Shoichi Kawano

New Perspectives on the Pollination Biology of Basal Angiosperms

Coleoptera and Diptera are the primary pollinators of extant basal angiosperms (wind pollination is rare); lineages of these insects were established by the Late Jurassic. Contemporary examples of insect pollination of nonangiosperm plants are present in Gnetales (flies, moths) and Cycadales (beetles). The breeding systems of extant basal angiosperms are dominated by bisexual, protogynous, fragrant flowers that may form chambers in the female phase. Floral thermogenesis is widely distributed throughout the extant basal angiosperms (Nymphaeaceae, Illiciaceae, Aristolochiaceae, Magnoliaceae, and Annonaceae), into the basal monocots (Araceae) and extends into the advanced monocots (Arecaceae and Cyclanthaceae) and eudicots (only one family, Nelumbonaceae). The cycads are the only other plant group with heat‐producing reproductive structures (male and female cones). Flower temperatures of thermogenic plants are in the range required by endothermic insects for purposes of mating and flight, and it is hypothesized that floral heat is a direct energy reward to insects (a resource). Floral fragrance and heat played major roles in early plant reproductive systems, and fragrance could signal not only food and sex but also heat.

Molecular Phylogeny of Magnolia (Magnoliaceae) Inferred from cpDNA Sequences and Evolutionary Divergence of the Floral Scents

Magnolia (disjuncts), however, have similar chemical profiles. A molecular phylogeny of Magnoliaceae was constructed to reveal phylogenetic relationships of taxa by sequencing the trnK intron (including the matK coding region), psbA-trnH, and atpB-rbcL intergenic spacer regions of chloroplast DNA from 25 Magnolia, two Michelia, and two Liriodendron taxa. The psbA-trnH spacer region showed twice the sequence divergence (0.0157) of the trnK intron (0.0073) or the matK coding region (0.0077). The strict consensus tree constructed from the combined data set (ca. 3,700 bp) indicated the genus Magnolia was polyphyletic containing Michelia species as ingroup. The clade of Magnolia liliifera var. obovata, M. coco, and M. delavayi formed the first branch. Among the remaining species, two additional large clades were recognized, i.e., one comprised of American evergreen Magnolia species and another of subgenus Yulania. The relationship among sect. Rytidospermum taxa was not clearly resolved. Parsimonious mapping of the floral scent chemical characters was performed onto the molecular phylogenetic tree to discuss evolutionary trends of the floral scent chemistries.

PROBABILITY OF CLONAL IDENTITY : INFERRING THE RELATIVE SUCCESS OF SEXUAL VERSUS CLONAL REPRODUCTION FROM SPATIAL GENETIC PATTERNS

1 For terrestrial plants capable of both vegetative propagation and sexual seed production, we can distinguish clones from the spatial genetic pattern of plants using multi-locus measurement of allozymes, or other molecular markers. 2 The probability of clonal identity F(r) is defined as the probability that a randomly chosen pair of plants separated by a distance r belong to the same clone. It can be estimated from spatial genetic patterns of plants determined by multi-locus molecular methods. 3 If genotypes have the same competitive ability (no local adaptation), diffusion approximation shows that the equilibrium clonal identity function F(r) is proportional to exp [-cr]/ r. 4 The exponential rate of decline with distance, c, equals /(2/ , and is determined by the relative success of sexual vs. vegetative reproduction (u/v) and the mean square parent-offspring distance in successful vegetative propagation (u2). 5 We carried out computer simulations to confirm the usefulness of this formula in inferring demographic processes from spatial genetic data. The results hold irrespective of the dispersal range of sexual seeds. The integral of the probability of clonal identity is closely related to the average clone size.

Naphthalene—a constituent of Magnolia flowers

Ether extracts of petals, gynoecia and leaves of nine Magnolia taxa were analysed using GC-mass spectrometry. The extracts of flowers and gynoecia of five taxa (M. denudata, M. liliiflora, M. tomentosa, M. p. var. praecocissima and var. borealis) contained naphthalene as their main component. The extracts of M. salicifolia characteristically contained several phenylpropanoids including eugenol methyl ether. Two well known sesquiterpene lactones, dehydrocostuslactone and porthenolide, were found in extracts of flowers and leaves of two taxa.

Phylogenetic relationships and evolution in Chrysosplenium (Saxifragaceae) based on matK sequence data

Chrysosplenium (Saxifragaceae) consists of 57 species widely distributed in temperate and arctic regions of the Northern Hemisphere, with two species restricted to the southern part of South America. Species relationships within the genus are highly problematic. The genus has traditionally been divided into two groups, sometimes recognized as sections (Oppositifolia and Alternifolia), based on leaf arrangement, or, alternatively, into 17 series. Based on morphological features, Hara suggested that the genus originated in South America and then subsequently migrated to the Northern Hemisphere. We conducted phylogenetic analyses of DNA sequences of the chloroplast gene matK for species of Chrysosplenium to elucidate relationships, test Haras biogeographic hypothesis for the genus, and examine chromosomal and gynoecial diversification. These analyses revealed that both sections Oppositifolia and Alternifolia are monophyletic and form two large sister clades. Hence, leaf arrangement is a good indicator of relationships within this genus. Haras series Pilosa and Macrostemon are each also monophyletic; however, series Oppositifolia, Alternifolia, and Nepalensia are clearly not monophyletic. MacClade reconstructions suggest that the genus arose in Eastern Asia, rather than in South America, with several independent migration events from Asia to the New World. In one well-defined subclade, species from eastern and western North America form a discrete clade, with Old World species as their sister group, suggesting that the eastern and western North American taxa diverged following migration to that continent. The South American species forms a clade with species from eastern Asia; this disjunction may be the result of ancient long-distance dispersal. Character mapping demonstrated that gynoecial diversification is dynamic, with reversals from inferior to half-inferior ovaries, as well as to ovaries that appear superior. Chromosomal evolution also appears to be labile with several independent origins of n = 12 (from an original number of n = 11) and multiple episodes of aneuploidy.

