A comparative study of floral and electrophoretic variation with life history variation in Limnanthes alba (Limnanthaceae)

Summary Plants derived from ten representative Limnanthes alba populations in Northern California, grown in a common environment, showed significant among-population genetic variation of certain floral and life history characters. Variation of these two sets of characters also correlated with the geographic distribution of populations, suggesting the influence either of common ancestry of neighboring populations, or of gradients of natural selection. In contrast, allozyme variation at eleven polymorphic loci showed little pattern. This suggests, if allozyme variants are assumed to accurately measure co-ancestry and each character set is assumed to give adequate and similar statistical power, that selection may have predominated over certain neutral processes during the evolution of some floral and life history characters.Life history characters, being closely tied to fitness, are particularly relevant to the postulated selection gradient. Studies of three representative populations in nature revealed significant differences in the sizes of dormant seed banks and several reproductive characters. These differences correlated with some field measures of soil and biotic variables, and were compared with certain predictions from reproductive strategy models in an attempt to identify any agents of selection. Alternative sets of life history characters were discernable corresponding to varieties identified on the basis of floral morphology, but these sets did not match those predicted the by r and k selection dichotomy; instead alternative selection regimes that may also favor some bethedging adaptations are postulated, although we emphasize our measures of habitat and climatic factors are too preliminary to clearly distinguish selective environmental factors.     

An evaluation of putative sympatric speciation within Limnanthes (Limnanthaceae)

Limnanthes floccosa ssp. floccosa and L. floccosa ssp. grandiflora are two of five subspecies within Limnanthes floccosa endemic to vernal pools in southern Oregon and northern California. Three seasons of monitoring natural populations have quantified that L. floccosa ssp. grandiflora is always found growing sympatrically with L. floccosa ssp. floccosa and that their flowering times overlap considerably. Despite their subspecific rank within the same species crossing experiments have confirmed that their F1 hybrids are sterile. An analysis of twelve microsatellite markers, with unique alleles in each taxon, also shows exceedingly low levels of gene flow between populations of the two subspecies. Due to the lack of previous phylogenetic resolution among L. floccosa subspecies, we used Illumina next generation sequencing to identify single nucleotide polymorphisms from genomic DNA libraries of L. floccosa ssp. floccosa and L. floccosa ssp. grandiflora. These data were used to identify single nucleotide polymorphisms in the chloroplast, mitochondrial, and nuclear genomes. From these variable loci, a total of 2772 bp was obtained using Sanger sequencing of ten individuals representing all subspecies of L. floccosa and an outgroup. The resulting phylogenetic reconstruction was fully resolved. Our results indicate that although L. floccosa ssp. floccosa and L. floccosa ssp. grandiflora are closely related, they are not sister taxa and therefore likely did not diverge as a result of a sympatric speciation event.     

Phytoecdysteroid levels and distribution during development in Limnanthes alba Hartw. ex Benth. (Limnanthaceae)

Phytoecdysteroid (PE) production and accumulation in Limnanthes alba Hartw. ex Benth. is associated with flowering. PE content per plant remains fairly constant during the primary growth phase of the plant and only begins to increase significantly above amounts found in the seed once the development of the flower stalk has begun. Both content and concentration increase concomitantly from this point. Distributions in individual plants also associated the highest levels of PE accumulation with the reproductive tissues. This substantiates the association of PE with tissues of greatest fitness value and therefore the hypothesis that they contribute to defence. Analysis of extracts of L. alba tissues by reversed-phase HPLC coupled with ecdysteroid-specific RIA was used to monitor ecdysteroid profiles. RIA-positive peaks co-chromatographing with 20-hydroxyecdysone, ecdysone and ponasterone A were detected and several tissues also contain PE conjugates. Seedmeal of L. alba appears to be a convenient and promising source for the commercial isolation of the potent PE ponasterone A.     

Pollinator-mediated competition between two congeners, Limnanthes douglasii subsp. rosea and L. alba (Limnanthaceae)

? Premise of Study: Pollinator visits are essential for reproduction in many plants, yet interspecific movements of pollinators can also lead to competitive interactions between coflowering species. Pollination-mediated reductions in fertility could potentially lead to exclusion of competing plant species, and may generate spatial variation in the associations among coflowering species across a landscape. ? Methods: I documented the potential for heterospecific pollen transfer to cause competitive interactions between two annual grassland species native to California, Limnanthes douglasii subsp. rosea and L. alba, two reproductively incompatible species that have broadly overlapping geographic ranges in the foothills of the Sierra Nevada. I observed pollinator movement in constructed arrays and controlled crosses in the greenhouse and field to investigate the consequences of heterospecific pollen transfer. ? Key Results: Pollinators move readily between species when they are presented together in experimental arrays. In the greenhouse, deposition of heterospecific pollen decreased fertility in both species. The decrease in seeds produced per flower was much more pronounced in L. d. rosea (90.6% reduction) than in L. alba (40.8% reduction). In field experiments, L. d. rosea plants that received pollen from heterospecific neighbors first showed >50% reduction in per-flower fertility. ? Conclusions: Under natural pollination conditions, heterospecific pollen transfer has the ability to decrease the fertility of L. d. rosea when it occurs at low frequency in mixed stands. Accordingly, pollinator-mediated competition may contribute to the locally disjunct distributions of these two species. It may also influence important restoration decisions in vernal pool habitats.     

Life history variation and infraspecific heterochrony inRhinanthus glacialis (Scrophulariaceae)

Comparative cultivation experiments were made with 14 populations of the annual, hemiparasitic speciesRhinanthus glacialis from seven different habitat types. Phenological data were recorded and plants from field samples and from corresponding experimental samples were morphologically analysed.There are up to ten weeks difference in the start of flowering between means of the extreme experimental populations. Flowering time variation correlates with the number of internodes and also with most of the other morphological characters. Flowering time also shows close relationships to different grassland types and the examined populations appear to be well-adapted to the environmental conditions in natural or man-influenced grassland types as far as flowering time is concerned. The number of internodes is mostly insensitive to the applied experimental influences. The rate of internode production is constant. Trade-offs are suggested for some morphological traits (i.e., few internodes with few branches and thus few flowers as trade-off for early flowering). — Previous studies of life history variation based on population data have not been incorporated into the theory of heterochrony. The pattern of life history variation of populations ofR. glacialis together with information about morphology, ecology, and phylogeny suggests that some variants have evolved from ancestors via heterochronic processes. Earlier flowering populations from montane hay meadows, litter meadows, and dry meadows belong to paedomorphic variants. These have fewer internodes and branches as well as reduced height in comparison with the suggested ancestor. Later flowering populations from subalpine limestone grassland belong to a peramorphic variant with more internodes, more branches, and taller stems in comparison with the suggested ancestor.     

Chloroplast DNA variation inDesmodium subgenusPodocarpium (Leguminosae): Infrageneric phylogeny and infraspecific variations

Chloroplast DNA (cpDNA) restriction site variation was examined in five species ofDesmodium subgenusPodocarpium (Leguminosae; Papilionoideae; Desmodieae). Twenty four phylogenetically informative cpDNA mutations were scored. The cladistic analysis of characters based on the 24 mutations resulted in the most parsimonious tree which supports the monophyly of the subgenus.Desmodium elegans of subgenusDollinera was the sister group of subgenusPodocarpium in this tree. The groupings obtained from the cpDNA characters were consistent with the present infrageneric classification system for the subgenus except for the infraspecific taxa ofD. podocarpum. Three groups withinD. podocarpum, which were incongruent with the infraspecific classification of the species, were distinguished by a total of four site mutations. The first group consisted of subsp.podocarpum, subsp.fallax, and subsp.oxyphyllum var.oxyphyllum; the second subsp.oxyphyllum var.oxyphyllum; and the last subsp.oxyphyllum var.oxyphyllum and var.mandshuricum.     

Numerical analysis of infraspecific variation in European Silene alba and S. dioica(Caryophyllaceae)

Infraspecific variation among European populations of Silene alba and S. dioica was analysed by non-metric multidimensional scaling, which was applied to K-dissimilarity matrices based either on 16 seed characters or on 34 seed, flower and capsule characters. The material used for analysis consisted of 167 collections of wild seed, largely obtained from European botanic gardens, and 97 sets of mature greenhouse-grown progeny. S. alba was found to show topoclinal variation, primarily along an axis from the Iberian peninsula through central Europe to Romania. This pattern is not reflected in current taxonomic treatments. N. and N.W. European S. alba is morphologically heterogeneous and has probably been introduced from various southern sources. S. dioica shows less total variation between populations than S. alba , and consists of local ecogeographic races that intergrade at their margins. The two species are completely discriminated by seed, flower and capsule characters when used in combination, but S. alba populations from the eastern end of the cline closely approach S. dioica in seed morphology. This convergence is unlikely to be an effect of recent introgression.     

Numerical-chemosystematic studies of infraspecific variation in Juniperus pinchotii

Twenty-seven populations of Juniperus pinchotii were sampled throughout the range of this taxon including several populations often referred to J. erythrocarpa. The terpenoids were extracted and analyzed by gas-liquid chromatography. Population differentiation was analyzed by analysis of variance and numerical taxonomy. Juniperus pinchotii appears to be fairly uniform in west Texas with considerable variation in the transPecos region of Texas and the populations at Saltillo and Chihuahua City, Mexico. One population in Mexico just south of the Chisos Mountains was more similar to typical J. pinchotii from west Texas than to adjacent populations, inferring a past (Pleistocene ?) connection with the west Texas populations. Pleistocene migrations are discussed. No evidence of hybridization nor introgression from other taxa was found. Juniperus erythrocarpa is informally treated as a part of J. pinchotii until additional studies have been completed.     

Reevaluations of infraspecific taxonomy in Polygonella (Polygonaceae)

Brittonia - Polygonella ciliata var.basiramia andP. fimbriata var.robusta are raised in rank toP. basiramia (Small) Nesom & Bates, comb. nov., andP. robusta (Small) Nesom & Bates,...     

New variation and biosystematic patterns detected by allozyme and morphological comparisons inLimnanthes sect.Reflexae (Limnanthaceae)

Sixty-one populations ofLimnanthes sect.Reflexae were surveyed for variation at 19 allozyme loci and reassessed for their morphological diversity and biosystematic relationships. Cluster analysis of allozyme data at individual population level provided evidence for a fairly good fit with the earlier systematic work on this genus but both morphological and allozyme data together defined some new clusters as well as exceptional entities. For example, only var.rosea of the fourL. douglasii varieties described byMason (1952) on the basis of geographical distribution, flower color and leaf morphology, remained as a distinct entity; the others were realigned along new geographic boundaries.L. striata appeared to have two well-developed subgroups, one of which was closely related to theL. douglasii complex. Further ecogeographic and hybridization studies are needed to fully describe these new phenetic findings in the context of phylogenetic inference. SectionInflexae was readily distinguished from sect.Reflexae by several diagnostic loci, thus supporting the validity of this division. Interspecific variation levels and population differentiation inLimnanthes were high when compared to other plant taxa, possibly indicating highly dynamic evolutionary processes for which variable habitats and extreme subdivision within species have been suggested as explanations.     

Conserved simple sequence repeats for the Limnanthaceae (Brassicales)

The Limnanthaceae (Order Brassicales) is a family of 18 taxa of Limnanthes (meadowfoam) native to California, Oregon, and British Columbia. Cultivated meadowfoam (L. alba Benth.), a recently domesticated plant, has been the focus of research and development as an industrial oilseed for three decades. The goal of the present research was to develop several hundred simple sequence repeat (SSR) markers for genetic mapping, molecular breeding, and genomics research in wild and cultivated meadowfoam taxa. We developed 389 SSR markers for cultivated meadowfoam by isolating and sequencing 1,596 clones from L. alba genomic DNA libraries enriched for AG _n or AC _n repeats, identifying one or more unique SSRs in 696 clone sequences, and designing and testing primers for 624 unique SSRs. The SSR markers were screened for cross- taxa utility and polymorphisms among ten of 17 taxa in the Limnanthaceae; 373 of these markers were polymorphic and 106 amplified loci from every taxon. Cross-taxa amplification percentages ranged from 37.3% in L. douglasii ssp. rosea (145/389) to 85.6% in L. montana (333/389). The SSR markers amplified 4,160 unique bands from 14 genotypes sampled from ten taxa (10.7 unique bands per SSR marker), of which 972 were genotype-specific. Mean and maximum haplotype heterozygosities were 0.71 and 0.90, respectively, among six L. alba genotypes and 0.63 and 0.93, respectively, among 14 genotypes (ten taxa). The SSR markers supply a critical mass of high-throughput DNA markers for biological and agricultural research across the Limnanthaceae and open the way to the development of a genetic linkage map for meadowfoam (x = 5).Electronic Supplementary Material Supplementary material is available in the online version of this article at Communicated by O. Savolainen     

