Comparative capitular morphology and anatomy of Coreopsis L. and bidens L. (compositae), including a review of generic boundaries

The capitular and floral morphology and anatomy ofBidens L. andCoreopsis L. were studied. All the North American species ofCoreopsis were studied. Selected species ofBidens from North and South America andCoreopsis from South America were included. The results were compared with previous observations on African species ofBidens (incl.Coreopsis). Emphasis was given to character states of the ray florets, paleae, stylearm apices, outer phyllaries, achenes, and pollen grains. Some of the character states are unique features ofCoreopsis, e.g., globular and elongately conical receptacles, deltoid outer phyllaries, truncate and indistinctly 3–5-dentate, 3–4-lobed ray florets, narrowly spathulate paleae, subulate paleae with linear-filiform upper half, hairy and apically 3-cleft paleae, truncate, convex or shallowly conical stylearm apices with the sweeping hairs limited to the area above the stigmatic surfaces and the orbicular to circular achenes. The cylindric setaceous pappus bristles so commonly encountered inBidens are unknown inCoreopsis. The pappus bristles inCoreopsis are paleaceous but similar, though thicker ones are also found in African species ofBidens (incl.Coreopsis) with winged achenes. Twin-celled hairs (setulae) with differing degrees of wall thickness are found on the achenes ofCoreopsis sect.Pseudoagarista (Mexico and South America),Coreopsis sect.Pugiopappus (California), AfricanBidens with winged achenes (e.g.,B. prestinaria, B. macroptera) and some North AmericanBidens (e.g.,B. aristosa). Similar sclerotic parenchyma make up the achenial wings of species in both genera. These may be interpreted as homologous structures, indicating the underlying similarity of these taxa and their derivation from a common ancestral stock.     

The phytomelanin layer in traditional members of Bidens and Coreopsis and phylogeny of the Coreopsideae (Compositae)

The phytomelanin layer on the pericarp of cypselae (achenes) of many members of traditional Bidens and Coreopsis, both considered polyphyletic, was studied with the help of scanning electron (SEM) and light (LM) microscopes. It is found to be more prominent in taxa kept within Bidens than in Coreopsis. The black ‘peg‐like’ phytomelanin found in traditional members of Bidens is also found in some members of Coreopsis. Some traditional members of Coreopsis display distinctive pericarp morphology but lack phytomelanin. The pericarp in Bidens is striated, i.e. it is interrupted by longitudinal bands of parenchyma through which the embryo emerges during seed germination. No striation was found in cypselae of traditional Coreopsis. Emergence of the seed in taxa with this type of pericarp morphology is observed to be by rupturing the carpel wall along the sutures. Characteristic morphology of the phytomelanin layer and other cellular secretions on the pericarp in representative species of these genera and segregates as well as the probable adaptive value of this layer and that of the parenchyma is discussed. Coreopsis sect. Tuckermannia (Nutt.) Blake, C. sect. Pugiopappus (A. Gray) Blake, and C. sect. Euleptosyne (A. Gray) Blake, are elevated to the genus Leptosyne DC., while Coreopsis sect. Electra (DC.) Blake is returned to Electra DC. A key to the segregate genera and the remaining sections of Coreopsis as well as new combinations and synonyms are provided.     

Low Allozymic Variation in the Bidens pilosa L. Complex (Asteraceae)

Bidens alba, B. subalternans, and B. pilosa form a complex group based on their morphological similarities. Bidens pilosa L. and B. subalternans DC. are herbs with a wide distribution in agricultural and disturbed areas. Bidens alba (L.) DC. varies in size from herb to subshrub and has a coastal distribution. Enzyme electrophoresis was used to evaluate genetic diversity in 12 populations of Bidens. All but three loci (Lap-1, Est, and Got) were monomorphic. Est-1 and Got were polymorphic only in B. alba. Lap-1 was polymorphic only in B. pilosa and B. subalternans. The estimates of genetic variability were low for all three taxa and all of the populations studied. Genetic diversity varied from 0.01 to 0.03. Mean genetic identities were high among populations of each species (0.99 for B. alba and 1.00 for B. pilosa and B. subalternans) and among the three species (1.00). Bidens pilosa and B. subalternans could be considered a single species if the taxonomy of the group were based solely on isozyme data.     

