Showing papers in "Plant Species Biology in 1997"

Chemical Divergence in Floral Scents of Magnolia and Allied Genera (Magnoliaceae)

Abstract: Floral scents emitted from Magnolia, Michelia and Liriodendron taxa native to or cultivated in North America, Mexico and Japan were collected by the headspace method and analyzed using gas chromatography – mass spectrometry (GC-MS) Volatile compounds are widespread in the flowers of angiosperms and the chemical property of the scents can be distinguished in taxa For example, the primary chemical in the scent of Magnolia virginiana growing in Louisiana (USA) is linalool, whereas in Maryland (USA) population flowers emit 2-phenylethanol The flowers of M grandiflora and M tamaulipana both emit a number of monoterpenes, mainly geraniol derivatives, but scents of M pyramidata yield mainly fatty acid esters Caryophyllene is exclusively emitted by M sieboldii ssp japonica, isobutyl acetate by Michelia figo, and 1,2-dimethoxybenzene by M salicifolia The flowers of L tulipifera and L chinense emit mainly hydrocarbon-terpenoids, the former dominated by limonene, the latter by afarnesene In some closely related disjunct taxa distributed in North America and eastern Asia the floral scents closely resemble each other, eg, Magnolia tripetala (North America) and M hypoleuca (Japan) both strongly emit methyl benzoate Another set of disjunct taxa, M acuminata (North America) and M heptapeta (China) both exclusively emit pentadecane, a hydrocarbon In some species of Magnolia, volatile compounds present in floral scents are also emitted in damaged leaves This suggests these chemicals play different roles in various plant organs (deter leaf herbivores, attract parasitoids, attract insects to flowers, etc)

A Preliminary Study of the Pollination Ecology of Pedicularis in the Chinese Himalaya

Abstract: The pollination ecology of fourteen species of Pedicularis (Scrophulariaceae) was studied in the subalpinealpine zone of the Sichuan Himalaya. Bumblebees (Bombus Latr.) sternotribically pollinated rostrate, nectarless species with very long corolla tubes by scraping pollen. Pollinators on short-tubed, nectarless, rostrate species scraped or vibrated pollen, and nectariferous species were pollinated nototribically by nectar foragers or sternotribically by pollen foragers. Stigmas contacted residual pollen in the midline of the insect body. No evidence of lepidopteran pollination was found in any Pedicularis species. Pedicularis floral structure and function are considered to have coevolved with foraging selection by bumblebees, but pollination syndromes are not specific for a single bumblebee species nor are Bombus foragers restricted to a single plant species. Analysis of corbicular pollen loads of foragers on Pedicularis revealed a moderate degree of flower constancy, especially among foragers on nectarless flowers, probably contributing to speciation in the genus. Up to nine Pedicularis species flowered sympatrically and synchronously, and some species exhibited microhabitat selection. No putative hybrids were identified. Concepts of floral evoution in Pedicularis are in need of revision in light of new evidence presented here.

Demographic Genetics of the Japanese Beech, Fagus crenata, at Ogawa Forest Preserve, Ibaraki, Central Honshu, Japan. I. Spatial Genetic Substructuring in Local Populations

Abstract: The demographic genetic substructuring of local Fagus crenata populations at Ogawa Forest Preserve, Ibaraki Prefecture, central Honshu, Japan, was analyzed by means of demographic parameters and genetic markers using protein polymorphisms (allozymes). All individuals, including seedlings, various sizes of juveniles, and adult trees within two transects were mapped; size-class structures were analyzed based on DBH and DGH measurements, and their genotypes determined for 11 different allozyme loci (a total of 46 alleles), i.e., Aap1(3 alleles), Adh (3), Amy2 (6), Dia (4), Fum (3), Got1 (5), Got2 (3), Lap (6), Pgi (4), Pgm1 (4), and Pgm2 (5). Critical analyses were conducted to test whether genetic substructuring patterns in these two transects are correlated with the underlying environmental regimes of the habitats. Measurements of relative light intensity, soil moisture, pH, and C-N content were made for each block in the two transects. Principal component analyses (PCA) of the environmental variables revealed that two components (Z1 and Z2) were closely related to variations in light intensity and soil moisture. The projection diagrams obtained by the environmental variables were then overlaid with the spatially localized patterns of size-classes and genotype distributions of 11 allozyme loci examined. The results revealed that genetic variations are pooled in the juvenile trees of certain size-classes, consisting of overlapping generations which occur in the particular sites characterized by environmental regimes. Throughout the regeneration processes, new genetic diversities are introduced through seedlings with new genotypes into the population.

Demographic Genetics of the Japanese Beech, Fagus crenata, at Ogawa Forest Preserve, Ibaraki, Central Honshu, Japan. II. Genetic Substructuring among Size‐classes in Local Populations

Abstract: We investigated chronological changes in allozyme diversities in Fagus crenata populations by means of size-class discriminations, using allozyme variations in two transects established in a mixed beech-oak forest in the Ogawa Forest Preserve. All individuals within transects were divided into six size-classes based on their diameters: class 0, seedlings; class 1, juveniles <5 mm; class 2, 5 < juveniles < 10 mm; class 3, 10 < juveniles <25 mm; class 4, 25< juveniles <600 mm; class 5, 600 mm

Demographic Genetics of the Japanese Beech, Fagus crenata, in the Ogawa Forest Preserve, Ibaraki, Central Honshu, Japan. III. Population Dynamics and Genetic Substructuring within a Metapopulation

Abstract: The demographic genetic structure of a metapopulation of the Japanese beech (Fagus crenata Blume) in the Ogawa Forest Preserve was analyzed using allozyme variabilities as genetic markers. A total of 138 mature trees in an area of 30 ha were first mapped; their DBH was measured and leaf samples were collected and genotyped. A total of 38 multilocus genotypes in a combination of six loci and 22 alleles were detected. Spatial analyses, using Moran's I and coancestry (Rij) showed there was no conspicuous pattern of associations between genetic similarities and individual distances in scales larger than 30 m. In smaller, 5 m interval scales, however, gene dispersal from mother trees to juvenile trees was found in the ranges of 10 to 20 m in distance. The indirect measures of gene flow using multilocus genotypes revealed that most progenies were derived from the nearest patch populations and also from neighboring patch populations. Genetic subdivisions of the Ogawa metapopulation were analyzed on the basis of patch populations (Gst=0.234) and local populations (Gst=0.094), reflecting the effects of population fragmentation. Genetic neighborhood area (A) obtained in Ogawa was 3050–4091 m2, and effective population size (Ne) was 1.2–2.1 mature individuals. A very small Ne in Ogawa may reflect topographic complexity and past artificial disturbances of the habitats.

Morphological Variance among Populations of Three Tropical Orchids with Restricted Gene Flow

Abstract: Variance in floral morphology among populations was investigated in three species of Lepanthes (Orchidaceae) from Puerto Rico. Populations that share a common gene pool and similar environment are expected to share similar phenotypes, so that populations that are physically close should be more similar to each other than populations that are separated by large distances as gene flow is usually leptokurtic. Univariate and multivariate analyses of floral characteristics were compared using MANOVA and Linear Discriminant Function Analysis. Most groups of individuals (populations) differed significantly when analyzed by univariate or multivariate methods. Floral characteristics of populations separated by only few meters were often significantly different. No correlation between amount of morphological difference (square Mahalanobis distances) and inferred gene flow (physical distances) was present in any of three species studied. Other research has shown that genetic population sub-structuring is high and effective population size is extremely small in all three species of orchids. It is thus argued that the large amount of morphological differences among populations are likely a result of genetic drift or phenotypic plasticity, and are unlikely to be the result of natural selection at the micro habitat level.

Marked Spatial Genetic Structure in Three Populations of a Weedy Fern, Pteris multifida Poir., and Reestimation of Its Selfing Rate

Abstract: Allozyme markers were used to characterize spatial genetic structure for the weedy fern Pteris multifida within three populations growing on the man made stone walls. Even visually distinct genetic substructures were observed in all the examined populations. Spatial autocorrelation analysis using Moran's /indicated that the patch size of P. multifida was as small as 4–9 m. Estimation of outcrossing rate is known to be severely biased downwards if the presence of spatial genetic structure is ignored. Mating system of this fern species was reported as mixed (mean selfing rate: 0.435). However, fixation indexes calculated in small patches less than 3–10 m wide were not significantly different from Hardy-Weinberg equilibrium and thus P. multifida's mating system was considered to be outcrossing.

