bluuebunny/crossref_metadata_2025 huggingface dataset:
Some Aspects of the Pollination Ecology of Wild Leek, Allium tricoccum Ait.
Authors: Nault Andrée , Gagnon Daniel
Published: February 2005

Abstract Some aspects of the pollination ecology of a wild leek (Allium tricoccum Ait.) population were studied in Gatineau Park, Southern Québec, Canada. Self‐compatibility was determined by a pollinator exclusion experiment. Pollinator limitation of seed production was tested by comparing naturally pollinated plants with hand cross‐pollinated plants. The insects observed on the umbels were collected for identification. Wild leek was found to be self‐compatible. Seed production does not seem to be limited by pollinator activity. An important year to year variability of pollinator activity was observed according to the flowering intensity within the population.
Nectar Sucking Pollinators in Hybrid Derivatives of Epimedium (Berberidaceae)
Authors: Suzuki Kazuo
Published: February 2005

Abstract The followings are detected in the plants derived from hybridization between Epimedium diphyllum and E. sempervirens. Bombus ardens queen sucked nectar from flowers with spurs of which lengths correspond to those of the bees' proboscides. Queens of B. ardens and males and females of Tetralonia nipponensis sucked nectar indiscriminately from reddish purple and white flowers. B. hypocrita queens, which were not pollinators, perforated spurs and thieved nectar.
The Life History Flora of Japan—A New Series
Authors: Kawano Shoichi
Published: February 2005

AbstractPlant Species Biology will publish a continuing series of papers on the biology and life history of vascular plant species indigenous to or well naturalized in the flora of Japan. This paper sets forth the guidelines and format for contributors to this series. This new series attempts to establish a record as complete as possible concerning all aspects of the life history characteristics as well as significant biosystematic characters of the species under consideration, and keen attention will be given to the species which are becoming very rare and endangered, especially in the lowland areas and aquatic habitats (e.g., rivers and ponds).
Floral Biology of Heterotropa tamaensis (Aristolochiaceae) in Japan
Authors: Sugawara Takashi
Published: February 2005

Abstract The floral biology of Heterotropa tamaensis (Makino) F. Maekawa was investigated in native populations. The flowers were protogynous, and the stigmas and anthers were distant from one another. These floral characters are significant for cross‐pollination, but breeding experiments showed that the flowers are fairly self‐compatible and their pollination is obligately dependent upon animal pollen vectors. The most efficient pollinator for H. tamaensis is a fungus gnat, a member of Mycetophylidae. The fungus gnat visited the flowers relatively frequently and often carried many pollen grains on their hairy bodies. Furthermore, their eggs were frequently found within flowers collected from native habitats. The fungus gnats actively moved about within the flowers and often touched the stigmas and anthers with their bodies. Therefore, H. tamaensis seems to be predominantly self‐pollinated, though cross‐pollination may occur rarely. The presence of fungus gnat eggs in many flowers strengthened Vogel's hypothesis that the flowers of Heterotropa species mimic the basidiomycetes, in which fungus gnats usually oviposit.
Leaf Survivals of Tree Species in Deciduous Broad‐Leaved Forests1)
Authors: Kikuzawa Kihachiro
Published: February 2005

Abstract Leaf survival patterns of tall trees, small trees and shrubs were surveyed in temperate deciduous broad‐leaved forests in northern Japan. Leaves of tall trees which constitute the crown layer of the forest emerge simultaneously in spring as a flush and also fall simultaneously in autumn. This was considered to be a “competitive type” of leaf survival strategy. Species which invade open sites near rivers show a “succeeding type” of leaf‐emergence and leaf‐fall. Their leaf longevities are short. They are pioneer strategists and are assumed to use abundant resources luxuriously by shedding older low‐efficient leaves and producing new, high‐efficient leaves. Intermediate between the two is a type considered to be adapted to light gaps in forests. Leaf longevities of species in forest understorys where shade stress prevails were long. To prolong leaf longevity is the method to utilize limited resource efficiently. Three strategies based on the two axes of stress and disturbance were applied to the leaf survival patterns of trees. Environmental conditions around a tree change with height growth of the tree. Leaf survival patterns also change with the development of trees. A three‐dimensional graph model which expresses such changes as a function of tree‐height is presented. Mean longevities of leaves compared between 1‐year‐old seedlings and adults revealed that differences between the two were larger in “intermediate type” species than for succeeding or flush type species.
Optimal Timing of Leaf Expansion and Shedding in a Seasonally Varying Environment1)
Authors: Harada Yasushi , Takada Takenori
Published: February 2005

Abstract Optimal utilization of a seasonally varying environment by deciduous trees is studied by analyzing two mathematical models. Both models are constructed from the viewpoint of carbon economy. First, optimal times for leaf expansion and shedding in the seasonal environment that maximize the total net gain of photosynthelic products are obtained. We show that both leaf ageing and leaf mortality select for delayed leaf expansion. We suggest that the delay of leaf expansion for canopy trees is important in allowing spring ephemeral species to survive in the temperate forest floor. Second, a two‐layer model, in which the lower layer of leaves is shaded by the upper, is analyzed to study the effect of self‐shading on the optimal pattern of leaf expansion. We show that the succeeding expansion of leaves is more advantageous than flushing expansion, even in the situation where all leaves are constructed by the products in the previous year.
Interactions between, Camellia japonica and its Seed Predator Curculio camelliae
Authors: Okamoto Motoharu
Published: February 2005

