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December 1983 - November 1985
September 1977 - September 1983
August 1976 - July 1977
Publications
Publications (93)
An agamic complex of 20- and 10-stamen, black-fruited hawthorns (Crataegus subg. Sanguineae, sect. Douglasianae) occurs in western North America, with a 10-stamen taxon disjunct in the upper Great Lakes basin. Here, we recircumscribe the 20-stamen taxa at the core of this complex (C. ser. Douglasianae). This is needed in order to distinguish betwee...
Background
Hawthorn species ( Crataegus L.; Rosaceae tribe Maleae) form a well-defined clade comprising five subgeneric groups readily distinguished using either molecular or morphological data. While multiple subsidiary groups (taxonomic sections, series) are recognized within some subgenera, the number of and relationships among species in these...
We compare biogeographic and morphological parameters of two agamic complexes of western North American hawthorns so as to evaluate possible explanations of the differences in range between sexually reproducing taxa and their apomictic sister taxa. We have documented range, breeding system, morphology, leaf vascular architecture, and niche breadth...
This paper updates earlier reviews of polyploidy and reproductive biology in the Rosaceae, and does so with a focus on hybridization in relation to polyploidy and (facultative) gametophytic apomixis. Taking data mainly from tribe Maleae, it also seeks to point out evidence for a potential role for fertilization of infrequent unreduced gametes in di...
Taxonomy is a scientific discipline that has provided the universal naming and classification system of biodiversity for centuries and continues effectively to accommodate new knowledge. A recent publication by Garnett and Christidis [1] expressed concerns regarding the difficulty that taxonomic changes represent for conservation efforts and propos...
Premise of the study
Constructing complete, accurate plant DNA barcode reference libraries can be logistically challenging for large-scale floras. Here we demonstrate the promise and challenges of using herbarium collections for building a DNA barcode reference library for the vascular plant flora of Canada.
Methods
Our study examined 20,816 speci...
Range and niche expansion are commonly associated with transitions to asexuality, polyploidy, and hybridity (allopolyploidy) in plants. The ability of asexual polyploids to colonize novel habitats may be due to widespread generalist clones, multiple ecologically specialized clones, or may be a neutral byproduct of multiple, independent origins of a...
Hawthorn is a widely used herbal alternative medicine for the treatment of various cardiovascular diseases. However, the attributed health benefits, purported to be due to the presence of phenolic compounds, may depend on both the specific species and plant part. Studies to date investigating effects of hawthorn on heart disease(s) have used well-d...
DNA barcodes can facilitate identification of organisms especially when morphological characters are limited or unobservable. To what extent this potential is realized in specific groups of plants remains to be determined. Libraries of barcode sequences from well-studied authoritatively identified plants represented by herbarium voucher specimens a...
Background and aims:
The taxonomic complexity of Crataegus (hawthorn; Rosaceae, Maleae), especially in North America, has been attributed by some to hybridization in combination with gametophytic apomixis and polyploidization, whereas others have considered the roles of hybridization and apomixis to be minimal. Study of the chemical composition an...
The impacts of ploidy level changes on plant physiology and ecology present interesting avenues of research, and many questions remain unanswered. Here, we examine the connections between cytotype, taxon, stomata characteristics, and environmental variables in black-fruited hawthorns of the Pacific Northwest (Crataegus ser. Douglasianae; Maleae, Am...
AbstractCrataegus monogyna Jacq. is naturalized in North America, where it has hybridized with native diploid hawthorns at least twice. We provide names for the two nothospecies (as well as for the corresponding nothosections and nothoseries), referring to existing documentation in the literature for nothosp. nov.
Crataegus ×ninae-celottiae K.I. Ch...
Aim
Asexual organisms frequently have larger ranges than their sexual progenitors, a phenomenon referred to as geographical parthenogenesis ( GP ). In plants, GP is associated not only with asexuality (apomixis), but also with polyploidization and hybridity (allopolyploidy). Dispersal is thought to play a role in range‐size differences in other tax...
Software interfaces for interactive multiple-entry taxonomic identification (polyclaves) sometimes provide a “best character” or “separation” coefficient, to guide the user to choose a character that could most effectively reduce the number of identification steps required. The coefficient could be particularly helpful when difficult or expensive t...
Abstract—
Members of the small genus Conopholis are perennial holoparasites. They are found growing in eastern and southwestern North America and in Central America, where they attach to the roots of their oak hosts. Two species were recognized in the last taxonomic
revision of the group based on geographic range and differences in floral, capsule,...
