摘要:

AbstractThe long‐term growth and coexistence of species with large mixed populations in varying environments were modelled for representative environments and life‐history characteristics of annual and perennial plants. The effects of the relationships between the means, variances, and covariances of seed yield, establishment, and survival, were explored by Taylor's expansion. The main findings are:1. Individual variation in reproductive successwithin generationshasno effecton long‐term growth, which is determined only by themean growth rateof the individuals of the species. 2. In annual species with nonoverlapping generations and without seed banks, the species with the largest mean log of the annual growth rateY, that is the product of the average seed yield per plant and the establishment probability per seed, will win in competition with other species, independent of the correlations between the growth rates of the different species. In this case there is a negative tradeoff between the mean and the variance. 3. In perennial species with a lottery type of equal access to vacant sites, a high annual survival probability allows stable coexistence between perennial species with independent or negatively correlated variance in their mean annual product of seed production and establishmentY.4. The coexistence range and the likely number of coexisting perennial species increase as a function of the variance of the common species, and is decreased by the variance of the rare species. The coexistence range is decreased by the covariance between the growth rates of the species, and between the survival of the rare species and its growth rate. 5. If mortality in the community of long‐lived perennials is synchronized, the generations become nonoverlapping, and the competitive dynamics become similar to that of annuals. 6. Coexistence between annual and perennial species is promoted if the covariances between theannualsurvival and the relative yield of perennials, and between the yields of perennials and annuals, decrease and become more negative. 7. Selection for seed yield and establishment in different conditions in annuals favours ageneralist strategywith low variance between years which provides a moderate yield and establishment over a wide range of environmental conditions. In perennial plants, long‐term growth rate is determined by the lifetime seed yield and establishment. Because of strong competition with annuals in the more common conditions, selection in perennials favours instead aspecialist strategy, with a high seed yield and establishment at relatively rare occasions in space and time, in which there is only weak competition with annuals. 8. Coexistence of annual species with a long‐lived seed bank in the soil is also made possible by independent variation in different years of the germination, seed yield and establishment of different species, analogous to the situation of peren

ISSN:0913-557X    

DOI:10.1111/j.1442-1984.1994.tb00075.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractPhylogenetic relationships among 11 species in the genusDisporumwere assessed by RFLP analysis of chloroplast DNA and their taxonomic status was re‐evaluated in the light of molecular, karyological as well as morphological data available at present. AmongcpDNAs from 17 plants of 11 species, 16 mutations were detected using 14 restriction enzymes and heterologouscpDNA probes. Restriction site data were analyzed cladistically, and a majority rule consensus tree was obtained. Species fell into four groups based oncpDNA, (1) a group containing seven species,D. uniflorum, D. taipingense, D. lutescens, D. sessile, D. kawakamii, D. multiflorum, andD. shimadai; (2) containing one speciesD. viridescens; (3) containing two speciesD. smilacinumandD. cantoniensevar.skimmense; (4) containingD. leucanthum.Among these groups the first one has two clades with high probability rate. The results suggest thatD. lutescensbelongs to the “D. sessilegroup” rather than the “D. smilacinumgroup”. But, the separation ofD. viridescensandD. smilacinuminto two groups as revealed by the present analysis is somewhat controversial, since bothD. viridescensandD. smilacinumshare a number of morphological and karyological characters in common. IntraspecificcpDNA variation ofD. sessilewas also

ISSN:0913-557X    

DOI:10.1111/j.1442-1984.1994.tb00076.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractEnzyme‐electrophoretic variation was examined in sporophytes ofWoodwardia japonica(2n= 68) and segregation was examined in gametophytes. Despite the high chromosome number,W. japonicadisplayed disomic segregation of isoenzyme patterns. This and karyotype analyses indicate thatW. japonicais a diploid derived from a base number of eitherx= 17 orx= 3

ISSN:0913-557X    

DOI:10.1111/j.1442-1984.1994.tb00077.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThe pollination biology ofHosta sieboldianaandH. sieboldiiis investigated comparatively in Central Japan. Both species have homogamous, one‐day flowers pollinated by bumblebees. The abdomens of the bees touch the stigma on the extended style when they land on the anthers inside the herkogamous flower, and autogamy is effectively prevented. However, the flowers are fairly self‐compatible, and geitonogamy may occur rather frequently because two or more flowers on a scape very often bloom at the same time and many ramets are contiguous. The pollen/ovule ratios suggest that these species are facultative outbreeders. The flower ofH. sieboldiiseems completely suited to bumblebee pollination. InH. sieboldianathe stigma of the flower, whose style strongly protrudes, is not always touched by bumblebees, but frequent visitation of bumblebees results in pollination of almost all the flowers. Both species have similar pollination systems but seem reproductively isolated by blooming times and habitats. Their common pollinators, however, may sometimes cause introgressive hybridization in contiguous populati

ISSN:0913-557X    

DOI:10.1111/j.1442-1984.1994.tb00078.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractTo elucidate the effects of herbivory by chrysomelid beetles onRumex japonicus, rosette leaves were clipped and the subsequent fruit production and root growth were observed. The increase of leaf biomass of some clipped plants was greater than that of control plants, although this varied among individual plants. The root growth of clipped plants was less than that of control plants. Fruit production increased with plant size, and there was no difference in fruit production between clipped and control plants. Reproductive allocation (fruit biomass, relative to fruit biomass plus root growth) increased with plant size; it was greater in clipped plants than in control ones. Based on these results, reproductive allocation strategy against herbivory was discussed.

