Collection and regeneration of populations of wild plants from seed

Four methods of obtaining seeds of wild species of plants for long-term conservation in Gene Banks were compared. (a) From collections growing within botanic gardens; (b) by making sample collections from wild populations and bulking up stocks by regeneration under cultivation; (c) by making arrangements with external collectors; (d) by organising plant collecting expeditions.Collections from plants in botanic gardens were unsatisfactory material on which to base collections. Regeneration under cultivation depends on expertise and knowledge of the plant's cultural requirements which were frequently not available, leading to unacceptably heavy losses of individuals and selection of populations, during cultivation. Collecting seeds directly from populations of wild plants was, scientifically, the most successful method and costings showed it also to be economically the least demanding of resources.The results suggest that, except in special cases—perhaps with rare plants where natural populations are small—every effort should be made to obtain initial collections of seed which are large enough to fulfil all the purposes intended by long-term conservation. Collections of small numbers of seeds which require bulking up before they can be used should be avoided, as a waste of effort, time and plant resources.     

The potential for genetic contamination vs. augmentation by native plants in urban gardens

Native plants in gardens can potentially aid conservation by contributing to genetic diversity and buffering small and otherwise isolated populations from extinction. However, gene flow from such plantings may threaten the genetic integrity of natural populations. We assessed the morphological and genetic diversity of garden plants in an urban population of Grevillea macleayana in south-eastern Australia. There were two main groups of garden plants: some similar to plants in nearby natural populations; others with unusual morphology. Multivariate analysis of morphological characters separated these groupings, which were confirmed by genetic analysis. Both groups produced seeds and flowering phenologies overlapped, indicating a potential for gene flow. Hand pollination showed that plants in each group could fertilize flowers of the other. Thus, these garden plants contributed to genetic variation in an urban/bushland metapopulation but there was potential for gene flow from the unusual plants. Unless carefully managed, garden plants may therefore cause disruption of the genetic integrity of nearby natural populations.     

Plantations of Convallaria majalis L. as a threat to the natural stands of the species: Genetic variability of the cultivated plants and natural populations

The level of polymorphism, genetic variability and relatedness of Convallaria majalis-populations (species native in Poland, under partial legal protection) obtained from three Polish regions and from commercial producers (Polish and Dutch) were studied. In addition the differences between the cultivated plants and those occurring in natural stands were analyzed. Each region was represented by at least 20 populations among which half were collected in natural stands and half from cultivation sites (botanical gardens, private gardens and cemeteries), and compared with samples obtained directly from commercial producers. Seven primer pairs used for AFLP profiling amplified 466 scoreable DNA fragments that were used for multidimensional scaling and clustering. The above analyses make it possible to clearly distinguish among individuals and revealed groups of populations according to their geographic origin. Samples from populations collected in natural stands and cultivated in the same region did not differ from each other significantly.These results suggested that cultivated plants were probably obtained directly from the natural stand and the influence of plant cultures on natural populations was rather small.     

The extinction of genetic resources of Asian wild rice, Oryza rufipogon Griff.: A case study in Thailand

Natural populations of wild rice, Oryza rufipogon Griff., are now threatened with the disturbance of their natural habitats by various human activities. To obtain basic information on genetic erosion or loss of genetic diversity in wild rice, we investigated how environmental changes of habitat affected the genetic structure of its natural population at a study site in the central plain of Thailand. During 10 years from 1985 to 1994, the wild-rice population at this site was seriously destroyed and fragmented. Using two sets of seed sample collected in 1985 and 1994 from the same population, allozyme variability at 17 loci of 11 enzymes were examined. Isozyme genotypes of mother plants of seed samples were estimated by the segregation in each progeny, and we calculated genetic parameters for the population. Gene diversity severely decreased in the 1994 sample compared with the 1985 sample. It is supposed that declining and fragmentation of the wild rice population, which happened during the 10 years, caused loss of genetic variability and forced the habitually outbreeding plants to inbreed, accelerating a reduction in gene variability. Pgi1-1 allele which was common in Indica rice cultivars of this region was found in the wild rice plants growing at the side of rice fields. Probably, introgression has occurred between wild and cultivated rice plants, and consequently the intrinsic nature of wild rice was gradually blurred by cultivar genes. We must realize that the genetic erosion of wild rice is rapidly proceeding and that an action for their conservation in natural environment, so called in situ conservation, is urgently needed.     

