A floristic-structural gradient related to land forms in the southern Chihuahuan Desert

Abstract. The purposes of this study were to elucidate the floristic and structural characteristics of the vegetationin the Mapimi subdivision of the Chihuahuan Desert, Mexico, and to relate them to environmental variation. The main question addressed was: How does floristic composition, total species richness and life-form species richness vary in relation to environmental change? 154 sites, randomly selected and stratified over seven landscape units, were analyzed. Results showed the existence of a land form gradient along which vegetation types were ordered. Species richness varied along the gradient, the richest land form was bajada, indicating that the maximum species richness did not occur at one extreme of the water availability gradient but in a moderately poor situation. The lowest species richness was found in the playa land form. Cover-based life form spectra varied significantly with land forms, while presence-absence based life form spectra did not. It is suggested that this may be a consequence of the relatively young age of this desert.     

茂兰喀斯特森林林隙植被恢复的物种组成及生活型特征

以贵州茂兰国家级自然保护区喀斯特森林为研究对象,以群落调查为基础,研究了林隙植被发育过程中物种组成、种间关系及生活型的动态变化规律。结果表明:在林隙发育的10年至30年时,林隙植物的科、属、种组成逐渐增加,至40年时有所下降,科和属组成与非林隙林分基本持平,但物种数继续增加。表征在林隙的恢复过程中,来自不同分类群的物种增加,群落组成更加复杂化和多样化。科、属、种三个等级均表现为林隙发育年龄越相近,相似性系数越大,林隙年龄相差越大时,物种组成的相似性越小,体现了林隙植被恢复的连续性。随林隙年龄的增大,高位芽植物和藤本植物逐渐增多,而地面芽和一年生植物则有减少的趋势,地上芽和地下芽植物随林隙的发育变化规律不明显。随林隙的发育,群落结构趋于稳定,生态功能增强。     

Identifying the most noxious invasive plants in China: role of geographical origin, life form and means of introduction

In a heterogenous world, invasive plants often differ in noxiousness and nature of impacts, and there is a difference between strong and weak invaders. That knowing which invaders are most noxious and their nature of impacts is of great value to invasive ecology and management. Here we show that in China the most notorious invasive plants are with a perennial life cycle, clonal growth ability and from the American continent. They often form monocultural populations in land and water, replacing almost all other plants, and are mainly distributed in Central and South China. Following are some accidentally introduced annuals. Annuals from the American continent are often common, dominant or in monocultural populations in ruderal and agricultural habitats whereas those from Eurasia are highly noxious only in agricultural habitats. Annuals are not restricted in distribution and could spread fast to all of the country. There are also two perennial grasses from Europe and Mediterranean area and four intentionally introduced annuals from South America that were identified in this study. Factors that may account for these patterns include relatedness between invasives and natives, vegetative propagation, and plant strategies. The invasive plants identified in this study have caused significant negative impacts to native biodiversity, environment, economics and agriculture, with different groups being different in their extent and nature of impacts.     

Diversity of non-native terrestrial arthropods on woody plants in Canada

A list of non-native phytophagous insects and mites on woody plants (trees, shrubs, vines) in Canada was compiled using information from literature and input from taxonomists. The 419 recorded species include Hemiptera (53% of species), Lepidoptera (22%), Coleoptera (13%) and Hymenoptera (9%). Almost all species originate from the Palearctic, especially Europe, reflecting historical trade patterns. About 41% of species were directly introduced to Canada from countries of origin, and the remainder spread from the United States of America (USA) after initial establishment there. Major ports on the east and west coasts, on Lake Erie and Lake Ontario are the main points of entry for exotic species directly introduced, and southern British Columbia (BC), Ontario (ON) and Quebec (QC) are the major points of entry for species spreading from the USA. Consequently, BC, ON, QC and Nova Scotia have the highest diversity of non-native species, and the prairie provinces and northern territories have the lowest. The extent of the distribution of individual species is related to length of time in Canada, number of introductions and dispersal abilities. Almost all native woody plant genera in Canada have been invaded by exotic phytophages. The large majority of phytophages occur on angiosperms. Woody plant genera with the largest distribution, highest species diversity and highest local abundances tend to host the greatest number of non-native species, including Picea, Pinus, Malus, Prunus, Salix, Betula, Quercus, Pyrus and Populus. The arrival rate of species in Canada increased from the late nineteenth century until about 1960, and declined rapidly thereafter. Quarantine legislation enacted in the USA in 1912 and in Canada in 1976 seems to have reduced the rate of insect invasion. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Perceptions, use and availability of woody plants among the Gourounsi in Burkina Faso

The present study was conducted in five villages around the Nazinga Game Ranch, Burkina Faso. Fifty informants of the Gourounsi ethnic group were used. Eighty-one useful woody species were identified, out of a total of 110 woody species in the area. Woody plant use was quantified as: edible fruits (28 species), vegetable sauce (22 species), firewood (33 species), construction (29 species) and medicine (64 species and 167 remedies). Further, species accumulation curves were used to estimate that more than 650 remedies for medicine are used in the area. The community's knowledge of plants was analysed in relation to age, gender, village of residence and amount of intercultural visits. The knowledge pattern was remarkably uniform, with only two variations: (1) men generally identified more edible fruit trees than women, and (2) one village reported more firewood species than the other four villages. The informants had a variety of opinions concerning the availability of useful plants, but the majority found the availability to be fine and 47% of the informants searched for useable products in the savanna on a daily basis. No correlation was found between an informant's impression of useful products availability and his/her frequency of visits into the savanna. The results show that the Gourounsi people live in intimate relation with the savanna surrounding their villages. They are aware of the environment and are willing to learn and adopt new conservation practices.     