ISSN:0913-557X    

DOI:10.1111/j.1442-1984.1994.tb00079.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractDryobalanops aromatica is an emergent canopy tree species with hermaphroditic bee‐pollinated flowers. This species is distributed in the lowland dipterocarp forests of Malaya, Sumatra, Rhio Archipelago and Borneo. The flowering of many different dipterocarp species was observed in some parts of Brunei in 1991, and all over Brunei in 1992. The outcrossing rates of D, aromatica were estimated in 1991 and 1992 in the secondary forest, and in 1992 in the primary forest. Selective harvesting of D. aromatica has occurred in the secondary forest about 20 years ago. Four enzyme systems with a total of six isozyme loci were used to estimate the single locus and the multilocus outcrossing rates. The multilocus outcrossing estimates ranged from 0.794 to 0.856, with a mean of 0.816. These estimates are similar to those for other tropical tree species. Although the flowering density of D. aromatica in the secondary forest was lower than in the primary forest, the multilocus outcrossing estimates were not significantly different. The variation between years in the secondary forest was also not significant. These findings may be largely the result of the high flowering tree density of this species, even in the secondary forest. In this study, the outcrossing rates of D. aromatica were maintained by high flowering density regardless of the size structure or the topography of the habita

ISSN:0913-557X    

DOI:10.1111/j.1442-1984.1994.tb00080.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractAndrodioecy (the presence of males and hermaphrodites in a breeding population) is a rare reproductive system in plants, withDatisca glomerata(Datiscaceae) representing the only well‐documented example. Recent reports of high outcrossing rates, inbreeding depression, and high male pollen production satisfy theoretical predictions for the continued maintenance of androdioecy in populations of this species. However, in prior studies pollen production was measured indirectly in terms of numbers of anthers per flower—based on the assumption that male and hermaphroditic plant have equal numbers of flowers and that anthers from the two sexual morphs produce equivalent amounts of pollen. Herein, we demonstrate that male and hermaphrodite plants do not differ significantly in terms of flower number, but that pollen production in anthers from hermaphroditic plants is 12.6% higher than in anthers from male plants, thus refining the estimate of relative pollen fecundity of male versus hermaphrodite plants. The differential lowers the frequency of males predicted by theory, but is still consistent with the maintenance of androdioecy in this spec

ISSN:0913-557X    

DOI:10.1111/j.1442-1984.1994.tb00081.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThe population structure and reproductive biology ofSaururus cernuus(Lizard's Tail; Saururaceae; Piperales), is documented in five sites in southern Louisiana (Mississippi Delta). The species is common throughout the southeastern United States in marshes, along streams, edges of lakes, and in the understory of moist forests. The clonal species exhibits sexual and vegetative reproduction. Wind and insects both play important roles in pollination. Pollen may be borne by insects directly. Alternatively, the pollen may be borne by wind after its release is triggered from pendulous floral spikes (the “Lizard's Tail”) by either wind or insect landings (insect‐mediated wind pollination). The plants are self‐incompatible and seed set results from a combination of pollination modes with wind pollination being the primary mode (rare in the Magnoliidae). Inflorescence and floral structure exhibit adaptive features that facilitate the various modes of pollen transfer, viz., numerous, small scented, protogynous flowers with no perianth, ultraviolet patterns produced by stamen filaments, small pollen grains, curved inflorescences, and exerted stamens, etc. Fruit production and seed germination are documented and plant growth and densities are compared in sunny versus fores

ISSN:0913-557X    

DOI:10.1111/j.1442-1984.1994.tb00082.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThis review article deals with the male function in agamospermous plants, which is still not fully recognized. Of particular interest are mating and paternity problems. Pollen of agamospermous donors may influence female fitness in early mating phases by contributing the recognition substances or inducing spontaneous seed development. Various interactions between the sperm cell(s) and the female gametophyte at later phases may include (1) occasional double fertilization, (2) occasional syngamy, (3) pseudogamy, and (4) hemigamy. In the first two processes the offspring are sired normally. In pseudogamy, the offspring is maternal, the male contribution being restricted to endosperm paternity. In hemigamy, male function may include induction of the egg cell development only (maternal offspring), or the induction of the egg cell development as well as independent participation of the sperm cell in the offspring development leading to the formation of chimeras. It is concluded that the sperm may be a limiting resource in at least some agamospermous plants. Possible directions of future research are briefly outlined.

ISSN:0913-557X    

DOI:10.1111/j.1442-1984.1994.tb00083.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

ISSN:0913-557X    

DOI:10.1111/j.1442-1984.1994.tb00084.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY