MORPHOMETRIC ANALYSIS OF POLLEN FROM FOUR SPECIES OF AMBROSIA (COMPOSITAE)

A morphometric approach proved useful for characterizing pollen from the Ambrosia species that are responsible for most ragweed hayfever and for correctly identifying individual pollen grains. Pollen was harvested from 4 species (A. trifida, A. artemisiifolia, A. bidentata, A. psilostachya) grown in Champaign County, Illinois, and observed with a scanning electron microscope. Quantitative measurements of 6 different exine characters were made on micrographs of 96 pollen grains from each species. Discriminant analysis based on these characters was used to obtain a population centroid for each species and indicated that these centroids were distinctly different. This analysis also included a species classification for individual pollen grains and indicated probability of species membership. About 86% of all individuals were correctly classified when the 4 species were included, with a range from 80% (A. artemisiifolia) to 95% (A. psilostachya). When three species (A. trifida, A. artemisiifolia, A. bidentata) were analyzed, about 87% of the individuals were correctly classified, and almost all individuals (97%) were classified correctly when only A. trifida and A. artemisiifolia were included. The validity of the derived discriminant functions was also tested by treating herbarium specimens as unknowns. The species and percentages of these individuals correctly classified were A. trifida (100%), A. artemisiifolia (58%), A. bidentata (100%), and A. psilostachya (31%). The classification results using three species were A. trifida (100%), A. artemisiifolia (75%), and A. bidentata (100%); and using two species were A. trifida (100%) and A. artemisiifolia (92%). Hence, the disciminant functions do seem valid for 3 species, but further investigation of A. psilostachya is needed. This type of approach may be useful in pollen analysis, especially where these species significantly contributed to aeroallergens.     

KARYOTYPES OF FIVE PLANT SPECIES WITH DISJUNCT DISTRIBUTIONS IN VIRGINIA AND THE CAROLINAS

Five species (Actaea pachypoda, Aralia nudicaulis, Cornus alternifolia, Panax quinquefolius, and Symplocarpus foetidus) display a disjunct distribution between the Mountains and Piedmont in North Carolina, South Carolina, and Virginia. The Piedmont populations are small and have apparently been isolated from the Mountain populations for several thousand years. Karyotype differences among populations were found only in A. pachypoda, and even in this species the differences were slight. The absence of population differences in four species, and the moderate differentiation found in A. pachypoda, indicate considerable cytological stability in these species.     

Plant responses to selective grazing by bison: interactions between light,herbivory and water stress

Two abundant tallgrass prairie forb species, Ambrosia psilostachya and Vernonia baldwinii, are commonly found intact in patches where the grasses have been selectively grazed by bison. Microclimatic patterns and physiological responses of these forbs were measured in grazed and ungrazed patches. These experiments demonstrated that bison herbivory indirectly enhanced water availability and productivity of forbs growing in grazed patches. This was due primarily to the reduction in transpiring grass leaf area in grazed patches and an increase in light availability. In grazed patches, incident light at forb mid-canopy height was 53% greater than ungrazed sites at midseason and soil temperatures were always warmer (e.g., 10°C at 5 cm), perhaps enabling forbs to initiate growth earlier in the spring. Enhanced leaf xylem pressure potential and stomatal conductance in plants in grazed areas were most evident when water availability was low (i.e., late in the growing season and over short-term dry periods characteristic of the tallgrass prairie environment). Relative to individuals in ungrazed areas, end-of-season biomass of A. psilostachya was 40% greater and reproductive biomass and head number of V. baldwinii was 45% and 40% greater, respectively, in plants in grazed patches. A favorable growing environment maintained in grazed patches during periods of water limitation enhances carbon gain in forbs leading to increased biomass and potential fitness.     

