Oenothera Subsection Research Articles

Comparative Analysis of Complete Chloroplast Genomes of 13 Species in Epilobium, Circaea, and Chamaenerion and Insights Into Phylogenetic Relationships of Onagraceae.

The evening primrose family, Onagraceae, is a well defined family of the order Myrtales, comprising 22 genera widely distributed from boreal to tropical areas. In this study, we report and characterize the complete chloroplast genome sequences of 13 species in Circaea, Chamaenerion, and Epilobium using a next-generation sequencing method. We also retrieved chloroplast sequences from two other Onagraceae genera to characterize the chloroplast genome of the family. The complete chloroplast genomes of Onagraceae encoded an identical set of 112 genes (with exclusion of duplication), including 78 protein-coding genes, 30 transfer RNAs, and four ribosomal RNAs. The chloroplast genomes are basically conserved in gene arrangement across the family. However, a large segment of inversion was detected in the large single copy region of all the samples of Oenothera subsect. Oenothera. Two kinds of inverted repeat (IR) region expansion were found in Oenothera, Chamaenerion, and Epilobium samples. We also compared chloroplast genomes across the Onagraceae samples in some features, including nucleotide content, codon usage, RNA editing sites, and simple sequence repeats (SSRs). Phylogeny was inferred by the chloroplast genome data using maximum-likelihood (ML) and Bayesian inference methods. The generic relationship of Onagraceae was well resolved by the complete chloroplast genome sequences, showing potential value in inferring phylogeny within the family. Phylogenetic relationship in Oenothera was better resolved than other densely sampled genera, such as Circaea and Epilobium. Chloroplast genomes of Oenothera subsect. Oenothera, which are biparental inheritated, share a syndrome of characteristics that deviate from primitive pattern of the family, including slightly expanded inverted repeat region, intron loss in clpP, and presence of the inversion.

Using fine-scale field data modelling for planning the management of invasions of Oenothera stucchii in coastal dune systems

Invasive alien species risk assessment and adaptive management are often hindered by a lack of information for most species. This work aims at predicting the probability of successful establishment and invasion of Oenothera stucchii Soldano, a neophyte invasive species belonging to the sect. Oenothera subsect. Oenothera, in xerophilous grasslands of grey dunes. Based on fine-scale field data, we modelled O. stucchii presence/absence and abundance as a function of environmental factors, human disturbance, and attributes of the recipient community through a zero-inflated Poisson model. The invasion success of O. stucchii depended on a combination of factors which differed when considering either the patterns of occurrence (species presence/absence) or those of species abundance. While human-driven disturbance strongly influenced the probability of presence/absence of O. stucchii, patterns of abundance were mostly driven by a combination of environmental and biotic features. Attributes of the recipient community remarkably influenced both O. stucchii presence and abundance. Based on fine-scale field data, we determined the mechanisms which drive the spatial patterns of presence and abundance of O. stucchii in xerophilous grasslands and provided quantitative thresholds to identify the most susceptible areas of grey dune habitats prone to invasion, which combine human disturbance (distance from the nearest beach access), attributes of the resident community (resident vegetation cover and structure), and environmental disturbance (foredune ridge height). These results provide useful insights to be used to plan cost-effective measures to prevent O. stucchii establishment and spread in sandy coastal systems. Our model may also be applied to closely related congener species included in the subsect. Oenothera, sharing similar biological and ecological traits.

Hybridization and a loss of sex shape genome-wide diversity and the origin of species in the evening primroses (Oenothera, Onagraceae).

Hybridization is thought to promote speciation in at least two ways - by fixation of heterozygosity from diploid progenitors in allopolyploids, and by generation of transgressive phenotypes and shifting fitness optima during homoploid hybrid speciation. While recent studies support a hybrid origin for a growing number of species, the extent to which hybrid origins shape patterns of diversity in asexual species remains underexplored. Here we employed transcriptome sequencing and population genomic analysis to describe patterns of genomic variation in the 13 species belonging to Oenothera subsection Oenothera. Eight of these species are functionally asexual and arose by hybrid speciation from parents spanning a range of phylogenetic divergence. We showed that genomic divergence between parents has been retained as heterozygosity in functionally asexual species, and that genome-wide levels of heterozygosity in these asexuals largely reflects the divergence of parental haplotypes coupled with a breakdown in recombination and segregation across the genome. These results show that divergence between parental species and loss of sex in hybrids shape patterns of whole-genome diversity and the origin of asexual species.

Validation of the name Oenothera italica (Onagraceae)

Oenothera italica Rostański & Soldano (1981: 376) (sect. Oenothera subsect. Oenothera) is one of about 100 taxa of the genus Oenothera Linnaeus (1753: 346) which have been formally recognized in Europe (Hudziok 1968, Soldano 1993, Rostański in Rostański et al. 2004, 2010). The species was described from Italy by Rostański and Soldano (1981) and assigned later to the typical series Oenothera by Rostański (1985). However, its name was not validly published because two different gatherings were indicated as syntypes. I have searched for a proper typification in several relevant sources (e.g. Soldano 1993, Rostański et al. 2004, Rostański et al. 2010), with no success.

Pollination biology and breeding system in five nocturnal species of Oenothera (Onagraceae): reproductive assurance and opportunities for outcrossing

The capacity to produce seed, both by selfing and outcrossing, or mixed mating strategies, is considered a mechanism for overcoming unpredictable pollinator availability. In the present study, we investigate breeding system, insect visitations and the role of insect visitors in the pollination of five species of Oenothera subsect. Oenothera. Field experiments showed that autonomous selfing occurs at bud stage, prior to the opening of the flower. Control flowers showed similar seed set to hand-pollinated flowers, whereas emasculated flowers and those subject to open pollination set fewer seed. These results are consistent with the hypothesis that the investigated Oenothera exhibit a great capacity for autonomous selfing and that selfing is selected in order to provide reproductive assurance. Although flowers were visited mostly by nocturnal lepidopterans, these insects did not precipitate pollination and are thus considered nectar thieves. Conversely, analysis of pollen loads and behavior during foraging by diurnal insect visitors revealed that honeybees and bumblebees are the probable pollinators. We conclude that production of flowers capable of autonomous selfing at bud stage, followed by anthesis and opportunities for outcrossing, probably improves the invasive potential of these Oenothera in Europe, together with a rapid increase in their populations, even when pollinators are scarce.

Validation of the name Oenothera hoelscheri var. albinervis (Onagraceae)

Oenothera hoelscheri Renner (1942: 460) ex Rostański (1968: 189) is one of about 100 taxa of the genus Oenothera (section Oenothera subsection Oenothera) observed in the European continent (based on research made by Hudziok (1968), Soldano (1992), Rostański (in: Rostański et al. 2010) and others). It originated as a result of hybridization: O. rubricaulis Klebahn (1914: 12) × O. hungarica (Borbás 1902: 204) Borbás (1903: 246) = O. depressa Greene (1891: 216) (Renner 1942). The first specimen of O. hoelscheri was collected in Włocławek (Poland: kujawsko-pomorskie) by R. Hölscher (Renner 1942). Currently, the taxon is relatively wide distributed in Central, East and North Europe (Rostański et al. 2010).

Identification of plastid genotypes in Oenothera subsect. Munzia by restriction fragment length polymorphisms (RFLPs)

Five discrete plastid genotypes (plastomes), designated I–V and typified by Oenothera Hookeri, biennis, Lamarckiana, parviflora and argillicola respectively, have been previously characterized within the European subsect. Euoenothera. The evolutionarily more-derived plastome types (I, II and V) are generally less tolerant of new hybridization events than the ancestral types (III and IV), and were first identified based on their incompatibility reactions with standard hybrid nuclei. Restriction maps for all five plastomes are available for the enzymes PvuII, SalI, KpnI and PstI (Gordon et al. 1982). The present study employs PvuII and KpnI restriction digests to compare 28 of the 45 species of subsect. Munzia with Euoenothera plastomes I–V. The results of plastome RFLP fingerprinting show uniform divergence of the South American taxa from their European congeners; all share the previously documented 45-kb inversion in the large single-copy region reported by Hachtel et al. (1991). However, at least six new plastome types have evolved within subsect. Munzia, giving rise to small-fragment size differences of 0.1–0.7 kb. In two of these cases (Oe. featherstonei and Oe. longiflora) unique fragments occurred. For Oe. featherstonei the unique KpnI fragment resulted from a novel 2.2 kb insertion, whereas in Oe. longiflora an additional PvuII restriction site has been created.

Notes on the genusOenothera subsect.Oenothera (Onagraceae) in the Czech Republic

Up-to-date results of taxonomic and phytogeographic studies of Oenothera subsect. Oenothera in the eastem part of the Czech Republic (Moravia and Silesia) are presented. A new hybridogenous species, Oe. moravica JEHLiK et ROSTANSKI (= Oe. fallax x Oe. victorini), is described from S Moravia. Several taxa and hybrids are reported for the first time for the Czech Republic: Oe. victorini GATES et CATCHESIDE (= Oe. rostanskii JEHLIK), Oe. xwienii RENNER ex ROSTANSKI, Oe. acutifolia x Oe. victorini. Other taxa are recorded from the eastem part of the Czech Republic for the first time: Oe. acutifolia ROSTANSKI, Oe. hoelscheri RENNER ex ROSTANSKI, Oe. parviflora L., Oe. subterminalis GATES. The taxonomy of Oe. pycnocarpa ATKINSON et BARTLETT is discussed. A survey of species and hybrids of Oenothera subsect. Oenothera in the Czech Republic is added.

Deletions/insertions, short inverted repeats, sequences resembling att-lambda, and frame shift mutated open reading frames are involved in chloroplast DNA differences in the genus Oenothera subsection Munzia.

A restriction fragment length mutation has been mapped in the large single copy region of the chloroplast DNA from two Munzi-Oenothera species. Fragments containing the deletion/insertion were cloned, further analysed by additional restriction enzymes, and sequenced. A deleted/inserted 136 bp sequence was identified upstream of the 5' end of a tRNA-Leu (UAA) gene and presumably is located in the spacer between this gene and a tRNA-Thr (UGU) gene. The endpoints of the 136 bp sequence are covered by short inverted repeats. Complementary inverted repeats are present in the middle of the deleted/inserted sequence. The repeats are part of sequences resembling the lambda chromosomal attachment site (att-lambda) which is essential for site specific recombination in the lambda/Escherichia coli system. Possible interactions of the repeats during the deletion/insertion process are discussed. The spacer also contains a 1 bp deletion/insertion within an open reading frame (ORF). Due to this frame shift mutation the ORF sizes are quite different between the two Oenothera species.

Chloroplast DNA differences in the genus Oenothera subsection Munzia: a short direct repeat resembling the lambda chromosomal attachment site occurs as a deletion/insertion within an intron of an NADH-dehydrogenase gene.

A small restriction fragment length mutation has been mapped in the large inverted repeats of the chloroplast (cp) DNA of Munzia-Oenothera species (vom Stein and Hachtel 1986). This mutation could be localized within the intron of a reading frame presumably coding for subunit B of an NADH-dehydrogenase (ndhB). Sequence analysis revealed a 24 bp duplication/deletion. The predicted secondary structure of the ndhB-intron is altered by this duplication/deletion. Part of the directly repeated segment shows remarkable similarity to the phage lambda attachment site. Evidence is presented for similar sequences in other plastome regions where deletions/insertions have been found. Furthermore, the locations of the genes for other components of the NADH-dehydrogenase (ndhA, ndhC, ndhD, ndhE, ndhF) were established by heterologous hybridization using gene probes from tobacco cpDNA.

A Systematic and Evolutionary Study of Oenothera (Onagraceae): Seed Coat Anatomy

On the basis of a study of 32 of the 124 species representing the 14 sections of Oenothera, we find that the seed coats exhibit considerable anatomical diversity, particularly the exotesta, mesotesta, and endotesta. Features throughout the genus are: (1) endotegmen is one cell thick and persistent and (2) consists of longitudinally elongate, tannin-containing cells; (3) exotegmen consists of longitudinally elongate, thick-walled, pitted, lignified fibers; and (4) endotestal cells contain crystals. Unequivocal relationships are demonstrated for species with essentially identical seed features: (1) between section Kleinia and section Oenothera subsection Raimannia; and (2) among sections Hartmannia, Kneiffia, Xylopleurum, and Anogra. A cladistic analysis, using seed anatomy data, indicates that (1) O. havardii differs in several characteristics from members of section Gauropsis and should be excluded; and (2) seed anatomy of O. maysillesii differs in several features from the other species of subsection Emersonia; these same differences are shared with sections Ravenia, Contortae, Eremia, and Pachylophus, indicating that O. maysillesii is their sister group. The analysis indicates an early divergence of Oenothera into two major lineages: (1) species with thick endotesta (sections Contortae, Eremia, Kleinia, Oenothera, Pachylophus, and Ravenia); and (2) species with radially flattened endotestal cells (sections Anogra, Gauropsis, Hartmannia, Kneiffia, Lavauxia, Megapterium, Paradoxus, and Xylopleurum). Subsequent changes in seeds of both lineages include multiplication of the fibrous exotegmen, development of a crushed mesotesta or multiplication of the cell layers of the mesotesta, and specialization of the exotesta involving various radial cell enlargements. Diversification of the first lineage has involved changes in seed anatomy that correlate with ecological shifts, while to a much greater extent the evolution of the second lineage has not. Outer layers of the seed appear to be more open to adaptive modifications than inner ones.

A New Combination and New Subspecies in Oenothera Elata Kunth (Onagraceae)

The new combination of Oenothera elata Kunth subsp. hookeri (Torrey & A. Gray) W. Dietrich & W. L. Wagner is made for plants of moist coastal or slightly inland sandy and bluff sites from Marin County south to San Diego County, California, previously known as 0. hookeri subsp. hookeri and subsp. montereyensis. Also, 0. elata subsp. texensis subsp. nov. is described from Brazos County, Texas. It appears to be a rare relictual entity most closely related to 0. elata subsp. hirsutissima which occurs disjunctly some 680 km to the west of subsp. texensis. These names are made available in anticipation of their use in regional floras and concurrent studies of flavonoids, cytology, and pollen morphology in advance of a detailed revision of Oenothera subsect. Oenothera (Dietrich & Wagner, in prep.). Detailed presentation of data and discussions will be given in the revision. Munz (1949, 1965) divided the large-flowered, bivalent-forming, outcrossing populations of sect. Oenothera subsect. Oenothera from the western United States south to Panama into two species, 0. hookeri Torrey & A. Gray and 0. elata Kunth. During the past ten years we have reevaluated the variation pattern of these plants by a detailed study of a large number of herbarium specimens, fieldwork, and study of plants cultivated in the experimental gardens at Dusseldorf. These studies have shown that the two entities are extremely similar and differ only in bract shape, capsule diameter, and modally in several other features. It was therefore suggested by Raven et al. (1979), in an outline of the systematics of Oenothera sect. Oenothera subsect. Oenothera (formerly Euoenothera), that they should be considered conspecific.

Chloroplast DNA differences between two species of Oenothera subsection Munzia: location in the chloroplast genome and relevance to possible interactions between nuclear and plastid genomes

The chloroplast DNAs (cpDNAs) of Oenothera berteriana and Oe. odorata (subsection Munzia) were examined by restriction endonuclease analysis with Sal I, Pvu II, Kpn I, Pst I, Hind III, and Bam HI. The fragment patterns show that these cpDNAs have all 133 restriction sites in common as well as a lot of individual bands. Nevertheless the cpDNAs of the two species can be distinguished by distinct differences in size between a small number of fragments. The 42 cleavage sites produced by Sal I, Pvu II and Kpn I were mapped on the circular cpDNAs. This was achieved by an approach which combined experimental and mathematical procedures. The overall serial order of the fragments was found to be the same for both cpDNAs. The size differences of individual fragments in the Sal I, Pvu II and Kpn I patterns between Oe. berteriana and Oe. odorata cpDNA are located within five regions scattered along the plastid chromosome. Two of these regions have been localized in the larger and one in the smaller of the two single-copy parts of the cpDNA molecule. The remaining two overlap the borders between the large single-copy and each of the duplicated parts of the molecule. The positions of distinct restriction sites are altered among the two Oenothera plastome DNAs by 0.02-0.4 MDa (30-600 base pairs). These alterations probably result from insertions/deletions.

Revision of Oenothera sect. Oenothera subsect. Emersonia (Onagraceae)

Oenothera sect. Oenothera subsect. Emersonia consists of four species, 0. stubbei sp. nov., O maysillesii, 0. macrosceles, and 0. organensis, which have scattered relictual distributions in central and northern Mexico and the Organ Mountains, New Mexico, United States. Diagnostic features of subsect. Emersonia include: perennial habit; stems decumbent, ascending or weakly erect, rooting at the nodes in 0. maysillesii and 0. stubbei; dentate to subentire leaves, erect buds; yellow vespertine hawkmoth-pollinated flowers; cylindrical to narrowly lanceoloid capsules; and seeds with the testa thickened distally, this thickened area with an internal cavity. Fully fertile hybrids can be made in most combinations between these four species, and it is in part because of this result that these somewhat heterogeneous species are grouped together. Based on morphology, distribution, and ability to form fertile hybrids, especially in the case of 0. maysillesii, with members of the other four subsections of sect. Oenothera, the species of subsect. Emersonia appear to represent a lineage that diverged relatively early in the evolution of the section. All four species of subsect. Emersonia are diploid, n = 7, but some of the plants of each species that we examined are heterozygous for usually one or two reciprocal translocations and up to four translocations in some populations of 0. maysillesii. Oenothera macrosceles is self-compatible, but modally outcrossing; the other three species are self-incompatible. Among the species in subsect. Emersonia, features of the seeds are heterogeneous, more so than in most other sections of Oenothera. Certain seed characters suggest relationships between species of subsect. Emersonia and those of other subsections of sect. Oenothera.

Physical mapping of plastid DNA variation among eleven Nicotiana species

Plastid DNA of seven American and four Australian species of the genus Nicotiana was examined by restriction endonuclease analysis using the enzymes Sal I, Bgl I, Pst I, Kpn I, Xho I, Pvu II and Eco RI. These endonucleases collectively distinguish more than 120 sites on N. tabacum plastid DNA. The DNAs of all ten species exhibited restriction patterns distinguishable from those of N. tabacum for at least one of the enzymes used. All distinctive sites were physically mapped taking advantage of the restriction cleavage site map available for plastid DNA from Nicotiana tabacum (Seyer et al. 1981). This map was extended for the restriction endonucleases Pst I and Kpn I. In spite of variation in detail, the overall fragment order was found to be the same for plastid DNA from the eleven Nicotiana species. Most of the DNA changes resulted from small insertions/deletions and, possibly, inversions. They are located within seven regions scattered along the plastid chromosome. The divergence pattern of the Nicotiana plastid chromosomes was strikingly similar to that found in the genus Oenothera subsection Euoenothera (Gordon et al. 1982). The possible role of replication as a factor in the evolution of divergence patterns is discussed. The restriction patterns of plastid DNA from species within a continent resembled each other with one exception in each instance. The American species N. repanda showed patterns similar to those of most Australian species, and those of the Australian species N. debneyi resembled those of most American species.

New Species and Combinations in the Genus Oenothera (Onagraceae)

Four new combinations in Oenothera sect. Megapterium and one each in sects. Pachylophus and Oenothera are made here to make them available for use in regional floras. Oenothera harringtonii (sect. Pachylophus) from southeastern Colorado, 0. clelandii (sect. Oenothera subsect. Raimannia) principally from the Great Lakes region south to Iowa and Illinois, and 0. heterophylla subsp. orientalis from two disjunct areas in Alabama and Arkansas are newly described here in order to also make them available.