Abstract Seeds of Camellia japonica are heavily attacked by Curculio camelliae. To evaluate the efficacy of fruit wall thickness against the curculio attack, correlations of fruit wall thickness with the ratio of seed survival (RSS) and with the ratio of oviposition success of the curculio beetles (ROS) were investigated on fruits collected at Camellia stands in Kinki District. While ROS exhibited negative correlations with the thickness of fruit wall in every stand, RSS showed different modes in accordance with the population density of the curculio. At low density, no significant difference was seen in RSS between trees with thicker fruit wall and those with thinner ones; the latter trees, generally bearing many fruits, had more seeds surviving than the former, generally bearing a few fruits. In high density curculio populations, RSS values showed correlation with the thickness of the fruit wall and more seeds survived in trees with thicker fruit walls. These facts suggest that two contrasting behavioral traits are present in a single species C. japonica and their efficacies differ in accordance with the curculio density.
The Pollination Biology of Heloniopsis orientalis (Thunb.) C. Tanaka (Liliaceae)
Authors: Takahashi Hiroshi
Published: February 2005

Abstract The pollination biology of Heloniopsis orientalis was investigated in the lowlands of south central Japan. The receptive stigma emerges from the perianth before the opening of the perianth, and anther dehiscence is late about two days for perianth opening. The flower therefore is protogynous even though no insects visit the unopen flowers. Receptivity of the stigma is maintained for about 8 days, and even the 10 day‐old flower can produce seeds. Self‐pollination may be rather common in H. orientalis, which is self‐compatible, in particular in the flowers which open on days unfavorable for insect activity. Many species of Diptera and Hymenoptera forage on the flowers, and almost any insect can be their pollinator. Long life, self‐compatibility of the flowers, and many kinds of pollinators seem to be factors favoring H. orientalis, which blooms in very early spring when the pollinator supply is unstable but which nevertheless bears many seeds.
Uniclonal Population Structure in the Pentaploid Obligate Agamosperm Taraxacum albidum Dahlst.
Authors: Menken Steph B. J. , Morita Tatsuyoshi
Published: February 2005

Abstract Electrophoretic data were used to assess levels of clonal diversity within and among populations of Taraxacum albidum Dahlst., a pentaploid obligate agamosperm indigenous to Japan. All specimens sampled from the entire distribution range shared the same 19‐locus genotypic profile except for one. This single mutant differed in one allele at one locus only. Contrary to this extreme monomorphism, clonally reproducing species usually consist of multiclonal populations. It is hypothesized that T. albidum recently originated through hybridization between a sexual diploid species of the section Mongolica (most likely T. japonicum Koidz.) and an unknown polyploid Mongolica species.
Distribution of Sexual and Agamospermous Populations of Eupatorium (Compositae) in Asia
Authors: Kawahara Takayuki , Yahara Tetsukazu , Watanabe Kuniaki
Published: February 2005

Abstract Examinations of chromosome number voucher specimens show that sexual diploid and agamospermous polyploid plants of Eupatorium in Asia can be distinguished by morphology, fertility, and stainability of pollen grains. Using these criteria, reproductive systems (sexual vs. agamospermous) were estimated for 558 herbarium specimens of Eupatorium in East Asia. Of 22 taxa examined, six included both sexual and agamospermous specimens; those of one taxon were all agamospermous; and those of 15 taxa were all sexual. This result shows that 21 taxa are not agamospermous microspecies but are differentiated at the diploid level. Sexual populations of most taxa had restricted geographical distributions. Eupatorium chinense var. chinense and var. oppositifolium consisted of both sexual and agamospermous populations. Sexual populations of these two varieties were allopatric and distinct in external morphology, suggesting differentiation at the species level. The specimens of E. heterophyllum s. str. were all agamospermous, while those of E. mairel, often treated as synonymous with E. heterophyllum, were sexual.

In comparing East Asian and North American Eupatorium for the distributional patterns of sexual and agamospermous populations, three differences can be pointed out: (1) Agamospermous plants of autopolyploid origin have evolved in eight species and are widespread in North America; while most agamospermous plants in East Asia may be of allopolyploid origin, have relatively restricted ranges, and are less frequent than the diploid plants with the exception of in E. chinense var. oppositifolium, (2) The number of sexual species with wide range is greater in North America than in East Asia. (3) The number of sexual species with restricted ranges is greater in East Asia than in North America. The results obtained suggest that speciation among the plants of Eupatorium has occurred more recently in East Asia than in North America.
The Floral Biology of Tricyrtis affinis Makino (Liliaceae)
Authors: Takahashi Hiroshi
Published: February 2005