Contribution to the cytotaxonomy of Oryzopsis (Poaceae)

Meiotic studies were performed in twelve populations of four Oryzopsis species (O. pubiflora, O. lateralis, O. holciformis var. longiglomis and O. barbellata) to obtain data on the ploidy level and cytological evolution of the genus. The chromosome number 2n=2x=24 was revealed in all the species and populations studied. The present and other studies show the occurrence of two basic chromosome numbers in the genus, i.e. x=11 and x=12. Although Oryzopsis species and populations studied are diploid and are expected to form only bivalents in metaphase of meiosis‐I, quadrivalents were observed in O. pubiflora and O. lateralis, possibly due to the occurrence of heterozygote translocations. B‐chromosomes of 0–2 were observed in all species and populations studied. This is the first report of the occurrence of B‐chromosomes in the genus Oryzopsis. Several meiocytes showed the presence of double chromosome number in O. lateralis, and multipolar cells were observed in populations of O. barbellata, O. lateralis and O. holciformis var. longiglomis. The occurrence of large pollen grains (possibly unreduced) was observed along with smaller (normal) pollen grains in these species. Significant differences observed in chiasma frequency and distribution among studied species may be of use in species delimitation. The Kakan population differed significantly from the other populations of O. lateralis in meiotic characteristics. If such cytological differences are accompanied by morphological variation (under investigation), we may consider this population as a new variety or subspecies.     

Relationships and Hybridization among Smilax china and Its Affinities: Evidence from Allozyme Data

Smilax china L. is a widespread species in China with different ploidy levels. It is morphologically similar to S. davidiana, S. trinervula, and S. glauco-china. In this study, the chromosome number and the variation in allozyme patterns of eight enzyme systems with 25 alleles in 11 populations of S. china and three affinitive species were investigated. The allozyme data, together with morphological and cytological data, suggest that S. glauco-china is not closely related to the other taxa investigated. The diploid species S. davidiana and S. trinervula are involved as ancestor species and share great introgressions with S. china. In S. china, populations from Guilin and Guiyang are allotetraploid; their diploid progenitors probably are diploid populations of S. china and S. trinervula. The results suggest this species arose from multiple origins.     

Examination of the hybrid origin of the wild potato Solanum ruiz-lealii Brücher

The common potato, tetraploid Solanum tuberosum spp. tuberosum L. (tbr), has a narrow genetic base but a large number of related tuber-bearing species that harbor genetic diversity for agronomic characters. The taxonomic status of Solanum ruiz-lealii Brücher (rzl), a diploid species endemic to Mendoza province, Argentina, is controversial. It has been described as a new species of non-hybrid origin and as a natural hybrid between S. kurtzianum Bitt. & Wittm. (ktz) and S. chacoense Bitt. (chc). The hypothesis of the hybrid origin of rzl is examined systematically for the first time by phenetic analyses of morphological and molecular (SSR markers) data, and cytological analyses of interspecific hybrids. The morphological, cytological and molecular data are congruent, and suggest that rzl is not a recent natural hybrid between the ktz and the chc populations studied but has probably originated by divergence of chc, or by hybridization between chc and another taxon.     

Evidence bearing on the origin of infraspecific disjunction inSophora gypsophila (Fabaceae)

Morphometrical, cytological, chemical and ecological data are presented concerning the origin of infraspecific disjunction inSophora gypsophila, its 2 varieties, var.gypsophila and var.guadalupensis, being known from only 2 very local sites which are separated by approximately 300 km. It is concluded that the populations are remnants of a much more widespread, highly variable sib of Wisconsin time.     

Genetic diversity of Philaenus spumarius and P. tesselatus (Hemiptera,Aphrophoridae): implications for evolution and taxonomy

The meadow spittlebugs Philaenus spumarius and P. tesselatus are closely related taxa with uncertain taxonomic position in the light of previous morphological, ecological, cytological and molecular research. Despite morphological homogeneity of P. spumarius (with the exception of high colour and pattern polymorphism) across its wide Holarctic range, it is possible that additional taxa (species or subspecies) exist. Philaenus spumarius is a potentially important pest in parts of its range where it was introduced. We used DNA markers to describe the genetic diversity of P. spumarius and P. tesselatus and to verify the taxonomic status of P. tesselatus and remote populations of the former species. The mitochondrial (cytochrome B) data showed that there are two main groups encompassing a northeastern (Asia and north‐central Europe) and a southwestern (Mediterranean area and western Europe, including North American specimens) clade. According to the elongation factor‐1α gene, there are three main clades: northeastern (Eurasiatic clade, E1), southeastern (east Mediterranean – Caucasus clade, E2) and southwestern (Iberian clade, E3). These two or three mitochondrial and nuclear clades could be considered as separate taxonomic units. On the other hand, all studied individuals of both species possessed the same internal transcribed spacer 2 haplotype. American specimens most probably originated from some western European populations. All studied specimens of P. tesselatus belong to the southwestern clade and western Mediterranean cluster. Therefore, together with cytological data, its species status is doubtful. To definitively solve the taxonomic status of P. tesselatus and populations of P. spumarius, further research using more samples and more genetic markers are needed.     