重庆南山植物园的植物造景

重庆南山植物园作为以山地为特色的植物专类园,在植物景观营造上有别于其它公园。文章从南山植物园的植被起源与构成、用地特点与各专类园的关系到植物园造景进行深入调查分析,初步总结出其植物造景规律,并重点阐述了该园的适地造景、建造植物群落、规则中求自然、突出绿地主题植物景观、表现自然野趣、合理修饰地形、展示季相变化、装点园林等植物造景特点。     

Eco-geographical distribution of <Emphasis Type="Italic">Lactuca aculeata</Emphasis> natural populations in northeastern Israel

The wild lettuce, Lactuca aculeata Boiss. et Ky., is closely related and fully interfertile with cultivated lettuce, Lactuca sativa L. Altogether, 155 accessions of this wild species, which is rare conserved within the world’s germplasm collections, were collected from 12 localities throughout northeastern Israel. Ten of these localities represent different sites across the Golan Heights, while two, high-density populations were suprisingly found at the Hula Plain (first report of this species in this region). Lactuca aculeata was recorded at various elevations (222–968 m a.s.l.) and habitats. The taxonomic status of 30 L. aculeata accessions was morphologically validated during ex situ seed regeneration of 31 random accessions representing all 12 localities. Characterization of 12 traits showed that the Israeli populations of L. aculeata do not exhibit broad morphological variability, but more great levels of variation were obtained for developmental traits. Relatively little variability was observed in the morphology of cauline leaves or in the distribution of anthocyanin pigmentation in bracteae. In two cases, L. aculeata plants lacked trichomes in the inflorescence, a typical feature in the majority of plants. These unique collections of wild lettuce may carry novel sources of genetic variation for a wide range of traits and, thus, should be of interest for careful evaluation and exploitation in lettuce breeding.     

美国市民农园生态植被景观营建及其启示

美国市民农园是一个值得借鉴的兼具生产、生态和生活等多功能的植被景观模式,本研究针对市民农园的生态服务功能,依据市民农园结构模式及经营群体的不同,随机选取了洛杉矶市14个市民农园,采用样地调查、半结构式访谈等方法,基于植被物种功能组合和乡土植物组成,定量化研究了城市植被物种多样性及其分布格局对种植者族裔背景及营建模式等影响因素的响应,进而评析对我国城市绿地建设和休闲农业的启示。本研究共计调查到439种植物,分属90科,242属,分析结果显示:市民农园是城市生态系统中重要的物种库,能维护较为丰富的乡土植物资源;其植物功能以食用植物为主,观赏植物、药用植物次之,这在保护族裔传统文化、区域乡土文化具有重要价值;其植被景观结构和功能受到族裔背景及营建模式等不同程度影响。研究证明,市民农园作为生态多样性和文化多样性的交汇景观,是实现城镇绿色基础建设和休闲农业发展的重要营建模式。以此为经验,我国在进行绿地规划和生态植被建设时要考虑不同利益相关者,尤其是关注外来者的生活习俗和选择偏好;同时也要注意监测外来物种,以防造成物种入侵,这对于建设文化强国背景下开展城镇生态植被建设和发展休闲农业具有启示意义。     

Tree populations bordering on extinction: A case study in the endemic Canary Island pine