Crown Architecture of Two Understory Palm Species of the Genus Licuala in a Tropical Rain Forest

Abstract: The crown architecture of two understory palms, Licuala arbuscula and L. bintulensis, was studied in a tropical lowland rain forest in West Kalimantan, Indonesia. The two species had only stagnant stems and developed a hemispherical crown formed with long petioles and fan-shaped leaf blades. Petioles at leaf emergence stood vertically, while petioles of older leaves were bent downward. Leaves were concentrated on the top of the crown. The leaf blade deflected ca. 40° from the horizon to the inside of crown when the petiole stood vertically. Because the divergence angle between the leaf blade and its petiole did not change, the zenith angle of the leaf blade changed with that of the petiole. This divergence angle between leaf blade and petiole allowed the formation of a compact foliage clump with less overlap at the top of the crown, and the horizontal expansion of leaves at the middle of the crown. The size and number of leaves within the crown increased with crown development, and the ratio of the petiole to the leaf blade length increased. This enabled the two palms to extend their assimilative area over the non-photosyn-thetic supportive part as petioles in the small size stage and to avoid the overcrowding of leaves within a crown with crown development. These results suggest that the two understory palms develop crowns as to avoid self-shading through adjusting the divergence angle between leaf blade and petiole and through the allometry between them.

Natural Variation in Flowering Time among Populations of the Annual Crucifer Arabidopsis thaliana

Abstract: Genetic variation in flowering time was studied in four natural populations of Arabidopsis thaliana, using greenhouse experiments. Two populations from ruderal sites flowered early, two others from river dykes late. However, the late flowering plants flowered almost as early as the others after cold treatment of the seeds. The observed differences in flowering time have consequences for the potential life cycles of plants in the field. Plants from ruderal sites can be summer or winter annual, perhaps even have two generations per year. The strong response to cold treatment of plants from the dyke vegetations makes their life cycle strictly annual. Segregation analyses of the F2-s from crosses between early and late plants suggests that this variation in flowering time was genetic, with a dominant major gene for late flowering. Lateness in combination with vernalization responsiveness appears to be mostly due to a single gene in A. thaliana. It is hypothesized that early flowering ecotypes have evolved from late flowering ecotypes in different habitats by a loss mutation in the inhibitory mechanisms that delays flowering until after a period of low temperatures.

Floral Ecology, Carinal‐Lobe Release, Pollination and Reproductive Success in the Wild and Domesticated Forms of Hyptis suaveolens (L.) Poit. (Lamiaceae) in Mexico

Abstract: Hyptis suaveolens is a weedy species growing wild in the tropics. In Mexico, additionally, it has two non-weedy domesticated forms. The wild form is designated as violeta and the domesticated ones as blanca-violeta and blanca, based on stem, flower and seed characters. The wild form has flowers with violent carinal explosion, while the domesticated forms have flowers with non-violent carinal explosion. The carinal structure is formed by the median lobe of the lower corolla lip which conceals the stamens and the stigma even after the unfolding of the other lobes of the corolla. The carinal lobe explodes when the flower visitor lands on the flower. All three forms are foraged indiscriminately by the same species of bees. Flies and a wasp also forage on these flowers, but their role in pollination is negligible. The foraging behaviour of bees suggests that selfing is promoted during forenoon hours and outcrossing during afternoon hours. There is a direct relation between flower density, bee frequency and reproductive success. Bees approach the flowers from the front probe in an upright position; and they effect carinal-tripping and sternotriby while probing for either pollen, nectar, or both. Apis and Exomalopsis probe the flowers also from above the upper corolla lip in which case pollination is not ordinarily effected. All three forms are both self- and cross-pollinating. The domesticated forms have higher fecundity than the wild. The wild form reseeds itself, while the domesticated ones cannot, as their larger fruiting calyx requires seed-dispersal agents. H. suaveolens, particularly its domesticated forms, can be best exploited as a potential new crop.

Self-incompatibility and Clonal Growth in Anemopsis californica

Abstract: The occurrence of self-incompatibility in Anemopsis californica (Saururaceae) was investigated in populations located in Irvine, California. Selfed and outcrossed pollinations (pollinations between two populations) carried out in 1995 in a natural population demonstrated that seed production for selfed inflorescences was significantly lower than for outcrossed inflorescences. Naturally pollinated inflorescences produced more seeds per inflorescence than artificially selfed individuals, but far fewer than the artificially outcrossed plants. Additional pollinations were performed the following year in a controlled greenhouse environment using plants collected from the experimental field population. Pollination treatments included selfed and outcrossed pollinations, plus an additional intra-population pollination to investigate the effect of clonal growth on seed production. Results from greenhouse crosses indicated that seed production for the outcrossed individuals was significantly higher than for selfed individuals or individuals used in intra-populational crosses. No electrophoretic variation was detected within any of the populations used in crosses, and most putative loci were identical across populations. Results from these studies indicate that self-incompatibility is present in Anemopsis californica, and that populations may consist of clonally replicated individuals with the same incompatibility reaction.