Reproductive system and pattern of genetic variation in two Limnanthes species

Summary Several populations of two species of the genus Limnanthes, (L. alba, an outbreeder and L. floccosa, an inbreeder) were examined with respect to variability of fifteen quantitative characters, allozyme variation at 11 loci, and response to different pollination conditions and moisture stress. Nearly equal amounts of phenotypic variability were found in the two species. L. alba had higher within-family variability than L. floccosa, but this result was highly heterogeneous among characters. A study of between- and within-population variance estimates did not reject the null hypothesis that L. alba and L. floccosa are similar with regard to the partitioning and amount of variability for quantitative characters. However, allozyme variation at 11 loci in a large number of populations showed L. alba to be highly polymorphic in contrast to the virtual monomorphism within L. floccosa populations. The average number of alleles per locus in L. alba and L. floccosa was 1.97 and 1.02, respectively, and on an average, L. alba and L. floccosa populations had 63% and 3% loci with polymorphism, respectively. Three groups of allozyme allelic combinations emerged which correlated well with the taxonomic delineation of allogamous L. alba, three semi-autogamous L. floccosa forms and two autogamous L. floccosa forms.All taxa showed a significant reduction in the seed output per plant due to moisture stress. L. alba suffered a further loss of fecundity under the paucity of pollinators, L. floccosa ssp. floccosa showed no significant effect from this factor, whereas L. floccosa ssp. grandiflora exhibited a curvilinear response which peaked at partial pollination and decreased to a lower level at full pollination.The geographic distribution of the two species with regard to the temperature and rainfall distribution did not suggest L. floccosa to be living in drier marginal areas. Patterns of variation in flowering time showed L. alba to be less variable than L. floccosa. Overall, there seemed to be little direct support for the thesis that inbreeding species originated from outcrossing taxa in marginal environments as a direct adaptation to a shortened growing season of xeric environments and to the lack of pollinators. Alternative hypotheses suggest that autogamy in L. floccosa might have evolved as a reproductive isolating barrier acting through either cleistogamy or divergence in flowering times.     

Origin of gynodioecy in Limnanthes: evidence from ecogeographic patterns of variation

Summary Evidence for hybrid origin of gene-cytoplasmic gynodioecy in Limnanthes douglasii is presented in terms of the parapatric distributions of putative parental taxa and the increased levels of genetic variation in gynodioecious populations. Attempts to produce gynodioecy through artificial hybridization between different accessions apparently failed due to the limited number of parental combinations used in making hybrids. Further studies are proposed on the hybrid origin model and on selective forces determining the fate of gynodioecy with its contributions to higher levels of hybridity and genetic variation.     

Somatic embryogenesis from immature embryos in meadowfoam (Limnanthes alba)

Developing embryos from immature seeds were excised and cultured. Optimal proliferation of differentiated secondary embryos occurred on Murashige-Skoog media containing 7% sucrose, 0.1 M 2,4-D, and 0.1–1.0 M zeatin. Higher levels of auxins inhibited embryo proliferation. Secondary embryos were subcultured to produce more embryos. The results indicate the feasibility of clonal propagation of meadowfoam.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - BA 6-Benzyladenine     

Developmental morphology of Odonthalia floccosa (Ceramiales, Rhodophyta) in laboratory culture

Material of the red alga Odonthalia floccosa (Esper) Fal-kenberg (Rhodomelaceae, Ceramiales), collected from California, was cultured in the laboratory and its life-history was completed. Tetraspores grew into bipolar sporelings that differentiated into a colorless rhizoidal portion and a pigmented upright shoot. The sporelings became compressed apically and formed lateral branches in a regularly distichous manner that were congenitally fused with the main axis. These tetraspore germlings grew into diecious gametophytes. Male ga-metophytes produced numerous spermatangia on modified fertile branchlets (male trichoblasts) that possessed three to four monosiphonous, proximal segments. Female gametophytes formed a single pro-carp on the suprabasal segment of unbranched female trichoblasts. Cystocarps developed on the female gametophytes cocultured with male gametophytes and released viable carpospores that developed into fertile te-trasporophytes. Tetrasporangia were produced from the third and fourth periaxial cells in each of 12–45 successive fertile segments and provided three (two lateral and one basal) cover cells. The occurrence of both spermatangia and procarps on fertile trichoblasts in O. floccosa suggests that the alga is the most derived in these two characters among the species of the genus Odonthalia. This species is distributed in cold temperate regions in the North Pacific, and it should be excluded from the North Atlantic marine algal flora.     

Micropropagation of meadowfoam (Limnanthes spp.)