ALLOPOLYPLOID SPECIATION IN TRAGOPOGON: INSIGHTS FROM CHLOROPLAST DNA

Tragopogon mirus and T. miscellus are classic examples of recent allopolyploid speciation. Previous studies documented that the diploid parents of T. mirus are T. dubius and T. porrifolius and those of T. miscellus are T. dubius and T. pratensis. Restriction fragment analysis of chloroplast DNA (cpDNA) provided additional evolutionary information regarding the origin of the allotetraploids. We analyzed 39 populations of the three diploid and two allotetraploid species with 18 restriction endonucleases. Six restriction site mutations and three length mutations were identified; these unambiguously differentiated the parental diploids. Previous morphological, cytological, and electrophoretic analyses indicated that T. mirus arose independently at least three times. Chloroplast DNA data suggest that T. porrifolius has consistently been the maternal parent of T. mirus. Chloroplast DNA data also document a minimum of two independent origins of T. miscellus: 1) populations from Pullman, Washington, have T. dubius as the maternal parent; 2) all other populations have T. pratensis as the maternal parent. Two restriction site mutations implicate certain populations of T. dubius in the formation of the Pullman populations of T. miscellus. The two rare diploid species, T. porrifolius and T. pratensis, typically appear as maternal parents of the allotetraploids; the widespread and common T. dubius is the maternal parent only for two populations of T. miscellus. These data suggest that pollen load may be an important factor in determining the male and female parents of allopolyploid angiosperms.     

A microsatellite linkage map for Drosophila montana shows large variation in recombination rates,and a courtship song trait maps to an area of low recombination

Current advances in genetic analysis are opening up our knowledge of the genetics of species differences, but challenges remain, particularly for out‐bred natural populations. We constructed a microsatellite‐based linkage map for two out‐bred lines of Drosophila montana derived from divergent populations by taking advantage of the Drosophila virilis genome and available cytological maps of both species. Although the placement of markers was quite consistent with cytological predictions, the map indicated large heterogeneity in recombination rates along chromosomes. We also performed a quantitative trait locus (QTL) analysis on a courtship song character (carrier frequency), which differs between populations and is subject to strong sexual selection. Linkage mapping yielded two significant QTLs, which explained 3% and 14% of the variation in carrier frequency, respectively. Interestingly, as in other recent studies of traits which can influence speciation, the strongest QTL mapped to a genomic region partly covered by an inversion polymorphism.     

CHARACTERIZATION OF POLLEN ANTIGENS FROM AMBROSIA L. (COMPOSITAE) AND RELATED TAXA BY IMMUNOELECTROPHORESIS AND RADIAL IMMUNODIFFUSION

The pollen antigens of various Ambrosia and related species were studied to learn whether substances closely related to antigen E (the major allergen of Ambrosia artemisiifolia) were present. After conventional immunoelectrophoresis, pollen extracts from six Ambrosia species each produced at least one pronounced precipitin line with antiserum for purified antigen E. Electrophoretic mobility was the same for several species (A. artemisiifolia, A. bidentata, A. psilostachya, and A. trifida) but was relatively lower for A. acanthicarpa and A. ambrosioides. Precipitin rings were also produced when pollen extracts of the various Ambrosia species were subjected to radial immunodiffusion in agarose which contained antiserum for purified antigen E. There was great variation among the Ambrosia species with respect to precipitin ring diameters. The variation may be due to differences among species in content of the antigen E-like substances or to altered interaction with the immobilized antibody. Crossed (2-dimensional) immunoelectrophoresis was shown to be useful for characterizing Ambrosia pollen antigens. Pollen extracts from A. artemisiifolia produced eight pronounced precipitin bands and at least eight faint, relatively fast-moving bands after crossed immunoelectrophoresis with antiserum against a whole pollen extract from the same species. One of the pronounced bands contained antigen E.     