Abstract The floral biology of Tricyrtis affinis was investigated and compared with that of four species of Tricyrtis which had been reported by the author. The flower opens for two days and is protandrous as in T. latifolia, T. flava, and T. ohsumiensis. The primary pollinators of T. affinis were Bombus diversus diversus and Amegilla sp., which were not different from those of the previous species although the shape and the color of the T. affinis flower are somewhat different from the others. The whole perianth of T. affinis absorbs UV light fairly well, and the large purple spotted area near the base absorbs it markedly well. The UV absorption pattern of the T. affinis flower is similar to that of T. latifolia. T. affinis is also self‐compatible, like the others, and seeds obtained by self‐pollination germinated well. Pollination of T. affinis is characterized by a refined system.
Regulatory Mechanisms of Reproductive Effort in Plants III. Plasticity in Reproductive Energy Allocation and Propagule Output of Two Grass Species, Oryza sativa cv. Akihikari and Coix ma‐yuen Cultivated at Varying Densities and Nitrogen Levels, and the Evolutionary‐Ecological Implications
Authors: Kawano Shoichi , Hayashi Seizo , Arai Hirohito , Yamamoto Masako , Takasu Hideki , Oritani Takashi
Published: February 2005

Abstract Plasticity in growth, reproductive energy allocation (RA), reproductive output (PN), propagule weight (Pw), fecundity, and relative cost of producing single propagules (RA) and their interlinked properties were critically investigated in two grass species, Oryza sativa L. ev. Akihikari and Coix ma‐yuen Roman., grown under varying densities and soil nitrogen levels.

In these two species, exceedingly marked plastic but parallel responses were detected in all significant yield and reproductive traits under changing growing conditions. The results obtained also corresponded very well with those for Coix ma‐yuen, Helianthus annuus and Glycine max reported in our previous works in this series (Kawano and Hayashi, 1977; Kawano and Nagai, 1986; Nagai and Kawano, 1986).

In Oryza sativa, plants cultivated at higher densities exhibited proportionately lower individual biomasses, lower seed outputs, and smaller grain size in response to increasing density, although RA remained more or less constant throughout all five different densities, and fecundity showed an abrupt decrease in the overcrowded cohort beyond 400 plants/m2. In this experiment, Coix ma‐yuen was grown only under conditions of extraordinarily overcrowded density (over ca. 4,500 plants/m2) with extremely broad nitrogen fertilizer levels from 20 N (20 kg ammonium sulfate/10 ARE) to 100 N (100 kg/10 ARE). This species likewise demonstrated a remarkably sharp responsive plasticity in significant reproductive parameters with increasing N‐levels, just as was found with changing density (Kawano and Hayashi, 1977).

One common significant conclusion obtained from the present series of studies was that sexual propagule production under limited resource availability—for example, a sharp decline in solar radiation and soil nutrients, due to strong interference in higher density plots—is exceedingly costly, implying that there occurs a significant change and variance in this important fitness component under changing environmental conditions. This was most conspicuously demonstrated by a very sharp increase in relative energy partitioning to a single propagule in response to increased density and decreasing nitrogen levels, the relative energy cost to a single seed (RA) increasing from 1.00 to 31.02, and from 1.00 to 10.31 in both paddy field and pot populations of Oryza sativa cv. Akihikari, respectively, and from 1.00 to 4.23 in field populations of Coix ma‐yuen. The adaptive significance of induced changes in several reproductive traits under changing environmental conditions was also discussed in the light of all the evidence available today.
Analysis on Pollen Flow in a Hybridizing Population between Farfugium hiberniflorum and F. japonicum (Asteraceae: Senecioneae): Derivation of an Empirical Formula Describing Frequency of Hybridization as a Function of Interspecific Plant Distance
Authors: Yamaguchi Hirofumi , Yahara Tetsukazu
Published: February 2005

Abstract The frequency of hybrids was monitored using progenies grown from seeds collected from open‐pollinated plants in mixed populations of Farfugium hiberniflorium and F. japonicum. The results showed that hybrids are more frequently derived from F. japonicum than from F. hiberniflorum. This directionality of hybridization and extraordinarily high frequency of hybrids among progenies grown from seeds from open‐pollinated plants of F. japonicum enabled us to derive an empirical equation describing the frequency of hybridization as a decreasing exponential function of interspecific plant distance. The relationship between these two variables fitted a function describing pollen flow from a particular plant. This finding suggests that interspecific pollen exchange can be viewed simply as a process dependent of interspecific plant distance, and the actual rate of hybridization is determined by the level of cross‐compatibility of a particular species.
Pollination Biology of Anisomeles indica and A. malabarica (Lamiaceae)
Authors: Raju A. J. Solomon , Reddi C. Subba
Published: February 2005

Abstract The flowers of Anisomeles indica and A. malabarica are zygomorphic, bilabiate, gulletshaped and nectariferous, and are visited by insects as well as birds for nectar and/or pollen. The bees Xylocopa latipes, X. Pubescens, Amegilla sp., Apis florea and Megachile sp., and the sunbirds of the genus Nectarinia are the principal pollinators of A. indica, while the former three and the last and the wasp Rhynchium metallicum are for A. malabarica. Pollination by Xylocopa and Nectarinia is nototribic and that by Apis, Megachile, Amegilla is noto‐ and/or sternotribic. The small bodied Trigona, Pseudapis and Ceratina collected pollen sternotribically. It is concluded that adaptation of both species to insect and bird pollination and to a flexible breeding system involving both selfing and crossing, safeguards their survival under changing environments.
Seed Germination Biology of the Narrowly Endemic Species Lesquerella stonensis (Brassicaceae)
Authors: Baskin Jerry M. , Baskin Carol C.
Published: February 2005