Marginal populations are usually located at the edge of the species’ range, constituting small isolates that grow in suboptimal environments. In widely distributed conifers, such as pines, marginal populations have often been considered recent or rare colonizing events without ecological relevance. The Canary Island pine provides an excellent case to study the significance of critically endangered marginal populations (from 20 to a few hundred trees) in an endemic conifer that is also extensively used in commercial plantations. Our chloroplast microsatellite (cpSSR) survey showed contrasting values of haplotypic genetic diversity in marginal populations of Canary Island pine, from very low at Garabato (northern La Gomera) and Anaga (Tenerife), located within broad-leaved tree formations, to very high in Gran Canaria marginal populations (Arguineguin and Galdar). Competition with broad-leaved vegetation, after rare long-distance colonization events, might explain present-day low levels of variation in Garabato and Anaga. Gran Canaria and southern La Gomera relict populations, which contain high haplotypic diversity, are probably remnants of larger populations severely reduced by adverse climatic conditions and human activities, the latter starting shortly after the European colonization of the islands in the XV century. Given the extremely low population numbers and a general lack of natural regeneration, the risk of extinction in the near future is high in marginal populations of Canary Island pine. Conservation activities are urgently required and should focus on the highly diverse Gran Canaria and southern La Gomera pine marginal populations. Here, the establishment of in situ genetic reserves (Arguineguin and Imada), and multifunctional ex situ collections (Arguineguin and Galdar), such as seed orchards, is highly recommended. In addition, common garden experiments to test the performance of potentially drought-tolerant genotypes from Arguineguin (southernmost Gran Canaria’s relict) and potential risks due to inbreeding and/or outbreeding depression should be established.     

Toward the restoration of a sustainable population of a threatened aquatic plant, Nymphoides peltata: Integrated genetic/demographic studies and practices

We provide a brief review of practices and relevant studies for restoration of Nymphoides peltata (yellow floating heart, Asaza), a distylous floating-leaf clonal plant, in Lake Kasumigaura, Japan to develop a model of integrated genetic and demographic conservation for threatened plants. Several theoretically expected issues, such as sudden extinction of small populations with low genetic diversity, limited seed production in small-sized local populations, and significantly high heterozygosity in adults that have survived environmental change, were ascertained through integrated studies on demography with discrimination of genets and genetics using highly polymorphic genetic markers. Investigation of genetic properties of the remnant soil seed bank suggested that the seed bank could potentially restore genetic diversity, although the fitness reduction of seed banks caused by inbreeding could affect the success of restoration. As a result of restoration efforts, increases in the number of local populations and genets in the Lake Kasumigaura metapopulation have led to population recovery.     

Ecological and genetic effects on demographic processes: pollination, clonality and seed production in Dithyrea maritima

The relative importance of ecological and genetic factors in regulating the demographic processes of small populations is unknown for most rare plants. Dithyrea maritima (beach spectacle pod; Brassicaceae) is a rare, rhizomatously spreading, and self-incompatible herbaceous perennial endemic to coastal sand dunes of southern California. Low seed production in this species may be caused by insufficient pollinator visits, which may be exacerbated by competition for pollinator visits from non-native plants that have invaded the coastal dunes. I tested this ‘ecological’ hypothesis by removing flowers of Cakile maritima and Carpobrotus spp. from three experimental plots on San Nicolas Island. A second possible limitation on seed set is low diversity of genets within subpopulations, which could lead to scarcity of compatible mates. I tested this ‘genetic’ hypothesis by assigning ramets to clones using isozymes, and by relating clonal diversity within populations to seed set. Removal of non-native plants had no detectable effect on pollination service to D. maritima or on seed set, and seed set was unrelated to natural variation in pollination service among populations within a single year. In contrast, clonal diversity within a 10 m² patch was a strong predictor of seed set. Hence a genetic factor explains spatial variation in seed set on San Nicolas Island. On larger spatial and temporal scales, however, pollination service also affects patterns of seed set: a shift in pollination from flies in 1998 to bees in 1999 probably caused a corresponding increase in seed set across San Nicolas Island, while extremely low seed set at another site (San Miguel Island) is probably caused by a virtual absence of pollinators there.     

The use of seed-banks for conservation of populations of species and ecotypes

For many years botanical gardens have offered for exchange seed obtained from plants growing in their collections. Recent improvements in the basic understanding of the factors governing the storage life of seeds, have reached the point where it has become practicable to set up seed-banks in which the seed of many species may be stored for many years without deterioration. This development is of great significance in providing a means by which botanical gardens may develop their traditional interests and activity in plant conservation. Storage of plant material in a seed-bank is one way of avoiding many of the problems of genetic erosion or selective change in genetic constitution which occur when plants are cultivated under artificial conditions. This paper describes recent experience gained during the development at the Royal Botanic Gardens, Kew, of a seed-bank primarily intended for the storage of seed of species and ecotypes.     

Phenotypic differentiation in fitness related traits between populations of an extremely rare sunflower: Conservation management of isolated populations

Knowledge of the genetic and demographic consequences of rarity is crucial when evaluating the effects of habitat loss and fragmentation on population viability, and for creating management plans in rare plant species. Reduction in population size and in the number of populations can lead to decreased genetic diversity and increased inbreeding. Genetic diversity is often correlated with fitness and is frequently used to identify populations of greatest conservation concern, or those that may be good candidates for ex situ conservation programs. However, an association between these factors is not always clear, and crossing studies evaluating whether there is phenotypic differentiation among populations in fitness related traits can inform managers of suffering populations or good sources for ex situ materials. Crossing studies can also evaluate the potential for genetic rescue to boost fitness in suffering populations. To address these questions, we conducted two generations of controlled crosses between populations of the extremely rare and fragmented sunflower, Helianthus verticillatus. We measured achene viability, germination, survival, and pollen viability (F₁ only) in 176 F₁ and 159 F₂ families. The populations were differentiated with respect to phenotypic fitness measures with one population having significantly lower achene viability and germination. Also, the potential for genetic rescue was observed as gene flow into the less fit population resulted in higher fitness measures in both the F₁ and F₂. Results are discussed with respect to the importance of combining genetic marker data with crosses and the implications for conservation in disjunct populations of rare species.     

Genetic consequences of using seed mixtures in restoration: A case study of a wetland plant Lychnis flos-cuculi

Sowing with seed mixtures is a common practice in restoring species-rich communities in areas with impoverished species pools. The potential genetic consequences of using these mixtures, however, are poorly understood and often not considered in practical restoration. We investigated genetic diversity, inbreeding and genetic structure of samples collected from 26 populations of the common wetland plant species Lychnis flos-cuculi in an agricultural region in Switzerland. Some of these populations were natural, while others had been sown several years ago. This enabled us to compare the genetic composition of populations of indigenous origin with those originating from commercially produced seed mixtures. Gene diversity and allelic richness were similar in natural and sown populations. In contrast, inbreeding coefficients were three times higher in sown than in natural populations. The sown populations were genetically distinct from the native populations. We distinguished two homogeneous gene pools that presumably originated from different source populations used to produce seed mixtures. The use of commercially produced seeds may alter the genetic diversity and structure of plant populations. The observed higher inbreeding coefficients of sown populations could lead to reduced population viability. To restore genetically diverse populations, the seeds for further propagation should be collected from numerous individuals in large and non-isolated populations nearby restored sites. Ex situ stocks for the production of commercial seed mixtures should only be propagated for a few generations to avoid negative effects such as inbreeding or loss of local adaptation.     

Morphological and genetic diversity and seed germination behavior of a snow lotus (<Emphasis Type="Italic">Saussurea involucrata</Emphasis>, Asteraceae) from the Mongolian Altay Mountains,Western Mongolia

Different conservation measures including domestication approaches are needed to preserve rare and extensively used plant species and to satisfy future market demands. Snow lotus (a common name used for a number of high altitude species in central Asia) species in Mongolia are important medicinal plants, mostly endangered at the regional level due to the extensive use for medicinal purposes and naturally limited distribution ranges. In order to develop effective conservation and cultivation approaches we studied the morphological and genetic diversity as well as the seed germination behavior of three populations of Saussurea involucrata in the Altay Mountains of Western Mongolia. Plant height and leaf length were measured on 41–53 randomly selected individuals in each population. Enhancement of seed germination was studied using either mechanical or chemical scarification with potassium nitrate and gibberellic acid. Genetic diversity within and among three populations of the species was analyzed using Amplified Fragment Length Polymorphisms. Plants in three populations differed in height and leaf length (P < 0.001). Plant size tended to be negatively correlated with habitat altitude. Seed germination rate was low and increased with seed soaking in gibberellic acid. However, the response of seeds to different treatments was rather population-specific. Most treatments did not significantly affect mean days to germination and the ratio of shoot to root dry weight of 2-weeks old seedlings. The level of genetic diversity in the studied populations was lower than the average value for other long-lived perennial herbs. Analysis of molecular variance revealed a high differentiation within populations (92 % of total variation) indicating sufficient gene flow among populations.     

Effect of seed storage on germplasm integrity of meadow fescue (Festuca pratensis Huds.)

Qualitative and quantitative changes in populations of meadow fescue (Festuca pratensis Huds.) after seed storage under different conditions were estimated. Phenotypic characters of plants grown from seeds stored for 54 months under two different storage conditions were compared. The germination of most of the seed accessions stored under favourable conditions remained at the initial level while storage under unfavourable conditions resulted in a decrease of the initial germination percentage as well as in an increase in the number of plants showing chlorophyll aberrations. There is great variability among the accessions resulting from storage under unfavourable conditions. In case of a few accessions a decrease in germination below 35% resulted in chlorophyll aberrations, faster flowering, shorter inflorescence and reduced viability of pollen grains.     

Assessment of Genetic Diversity in Oil Palm (Elaeis guineensis Jacq.) using Restriction Fragment Length Polymorphism (RFLP)

A total of 359 accessions of oil palm (Elaeis guineensis Jacq.) originating from 11 African countries (Nigeria, Cameroon, Congo DR, Tanzania, Angola, Senegal, Sierra Leone, Guinea, Ghana, Madagascar and Gambia) were characterized using the RFLP method using the standard Deli dura as the check. Genomic DNA from each sample was digested using five restriction enzymes and hybridized with four oil palm cDNA probes. Data were analyzed using Biosys-1 computer software to calculate the genetic variability parameters. In general, all the collections exhibited higher levels of diversity than the standard variety, Deli dura. The standard variety, Deli dura, lost 36 alleles as compared to the natural populations indicating a reduction in genetic variability. Material from Nigeria showed the highest mean number of alleles per locus (1.9) and percentage of polymorphic loci (67.2%). These findings, combined with others, suggest that Nigeria may be the center of diversity of wild oil palm. It further suggests that oil palm natural populations maybe possessing adequate genetic variability that are potentially useful for improvement programs.     

Isozyme studies of genetic diversity and evolution in Hippophae

Summary To provide information on the genetic variation, differentiation and evolution in Hippophae seed samples of 25 populations from China, Finland and Russia were electrophoretically analyzed. Of six loci investigated, four were good genetic markers for identifying species and subspecies. The percentages of polymorphic loci per population were 40.3% and 62.5% at 0.95 and 0.99 polymorphic criteria respectively. The mean number of alleles per locus per population was 2.1. Total genetic diversity in the material was 0.4614. Genetic diversity partitioning showed that there was a large amount of diversity residing within geographical populations (0.1354), between subspecies within species (0.1046) and between species (0.2566) but not between geographical populations (0.0114). There were nearly twice as many negative fixation indices as positive ones in Hippophae populations. The phylogenetic tree agreed very well with botanic classifications of the species and subspecies and their geographical distributions, and quantitatively presented the genetic relationships of 25 populations. A detailed view of the evolutionary stages in Hippophae showed clearly a general decline of similarity as evolutionary divergence continued, which further explained the evolution process in Hippophae.     

Gardens benefit bees and enhance pollination in intensively managed farmland

The recent loss of pollinating insects and out-crossing plants in agricultural landscapes has raised concern for the maintenance of ecosystem services. Wild bees have been shown to benefit from garden habitats in urban and suburban areas. We investigated the effects of distance from garden habitats on wild bees and seed set of a native out-crossing plant Campanula persicifolia, in intensively managed agricultural landscapes in Southern Sweden. Bee abundance and species richness, as well as plant seed set, were higher closer to gardens (<15 m) than further away (>140 m). This highlights private gardens as a landscape wide resource for pollinators but also the lack of sufficient pollination of wild plants in contemporary agricultural landscapes.     

The unappreciated ecology of landrace populations: Conservation consequences of soil seed banks in Cassava

Failure to take into account the ecological complexity of landrace populations of crop plants limits our ability to conserve their genetic resources in situ. Soil seed banks are a central feature of the ecology of landrace populations of cassava; their existence has consequences for conservation. Seedlings recruited from seed banks are incorporated by farmers into their stocks of clones of this vegetatively propagated crop, transforming pure clonality into a mixed clonal/sexual reproductive system. Soil seed banks, and farmers’ responses to them, play an important role in maintaining diversity in populations of cassava landraces. In a study combining genetic and ethnobiological approaches, we showed the following: (i) Recruitment from soil seed banks increased diversity of populations at the local scale. At the level of a field, the presence of plants issued from seeds resulted in significantly greater diversity of genotypes and phenotypes than if only individuals planted by farmers had been present. (ii) Farmers’ use of seed banks has enabled indirect ‘exchange’ of locally adapted cassava germplasm between cultural groups, without requiring that groups actually encountered one another and engaged in social exchange of cultivars. (iii) Farmers have responded to catastrophic crop failure by using seed banks to regenerate stocks of clones. This use of seed banks should enable cassava populations to respond to disasters by an increase of genetic diversity, rather than by a narrowing of the genetic base, often feared in such situations.     

Effects of pollination distance on reproduction and offspring performance in Hypochoeris radicata: Experiments with plants from three European regions

Fragmentation of habitats has resulted in increased inbreeding for many plant species, while the introduction of foreign seed material for ecological restoration has resulted in crosses between plants from distant populations. Both processes may reduce plant fitness and increase the risk of extinction. Variation in the expression of inbreeding and outbreeding depression has been found among different genotypes and among populations, but little is known about large scale geographical patterns within species. We studied the effects of cross-proximity on seed production and offspring performance in the perennial meadow plant Hypochoeris radicata (Asteraceae) from five populations in each of three European regions (Bohemia in northwest Czechia, Northern Hesse in central Germany, and Salland in the central Netherlands). Five artificial cross types were conducted with varying proximity of mates: selfing (self), within family crosses (WF), within population crosses (WP), between population crosses (BP), and between region crosses (BR), and the offspring were grown in a common garden. Independent of the region of origin of the maternal plant, selfing, WF and BP crosses resulted in lower seed set and germination than WP crosses, indicating partial self-incompatibility, inbreeding depression and reduced performance in the F1 progeny resulting from outbreeding. However, crosses between regions resulted in similar seed set and germination as within population crosses. For late traits, the effects of inbreeding and interpopulation crosses differed among regions. WP crosses exhibited the highest survival, flowering and multiplicative fitness only in progeny from Czech maternal plants. Our results suggest that the sensitivity of populations to introgression may vary among regions and that outbreeding depression does not necessarily increase with interpopulation distance. However, the current study investigated only effects in the F1 in a common garden and outbreeding depression may be stronger in the F2 and in field populations.