We have demonstrated geographical parthenogenesis in Crataegus series Douglasianae, an agamic complex comprising exclusively tetraploid Crataegus douglasii sensu lato and the morphologically distinct Crataegus suksdorfii complex that comprises diploids and polyploids. Here we characterize ploidy level and breeding system by detailed flow cytometric...
Since the 1800s, natural health products that contain hawthorn (Crataegus spp.) have been used in North America for the treatment of heart problems such as hypertension, angina, arrhythmia, and congestive heart failure. Traditionally, Native American tribes used hawthorn (Crataegus spp.) to treat gastrointestinal ailments and heart problems, and co...
Hawthorns (Crataegus L., Rosaceae) have well-established uses in natural health products (NHPs), and a handful of Eurasian species have demonstrated efficacy in treating symptoms of chronic heart failure. Until recently, however, almost nothing was known about the NHP potential of native North American hawthorns, of which approximately 50 occur in...
Unlike their diploid relatives, some triploid and tetraploid Crataegus frequently produce unreduced megagametophytes. In all cases, pollination is required for successful seed set, but in polyploids, endosperm formation can involve fertilization by either one or both sperm. Apomixis, in which the egg develops parthenogenetically, is widely document...
To investigate the nature of infraspecific variation in Larix laricina (Du Roi) K. Koch, 60 naturally established stands constituting 44 provenances were sampled from throughout the species' range. Cones were scored for nine traits and short-shoot needle transverse sections were scored for seven traits and 20 radial distances. Variation in all trai...
In the taxa that constitute Crataegus crus-galli L. sensu lato short-shoot leaves vary progressively from node to node in both size and shape. The pattern of this variation may differ not only between taxa but also within taxa, among local stands. Failure to recognize such variation may confound taxonomic studies based on leaf shape, judging from t...
Variation in the two-dimensional shape of short-shoot subterminal leaves was examined quantitatively in samples of nine topodemes of Crataegus section Crus-galli Loud. (representing C. crus-galli L. s.str., C. fontanesiana (Spach) Steud., C. ?disperma Ashe, and C. ?grandis Ashe) plus three of section Punctatae Loud. (C. punctata Jacq.). Shape was d...
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 th...
The reproductive system is one of the key mechanisms that determine genetic diversity at different biological levels. However, few attempts have been made to assess the consequences of asexual reproduction by comparing genetic structure and fecundity of seed families in asexually and sexually reproducing individuals. We have examined two similar ha...
Phylogeographic relationships were constructed for 72 Old and New World Crataegus species using combinations of four chloroplast and up to five nuclear regions. Maximum parsimony, maximum likelihood, and Bayesian results yield consistent relationships among major lineages. The close associations of the East Asian and western North American species...
The taxonomic integrity of Vaccinium section Bracteata sensu Sleumer was assessed using a variety of numerical measures on a data matrix created from 46 OTUs scored for 65 descriptors. These analyses supported a much restricted ambit for section Bracteata and the concomitant resurrection of section Nesococcus and section Euepigynium, a more cosmopo...
Polyploidy and gametophytic apomixis are two important and associated processes in plants. Many hawthorn species are polyploids and can reproduce both sexually and apomictically. However, the population genetic structure of these species is poorly understood. Crataegus douglasii is represented exclusively by self-compatible tetraploid pseudogamous...
Black-fruited hawthorns in North America comprise two taxonomic groups within the genus Crataegus, section Brevispinae and section Douglasianae. The first of these has recently been shown to be monospecific, consisting of the blueberry haw, Crataegusbrachyacantha Sarg. & Engelm., of Louisiana and Texas. Crataegus section Douglasianae, however, comp...
The inflorescence primordium of Phyllonoma integerrima (Turcz.) Loes. is initiated on the adaxial side of the leaf primordium. At about the same time, a vegetative bud is formed at the base of the same leaf primordium. The vascular anatomy is the same in the fertile and sterile leaves, except that in the fertile leaf an inflorescence trace departs...
Generic relationships in the Pyrinae (equivalent to subfamily Maloideae) were assessed with six chloroplast regions and five
nuclear regions. We also plotted 12 non-molecular characters onto molecular phylogenies. Chloroplast DNA trees are incongruent
with those from nuclear regions, as are most nuclear regions with one another. Some of this confli...