Regional Differentiation in Genetic Components for the American Beech, Fagus grandifolia Ehrh., in Relation to Geological History and Mode of Reproduction

Fagus grandifolia, were investigated throughout its geographical range, using allozyme polymorphisms. A total of 1,131 trees from 21 populations were examined for 32 alleles of 10 polymorphic and two monomorphic loci in eight enzyme systems. The mean expected heterozygosity was 0.186, which indicates a relatively high genetic diversity within the populations. The levels of population differentiation were high, as revealed by genetic parameters, i.e., GST=0.168 and FST=0.167. The results of principal component analysis on allele frequencies clearly revealed unique regional patterns of differentiation in genetic components among populations “with” and “without” vegetative regeneration by root suckers. The American beech populations consist of two genetically distinct clusters, one from the Gulf-coastal plain, eastern coastal plain, Piedmont Plateau and Ozark Plateau; and the other from the remaining northern glaciated territories. Populations from the Blue Ridge and Great Smoky Mountains turned out to belong to the latter cluster, which is also characterized by extensive regeneration via root suckers. The consequences of regional differentiation in genetic components are discussed in relation to the postglacial spread from refugia to the current geographic distributions and the mode of reproduction.

Molecular Systematics of Trilliaceae I. Phylogenetic Analyses of Trillium Using matK Gene Sequences

matK was conducted using 41 Trillium taxa and two out-group taxa (Veratrum maackii and Helonias bullata). A total of 1608 base pairs were analyzed and compared., and then there were 61 variable (36 informative) sites among Trillium species. Fifteen insertion/deletion events (indels) of six or fifteen base pairs were also detected. Phylogenetic analyses of the sequence data revealed that the subgenus Phyllantherum (sessile-flowered species) forms a distinct monophyletic group, whereas the subgenus Trillium (pedicellate-flowered species) does not form a monophyletic group, and is composed of three distinct groups and three basally located species in the tree: (1) the Erectum group, (2) the Grandiflorum group, and (3) the Pusillum group and (4) the three species, including T. govanianum, T. undulatum, and T. rivale. T .rivale appears to be the most basally diverged and a very specialized taxon among the ingroup members. Our matK data indicated that the closest relative of the subgenus Phyllantherum is the Grandiflorum group. The results are concordant with the results of the RFLP analysis of cpDNA and also more or less with those of the cladistic analysis of morphological characters.

Distribution and differential expression of (E)-4,8-dimethyl-1,3,7-nonatriene in leaf and floral volatiles of Magnolia and Liriodendron taxa

Analyses of volatiles emitted from artificially damaged leaves attached to branches of seven Magnolia taxa revealed the presence of (Z)-3-hexenyl acetate, (Z)-3-hexenol (the green odor compounds), and several mono- and sesquiterpenes, e.g., (Z)- and (E)-β-ocimene and caryophyllene. An herbivore-induced leaf volatile, (E)-4,8-dimethyl-1,3,7-nonatriene, known as a predator attractant in agricultural plants, was emitted 4–6 hr after leaves were damaged in M. hypoleuca. The damaged leaves of M. grandiflora, however, immediately released (E)-4,8-dimethyl-1,3,7-nonatriene. Undamaged leaves of Magnolia species examined did not emit volatile compounds. In addition, detached flowers of six Magnolia taxa and Liriodendron tulipifera also emit (E)-4,8-dimemyl-1,3,7-nonatriene as a floral volatile (up to 30% in some species); the chemical was also emitted from the intact flowers of M. heptapeta and M. salicifolia.

Phenotypic plasticity in Cardamine flexuosa: variation among populations in plastic response to chilling treatments and photoperiods

Variability in the plastic responses of seven life history traits to different chilling and photoperiod regimes was studied in four wild populations of Cardamine flexuosa. This species, a winter-green or year-long annual, showed a facultative long-day and chilling requirement for flowering. Considerable variation among populations was noted in plasticity of all traits. Differences in plasticity were greater among three paddy field populations from different climatic areas than between adjacent populations under different disturbance regimes. A paddy field population (OP) and an adjacent orchard population (OG) exhibited similar plasticity, in both amounts and patterns of response. TP, a Japan Sea coast population, was distinct from three other populations, especially in the small amounts of plasticity. Differences in amount of response were much more common than differences in pattern of response. Character expressions of five traits were significantly correlated with the number of days to flowering. Days to flowering and the numbers of inflorescences and siliques showed high negative correlations because the branching ability of meristems decreased with delay of flowering.

The changing prevalence of respiratory symptoms in atopic children in response to air pollution

Following the promotion of anti‐air pollution measures in steam power stations using crude oil, atmospheric concentrations of sulphur dioxide, nitrogen dioxide and suspended particulates have declined. These changes in atmospheric concentrations were accompanied by a decline in the prevalence of respiratory symptoms among schoolchildren living near the power stations. In analysing the correlation between air pollutant concentrations and the prevalence of respiratory symptoms, those with positive skin reactions to house dust extract (the positive group) showed a more significant correlation coefficient compared to those who had never had a positive skin reaction (the negative group). In addition, schoolchildren more heavily exposed to air pollutants showed the higher prevalence of respiratory symptoms than the others. With regard to the kind of air pollutants, both sulphur dioxide and nitrogen dioxide were more closely associated with the prevalence of respiratory symptoms than suspended particulates. This study has therefore demonstrated that the positive group is a useful population for monitoring the health effects associated with low‐degree air pollution of gaseous agents.