Abstract Lesquerella stonensis (Brassicaceae) is an obligate winter annual endemic to a small portion of Rutherford County in the Central Basin of Tennessee, where it grows in disturbed habitats. This species forms a persistent seed bank, and seeds remain viable in the soil for at least 6 years. Seeds are dormant at maturity in May and are dispersed as soon as they ripen. Some of the seeds produced in the current year, as well as some of those in the persistent seed bank, afterripen during late spring and summer; others do not afterripen and thus remain dormant. Seeds require actual or simulated spring/summer temperatures to come out of dormancy. Germination occurs in September and October. Fully afterripened seeds germinate over a wide range of thermoperiods (15/6–35/20°C) and to a much higher percentage in light (14 h photoperiod) than in darkness. The optimum daily thermoperiod for germination was 30/15°C. Nondormant seeds that do not germinate in autumn are induced back into dormancy (secondary dormancy) by low temperatures (e.g., 5°C) during winter, and those that are dormant do not afterripen; thus seeds cannot germinate in spring. These seed dormancy/ germination characteristics of L. stonensis do not differ from those reported for some geographically widespread, weedy species of winter annuals and thus do not help account for the narrow endemism of this species.
Pollination Ecology ofPedicularis punctataDecne. (Scrophulariaceae) in the Kashmir Himalaya
Authors: Macior Lazarus Walter
Published: February 2005

AbstractThe pollination ecology ofPedicularis punctatawas studied in the Pir Panjal Range of the Kashmir Himalaya in the summer of 1989. Its nectarless, rostrate, long‐tubed flower was found to be pollinated exclusively byBombusforagers vibrating pollen while the stigma contacted pollen in the pollinator's cervical crevice. Workers ofBombus tunicatusandB. flavothoracicuscomprised 95% of its pollinators. Pollen‐foraging fidelity of its pollinators was greatest where diversity ofBombus‐pollinated plant species in three plant communities was least. Foragers on other plants carried virtually noPedicularispollen.P. punctatais a mid‐season blooming species similar in its pollination syndrome to comparable species in other geographic regions. The enigmatic function of its long, nectarless corolla tube, even more exaggerated in other Asiatic species, requires further investigation.
Sex Change and Population Dynamics in Arisaema (Araceae) II. An Examination on the Evolutionary Stability of Sex Changing Schedule of A. serratum (Thunb.) Schott
Authors: Kinoshita Eiichiro , Harada Yasushi
Published: February 2005

Abstract The evolutionary stability of the sex‐changing habit of Arisaema serratum was examined. To evaluate reproductive success through male functioin properly, the mathematical formulation of Kakehashi and Harada (1987) was employed. Individuals were classified by both their size and sexual state, and the genetic contribution of individuals was estimated by calculating their reproductive value. It was shown that in the size classes where sex change actually occurs, the reproductive values of males and females are basically the same. This means that the genetic contribution of individuals in these size classes is the same whether they are male or female, and no selection pressure is working to change the male ratio in these classes. Thus, it is concluded that the size at which sex change occurs is evolutionarily stable. The adaptive significance of the size of first reproduction was also discussed.
Flowering and Fruiting Phenology of Magnolia hypoleuca
Authors: Kikuzawa Kihachiro , Mizui Norio
Published: February 2005

Abstract The floral biology of Magnolia hypoleuca, a tall tree species widely distributed in Japan, was studied in a deciduous broad‐leaved forest in Hokkaido near the northern limit of distribution of the species. The flower is large, protogynous and nectarless. Its petals close after the female stage and again after the male stage. The mean duration of flowering of an individual flower is 3–4 days, while the flowering period of an individual tree lasts up to 40 days. The main pollinators of the flowers were beetles. Success of pollination is assumed to be affected by weather conditions at anthesis. Average fruit sets (ratios of fruits to flowers) were 13–25%. Hand‐pollination of 44 flowers produced a significantly higher fruit set (28 fruits) than control flowers (33/133). These results suggest that the fruit set is limited by pollination. The frequency of infertile ovules was higher in controls than in hand‐pollinated fruits, indicating that the seed set was also limited by pollination. We propose a mimicry hypothesis in which the non‐rewarding female‐stage flower mimics the rewarding male‐stage flower to explain the short life‐span of an individual flower, the long flowering period of an individual tree, and the coexistence of flowers of various stages on a single tree.
Evolution of Inbreeding and Outcrossing in Ferns and Fern‐Allies
Authors: Soltis Pamela S. , Soltis Douglas E.
Published: February 2005

Abstract Mating systems of 18 species of homosporous ferns follow a bimodal distribution, similar to that observed for seed plants (Schemske and Lande, 1985). Most species are highly outcrossing, a few are inbreeding, and two species examined to date have mixed mating systems. Equisetum arvense and several species of lycopods are also highly outcrossing. Several mechanisms, including inbreeding depression, antheridiogen, and ontogenetic sequences that result in effectively unisexual gametophytes, promote outcrossing in homosporous ferns and perhaps other homosporous pteridophytes as well. In some species of homosporous ferns, selection has favored the evolution of inbreeding as an adaptation for colonization. High levels of intra‐ and interpopulational gene flow via spore dispersal, coupled with high levels of intergametophytic crossing, generally lead to genetically homogeneous populations and species of homosporous ferns. However, rock‐dwelling ferns and ferns from xeric habitats may exhibit significant population genetic structure due to physically patchy habitats. Reticulate evolution in homosporous ferns may be enhanced by high levels of intergametophytic crossing.
Mating System and Genetic Structure of Natural Populations in Wild Rice Oryza rufipogon*
Authors: Morishima Hiroko , Barbier Pascale
Published: February 2005

