Intermediate perennial-annual populations ofOryza perennis found in Thailand and their evolutionary significance

To reexamine the mode of variations in adaptive mechanisms in the Asian form ofOryza perennis, the breeding behavior of natural populations was observed at eight sites selected in Thailand. One population consisted of seedlings only (annual), and five consisted of ratooned plants only (perennial), while two others were mixtures of both. The annual population had a larger number of buried seeds at the habitat than had the others. In the habitat of the annual population, annual species were predominant, while perennial populations tended to coexist with perennial species. The annual population was in a temporary swamp, while perennial populations were found at sites more deeply inundated in the rainy season and retaining moisture in the dry season. This indicated the role of water stress in conditioning the reproductive strategy. Observations of character variations among plants from those populations in a uniform condition proved that the seedling population was of an annual type while those performing mixed sexual and asexual propagations were of an intermediate perennial-annual type. Isoenzymic variations controlled by alleles at two known loci indicated that the two intermediate populations were highly polymorphic and heterozygous. One of them consisted of nine separate clumps which differed in their characteristics. On the basis of these observations, the dynamics of differentiation of this species in adaptive strategy is discussed. It is further suggested that the intermediate perennial-annual type is probably the wild progenitor ofO. sativa. Contribution from National Institute of Genetics, Japan, No. 1308. Partly presented by H.I. Oka at a Symposium, “Problems in evolutionary and population genetics”, XIV International Congress of Genetics, Moscow, August 1978.     

Cytotaxonomy and breeding system of the genusBiscutella (Cruciferae)

Chromosome counts were determined for 46 populations ofBiscutella representing 28 taxa. The genus was found to contain diploid taxa with 2n = 12, 16 and 18, tetraploid taxa with 2n = 36 and hexaploid taxa having 2n = 54.B. laevigata L. s. l. consists of diploid and tetraploid populations which are poorly differentiated morphologically. TetraploidB. laevigata s. l. and hexaploidB. variegata Boiss. & Reuter (s. l.) are characterized by chromosomal instability. The variation in chromosome numbers and the occurrence of polyploidy is discussed in relation to the taxonomy of the genus. An investigation of the breeding system showed that most of the annual species were self-compatible and partly inbreeding and most of the perennial species self-incompatible and, therefore, outbreeding, while one annual species,B. cichoriifolia Loisel., showed both systems.     

Variation in species richness within and between calcareous (alvar) grassland stands: the role of core and satellite species

Anoda cristata is a widelydistributed annual weed in Mexico, which grows as agrestal or naturally indisturbed and undisturbed vegetation, respectively. Plants of this species aretolerated in orchards and corn-bean fields by Mexican ethnic groups ofCentral Mexico. Leaves of the plants are used as a food source, andoccasionallyseeds are sown in orchards. Because Mexicans have used Anodacristata for a long time, it is possible that ecological andmorphological characteristics of managed populations differ from those of wildpopulations. In this study, we analyzed phenotypic responses of two populationsof A. cristata (wild and agrestal) growing in twohabitats (forest and cultivated field) comparing survivorship, andlife history traits. Natural progenies from wild and agrestal populations ofA. cristata were transplanted into a cultivated field andin the understory of a pine forest in a reciprocal transplant experiment.Results showed that the habitat of transplant and the origin of populations hadsignificant effect on all plant characters measured (growth, phenology, andbiomass allocation), but the habitat x origin interaction wasnon-significant. In general, plants from the agrestal population grewfaster, reproduced earlier, and allocated more biomass to reproduction, thanplants from the wild population. Similarly, significant effects of habitat andorigin on plant survivorship were detected, but the origin of populationsexplained the largest proportion of variance in plant survival. Most traitswerephenotypically plastic but there were no differences in the magnitude ordirection of the response between populations. In contrast both populationsshowed differentiation for most character mean values. Populationdifferentiation is possibly the result of genetic differences driven byprocesses other than incipient domestication.     

Forest fragmentation and plant reproductive success: a case study in four perennial herbs

We assessed the effects of habitat fragmentation on reproductive success in natural populations of four forest herbs with differing life-history traits and whose distribution patterns appeared to be negatively affected by decreased habitat size and/or increased isolation: Carex sylvatica, Galium odoratum, Sanicula europaea and Veronica montana. Our aims were to test (1) whether habitat size and isolation are positively correlated with population size and isolation, respectively, (2) whether plant reproductive success, a major component of plant fitness, is reduced in small and/or isolated populations when also accounting for differences in habitat quality (edaphic conditions, light intensity) and the effects of plant size, and (3) whether species with different life histories are affected differently. There were significant positive relationships between habitat and population size and between habitat and population isolation in some, but not all of the species. We mostly found no negative effects of small population size or isolation on reproduction. However, reproductive success was reduced in small populations of Sanicula, and this effect was independent of differences in plant size and environmental conditions. The reduced fecundity in small populations may be a consequence of the Allee-effect, a possible mechanism being pollen limitation. Furthermore, the proportion of flowering ramets was reduced in small and isolated populations of Galium, which may have been caused by changes in population structure. Lastly, we found some evidence for largely outcrossing, non-clonal species to be more sensitive to reductions in population size, at least in terms of their reproductive success.     

Comparative floral and vegetative differentiation between two European Aquilegia taxa along a narrow contact zone

As a first step in determining the identity and relative importance of the evolutionary forces promoting the speciation process in two closely related European taxa of Aquilegia, we investigated the levels of morphological variation in floral and vegetative characters over the narrow region where their ranges enter into contact, and evaluate the relative importance of both types of traits in their differentiation. A total of 12 floral and ten vegetative characters were measured on 375 plants belonging to seven A. vulgaris populations and six A. pyrenaica subsp. cazorlensis populations located in southeastern Spain. Floral and vegetative morphological differentiation occur between taxa and among populations within taxa, but only vegetative characters (particularly plant height and leaf petiolule length) contribute significantly to the discrimination between taxa. Differentiation among populations within taxa is mostly explained by variation in floral traits. Consequently, morphological divergence between the two taxa cannot be interpreted as an extension of among-population differences occurring within taxa. Multivariate vegetative, but not floral, similarity between populations could be predicted from geographical distance. Moreover, the key role of certain vegetative traits in the differentiation of A. vulgaris and A. p. cazorlensis could possibly be attributable to the contrasting habitat requirements and stress tolerance strategies of the two taxa. These preliminary findings seem to disagree with the currently established view of the radiation process in the genus Aquilegia in North America, where the differentiation of floral traits seems to have played a more important role.     

Selective elimination of perennial ryegrass by activation of a pro-herbicide through engineering <Emphasis Type="Italic">E. coli argE</Emphasis> gene

Perennial ryegrass is widely used for overseeding dormant bermudagrass on golf courses and sports fields in Southeastern United States to provide green color and improved playability. Late spring and summer persistence of perennial ryegrass may decrease the quality of the bermudagrass turf and reduce its winter hardiness. To help solve this problem, we developed a strategy to activate a pro-herbicide within the transgenic perennial ryegrass plants and to cause self elimination of the plants. An E. coli argE gene was introduced into perennial ryegrass by the biolistic method, which resulted in four independently transformed green plants. The mRNA of argE gene was detected in three of the plants by RT-PCR. Perennial ryegrass plants expressing the argE transgene were selectively controlled upon application of a pro-herbicide, N-acetyl-l-phosphinothricin (or N-acetyl-PPT), since the N-acetylornithinase encoded by argE gene is able to convert N-acetyl-PPT to the herbicide phosphinothricin (PPT). The non-transgenic bermudagrass plants were unaffected by the treatment. This approach provides a means to selectively remove a group of transgenic plants without affecting other plants growing with them.     

Genetic Variation in Hippophae rhamnoides ssp. sinensis (Elaeagnaceae) Revealed by RAPD Markers

Hippophae rhamnoides ssp. sinensis is endemic to China, and it is a dioecious, outcrossing plant. Although many studies have been undertaken mainly on its agricultural, nutritional, medical, and ornamental value, little is known about its population genetics. This study uses random amplified polymorphic DNA to investigate the genetic diversity and population genetic structure of 13 natural populations of the subspecies sinensis. Fifteen primers amplified 107 reproducible bands, with 95 (88.79%) being polymorphic. The gene diversity within population was 0.168, considerably lower than that of tree species and most perennial, outcrossing species, but higher than that of annual or short-lived, selfing species. The Gst value showed that 18.3% of the total genetic variation resided among populations, a little lower than that of outcrossing species. The present results are quite similar to those previously reported in another subspecies, H ssp. . rhamnoides rhamnoides. The low genetic differentiation among populations in ssp. sinensis may be attributed to the long-distance dispersal of seeds facilitated by birds, in addition to its characteristics of outcrossing, wind pollination, and widespread distribution. No association between genetic distance and geographical distribution was found. The population relationships revealed by the UPGMA dendrogram parallel this result, in that genetic distance did not increase with geographic separation. This pattern of population differentiation may imply the adaptation of ssp. s populations to the local environment, given that its habitats vary greatly across its distribution.     

梁王山大花香水月季居群表型多样性分析

以云南省澄江市梁王山一带3个大花香水月季居群240个个体为研究对象,采用巢式方差分析、表型变异系数分析、Pearson相关性分析等方法,对大花香水月季的花、叶等16个表型性状进行分析.结果表明:大花香水月季居群内和居群间均存在丰富的表型多样性,表型分化系数在-1.51％～26.18％之间,在较近的距离内,居群内多样性远...     

Reproduction strategies of Macrocystis pyrifera (Phaeophyta) in Southern Chile: The importance of population dynamics

Macrocystis pyrifera is an ecologically dominant species along the temperate Northern and Southern Pacific Coast of America, showing some similarities and differences at population and community level. In general, this kelp is reported to be reproductive all year round. Annual populations present in wave-protected areas of southern Chile suggest that the reproductive strategies of this population can be different. In this study we explore the reproductive strategies of annual M. pyrifera present in wave-protected areas and perennial populations encountered in exposed areas of southern Chile (41^∘S). Our results show that M. pyrifera present in wave-exposed locations has a reproductive strategy that is similar to populations in the northern hemisphere. These populations reproduce all year round and their strategy is to produce high numbers of sporophylls and ensure that most of them (over 90%) become sporogenous. On the other hand, the protected populations with an annual life cycle, produce more spores per area of sorus. In a few months, they are able to produce sufficient propagules to recolonize areas before the adult plants disappear in autumn.     

Low levels of quantitative and molecular genetic differentiation among natural populations of Medicago ciliaris Kroch. (Fabaceae) of different Tunisian eco-geographical origin

In this paper, we analyze the genetic variability in four Tunisian natural populations of Medicago ciliaris using 19 quantitative traits and six polymorphic microsatellite loci. We investigated the amplification transferability of 30 microsatellites developed in the model legume M. truncatula to M. ciliaris. Results revealed that about 56.66% of analyzed markers are valuable genetic markers for M. ciliaris. The most genetic diversity at quantitative traits and microsatellite loci was found to occur within populations (>80%). Low differentiations among populations at quantitative traits Q _ST  = 0.146 and molecular markers F _ST  = 0.18 were found. The majority of measured traits exhibited no significant difference in the level of Q _ST and F _ST . Furthermore, significant correlations established between these traits and eco-geographical factors suggested that natural selection should be invoked to explain the level of phenotypic divergence among populations rather than drift. There was no significant correlation between population differentiation at quantitative traits and molecular markers. Significant spatial genetic structure consistent with models of isolation by distance was detected within all studied populations. The site-of-origin environmental factors explain about 9.07% of total phenotypic genetic variation among populations. The eco-geographical factors that influence more the variation of measured traits among populations are the soil texture and altitude. Nevertheless, there were no consistent pattern of associations between gene diversity (He) and environmental factors.     

岳麓紫菀（菊科）的分布及其形态学与核型研究

岳麓紫菀（Aster sinianus Hand. Mazz.,菊科紫菀族）为多年生草本,特产于中国湘赣毗邻地区。在对其整个分布区进行野外采集和生境观察时,发现了2个新的分布地点,同时确认其已在模式产地湖南省长沙市岳麓山灭绝。该研究将岳麓紫菀从浏阳市沙市镇回迁至岳麓山,以期恢复模式产地的居群。形态学研究表明,现有文献对该种的描述多处不准确,如对基生叶、株高、茎下部叶、托片和海拔等的记载。基于形态性状,讨论了岳麓紫菀的系统学地位,并首次报道了该种的核型特征：岳麓紫菀为二倍体,核型为2n=2x=16m+2m(SAT),属于1A型。该研究结果为岳麓紫菀的分类地位的修订和物种保护提供了重要的资料。     

Pollination biology of annual and perennialLeonotis species (Lamiaceae)

The pollination syndromes ofLeonotis (Pers.)R. Br. are discussed. Ornithophily accounts for most of the nutlets set in perennialLeonotis species but in the annual species [L. nepetifolia (L.)R. Br.] autogamy prevails.Leonotis species are predominantly pollinated by a variety of sunbirds, although bees are also involved. Nectar is sucrose-dominant in perennial species but hexose-dominant in the annual.     

Genetic diversity and population structure of<Emphasis Type="Italic">Kalopanax pictus</Emphasis> (Araliaceae)

Kalopanax pictus (Araliaceae) is a long-lived woody species primarily distributed throughout East Asia. This species is regarded as medically and ecologically important in Korea. We used starch gel electrophoresis to investigate its allozyme variation and genetic structure in samples from Korean populations (both natural and cultivated). Our analysis of 10 enzymes revealed 18 loci, of which 10 were polymorphic (35.6%). Genetic diversity at the species and population levels were 0.200 and 0.149, respectively, with the mean for cultivated populations (0.124) being lower than for natural (wild) populations (0.181). Asexual and sexual reproduction modes, perennial habitat, and longevity all were possible factors contributing to such high diversity. An indirect estimate of the number of migrants per generation (N _m = 1.08) indicated that gene flow was not extensive among these Korean populations. Therefore, we suggest that geographical distance as well as reproductive isolation between wild and cultivated plants may play roles in shaping the population structure of this species.     

Genetic diversity and morphological differentiation in Liatris helleri (Asteraceae), a threatened plant species

Liatris helleri (Asteraceae) is an insect-pollinated herbaceous perennial endemic to several high-elevation sites in the Blue Ridge Mountains of North Carolina. Allozymes were used to describe the genetic diversity and population structure in nine populations of this rare, federally listed species. Differences in leaf morphology were also examined for greenhouse-grown plants representing several populations. The proportion of the total genetic diversity found among populations, as indicated by the allozyme data, was 16%. Higher levels of population differentiation were found for differences in leaf shape; population of origin accounted for 37% of the variation in maximum leaf width, while families within populations accounted for 7%. In contrast to many endemic species, L. helleri maintains fairly high levels of genetic diversity. For the species, the percent polymorphic loci was 87.5, the average number of alleles at variable loci was 3.00 and the gene diversity was 0.276. Mean population values were percent polymorphic loci =58.4, mean number of alleles per polymorphic locus =2.59 and gene diversity =0.219. The estimated gene flow was low (Nm=0.85–1.32) and a relatively high correlation (r=0.55; p<0.005) was found between linear geographic and genetic distance. This suggests that the populations are partially isolated by distance, despite the limited range (<60 km) of the species. We recommend that population distinetiveness be maintained in restoration efforts.     

Genetic diversity and phenotypic variation in marginal populations of the locally endangered speciesHordeum secalinum (Poaceae)

Electrophoresis was used to compare variation in hordein polypeptide patterns and isozymes in five marginal populations ofHordeum secalinum (four Swedish and one Danish population) and four populations along the Atlantic coast from Denmark to Spain. Hordein patterns were uniform within and among Swedish and Danish populations whereas the materials from France and Spain were divergent. The banding patterns for nine isozymes (AAT, IDH, MDH, PGD, GPI, ME, ACP, EST, and PRX) agreed with those reported for otherHordeum species. All putative loci were monomorphic with the exception of PRX, which showed three different phenotypes. The five marginal populations varied in seed set and cultivated plants differed in phenological traits.Dedicated to emer. Univ.-Prof. DrFriedrich Ehrendorfer on the occasion of his 70th birthday     

Morphological and microsatellite diversity associated with ecological factors in natural populations of Medicago laciniata Mill. (Fabaceae)

Genetic variability in 10 natural Tunisian populations of Medicago laciniata were analysed using 19 quantitative traits and 12 polymorphic microsatellite loci. A large degree of genetic variability within-populations and among-populations was detected for both quantitative characters and molecular markers. High genetic differentiation among populations for quantitative traits was seen, with Q _ST = 0.47, and F _ST = 0.47 for microsatellite markers. Several quantitative traits displayed no statistical difference in the levels of Q _ST and F _ST . Further, significant correlations between quantitative traits and eco-geographical factors suggest that divergence in the traits among populations may track environmental differences. There was no significant correlation between genetic variability at quantitative traits and microsatellite markers within populations. The site-of-origin of eco-geographical factors explain between 18.13% and 23.40% of genetic variance among populations at quantitative traits and microsatellite markers, respectively. The environmental factors that most influence variation in measured traits among populations are assimilated phosphorus (P₂0₅) and mean annual rainfall, followed by climate and soil texture, altitude and organic matter. Significant associations between eco-geographical factors and gene diversity, H _e , were established in five-microsatellite loci suggesting that these simple sequence repeats (SSRs) are not necessarily biologically neutral.     

Vegetative growth inRumex acetosella (Polygonaceae) originating from different geographic regions

Vegetative growth patterns ofRumex acetosella L. were investigated both in experimental conditions and in the field. Plants originating from geographically and ecologically contrasting areas expressed significant differentiation in height, weight, and leaf production, even at early stages. The plants belonging to subsp.angiocarpus grew thaller than other plants. The differences among populations grown in a uniform environment provide evidence for genetic differentiation in morphology. Plants in natural populations were considerably lighter than experimental plants, which intensively produced a large number of rosette leaves. These differences can be attributed to substantial phenotypic plasticity. When the correlation structure among the growth traits was analyzed, seed weight and early plant size appeared to influence future plant size.     

Adaptive genetic differentiation in life-history traits between populations of <Emphasis Type="Italic">Mimulus guttatus</Emphasis> with annual and perennial life-cycles

The optimal allocation to sexual and vegetative reproduction as well as the optimal values of other life-history characteristics such as phenology, growth and mating system are likely to depend on the life-cycle of the organism. I tested whether plants of Mimulus guttatus originating from temporarily wet populations where the species has an enforced annual life-cycle have higher allocation to sexual reproduction, lower allocation to vegetative reproduction, more rapid phenology, faster growth, and floral traits associated with a self-fertilizing mating system than plants from permanently wet populations where the species has a perennial life-cycle. I grew a total of 1377 plants originating from three populations with an annual life-cycle and 11 populations with a perennial life-cycle in a greenhouse under permanently and temporarily wet conditions. Plants of M. guttatus in permanently wet conditions had significantly more vegetative reproduction and tended to have a faster growth than plants in the temporarily wet conditions, indicating plasticity in these life-history traits. Plants from populations with an annual life-cycle invested significantly more in sexual reproduction and significantly less in vegetative reproduction than the ones from populations with a perennial life-cycle. Moreover, this study showed that plants originating from populations with an annual life-cycle have a significantly faster development and floral traits associated with autonomous self-fertilization. In conclusion, this study suggests that there has been adaptive evolution of life history traits of M. guttatus in response to natural watering conditions that determine the life span of the species.     

Divergent selection along climatic gradients in a rare central European endemic species,Saxifraga sponhemica

Background and Aims The effects of habitat fragmentation on quantitative genetic variation in plant populations are still poorly known. Saxifraga sponhemica is a rare endemic of Central Europe with a disjunct distribution, and a stable and specialized habitat of treeless screes and cliffs. This study therefore used S. sponhemica as a model species to compare quantitative and molecular variation in order to explore (1) the relative importance of drift and selection in shaping the distribution of quantitative genetic variation along climatic gradients; (2) the relationship between plant fitness, quantitative genetic variation, molecular genetic variation and population size; and (3) the relationship between the differentiation of a trait among populations and its evolvability.Methods Genetic variation within and among 22 populations from the whole distribution area of S. sponhemica was studied using RAPD (random amplified polymorphic DNA) markers, and climatic variables were obtained for each site. Seeds were collected from each population and germinated, and seedlings were transplanted into a common garden for determination of variation in plant traits.Key Results In contrast to previous results from rare plant species, strong evidence was found for divergent selection. Most population trait means of S. sponhemica were significantly related to climate gradients, indicating adaptation. Quantitative genetic differentiation increased with geographical distance, even when neutral molecular divergence was controlled for, and Q_ST exceeded F_ST for some traits. The evolvability of traits was negatively correlated with the degree of differentiation among populations (Q_ST), i.e. traits under strong selection showed little genetic variation within populations. The evolutionary potential of a population was not related to its size, the performance of the population or its neutral genetic diversity. However, performance in the common garden was lower for plants from populations with reduced molecular genetic variation, suggesting inbreeding depression due to genetic erosion.Conclusions The findings suggest that studies of molecular and quantitative genetic variation may provide complementary insights important for the conservation of rare species. The strong differentiation of quantitative traits among populations shows that selection can be an important force for structuring variation in evolutionarily important traits even for rare endemic species restricted to very specific habitats.     

Electrophoretic analysis of the phylogeny of the self-pollinating populations ofClarkia xantiana

Electrophoretic variation in isozymes coded by 40 loci was examined in two self-pollinating populations, one with white and the other with pink flowering plants, and four outcrossing populations ofClarkia xantiana (Onagraceae) native to California. The study was carried out to test theMoore & Lewis (1965) hypothesis that the pink selfer originated from the sympatric outcrossing population and then gave rise to the white selfer. The hypothesis could be rejected if one or the other selfer was more similar genetically to an allopatric population than to the sympatric one. Both selfers were monomorphic at all loci whereas the outcrossing populations were polymorphic at nearly half of them. The two selfers had the same genes at 32 loci but had different ones at eight loci. The pink selfer was not more similar to the allopatric populations than to the sympatric one, consistent with theMoore & Lewis model. The evidence also supported their proposal that the white selfer originated from the pink one and not independently. The electrophoretic evidence was valuable because it permitted qualitative comparisons (presence versus absence of particular alleles) between the selfer and the several outcrossing populations; such analysis was not previously possible because the latter populations are morphologically and cytologically similar.