The relationship between polyploidy and breeding system is of critical importance for understanding evolution and improving
the taxonomy of large Rosaceous genera. Reviewing the data available for the family and for tribe Pyreae (formerly subfamily
Maloideae) in particular, it appears that hybridization, pseudogamous gametophytic apomixis, polyploi...
Phylogenetic relationships among 88 genera of Rosaceae were investigated using nucleotide sequence data from six nuclear (18S,
gbssi1, gbssi2, ITS, pgip, and ppo) and four chloroplast (matK, ndhF, rbcL, and trnL-trnF) regions, separately and in various combinations, with parsimony and likelihood-based Bayesian approaches. The results were
used to e...
Mespilus and Crataegus are sister genera in Rosaceae tribe Pyreae. Mespilus has been seen to comprise not only the medlar, Mespilus germanica, of western Eurasia but also the Arkansas, U.S.A. endemic, Mespilus canescens. Crataegus, on the other hand, consists of 140–200 species found throughout the northern hemisphere. Diagnoses of these two genera...
Apomixis in Crataegus is primarily aposporous and requires pollination. The embryo sac is of the Polygonum type. A combination of meiotically unreduced embryo sacs with apparently reduced pollen would violate the usual requirement for a 2 : 1 ratio of maternal to paternal contributions to the endosperm. We therefore investigated the origin of endos...
Polyploidy has been described both as an evolutionary dead end and as a major engine of diversification for angiosperms. Two recent studies have found that genera with higher proportions of polyploid species are more species rich. Here, we investigate patterns of diversification and polyploidy by performing traditional and phylogenetically correcte...
Hawthorns and medlars are closely related genera in Rosaceae subfamily Maloideae, whose taxonomy remains poorly understood. Gametophytic apomixis occurs in polyploids, and diploids are sexual out-crossers, so ploidy level is of great interest, but suitable material for chromosome counts is of limited availability each year. The promise of flow cyto...
The inflorescence of Vaccinium hiepii is described for the first time, and as predicted, its floral features are similar to those of V. chunii. However, this floral axis has nothing in common with the type of its putative section, i.e. Vaccinium sect. Galeopetalum. Subsequent numerical analyses of inflorescence types in Vaccinium using 43 taxa and...
A comparison of floral development in Gillenia (Rosaceae subfamily ''Spiraeoideae'') with that in seven genera in subfamily Maloideae was undertaken to ascertain similarities between Maloideae and Gillenia floral development, as well as to ascertain the developmental basis for variation in mature Maloideae floral morphology. The analysis also sough...
Floral instability in the mid-styled morph of tristylous Eichhornia paniculata (Spreng.) Solms (Pontederiaceae) was investigated in 14 genotypes from three Brazilian populations of contrasting morph structure (trimorphic, dimorphic, and monomorphic) and levels of inbreeding. Floral instability was described using uni- and multivariate methods, in t...
We sampled the 5' end of the granule-bound starch synthase gene (GBSSI or waxy) in Rosaceae, sequencing 108 clones from 18 species in 14 genera representing all four subfamilies (Amygdaloideae, Maloideae, Rosoideae, and Spiraeoideae), as well as four clones from Rhamnus catharticus (Rhamnaceae). This is the first phylogenetic study to use the 5' po...
An identification database for seeds in coastal habitats at La Pérouse Bay, Manitoba, Canada, was developed using the DELTA (DEscriptive Language for Taxonomy) format and the program INTKEY. The database should be ap- plicable throughout the coastal lowlands of the Hudson Bay and James Bay regions as similar plant assemblages are present. The datab...
Relationships within the Amygdaloideae have long been a point of discussion in Rosaceae systematics. Oemleria, a monotypic genus, has been removed from the Amygdaloideae because of its five-pistillate gynoecium since all other genera have a single pistil. Exochorda, with its capsular fruit, has traditionally been placed in Spiraeoideae. Nevertheles...
"Spiraeoideae," as traditionally circumscribed, contain the greatest diversity of floral organ morphology of any of the four subfamilies in the Rosaceae. Comparisons of mature floral morphology in 10 spiraeoid genera demonstrate that genera in this subfamily exhibit many floral character states present in the other three subfamilies. Inflorescence...
Phenetic analyses of 218 OTUs belonging toVaccinium sectionMyrtillus and scored for 13 characters generated five robust clusters.Vaccinium parvifolium is the most distinct cluster, followed by the “myrtillus-scoparium” complex, thenV. membranaceum, V. caespitosum, and the “ovalifolium-deliciosum” complex. Biosystematic studies suggest that the five...
The argument is made that species should be comparable with respect to the numbers of genotypes they include, regardless of
whether their reproduction is exclusively sexual or not. Specifically, this means recognizing species at a level comparable
to that of the section or series, as these are used in genera likeCrataegus L. orTaraxacum
Weber ex F....
One hundred and sixty isolates of ectomycorrhizal agarics, boletes, and related gasteromycetes were examined for 25 morphological and biochemical characters. A wide range of analytical methods are available with which to obtain efficient summaries of the patterns of variation present in data such as these. Agglomerative clustering of 156 isolates a...
Differences in the numbers of stamens and styles per flower are conspicuous features of variation in North American hawthorns
(Crataegus L.). Variation in stamen number between individuals is discontinuous, with modes of approximately 20 and 10 (or fewer). In
North American black-fruited sectionDouglasii
Loudon the 10-stamen morphotype is exclusive...
Crataegus section Douglasii exhibits variation in stamen number per flower typical for the genus throughout North America. To understand the developmental basis for this variation we studied the early floral ontogeny of the three taxa in section Douglasii: C. douglasii (both Pacific northwest and the upper Great Lakes basin), C. rivularis, and C. s...
Crataegus section Douglasii exhibits variation in stamen number per flower typical for the genus throughout North America. To understand the developmental basis for this variation we studied the early floral ontogeny of the three taxa in section Douglasii: C. douglasii (both Pacific northwest and the upper Great Lakes basin), C. rivularis, and C. s...
Environmentally induced heterophylly provides a useful model system for studying the developmental basis of differing leaf shapes. The semiaquatic Ranunculus flabellaris exhibits typical heterophyllous shape variation with change in water level: aerial leaves have short lobes, while lobes of leaves produced underwater are elongate. Submergence in a...
Intraspecific variation in floral development was studied in four morphologically distinct strains of Pseudolysimachion longifolium and two of P. spicatum. Size increase of whole buds from Living plants of P. longifolium was followed in absolute time. Growth rates were homogeneous within inflorescences and within individual plants, and significantl...
Intraspecific variation in floral development was studied in four morphologically distinct strains of Pseudolysimachion longifolium and two of P. spicatum. Size increase of whole buds from living plants of P. longifolium was followed in absolute time. Growth rates were homogeneous within inflorescences and within individual plants, and significantl...
Development in Veronica and Veronicastrum was studied to elucidate the growth patterns responsible for differences between their mature flowers. Nineteen floral dimensions were measured on buds from initiation to anthesis, and representative stages were recorded with the scanning electron microscope. Bivariate plots indicate the heterochronic chang...
Development in Veronica and Veronicastrum was studied to elucidate the growth patterns responsible for differences between their mature flowers. Nineteen floral dimensions were measured on buds from initiation to anthesis, and representative stages were recorded with the scanning electron microscope. Bivariate plots indicate the heterochronic chang...
In view of their awnless stamens and pseudo-10-loculed berries borne on short racemes several NE Asian species ofVaccinium (includingV. hirtum, V. smallii, V. versicolor, andV. yakushimense) were transferred toVaccinium sectionCyanococcus by Sleumer (1941). Subsequently, however, Stevens (1969) and Vander Kloet (1972, 1981) argued on the basis of f...
Maloids are versatile in reproductive mode-vegetative spreading, self-incompatibility, self-compatibility, and apomixis all occur-and they engage in extensive hybridization and polyploidy. Naturally occurring gametophytic apomixis has been reported from almost 100 taxa in six genera-Aronia, Amelanchier, Cotoneaster, Crataegus, Malus, and Sorbus s.l...
The available data suggest that the population structure of maloid species may be affected dramatically by features of their breeding system, and by their reproductive ecology in general. Morphometric data from Amelanchier, Crataegus, and Sorbus demonstrate associations between the occurrence of uniparental reproduction (apomixis and selfing) and p...
Ranunculus flabellaris Rafin., an aquatic buttercup, exhibits heterophylly at the level of cellular ultrastructure. Compared to terrestrial leaves, underwater leaves have thinner epidermal cell walls and more numerous paramural bodies per epidermal and mesophyll cell cross-section. The number of chloroplasts and mitochondria in cell cross-sections...