Abstract Variation in mating system in the common wild rice Oryza rufipogon was studied in relation to life‐history traits to examine its effect on the genetic structure of natural populations. Results of general survey in Asian populations and of a detailed population study carried out in Thailand are presented. Estimated outcrossing rates of Asian wild rices ranged from 5 to 60%, though cultivated rices are predominantly selfing. Interpopulational comparison showed mating system is associated with life‐history traits, resulting in the differentiation into two ecotypes; predominantly selfing annuals having high reproductive effort and mixed‐mating perennials having low reproductive effort. Resource allocation to pollen production vs. seed production (pollination effort) proved to be correlated with outcrossing rate. Isozyme study showed that both mating system and reproductive system jointly influence genetic structure of populations such as the level of intrapopulational variability and the extent of interpopulational differentiation. Evolution of selfing in this plant group might have been promoted by selection for seed propagation which was brought by environmental change and/or habitat disturbance.
Evolution of Mating Systems in Island Populations ofCampanula microdonta: Pollinator Availability Hypothesis
Authors: Inoue Ken
Published: February 2005

AbstractIsland populations ofCampanula microdontaand mainland Honshu populations ofC. punctatahave several different mating systems: self‐incompatible (SI) and therefore obligately outcrossing in mainland Honshu and Oshima Island; self‐compatible (SC) and largely outcrossing in the northern islands of Toshima and Niijima; and SC and predominantly inbreeding southern ones of Miyake and Hachijo. Several features possibly associated with the mating systems are described. A hypothesis is proposed that the mean and variance of pollinator availability together with inbreeding depression could explain the observed patterns of mating system as the results of evolution.
Breeding Systems in American and Asian Trillium Species by Means of Chromosome Analyses
Authors: Fukuda Ichiro
Published: February 2005

Abstract Species of Trillium have a disjunct distribution occurring in both North America and eastern Asia. In North America all 36 species are diploid. The 11 species of eastern Asia, however, include only a single diploid with all the other species being polyploids. Why do different patterns of speciation develop in North America and in eastern Asia? The breeding systems of populations in the North American T. erectum, T. grandiflorum and T. ovatum, and in Asian T. kamtschaticum were investigated by estimating the inbreeding coefficient from cold‐induced banding patterns which reveal homozygotes and heterozygotes. From the analyses of the inbreeding coefficients, T. erectum, T. grandiflorum and the Pacific coastal species, T. ovatum are predominantly inbreeding species. T. ovatum populations from the Rocky Mountain region are outbreeders. However the Japanese species, T. kamtschaticum has a mixture of outbreeding and inbreeding among populations. The development of polyploid systems in Asia is possibly the result of the diversity of the breeding systems among the populations. The shift from outbreeding to inbreeding appears to be an important key step in the occurrence of poliploids by hybridization between the different species.
The Evolution of Dicliny in Schiedea (Caryophyllaceae), an Endemic Hawaiian Genus
Authors: Weller Stephen G. , Sakai Ann K.
Published: February 2005

Abstract The evolution of dioecy was studied in Schiedea (Caryophyllaceae), a genus endemic to the Hawaiian Islands. Eight of the 22 species are diclinous, possessing gynodioecious, subdioecious, or dioecious breeding systems. A biogeographic analysis of the genus indicates that the ancestor of Schiedea colonized early in the history of the Hawaiian Islands. Subsequently, hermaphroditic species appear to have engaged in inter‐island colonization more frequently than diclinous species. For this reason, single‐island endemism and dicliny are more common on the older Hawaiian Islands. Strong inbreeding depression was detected in three species of Schiedea, indicating that genetic factors have played a role in the evolution of dicliny. Depending on the level of natural selfing, the expression of inbreeding depressioin may have favored the outcrossed progeny of rare females in populations, and eventually the evolution of dioecy. In contrast to evidence for inbreeding depression, there was very little evidence that resource allocation, sex lability, or habitat partitioning have played an important role in the evolution of dioecy. In subdioecious S. globosa hermaphrodites were largely male in function, and in gynodioecious S. salicaria females and hermaphrodites were equivalent in nearly all aspects of female function that could be measured. Variation in breeding systems in Schiedea and the closely related Alsinidendron may result from the past history of population bottlenecks that have resulted in varying levels of inbreeding depression.
Reproductive Biology of an Amphicarpic Annual, Polygonum thunbergii (Polygonaceae): Spatio‐temporal Changes in Growth, Structure and Reproductive Components of a Population over an Environmental Gradient
Authors: Kawano Shoichi , Hara Toshihiko , Hiratsuka Akira , Matsuo Kazuhito , Hirota Izumi
Published: February 2005

Abstract The process and mechanisms of spatio‐temporal changes in growth, population structure, as well as various yield and reproductive components of a population of an amphicarpic annual, Polygonum thunbergii (Polygonaceae), with two reproductive systems (aerial chasmogamous flowers and subterranean cleistogamous flowers) along an environmental gradient (light, moisture and soil nitrogen levels) were investigated in the field.