The role of the transposable element hobo in the origin of endemic inversions in wild populations of Drosophila melanogaster

Evidence from in situ hybridizations of DNA from the transposable element hobo to polytene salivary gland chromosome squashes reveals that hobo occupies both cytological breakpoints of three of four endemic inversions sampled from natural populations of Drosophila melanogaster in the Hawaiian islands. The fourth endemic inversion has a single hobo insert at one breakpoint. Cosmopolitan inversions on the same chromosomes do not show this association. Frequencies of both endemic and cosmopolitan inversions in Hawaiian populations fall in ranges typical for natural populations of D. melanogaster sampled worldwide, suggesting that these results may be typical of other regions besides Hawaii. This appears to be the first direct demonstration that transposable elements are responsible for causing specific rearrangements found in nature; consequently, it is also the first direct demonstration that chromosome rearrangements can arise in nature in a manner predicted by results of hybrid dysgenic crosses in the laboratory. Possible population genetic and evolutionary consequences are discussed.     

Taxonomical and chorological study on the central Mediterranean Basin endemic Arenaria bertolonii Fiori & Paol. (Caryophyllaceae)

Arenaria bertolonii Fiori & Paol. is an orophyte and endemic European species of Italy and France. The name Stellaria saxifraga Bertol. (basionym of A. bertolonii) is typified on a herbarium specimen kept in BOLO. Infraspecific variability of the species is discussed and a comparison with related taxa included in the Subg. Arenaria was made on the basis of morphological analyses and chorological and cytological data. At the sectional level, the results show that A. bertolonii is clearly separate from the morphological and chorological points of view, thus supporting the proposal for a new monotypic section (Sect. Italiae Iamonico) of central Mediterranean species. The analysis of infraspecific variability instead highlighted overlapping morphological characteristics; the distribution areas of the infraspecific taxa are sympatric and any cytological difference is lacking, thus pointing to a synonymization of the names. Notes on the ecology and distribution of A. bertolonii are also provided.     

CHROMOSOME NUMBERS AND PHYLOGENY IN MELAMPODIUM (COMPOSITAE)

The haplord chromosome numbers of n = 9, 10, 11, 12, 18, 20, 23, 25 ± 1, 27, 30, and 33 have been reported by various authors from 26 of the 37 recognized species of Melampodium. A chromosomal survey of 375 plants from 275 different populations suggests that the recorded numbers are stable within the genus and that infraspecific euploidy and aneuploidy are uncommon. These chromosome numbers can be arranged numerically, with morphological and limited cytogenetic substantiation, into four euploid series of x2 = 9, 10, 11, and 12. Of these four groups of species, the x = 10 series is the largest and morphologically most diverse. This consideration, along with additional evidence from the morphology of sterile disc ovaries, suggests that x = 10 is the ancestral chromosomal base in Melampodium. A comparison of morphological and cytological data from the closely related genera, Acanthospermum and Lecocarpus, indicates that the latter are probably on a common base of x = 11. Present day distributional patterns of all three genera support the hypothesis that x = 10 is the ancestral base for the entire complex.     

Genetic characterization and intra-generic relationships of Artemia monica Verrill and A. urmiana Günther

Allozyme variation encoded for by 22 enzyme loci analyzed with starch-gel electrophoresis from samples of gonochoristic Artemia monica and A. urmiana collected from Lake Urmia, Iran and from Mono Lake, CA, USA, respectively, are compared and contrasted with data from representative gonochoristic populations of A. franciscana, A. persimilis and A. salina, as well as diploid, triploid, tetraploid, and pentaploid parthenogenetic forms. Values for parameters measuring degree of genetic variability (number of alleles per locus, proportion of polymorphic loci, and expected heterozygosity) in A. monica and A. urmiana were among the highest in the genus (1.76, 0.46, 0.19, and 2.19, 0.55, and 0.14, respectively). For A. monica, possible factors promoting its high genetic variability are discussed. Mean values for Nei's D between A. monica and A. franciscana were very low (0.09) and consistent with reported cytological and morphological similarities, thus the physiological differentiation which distinguishes the former must involve differences at very few loci. D values from A. urmiana to rest of the gonochoristic species (0.95) are consistent with its taxonomic status and distinctive morphology, while its low genetic distance to the monophyletic Artemia parthenogenetic lineage (mean D = 0.48) suggests a recent common ancestry.     