Pollination of Goodyera foliosa var. maximowicziana (Orchidaceae) by the Bumblebee Bombus diversus diversus

Abstract: Pollination of the orchid Goodyera foliosa var. maximowicziana was studied during the autumn of 1995 and 1996 in Matsue, Japan. The flowers were rarely visited by 5 insect species, among which only the bumblebee Bombus diversus diversus, usually workers, was the legitimate pollinator. They received the pollinarium on the galea of proboscis. Nectar-robbing ants frequently adhered to the viscidium of the pollinarium, and such pollinaria were never dislodged by the pollinator. The percentage of pollinated flowers was 60.1%, and mean fruit set per rachis was 57.1%. The percentage of flowers that lost a pollinarium was only 17.5%. Such effective pollination should be due to the property of sectile pollinia; a single pollinarium sticking to a bumblebee's proboscis was used repeatedly to Pollinate more than one flower. Protandry and longevity of individual flowers were also described in relation to pollination.

Aerial Seed Bank and Intra‐population Variability in Germinative Strategies of Verbascum phlomoides L.

Abstract: Study of germination using fresh seeds and seeds from an aerial seed bank of a young Verbascum phlomoides population revealed the existence of primary dormancy that blocks immediate germination and of substantial variations in the subsequent germination capability. The heterogeneity of desynchronized individual responses in a species with a high germination capacity would make it possible for the descendants of one or more individuals to occupy a disturbed site. Exposure to cold followed by a return to the light accelerating germinative response would appear to enhance late spring germination.

Comparative Studies of the Hanabusaya asiatica and its Allied Groups by RAPD Analysis

Abstract: The phylogenetic relationships between Hanabusaya asiatica and its allied groups were assessed by Randomly Amplified Polymorphic DNA (RAPD) analysis of genomic DNA, and their taxonomic status was reevaluated at the molecular level. The analyzed plants consisted of 36 populations of eight genera and 27 taxa. Forty-two out of 101 primers(10-mer) screened were able to amplify DNA. Only 19 primers, however, actually succeeded in DNA amplification, resulting in 523 randomly amplified DNA fragments. The analyzed taxa showed very high polymorphism, allowing each individual taxon to be identified based on RAPD analysis. All eight genuses were differentiated from each other at the 0.86 level of similarity index value. In particular, Hanabusaya asiatica was distinguished from its closely related genus. Intraspecific and interspecific relationships were quite close, at levels ranging from 0.77 to 0.99. Our RAPD analysis supports the previous data based on morphological and palynological studies.

Genetic variation and relationships of Japanese populations of Oxalis corniculata L. (Oxalidaceae) detected by random amplified polymorphic DNa (RAPD)

Abstract: RAPD analysis was applied to estimate the genetic variability in Japanese populations of Oxalis corniculata. This species comprises two floral morphs, homostyled and long-styled, with different breeding systems (i.e., autogamy in the homostyled populations and mixed mating in the long-styled populations). The number of RAPD phenotypes tended to be larger in homostyled populations than in long-styled ones, and genetic diversity expressed by Simpson's indices of diversity was also generally larger in the former than in the latter. To examine the effects of breeding system on the levels of genetic differentiation among populations, two- and one-level hierarchical variance partitionings were performed by the analysis of molecular variance (AMOVA). In two-level AMOVA, significant variance component between the floral morphs was observed. In one-level AMOVA, the proportions of variance partitioned among populations within each floral morph and among individuals within populations were similar in the homostyled and long-styled populations, despite the difference in breeding system. To obtain insight into the relationships among individuals and/or populations, principal co-ordinate analysis using 184 individuals (PCOA), and clustering analysis of 12 populations (UPGMA) were performed. PCOA indicated that the range of variation for homostyled individuals was more inclusive than that for long-styled ones. A UPGMA dendrogram that consisted of two clusters showed that the long-styled populations were nested in the homostyled ones.