravia and Polygonella have the exine which is semitectate-reticulate at the mesocolpium and the poles, and rugulate/reticulate or sometimes foveolate with microspinules around the ectoapertures. The pollen grains in four taxa (viz Polygonum section Pseudomollia, P. section Duravia and genus Polygonella) have a well-marked dimorphism of the ektexine, which is considered to be a synapomorphic condition. The differences of pollen grain between the genus Polygonella and Polygonum section Duravia are almost non existent and clearly interrelated. It is therefore postulated that the similarity in pollen of both taxa is not the result of convergency, but is interpreted as a homology. It is noteworthy that the pollen of Polygonum molliaeforme (section Pseudomollia) appears as intermediate between the Avicularia-type and the Duravia-type, and is well supported the value of separated section for its own. Additionally, in TEM, some exine ultrastructures (e.g. columellae, foot layer, endexine) appear to be valuable characters for comparison between/among taxa. The systematic potentialities of the pollen data of the studied taxa at various systematic levels are also discussed.     

Evaluation of genetic relationships in Dalbergia species using RAPD markers

Conservation of identified germplasm is an important component forefficient and effective management of plant genetic resources. Traditionally,species identification has relied on morphological characters like growth habit,floral morphology like flower colour, and agronomic characteristics of the plant.Dalbergia species are important wind-dispersed tropicaltimber trees which exhibit high intrafruit seed abortion because of intensesibling competition for maternal resources. Studies were undertaken foridentification and genetic relationships in five species ofDalbergia and to evaluate genetic diversity withinpopulations of Dalbergia sisso, D.latifolia, D. paniculata, D.assamica and D. spinosa by using randomamplified polymorphic DNAs (RAPD) markers. Analysis was started by using 30decamer primers that allowed to distinguish five species and to select a reducedset of primers. The selected primers were used for identification and forestablishing a profiling system to estimate genetic relationships and toevaluate the genetic variability among the individuals in a population ofDalbergia species. A total of 120 distinct DNA fragments(bands), ranging from 0.3 to 4.0 kb, were amplified byusing nine selected random decamer primers. The genetic similarity was evaluated onthe basis of presence or absence of bands, which revealed a wide range ofvariability within the species. The cluster analysis indicated that five speciesof Dalbergia formed two major clusters. The first clusterconsisted of D. spinosa, D. latifolia and D.sisso. The second cluster was represented by two species, i.e.D. paniculata and D. assamica.A maximum similarity of 60% was observed in D. paniculata andD. assamica and they formed a minor cluster.Dalbergia latifolia and D. sissoformed another minor cluster with more than 50% similarity. Dalbergiaspinosa shared up to 40% similarity with D.latifolia and D. sisso. All the species sharemore than 20% similarity among themselves. The closest genetic distance existedwithin populations of different Dalbergia species. Thus,these RAPD markers have the potential for conservation of identified clones andcharacterization of genetic relatedness among the species. This is also helpful intree breeding programs and provides an important input into conservation biology.