The results clearly demonstrate that growth and allocation patterns, population structure, and reproductive output of individuals changed sharply along the environmental gradient in response to seasonal and spatial changes in resource availability. Models predicted that light conditions bring about one‐sided competition, whereas nutrient conditions in the soil engender two‐sided competition. As expected, the degree of one‐sided competition was prominent in the case of a planophile, Polygonum thunbergii. Allocation patterns, seed outputs, individual seed size as well as relative energy costs of chasmogamous and cleistogamous seed as affected by light and nutrient levels were also critically analyzed. The most noteworthy finding was that the size of chasmogamous seeds sharply decreased in response to a decrease in the light regime, while cleistogamous seed size remained constant along the gradient. However, relative cost of both chasmogamous and cleistogamous seeds sharply increased with decrease in the light level, reflecting different degrees of environmental stress, biotic interference, or both.
Plant Parenthood in Milkweeds: A Direct Test of the Pollen Donation Hypothesis
Authors: Broyles Steven B. , Wyatt Robert
Published: February 2005

Abstract For hermaphroditic plant species whose fruit production is limited by maternal resources, the “pollen donation hypothesis” views large floral displays as an adaptation to enhance the probability of fathering seeds on other plants. This hypothesis has frequently been used to describe the evolution of large floral displays in milkweeds (Asclepias). Most tests of the pollen donation hypothesis, however, have used indirect measures, such as flower production or pollen removal, to estimate male reproductive success. To test the pollen donation hypothesis directly, we performed a paternity analysis and determined the number of seeds sired by individual genotypes in a natural population of poke milkweed, A. exaltata, in southwestern Virginia. Seeds sired (male success) and seeds produced (female success) were significantly correlated with flower number per plant (for male success: r= 0.32, P < 0.05; for female success: r= 0.66, P < 0.0001). Functional gender of plants that reproduced both as males and females (N = 17) was not correlated with flower number per plant (r= 0.35, P>0.05), indicating that plants with large floral displays did not reproduce primarily as males. Percent fruit‐set and seed number per fruit were higher in 1986, when levels of pollinarium removal also were higher. Furthermore, several umbels that experienced high pollinator activity selectively matured fruits that contained many seeds. We argue that the evolution of large floral displays in milkweeds is the result of selection to increase overall reproductive success rather than male reproductive success alone.
The Significance of Agamospermous Triploid Pollen Donors in the Sexual Relationships between Diploids and Triploids in Taraxacum (Compositae)
Authors: Morita Tatsuyoshi , Sterk Adri A. , den Nijs Joannes C. M.
Published: February 2005

Abstract We review in this article the investigations of the significance of agamospermous triploid pollen donors in the sexual relationships between diploids and triploids in Taraxacum. Crossing experiments between diploid sexual mother plants and agamospermous polyploid pollen donors and recent isozyme analyses of the progeny have exhibited the following results: 1) Pollen from Agamospermous polyploid pollen donors have the potential to give rise to the polyploid agamospermous offspring when fertilizing diploid sexual plants. Ploidy level of the progeny is usually the same or higher, but occasionally lower, compared to the pollen donor. 2) Diploid progeny also occur from diploid (♀)‐polyploid (♂) crosses, however, these diploids were in our results not hybrids but the results of self‐fertilization of the diploids. The self‐fertilization is regarded as a cosequence of the breakdown of the self‐incompatibility barrier through the sterile triploid's pollen. This breakdown is in all probability a common phenomenon in diploid (♀)‐polyploid (♂) crosses. Some examples suggest that agamospermous polyploids can increase their genetic diversity through obtaining genes from coexisting diploids. The evolutionary implications of this phenomenon and the reduction mechanism of chromosome number through agamospermous pollengenesis are discussed.
Evolution of Agamospermous Races in Boehmeria and Eupatorium
Authors: Yahara Tetsukazu
Published: February 2005

Abstract Recent progress in research on the evolution of agamospermy in Boehmeria (Urticaceae) and Eupatorium (Asteraceae) is reviewed. Specific questions addressed are: (1) Is there any trend in distributions and habitat preferences of sexual and agamospermous races? (2) Is hybridity or a high level of heterozygosity a prerequisite for the evolution of agamospermous races? (3) Do agamospermous plants produce genetically variable offsprings through hybridization with sexual relatives? and (4) Do agamospermous plants have the theoretically predicted reproductive advantage over sexuals? From the results presented, the following conclusions can be drawn. (1) Sexual and agamospermous relatives are usually ecologically differentiated; sexuals tend to require extreme habitats, while agamosperms prefer disturbed places. (2) Hybridity or a high level of heterozygosity is not a prerequisite to the evolution of agamospermous races. (3) Agamospermous races produce genetically variable offspring through hybridization with sexual relatives and subsequent segregation. (4) Agamospermous plants have a reproductive advantage often greater than twofold; part of this advantage is attributed to polyploidy. The question of why agamospermous races do not replace sexuals remains open. Male recovery in agamosperms through hybridization and/or the disadvantage of polyploidy associated with agamospermy might work as mechanism(s) enabling sexuals to resist colonization of reproductively superior agamosperms under some extreme ecological conditions.
Allozyme Variation in the Rare Gulf Coast Endemic Polygonella macrophylla Small (Polygonaceae)
Authors: Lewis Paul O.
Published: February 2005

Abstract Polygonella macrophylla Small is a rare, perennial, primarily gynodioecious plant species endemic to a narrow zone of coastal sand pine scrub habitat along the Gulf of Mexico from Carrabelle, Florida, to Gulf Shores, Alabama (U.S.A.). The species is comprised of a crimson‐red flowered form (“rubra”), known from only two populations at the eastern distributional limit of the species, and a white/pink flowered form ("alba") represented by several populations throughout the remainder of the range of the species. An electrophoretic investigation revealed that commonly used measures of gene diversity are very close to expected values in “rubra” given the combination of ecological attributes displayed by the species; however, gene diversity in “alba” is much lower than expected. Population differentiation is high, with estimates of the coefficient of gene differentiation (GST) indicating that more than 30% of the diversity is among populations. Lack of gene flow among populations, estimated to be at most 0.6 migrating individuals per generation for the species, is a likely cause of greater population differentiation. High inbreeding, detected both within populations and within the species, is suggestive of high rates of self‐fertilization in hermaphroditic plants and/or biparental inbreeding in small populations.
Proximate Limitations to Fruit and Seed Set in Phellodendron amurense var. sachalinense
Authors: Mizui Norio , Kikuzawa Kihachiro
Published: February 2005

Abstract Fruit and seed set in a dioecious tree, Phellodendron amurense var. sachalinense grown in isolation, were studied for three years in Hokkaido, northern Japan. Hand pollination did not affect fruit set during the three years, but did affect seed‐set by increasing the proportion of fruits with higher seed numbers. Artificial defoliation resulted in decreased mean seed mass, but caused no significant differences in mean seed number per fruit. Total seed mass per infructescence increased with inflorescence size except with artificial defoliation where it reached an upper limit. Although the results of the artificial defoliation treatment indicate that resources are most important for fruit and seed set, it is concluded that fruit and seed set of the tree are not limited by resources, since the number of fruits increased with inflorescence size and an artificial defoliation treatment did not decrease seed‐number.
Pollination in Bruguiera gymnorrhiza (Rhizophoraceae) in Miyara River, Ishigaki Island, Japan, and Phangnga, Thailand
Authors: Kondo Katsuhiko , Nakamura Takehisa , Piyakarnchana Twesukdi , Mechvichai Wina
Published: February 2005

Abstract The bird species Hypsipetes amaurotis and Zosterops palpebrosa var. yonakuni, but no insects, were recorded regularly feeding on flower‐nectar of Bruguiera gymnorrhiza in the Miyara River Biological Preserve, Ishigaki Island, Japan, at 7:00‐9:15 a.m. during the investigation from December 20, 1987, to January 19, 1988. In contrast, Anthreptes malacensis foraged for nectar from 7:00 a.m. to 17:00 p.m. Oriolus chinensis visited the flowers mainly between 6:30 and 7:30 a.m. in Phangnga, Thailand, during the investigation from November 30 to December 19, 1986. Pollen grains were sprayed onto the birds’faces and bills and into the air. The highest mean volume of 0.24 pollen grains/l/minute was triggered in calm air by the most frequent nectarivore between 6:45 and 7:00 a.m. at a height of 1.5m under a tree‐branch carrying 145 fresh flowers in the Miyara River population, Japan. The highest mean volume of 0.27 pollen grains/l/minute under the same conditions in the Phangnga population, Thailand. Bruguiera gymnorrhiza is bird‐pollinated but with the possibility of some pollination indirectly by wind.
Temperature Response Pattern during Afterripening of Achenes of the Winter Annual Krigia oppositifolia (Asteraceae)
Authors: BASKIN CAROL C. , BASKIN JERRY M. , CHESTER EDWARD W.
Published: February 2005

Abstract Freshly‐matured achenes of Krigia oppositifolia Raf. were buried in soil at near‐natural temperatures for 0–35 months and then exhumed and tested in light and darkness at (12/12 hr) daily thermoperiods of 15/6, 20/10, 25/15, 30/15 and 35/20°C. Achenes required light for germination and exhibited an annual dormancy/nondormancy cycle, being dormant in spring and nondormant in autumn. High summer temperatures (30/15, 35/20°C) fully promoted afterripening, whereas low temperatures (5, 15/6°C) prevented it. As buried seeds came out of dormancy in summer, they first germinated at medium temperatures (20/10, 25/15°C), but with additional afterripening the maximum and minimum temperatures for germination increased and decreased, respectively. Thus, during afterripening, achenes exhibit type 3 temperature responses, which otherwise are known only in two perennial Asteraceae and one perennial Liliaceae. The physiological responses of achenes of K. oppositifolia are unlike those of most winter annuals, which have type 1 responses—i.e., the maximum temperature for germination increases during afterripening. Also, they are unlike the majority of Asteraceae, which have type 2 responses—i.e., the minimum temperature for germination decreases during afterripening. Type 1 responses, typical of most winter annuals, have yet to be reported in the Asteraceae.
Allozyme Variation and Ramet Distribution in Two Species of Athyrioid Ferns
Authors: HAMILTON ROBERT G.
Published: February 2005

Abstract Sympatric local populations of leptosporangiate ferns found to vary in phenotypic tolerances of environmental variation in the common habitat were surveyed for allozymes as indicators of genetic variation. Each local population was also surveyed for pattern of ramet distribution. The species with the greater phenotypic tolerances, Deparia acrostichoides, was found to be more variable genetically than the species with lower phenotypic tolerances, Diplazium pycnocarpon. Levels of genetic variation among the two species indicated that Deparia acrostichoides is a late‐successional species and Diplazium pycnocarpon is an early‐successional species, in agreement with a previous prediction. Ramet distribution patterns indicated a greater effect of intraspecific competition among ramets of Diplazium pycnocarpon than among ramets of Deparia acrostichoides.
Size‐Structures and Reproductive Characteristics in Diploid and Triploid Populations of Disporum sessile D. Don (Liliaceae)
Authors: HORI YOSHIMICHI , YOKOI TOMOKO , YOKOI YOTA
Published: February 2005

Abstract Disporum sessile (Liliaceae), a perennial herb of temperate forests is composed of diploid (2n=16) and triploid (2n=24) populations. The size structure differed remarkably as triploid populations had few small plants and no seedlings. Triploid flowering plants were considerably larger than diploids. Triploids that flowered were 2.5 times larger than diploids that flowered and the size of vegetative ramets produced by triploids was twice as large. In triploids, fruiting rates were quite low only with inviable seeds and vegetative propagule size was greater than that of diploids. As regards growth parameters that help to increase plant size, triploids were superior to diploids. Differences in growth and reproductive parameters between diploids and triploids may contribute to forming different patch sizes.
Reproductive and Pollination Biology of Magnolia and its Allied Genera (Magnoliaceae). I. Floral Volatiles of Several Magnolia and Michelia Species and their Roles in Attracting Insects
Authors: YASUKAWA SHOKO , KATO HIDETOSHI , YAMAOKA RYOHEI , TANAKA HAJIME , ARAI HIROHITO , KAWANO SHOICHI
Published: February 2005

Abstract Volatile substances emitted from the flowers of eight Magnolia taxa (M. sieboldii ssp. japonica, M. praecocissima var. praecocissima and var. borealis, M. tomentosa, M. salicifolia, M. obovata, M. denudata, and M. grandiflora) and one Michelia species (M. compressa) (Magnoliaceae) were examined and identified using GC‐MS. Volatile substances of these Magnolia and Michelia species consist primarily of monoterpenoids and sesquiterpenoids produced by the mevalonate pathway, acetogenins by the acetate‐malonate pathway, and phenyl‐propanoids by the shikimate pathway. These Magnolia and Michelia species all possessed various combinations of volatile monoterpenoids, acetogenins, and phenylpropanoids, except for Magnolia obovata, which emitted primarily sesquiterpenoids. Free amino acids in pollen of 12 Magnolia and one Liriodendron species were also analyzed, and their value as food sources for pollinators evaluated.

Pollinators visiting the flowers of five Magnolia species were collected in their native sites and identified. Their behaviors and roles as pollinating agents were assessed.
Antheridiogen Production and Response in Gymnocarpium dryopteris ssp. disjunctum
Authors: KIRKPATRICK RUTH E. B. , SOLTIS PAMELA S.
Published: February 2005

Abstract Although most species of homosporous pteridophytes investigated to date are highly outcrossing, there is little conclusive evidence of the mechanisms promoting intergametophytic matings in natural populations. The hormone antheridiogen, produced by meristematic and usually archegoniate gametophytes, has been implicated as an effective promoter of intergametophytic matings in natural populations. In this study, antheridiogen production and response were analyzed in laboratory‐cultured gametophytes from five outcrossing populations of Gymnocarpium dryopteris ssp. disjunctum. The numbers of antheridia present in gametophytes grown on antheridiogen‐enriched and control nutrient agar were recorded over an 84‐day period; approximately 4200 gametophytes were observed. Contingency table analyses indicated a statistically significant positive response to treatment medium in the majority of cultures analyzed. However, consistently insignificant responses to treatment medium in two gametophyte cultures suggest intrapopulational variation in gametophytic response to antheridiogen. Antheridiogen production and response in gametophytes of G. dryopteris ssp. disjunctum suggest that this antheridiogen system effectively promotes intergametophytic matings in natural populations. The selection pressures under which antheridiogen systems may have evolved are also discussed.
Effects of Seed Size and Seedling Emergence Time on the Fitness Components of Ambrosia trifida and A. artemisiaefolia var. elatior in Competition with Grass Perennials
Authors: WASHITANI IZUMI , NISHIYAMA SATOYUKI
Published: February 2005

Abstract Germination physiology responsible for seedling emergence timing of Ambrosia trifida and A. artemisia‐efolia var. elatior as well as the effects of seed size and seedling emergence time on the fitness were studied in order to understand successful invasion by these annuals of a perennial grass community. Seed biomasses of these species differ greatly (A. trifida, 34.6±14.7 mg; A. artemisiaefolia var. elatior, 4.7±1.8 mg). Seed germination /dormancy responses to temperature were rather similar. The primary dormancy of the seeds of both species could be effectively removed by a combination of moist chilling and alternating temperature regimes. The variation of the rate of germination among individual seeds in the laboratory tests well explains the variation of seedling emergence time in the field. Microsite variation of light availability had little effect on the fitness and its components in either species. In A. trifida, both initial seed biomass and emergence time significantly influenced the fitness and its components. No significant correlation between the fitness and seed size was found for A. artemisiaefolia var. elatior.