Sesquiterpene and polyacetylene profile of the Bidens pilosa complex (Asteraceae: Heliantheae) from Southeast of Brazil

The pantropical weed Bidens pilosa (Asteraceae) is a species with several taxonomic problems. Recently it has been shown to be a complex of different species. To shed light on this problem in Brazil, dichloromethane extract of leaves of several populations corresponding to three proposed species for the complex in southeastern Brazil (B. pilosa, Bidens alba and Bidens subalternans) were analyzed by GC–MS. Twenty-four substances were detected, of which four resemble polyacetylenes, the others sesquiterpenes. Five sesquiterpenes tentatively identified as E-caryophyllene, α-humulene, germacrene-D, bicyclogermacrene and α-muurolene were found in all three Bidens species. The polyacetylene phenylhepta-1,3,5-triyne was identified only in B. alba. Multivariate analysis (cluster and principal component analyses) separated the three entities, suggesting that these compounds could represent a useful tool to distinguish species in the B. pilosa complex.     

Insect herbivores associated with the introduced weed Bidens frondosa L. (Asteraceae) in Korea,and their potential role as augmentative biological control agents

The annual herb Bidens frondosa L., native to North America, is an invasive weed. Currently no information is available on the insect herbivores associated with this weed in Korea. A survey was carried out at two‐weekly intervals from May to October 2008 at two sites, and the incidence and abundance of various insect herbivores studied. A total nine species of insects was recorded and among them the defoliating caterpillar Hadjina chinensis (Wallengren) (Lepidoptera) was the only species known to have host plants restricted to genus Bidens. Further host specificity studies are required to evaluate the potential of this insect as a candidate for augmentative biological control agent for B. frondosa in Korea. All other insect species are either polyphagous or known crop pests.     

Generic relationships of Oparanthus and Petrobium,especially with reference to Bidens (Compositae,Heliantheae, Coreopsidinae)

Oparanthus with two species from the Tubuai Islands of the South Pacific Ocean and the monotypicPetrobium from St. Helena in the South Atlantic are judged to belong more properly withinBidens. Comparisons of diagnostic morphological features are provided, and the necessary combinations are made, includingBidens rapensis (F. Brown) Stuessy andB. tubuaiensis (F. Brown) Stuessy.     

Isozyme variability among cryptic species of Botrychium subgenus Botrychium (Ophioglossaceae)

The systematics of Botrychium subgenus Botrychium has been controversial, primarily because reduction in frond size and complexity has limited the number of characters available for discrimination of species. The recognition of many polyploid species has magnified the difficulty of classification because allopolyploids are often morphologically intermediate between their progenitor diploids. In order to evaluate species limits and sectional boundaries, we surveyed and compared 16 of the 24 currently recognized species for isozymic variation. Little or no intrapopulational variation was detected, but the variation present was consistent with the hypothesis that Botrychium species are primarily inbreeding. Interspecific comparisons distinguished six diploid species and provided evidence of molecular differentiation between the cryptic sister species B. lunaria and B. crenulatum. Evidence of possible progenitor/descendant relationships was found for certain diploid/polyploid relationships. Using enzyme bands shared between species, realignment of the sectional assignment of several species is proposed. Anomalous banding patterns in certain individuals suggested that gene silencing or homoeologous chromosome pairing might be operating in B. minganense, B. hesperium, and B. matricariifolium. Isozyme data also showed that some populations of species presumed to be uniformly diploid possessed isozyme patterns typical of polyploids. All available molecular data indicate that members of Botrychium subgenus Botrychium are actively evolving at diploid and polyploid levels.     