Physical mapping of differences in chloroplast DNA of the five wild-type plastomes in Oenothera subsection Euoenothera

1) DNA has been isolated from the five genetically distinguishable plastid types of Oenothera, subsection Euoenothera. DNA of plastomes I to IV was obtained from plants with identical nuclear backgrounds containing the genotype AA of Oenothera hookeri whereas the DNA of plastome V came from Oenothera argillicola (genotype CC). 2) The DNAs of the five basic Euoenothera wild-type plastomes can be distinguished by restriction endonuclease analysis with Sal I, Pst I, Kpn I, Eco RI and Bam HI. The fragment patterns exhibit distinct common features as well as some degree of variability. 3) Physical maps for the circular DNAs of plastome I, II, III and V could be constructed using the previously detailed map of plastome IV DNA (Gordon et al. 1981). This has been achieved by comparing the cleavage products generated by restriction endonucleases Sal I, Pst I and Kpn I which collectively result in 36 sites in each of the five plastome DNAs, and by hybridization of radioactively labelled chloroplast rRNA or chloroplast cRNA probes of spinach to Southern blots of appropriate restriction digests. The data show that the overall fragment order is the same for all five plastome DNAs. Each DNA molecule is segmentally organized into four regions represented by a large duplicated sequence in inverted orientation whose copies are separated by two single-copy segments. 4) The alterations in position of restriction sites among the Euoenothera plastome DNAs result primarily from insertions/deletions. Eleven size differences of individual fragments in the Sal I, Pst I and Kpn I patterns measuring 0.1-0.8 Md (150-1,200 bp) relative to plastome IV DNA have been located. Most changes were found in the larger of the two single-copy regions of the five plastomes. Changes in the duplication are always found in both copies. This suggests the existence of an editing mechanism that, in natural populations, equalizes or transposes any change in one copy of the repeat to the equivalent site of the other copy. 5) Detailed mapping of the two rDNA regions of the five plastomes, using the restriction endonucleases Eco RI and Bam HI which each recognize more than 60 cleavage sites per DNA molecule, disclosed a 0.3 Md deletion in plastome III DNA and a 0.1 Md insertion in plastome V DNA relative to DNA of plastome IV, I and II. These changes are most probably located in the spacer between the genes for 16S and 23S rRNA and are found in both rDNA units.

RECOMBINATION SYSTEM AND POPULATION STRUCTURE IN OENOTHERA.

Reproduction involves one of three recombination systems-outcrossing, selfing, or cloning-or some combination of the three (Fryxell, 1957). How these reproductive modes affect the population structure of a species has been the subject of considerable discussion (Fryxell, 1957; Grant, 1958, 1971; Baker, 1959; Wright, 1969; Levin and Kerster, 1971; Jain, 1976). The theory generated by this discussion predicts that different recombination systems ought to strongly influence how the genetic variation of a species is organized. Patterns of heterozygosity and population differentiation may be influenced by the recombination system (Baker, 1959; Wright, 1969; Levin and Kerster, 1971; Jain, 1976; Lokki, 1976; Brown, 1979). Populations of predominant selfers are expected to have lower levels of heterozygosity and intrapopulation polymorphism, but higher levels of interpopulation differentiation than obligate outcrossers (Wright, 1969; Jain, 1976). Selfing species as a whole are expected to be less heterozygous and polymorphic than outcrossers (Jain, 1976). On the other hand, clonal species should have higher levels of heterozygosity than outcrossing species, both within populations and species-wide, since they can retain mutant alleles by sheltering them from segregation (Lokki, 1976). But, like selfers, clonal species are expected to have low levels of within-population polymorphism and high interpopulation differentiation (Baker, 1959; Levin and Kerster, 1971). The ideal test of these hypotheses would be to compare population structure of three closely related, sympatric species: an obligate outcrosser, a selfer, and a clonal species. However, studies attempting to determine the influence of recombination system on population structure have compared related taxa representing only two reproductive modes; in most cases, the related taxa were allopatric. Comparisons among animals have been those of obligate outcrossing to unisexual species (Parker and Selander, 1976; Atchley, 1977; Parker et al., 1977; Schultz, 1977; Suomalinen et al., 1977). Conversely, students of plant population structure have concentrated mainly on comparing outcrossers with selfers (Solbrig, 1972; Gottlieb, 1973, 1977; Levy and Levin, 1975; Levin, 1978; Brown and Jain, 1979). But no one has yet investigated sympatric congeners, each with one of the three different reproductive modes. A model system for the study of how reproductive mode affects population genetic structure is provided by three closely related, geographically and ecologically sympatric species of Oenothera subsection Raimannia (Stubbe and Raven, 1979): Oenothera grandis Smyth, 0. mexicana Spach, and 0. laciniata Hill. Each of these annuals utilizes a different recombination system: Oenothera grandis is a self-incompatible outcrosser (Cleland, 1968); Oenothera mexicana exhibits a high degree of selfing (Ellstrand, 1978); and Oenothera laciniata is a permanent translocation heterozygote (Cleland, 1968), functionally a clonal species (see Cleland, 1972, for a detailed description of this unusual syndrome). These three species cooccur in disturbed areas of south and central Texas, often in mixed populations (see Ellstrand, 1978 for distribution). The purpose of this study is to determine the population genetic correlates of different re-

Genetic Self-Incompatibility in Oenothera subsect Euoenothera

Although it has been postulated that genetic self-incompatibility was involved in the origin of complex heterozygotes in Oenothera subsect Euoenothera, it has not been detected in any species of this well-studied group. It is now reported for populations of Oenothera grandiflora from west central Alabama, and should be sought in other populations of this species, which has been in cultivation for nearly two centuries.

An Outline of the Systematics of Oenothera Subsect. Euoenothera (Onagraceae)

A new taxonomy is proposed for Oenothera subsect. Euoenothera (Ona- graceae). In this group, the species that are homozygous for the three major genomic complexes, A, B, and C, are well separated from one another. Within each of these three complexes, species that form bivalents or relatively small rings of chromosomes are represented: AA (0. elata, 0. Iongissima, 0. jamesii), BB (0. grand flora), and CC (0. argillicola). There are also complex heterozygotes with the AA (0. villosa, 0. woifil) and BB (0. austromontana) genomic constitutions. The entity that has been called 0. hookeri subsp. wolfii is an AA complex heterozygote, probably of separate origin from 0. villosa and here accorded taxonomic recognition as a species, as is the BB homozygote hitherto called 0. biennis subsp. austromontana. Each of the three possible combinations between the A, B, and C genomes is also recognized taxo- nomically: AB (0. biennis), AC (0. oakesiana, earlier considered a subspecies of 0. parv flora), and BC (0. parviflora). Oenothera glazioviana (0. lamarckiana auct., 0. erythrosepala) has the constitution AB, like 0. biennis, and may have originated fol- lowing hybridization between 0. biennis or 0. grand flora as the pistillate parent and 0. elata (0. hookeri) as the staminate parent: this probably occurred in a garden in Europe. Minor forms, many of hybrid origin, that have originated in Europe are relegated to the species they resemble most closely. To recapitulate the taxonomic changes with respect to the most recent North American taxonomic treatment (Munz, 1965), the complex heterozygote 0. wololi (AA) is separated as a species from the bivalent-forming 0. elata; 0. austromontana (BB) is separated as a species from 0. biennis (AB); and 0. parviflora (BC; = Parviflora-1) is separated from 0. oakesiana (AC; = Parviflora-2). The races that have been called Biennis-1, in which the B-complex is transmitted through the egg, and Biennis-2, in which the A-complex is transmitted through the egg, are not separated taxonomically, not usually being distinguishable in nature, despite the subspecific recognition accorded them by Munz. Among the non-com- plex-heterozygotes, 0. hookeri is regarded as a synonym of 0. elata, because of the limited distinctiveness of these two entities as recognized earlier, and their broad geographical intergradation. Oenothera glazioviana (1882) is an earlier name for what has recently been called 0. erythrosepala (1903), and, prior to that, 0. lamarckiana by de Vries. Earlier attempts to create a taxonomy for this subsection, particularly in recent years in Europe, have split the species too finely for a general purpose tax- onomy, mainly in imitation of genetic analyses but without the requisite genetic information in most cases to do this consistently.