Genetic diversity of Artemisia populations in central and north Saudi Arabia based on morphological variation and RAPD polymorphism

The analysis of morphological variation and RAPD polymorphism distinguished populations of A. herba alba from populations of A. judaica and A. monosperma. Higher morphological diversity is found in A. herba alba compared to the other two species, but molecular data derived from RAPD polymorphism also indicated that A. herba alba is more polymorphic than the other two species. However, RAPD fingerprinting also indicated sharp polymorphism among populations of both A. judaica and A. monosperma. Geographic and local ecological variations related to elevation of the sites of the examined populations may be regarded to have played a role in the genetic diversity of the examined populations of Artemisia species in the study area. The results are important for future plans for sustainable conservation of medicinal plants in Saudi Arabia. However, extensive sampling of the examined Artemisia species populations is required, and more regional data should be obtained from other distribution areas.     

Cytotaxonomy of the Prosimulium (Diptera: Simuliidae) of Western Asia

Chromosomal analysis of more than 500 larval black flies from 19 sites in Armenia and Turkey revealed five taxa in the Prosimulium hirtipes group: Prosimulium frontatum Terteryan, Prosimulium rachiliense Djafarov cytoform ‘A,’ P. rachiliense Djafarov cytoform ‘B,’ Prosimulium tomosvaryi (Enderlein), and a new species of Prosimulium. To associate the names rufipes (Meigen) and tomosvaryi with cytological entities, larvae from the respective type localities in Germany were characterized chromosomally. Prosimulium frontatum is restricted to the Caucasus Mountains where studied populations have five unique inversions. It is most closely related to cytoforms ‘A’ and ‘B’ of P. rachiliense, the three taxa sharing one unique inversion. The two cytoforms of P. rachiliense are separated by about 1200 km, obscuring decisions about their reproductive isolation. The names rachiliense and possibly pronevitschae Rubtsov apply to cytoform ‘A’ in Armenia, whereas the name fulvipes (Edwards) might apply to cytoform ‘B’ in Turkey and to material formerly identified in Turkey as P. rufipes. Populations of P. tomosvaryi in Armenia are chromosomally distinct from previously studied populations in Europe and Morocco, although tied to European and Turkish populations by a shared X‐linked inversion. We conservatively view Armenian, European, and Turkish populations of P. tomosvaryi as a single, polymorphic species. A new species, chromosomally related to P. hirtipes (Fries) and P. tomosvaryi by two uniquely shared inversions, was discovered in Turkey. © 2014 The Linnean Society of London     

The distribution of diploids and polyploids of theScilla scilloides complex in the northeastern district of China

A cytological analysis was made of 1504 individuals ofScilla scilloides Druce from the northeastern district of China. In terms of genome combination four cytotypes were found: AA (90.95%), AAAA (0.07%), AABB (8.92%) and AABB+2 (0.07%). In the cytotypes A and B denote genome A (x=8) and genome B (x=9), respectively. Most of 18 natural populations examined consist of one cytotype: indeed, all individuals examined of 15 of the populations are AA diploids, those of one population AABB allotetraploids, and individuals examined of two other populations have two cytotypes each, AA and AAAA, and AABB and AABB+2. In karyotype the genome A of the AA and AAAA was different from that of the AABB, and a direction of morphological change of chromosomes in the genome A is discussed in light of results of hybridization experiments reported elsewhere. Taken together with information available for the distribution of different cytotypes in China, Korea and Japan, the results of the present study support the view of Maekawa thatScilla scilloides was native to mainland China and lately introduced to Japan.     

Electrophoretic and cytological evidence for genetic heterogeneity and the hybrid origin ofAthyrium oblitescens

Athyrium oblitescens, a putative hybrid species, was examined electrophoretically and cytologically to clarify its origin. Allozyme data showed thatA. oblitescens consisted of at least three allozyme types, designated Type C, Type O and Type W. Genotypic compositions of Type C and Type W suggested that they were derived from independent hybridizations betweenA. otophorum andA. clivicola and betweenA. otophorum andA. wardii, respectively. Contrary to previous reports of tetraploidy inA. oblitescens and its hypothesized parent species, cytological observation revealed that Type C and Type W were both hexaploids. Possible pathways for the origin of these hexaploids are proposed. Type O was not genetically distinct fromA. otophorum by either electrophoretic or cytological analyses, and thus there was no evidence of hybrid origin.