Chloroplast DNA variation in diploid and polyploid species of Bromus (Poaceae) subgenera Festucaria and Ceratochloa

Summary Chloroplast DNA (cpDNA) restriction endonuclease patterns are used to examine phylogenetic relationships between Bromus subgenera Festucaria and Ceratochloa. Festucaria is considered monophyletic based on the L genome, while Ceratochloa encompasses two species complexes: the B. catharticus complex, which evolved by combining three different genomes, and the B. carinatus complex, which is thought to have originated from hybridization between polyploid species of B. catharticus and diploid members of Festucaria. All species of subgenus Ceratochloa (hexaploids and octoploids) were identical in chloroplast DNA sequences. Similarly, polyploid species of subgenus Festucaria, except for B. auleticus, were identical in cpDNA sequences. In contrast, diploid species of subgenus Festucaria showed various degrees of nucleotide sequence divergence. Species of subgenus Ceratochloa appeared monophyletic and phylogenetically closely related to the diploid B. anomalus and B. auleticus of subgenus Festucaria. The remaining diploid and polyploid species of subgenus Festucaria appeared in a distinct grouping. The study suggests that the B. catharticus complex must have been the maternal parent in the proposed hybrid origin of B. carinatus complex. Although there is no direct evidence for the paternal parent of the latter complex, the cpDNA study shows the complex to be phylogenetically very related to the diploid B. anomalus of subgenus Festucaria.     

CHLOROPLAST DNA RESTRICTION SITE VARIATION AND THE PHYLOGENY OF COREOPSIS SECTION COREOPSIS (ASTERACEAE)

Restriction site variation in chloroplast DNAs (cpDNAs) of Coreopsis section Coreopsis was employed to assess divergence and phylogenetic relationships among the nine species of the section. A total of fourteen restriction site mutations and one length mutation was detected. Cladistic analysis of the cpDNA data produced a phylogeny that is different in several respects from previous hypotheses. CpDNA mutations divide the section into two groups, with the two perennial species C. auriculata and C. pubescens lacking any derived restriction site changes. The other seven species are united by five synapomorphic restriction site mutations and the one length mutation. These seven species fall into three unresolved clades consisting of 1) the remaining three perennial species, C. grandiflora, C. intermedia, and C. lanceolata; 2) three annual species, C. basalis, C. nuecensoides, and C. nuecensis; and 3) the remaining annual, C. wrightii. The cpDNA data suggest that, although the perennial habit is primitive within the section, the annual species of section Coreopsis have likely not originated from an extant perennial species. The estimated proportion of nucleotide differences per site (given as 100p) for the cpDNAs of species in the section ranges from 0.00 to 0.20, which is comparable to or lower than values reported for other congeneric species. The low level of cpDNA divergence is concordant with other data, including cross compatibility, interfertility and allozymes, in suggesting that species of the section are not highly divergent genetically.     

Winter low temperature disturbance in the southern subtropics of China promotes the competitiveness of an invasive plant

Winter low temperature disturbance in the southern subtropics has important effects on the weed community structure, but the role of uniquely low temperatures in biological invasions is unclear. Here, we examined the competitive effects of an invasive plant, Bidens pilosa L., and its native congener, Bidens biternata (Lour.) Merr. et Sherff, during high and low temperature seasons to determine whether low temperatures promote the competitiveness of B. pilosa in the southern subtropics of China. The growth and physiological responses of the two Bidens species to low (10/5 °C) and optimum (30/25 °C) temperatures were examined to determine how the invasive B. pilosa responds to low temperature stress. Our results showed that the competitive balance index values of B. pilosa in low temperature seasons were significantly higher than those in high temperature seasons, which implied that low temperatures may be more beneficial to the competitiveness of B. pilosa than high temperatures in the southern subtropics. The smaller decline in the relative growth rate and the photosynthetic ability of B. pilosa compared with B. biternata under low temperature stress indicated that the former was less negatively affected by low temperature than the latter. A higher DPPH^· (1.1-diphenyl-2-picrylhy-drazyl) scavenging rate and greater heat-stable protein content in B. pilosa under low temperatures might help the invasive plant to maintain more effective physiological functions and thus a higher growth rate. Overall, the uniquely low temperature in the southern subtropics of China is expected to promote the invasiveness of the exotic B. pilosa.

     

PHYLOGENETIC IMPLICATIONS OF DIFFERENCES IN NUMBER OF PLASTID PHOSPHOGLUCOSE ISOMERASE ISOZYMES IN NORTH AMERICAN COREOPSIS (ASTERACEAE: HELIANTHEAE: COREOPSIDINAE)

Enzyme electrophoresis was employed to ascertain the number of loci encoding plastid phosphoglucose isomerase (PGI) in species representing all sections of North American Coreopsis. Several species from each of the closely related genera Bidens, Coreocarpus, Cosmos, and Thelesperma were also examined. Species in nine of the 11 sections of North American Coreopsis have two isozymes for plastid PGI, and nearly all species examined in the four other genera also have two (one species has three) isozymes. Since most diploid vascular plants have one plastid PGI isozyme, a gene duplication probably occurred in an ancestor that is common to Coreopsis and the other four genera. That is, two isozymes represent the ancestral number for Coreopsis. The two sections (Electra and Anathysana) apparently lacking the duplication are closely related woody plants restricted largely to Mexico. One gene encoding plastid PGI ostensibly was silenced in a common ancestor of these two sections. This is concordant with other data suggesting a close relationship between the two sections, i.e., they appear to represent a monophyletic group. The electrophoretic data also indicate that 1) the enigmatic monotypic section Silphidium is more closely related to eastern North American sections and not derived from section Electra; and 2) section Anathysana is not ancestral to the three California sections Leptosyne, Pugiopappus, and Tuckermannia; rather, it represents a terminal element closely related to and possibly derived from section Electra.     

Anti-diabetic properties of three common Bidens pilosa variants in Taiwan

Bidens pilosa L. var. radiata (BPR), B. pilosa L. var. pilosa (BPP), and B. pilosa L. var. minor (BPM) are common variants of a plant often used as a folk remedy for diabetes in Taiwan. However, the three variants are often misidentified and little is known about their relative anti-diabetic efficacy and chemical composition. In this paper, we have first developed a method based on GC–MS and cluster analysis with visualization to assist in rapidly determining the taxonomy of these three Bidens variants. GC–MS was used to determine the chemical compositions of supercritical extracts, and differences and similarities in the variants were determined by hierarchical cluster analysis. Next, the HPLC profiles of the methanol crude extracts in the Bidens plants and evaluated anti-diabetic effects of methanol crude extracts were compared, as well as three polyacetylenic compounds of the Bidens plants using db/db mice. Single-dose and long-term experiments showed that the BPR extract had higher glucose-lowering and insulin-releasing activities than extracts from the other two variants, and that cytopiloyne was the most effective pure compound among the three polyacetylenic compounds. BPR extract and cytopiloyne also significantly reduced the percentage of the glycosylated hemoglobin A1c in db/db mice. Besides, both animal studies and HPLC analysis demonstrated a good correlation between anti-diabetic efficacy of the Bidens extracts and the particular polyacetylenes present.     

MICROSPOROGENESIS IN MALE-STERILE AND HERMAPHRODITIC PLANTS OF NINE GYNODIOECIOUS TAXA OF HAWAIIAN BIDENS (ASTERACEAE)

Microsporogenesis was investigated in hermaphroditic and male-sterile plants in nine gynodioecious taxa of Hawaiian Bidens. Normal microsporogenesis in hermaphrodites and the onset of abortion in male steriles were similar in all taxa and in a hybrid between two gynodioecious species. The early abnormal vacuolation of tapetal cells is the first visible evidence leading to premeiotic abortion of microsporogenesis in male steriles. The sporogenous cells disintegrate rapidly after the vacuolation of the tapetum, resulting in a shrunken, indehiscent anther which is composed of only the epidermal layer with some remnant cells of the endothecium and the connective at anthesis. In hermaphrodites, the tapetal cells remain dense and undergo karyokinesis to become binucleate during meiosis I. The tapetum becomes plasmodial after microspores are released from tetrads and gradually disappears during pollen formation. The genetic factor(s) which cause the abortion act with remarkable precision and consistency in all taxa investigated. This suggests that gynodioecy in all Hawaiian Bidens is homologous and the establishment of male sterility in Hawaiian Bidens occurred only once. The spread of the genetic male-sterile factor(s) may be the result of adaptive radiation of the original gynodioecious species or natural interspecific hybridization.     

The application of chloroplast DNA clones in identifying maternal donors for polyploid species of Stylosanthes

Organelle inheritance is strictly maternal for most plant species. This property makes organelle DNAs ideal material for identifying the maternal parents of polyploid species. A chloroplast DNA (cpDNA) clone from Stylosanthes was identified. Together with rice cpDNA clones, it was used in identifying putative maternal donors for polyploid Stylosanthes species. Of 15 taxa for which 2 or more accessions each were analysed, intra-taxon cpDNA variation was only identified within the diploid species S. viscosa. Of the nine basal diploid genomes identified, results from the cpDNA probes strongly suggested that Genome A1 is the maternal donor to S. aff. hamata, S. scabra, S. aff. scabra, S. sericeiceps and S. tuberculata and that it may also be the maternal donor to the hexaploid S. erecta; Genome C is the maternal donor to S. sp. A, S. mexicana, S. subsericea and S. sundaica; Genome E is the maternal donor to S. capitata. The maternal donor to S. fruticosa is likely to be Genome B3, and that to S. ingrata is likely to be Genome A1. The maternal donor to S. sympodialis, although similar to those of S. sp. genotypes, may not be included amongst the diploid taxa analysed in this study. The fact that none of the polyploid genotypes produced cpDNA fragments from more than one of their respective progenitors indicated that cpDNA in Stylosanthes is strictly maternally inherited. Received: 17 September 1999 / Accepted: 20 April 2000     

Differential responses to fertilization and competition among invasive,noninvasive alien,and native Bidens species

Comparative studies of invasive, noninvasive alien, and native congenic plant species can identify plant traits that drive invasiveness. In particular, functional traits associated with rapid growth rate and high fecundity likely facilitate invasive success. As such traits often exhibit high phenotypic plasticity, characterizing plastic responses to anthropogenic environmental changes such as eutrophication and disturbance is important for predicting the invasive success of alien plant species in the future. Here, we compared trait expression and phenotypic plasticity at the species level among invasive, noninvasive alien, and native Bidens species. Plants were grown under nutrient addition and competition treatments, and their functional, morphological, and seed traits were examined. Invasive B. frondosa exhibited higher phenotypic plasticity in most measured traits than did the alien noninvasive B. pilosa or native B. bipinnata. However, differential plastic responses to environmental treatments rarely altered the rank of trait values among the three Bidens species, except for the number of inflorescences. The achene size of B. frondosa was larger, but its pappus length was shorter than that of B. pilosa. Two species demonstrated opposite plastic responses of pappus length to fertilization. These results suggest that the plasticity of functional traits does not significantly contribute to the invasive success of B. frondosa. The dispersal efficiency of B. frondosa is expected to be lower than that of B. pilosa, suggesting that long‐distance dispersal is likely not a critical factor in determining invasive success.     

Hybridization of alien and aboriginal taxons of <Emphasis Type="Italic">Bidens</Emphasis> L. genus in Eastern Europe

Earlier it was suggested, based on study of the morphological features, that a new taxon of burmarigold, which had been noted in recent decades in several locations on the territory of Russia and neighboring countries and described as an alien species of Bidens connata, is in fact a hybrid species that arose in Europe. This hypothesis was confirmed by the molecular genetic method. A complex of taxa of the genus Bidens from various parts of the areal and their F1 first generation offspring were studied, and a polymerase chain reaction was performed using ISSR primers. It was established that the taxon investigated represents a complex of hybrids and recurrent hybrids that arose in the European part of Russia independently by hybridization of the alien B. frondosa and the aboriginal B. cernua.     

A chromosome-specific sequence common to the B genome of polyploid wheat and Aegilops searsii

A low-copy, non-coding chromosome-specific DNA sequence, isolated from common wheat, was physically mapped to the distal 19% region of the long arm of chromosome 3B (3BL) of common wheat. This sequence, designated WPG118, was then characterized by Southern hybridization, PCR amplification and sequence comparison using a large collection of polyploid wheats and diploid Triticum and Aegilops species. The data show that the sequence exists in all polyploid wheats containing the B genome and absent from those containing the G genome. At the diploid level, it exists only in Ae. searsii, a diploid species of section Sitopsis, and not in other diploids including Ae. speltoides, the closest extant relative to the donor of the B genome of polyploid wheat. This finding may support the hypothesis that the B-genome of polyploid wheat is of a polyphyletic origin, i.e. it is a recombined genome derived from two or more diploid Aegilops species.     