Summary A rapid micropropagation system was developed for meadowfoam (Limnanthes spp. Brown) using four genotypes of three species. Murashige and Skoog (MS) medium supplemented with N⁶ benzyladenine (BA) and indole-3-acetic acid (IAA) at 0, 0.1, 0.5, 1.0 and 2.0 mg/l was tested for multiplication, shoot elongation and rooting. Expiants were taken from pot-grown plants. The most useful level for shoot growth and multiplication of both floral induced and non-induced plants was 0.5 mg/l BA. IAA failed to affect shoot growth or multiplication. Expiants from non-induced plants multiplied at moderate to high rates on 0.5 mg/l BA, while those from induced plants multiplied slowly and tended to elongate and flower. Non-induced plants on 2 mg/l BA produced large numbers of tiny shoots; induced plants did not respond. Shoots of all genotypes rooted on MS medium without hormones and all plants grew normally after transplanting to soil. This system provides a new tool for the development of meadowfoam as a crop plant.Abbreviations (BA) N ⁶ -benzyladenine - (IAA) indole-3-acetic acid - (MS) Murashige and Skoog medium, 1962     

Chloroplast and nuclear DNA variation among homozygous plants in a population of the autogamous annualMicroseris douglasii (Asteraceae,Lactuceae)

The autogamous diploid annualMicroseris douglasii of California occurs in many isolated populations. The populations consist of one to many highly inbred biotypes. Morphological variation among populations usually is greater than within populations. In spite of the virtual absence of gene flow even within populations, genetically determined character differences are randomly distributed and associated throughout the range of the species. Recent evidence even suggests introgression of chloroplasts from the relatedM. bigelovii. Offspring families from 25 plants of a very variable population were raised and examined for segregation of morphological and molecular (RAPD) markers. All 25 original plants were completely homozygous for all markers, but each differed from all others at least in some markers. The population consisted of two genetically isolated groups of plants: a distinct inbred line (3 plants) and 22 plants with random associations of a common set of markers and characters, possibly recombinant inbreds from a past hybridization event. One of these 22 plants contained a chloroplast genome found inM. bigelovii, the other 24 plants a chloroplast genome found only inM. douglasii.     

Sero-systematic and taximetric studies on the Phaseoleae (Fabaceae) and related tribes

VIVIANI, T., CONTE, L., CRISTOFOLINI, G. & SPERANZA, M., 1991. Sero-systematic and taximetric studies on the Phaseoleae (Fabaceae) and related tribes. One hundred and fifty-two species of Phaseoleae, Desmodieae, Indigofereae, Millettieae, Sophoreae and Swartzieae were subjected to a taximetric study. The serological relationships were analysed using 37 antigenic systems and 12 antisera upon a representative sample from the six tribes. The comparative use of taximetric and serological data allowed the following conclusions to be drawn: (1) the tribe Phaseoleae is not a natural taxon; the primitive complex Diocleinae-Glycininae, the more derived Phaseolinae, and the Cajaninae deserve tribal rank; the position of the remaining subtribes requires further examination. (2) The Desmodieae are related to the Phaseoleae, whereas the Indigofereae have little relation to them. (3) The Baphia -group in the Sophoreae is possibly related to the Phaseoleae ancestors, while the other Sophoreae belong to different phyletic lines. (4) Swartzia is morphologically related to the Sophoreae, but does not belong to the same natural group. (5) Sophoreae, Millettieae and Phaseoleae are three heterogeneous aggregates representing stages of increasing specialization, rather than elements of a single phyletic line.     

Differential gene expression patterns in the autogamous plant Hordeum euclaston (Poaceae)

Sib-seedlings of 95 strains of the strictly autogamous grass Hordeum euclaston were analyzed by horizontal polyacrylamide gel electrophoresis for four isoenzyme systems at a specific ontogenetic stage. We found differences in the activity of some genes among individuals of this species. Hence, an ontogenetic analysis was carried out to investigate 12 strains at five ontogenetic stages, to determine the patterns of expression of these genes during development. The differences in the presence versus absence of certain isoenzyme bands may be due to differential regulatory activation in response to environmental differences, as all plants showed the same structural genes, although these genes were active in different tissues and/or times of development. These results indicate the importance of differential gene activation in the metabolic phenotype variability of this strictly autogamous, highly homozygous species. The same structural alleles for isoenzymes showed the active form of the enzymes (phenotypic expression) to be present in different tissues and/or stages of development. Differential isoenzyme gene activation was shown to be directly responsible for the enzymatic variability (metabolic phenotype) presented by the plants, which seem to possess almost no heterozygosis.