Asexuality and self-fertilization weaken the correlation between morphological, reproductive, and genetic units. The pattern and tempo of evolution may thus differ fundamentally between uniparentally reproducing groups and outbreeders. Apomixis, which is widespread in angiosperms, is reported from about 90 species from five of the largest genera of...
Maternal genotypes and three morphometric data sets (cone morphology, short shoot needle cross-sectional anatomy and shape) are available for samples (N = 8 to 11) from two populations of tamarack from each of five provenance regions in northern Ontario (North Bay, Kenogami R., Thunder Bay, Fort Frances, Red Lake). Data sets were compared using mul...
We describe forests from three areas of Jamaica, all on White Limestone but with markedly different rainfall regimes. The areas are Hog House Hill in the north-east with lower montane rain forest at c. 450 m altitude with a rainfall of c. 4000 mm yr ⁻¹ ; Broom Hall in the centre of the island with evergreen seasonal forest at c. 670 m altitude and...
Methods for shape comparisons among groups originally developed in zoological studies are found to be useful in examining variation in leaf shape. These methods (sampling outlines by means of truss networks connecting landmarks or pseudolandmarks, and sheared principal components analysis) take advantage of electronic methods of data capture and mu...
Methods for shape comparisons among groups originally developed in zoological studies are found to be useful in examining variation in leaf shape. These methods (sampling outlines by means of truss networks connecting landmarks or pseudolandmarks, and sheared principal components analysis) take advantage of electronic methods of data capture and mu...
Polyploidy in C. crus-galli is accompanied by self-compatibility. The weediness of the component taxa of C. crus-galli s.l., in general, and their tendency toward uniparental reproduction, in particular, may explain the homogeneity of their topodemes. -from Authors
Crataegus crus-galli L. sensu lato in southern Ontario is a complex of taxa, two of which appear to consist exclusively of both triploid and tetraploid individuals. While pollen fertility is reduced in triploids, both ploidy levels are characterized by production of eight nucleate aposporous embryo-sacs and hence remain seed-fertile; in addition, s...
Local names of vascular plants, accompanied by botanical specimens, were collected in the John Crow Mountains, Portland Parish,
Jamaica. Each of the names was volunteered by one local informant; many were independently corroborated by others. We recorded
91 names of forest trees and shrubs, 20 names of climbers, and 33 names of other plants. The un...
Crataegus crus-galli L. sensu lato (cockspur hawthorn) is one of the most readily identified Canadian hawthorns. It occurs frequently, and often in great abundance, on abandoned or poorly managed agricultural land in southern Ontario. These shrubs or small trees are difficult to remove and because of their thorns highly resistant to grazing. The we...
Multivariate studies of flower, fruit, and leaf variation in Crataegus crus-galli L. s. l. have largely confirmed a priori notions of the structure of this species complex in Ontario. Four morphotypes are recognized and these are assigned to taxa published by earlier workers. Intensive sampling of local stands of the two most common morphotypes ind...
Three new descriptors of dendrogram structure (cluster membership divergence, subtree membership divergence, and partition membership divergence) have been proposed which supplement existing ones (cophenetic difference and topological difference). These enable multivariate comparisons among dendrograms in a manner that minimizes the drawbacks of in...
Epiphylly is the occurrence of structures (leaves, shoots, inflorescences, etc.) on leaves. Although its occurrence was recognized without comment early in the history of descriptive botany, with the development of the classical shoot theory it became necessary to explain the deviation of leaves bearing epiphyllous structures (ES) from the position...
A B S T R A C T The inflorescence of Helwingia japonica (Thunb.) Dietr. is initiated adjacent to the leaf axil on the adaxial side of the base of a leaf primordium during its second plastochron. The inflorescence which develops from the resulting primordium comes to be situated on the midrib of the mature fertile leaf, through the action of a basal...
The inflorescence of Helwingia japonica (Thunb.) Dietr. is initiated adjacent to the leaf axil on the adaxial side of the base of a leaf primordium during its second plastochron. The inflorescence which develops from the resulting primordium comes to be situated on the midrib of the mature fertile leaf, through the action of a basal, intercalary me...
The inflorescence primordium of Phyllonoma integerrima (Turcz.) Loes. is initiated on the adaxial side of the leaf primordium. At about the same time, a vegetative bud is formed at the base of the same leaf primordium. The vascular anatomy is the same in the fertile and sterile leaves, except that in the fertile leaf an inflorescence trace departs...