AFLP characterization of natural populations of Berberis (Berberidaceae) in Patagonia, Argentina

 AFLP markers were used to analyse the intra- and interspecific relationships among 22 natural populations of 13 Patagonian species of Berberis and the relationships among the taxa belonging to homoploid and polyploid complexes. Seven primer combinations gave rise to 231 AFLP bands, of which 199 were polymorphic. Correspondence between AFLP data, morphological traits and seed protein bands was also assessed. The dendrogram inferred from AFLP fingerprints showed that, in general, populations of the same species formed closely related groups with high coefficients of similarity. Principal co-ordinates analysis showed two separate subgroups: (i) B. bidentata and their putative ancestors –B. darwinii and B. linearifolia– which form a homogamic group, and (ii) B. buxifolia, B. heterophylla and B. parodii– which could form a polyploid hybrid complex. Received March 21, 2001 Accepted September 11, 2001     

RAPD analysis of the intraspecific and interspecific variation and phylogenetic relationships of <Emphasis Type="Italic">Aegilops</Emphasis> L. species with the U genome

RAPD analysis was used to study the genetic variation and phylogenetic relationships of polyploid Aegilops species with the U genome. In total, 115 DNA samples of eight polyploid species containing the U genome and the diploid species Ae. umbellulata (U) were examined. Substantial interspecific polymorphism was observed for the majority of the polyploid species with the U genome (interspecific differences, 0.01–0,2; proportion of polymorphic loci, 56.6–88.2%). Aegilops triuncialis was identified as the only alloploid species with low interspecific polymorphism (interspecific differences, 0–0.01, P = 50%) in the U-genome group. The U-genome Aegilops species proved to be separated from other species of the genus. The phylogenetic relationships were established for the U-genome species. The greatest separation within the U-genome group was observed for the US-genome species Ae. kotschyi and Ae. variabilis. The tetraploid species Ae. triaristata and Ae. columnaris, which had the UX genome, and the hexaploid species Ae. recta (UXN) were found to be related to each other and separate from the UM-genome species. A similarity was observed between the UM-genome species Ae. ovata and Ae. biuncialis, which had the UM genome, and the ancestral diploid U-genome species Ae. umbellulata. The UC-genome species Ae. triuncialis was rather separate and slightly similar to the UX-genome species.     

RECONSTRUCTING RETICULATION HISTORY IN A PHYLOGENETIC FRAMEWORK AND THE POTENTIAL OF ALLOPATRIC SPECIATION DRIVEN BY POLYPLOIDY IN AN AGAMIC COMPLEX IN CRATAEGUS (ROSACEAE)

Polyploidy plays a prominent role in the speciation process in plants. Many species are known to be part of agamic complexes comprising sexual diploids and more or less exclusively asexual polyploids. However, polyploid formation has been studied in very few cases, primarily because of the challenges in examining these cases phylogenetically. In this study, we demonstrate the use of a variety of phylogenetic approaches to unravel origins and infer reticulation history in a diploid–polyploid complex of black‐fruited Crataegus. The tree approaches are shown to be useful in testing alternative hypotheses and in revealing genealogies of nuclear genes, particularly in polyploid organisms that may contain multiple copies. Compared to trees, network approaches provide a better indication of reticulate relationships among recently diverged taxa. Taken together, our data point to both the autopolyploid and allopolyploid origins of triploids in natural populations of Crataegus suksdorfii, whereas tetraploids are formed via a triploid bridge, involving the backcross of allotriploid offspring with their diploid C. suksdorfii parent, followed by gene introgression from sympatric C. douglasii. Our findings provide empirical evidence for different pathways of polyploid formation that are all likely to occur within natural populations and the allopatric establishment of neopolyploids subsequent to their formation.