A morphological classification of plants,with special reference to the New Zealand alpine flora

Abstract. A plant is a complex of integrated systems (leaves, leaf groups, stems, roots, inflorescences), coexisting side by side or superimposed on each other to produce the life form (orphysiognomy) of the individual. The classic Raunkiaer classification based fundamentally on one character (apex position) is insufficient for the purpose of a functional classification. Five keys are given to determine the categories of:

• 1) the plant silhouette or general shape resulting from a combination of other systems, with 11 categories proposed;
• 2) the leaf group, with 14 categories;
• 3) the stem, with 27 categories;
• 4) the root, with 5 categories; and
• 5) the inflorescence, with 3 categories.

Each plant can be named according to the category or model of each of the five different systems that they most resemble, or by using only the name(s) of systems which are more conspicuous than others. Characters are selected primarily for their influence on form and secondarily on size. This scheme allows for detailed studies of a flora in terms of morphological characteristics (alone or in systems), expressed as frequency of occurrence of each character in the flora. Characters can be analysed separately (e.g. entire margined leaves), as a combination of characters (e.g. leaf groups) or as a combination of systems (e.g. rosettes without stems). Thus correlations between environmental variables and plants canbe made with more precision than in previous classification schemes. The classification also serves as the framework for including additional morphological data and incorporating new models. The New Zealand alpine flora is used as a test case and to exemplify the classification.     

Successful city dwellers: a comparative study of the ecological characteristics of urban birds in the Western Palearctic

Numerous species have adapted to the proximity of humans, and this feature is no clearer than among species that have invaded towns and cities. The characteristics of species that have successfully managed to expand their range into urban areas remain largely unexplored, although they are of general interest in a world that is increasingly urbanised. I hypothesised that widely distributed species with high dispersal abilities, species with a high rate of innovation, a high level of risk-taking, and a fast life history would have a selective advantage in habitats influenced by humans. Consistent with this hypothesis, in a comparative analysis of 39 independent evolutionary events of urbanisation of birds in the Western Palearctic (thus taking the fact that closely related species that have become urbanised are caused by common phylogenetic descent rather than convergent evolution), bird species that adapted to urban habitats were characterised by large breeding ranges, high propensity for dispersal, high rates of feeding innovation (novel ways of acquiring food), short flight distances when approached by a human, and a life history characterised by high annual fecundity and high adult survival rate. Urban species may be disproportionately resistant to parasitism and predation because they had disproportionately strong immune responses, as reflected by the size of the bursa of Fabricius, and a history of weak predation-mediated natural selection, as reflected by the force required to remove feathers from the rump. Urban species had high overall ecological success as indicated by large range size and population size and high population density. This suggests that a suite of ecological features providing them with general ecological success characterises species of birds that have successfully invaded urban environments. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Introduction of Glossostigma (Phrymaceae) to North America: a taxonomic and ecological overview

Field surveys in eastern North America confirm the naturalization of Glossostigma plants at 19 localities in four states: Connecticut, New Jersey, Pennsylvania, and Rhode Island. DNA sequence analysis of individuals from 14 sampled populations identifies these nonindigenous plants as Glossostigma cleistanthum, a species native to Australia and New Zealand. These results correct prior misidentifications of North American plants as G. diandrum. The earliest North American record of G. cleistanthum (1992) is from a Ramsar tidal wetland in Connecticut. Morphological analyses demonstrate that G. cleistanthum differs from G. diandrum by its longer leaves and ability to produce both cleistogamous and chasmogamous flowers in response to ecological conditions. Glossostigma cleistanthum has a high reproductive potential and spreads rapidly within and between both artificial and natural habitats. A survey of more than 100 lakes indicated that G. cleistanthum occurs most often in waters with high clarity and low pH, alkalinity, conductivity, and phosphorous. Because of its affinity for oligotrophic conditions, this species is a particular threat to pristine natural aquatic communities, which often contain imperiled plants.     

Nitrate,nitrate reduction and organic nitrogen in plants from different ecological and taxonomic groups of Central Europe

Summary 48 plant species of the families Asteraceae, Chenopodiaceae, Ericaceae, Fabaceae, Lamiaceae, Polygonaceae and Urticaceae were investigated in 14 natural habitats of Central Europe having different nitrate supplies, with respect to their nitrate content, nitrate reductase activity (NRA) and organic nitrogen content. Plants that were flowering were selected where possible for analysis. The plants were subdivided into flowers, laminae, petioles+shoot axes and below-ground organs. Each organ was analyzed separately. Differences among species were found for the three variables investigated. Apart from the Fabaceae, which had particularly high concentrations of organic N, these differences reflect mainly the ecological behaviour, i.e. high nitrate and organic N contents and NRA values per g dry weight were found in species on sites rich in nitrate, and vice versa. Nitrate content, NRA and organic N content were correlated with nitrogen figures of Central European vascular plants defined by Ellenberg (1979). By use of regression equations this correlation was tested with species from other systematic groups. Some species were attributed with calculated N figures for the first time.     

Assessing the risk of invasive success in Pinus and Banksia in South African mountain fynbos

Abstract. South African mountain fynbos has been severely invaded by trees and shrubs introduced from other mediterranean-climate regions. Management of these invasions should involve controlling current invaders and screening future introductions. Invasion windows are described and functional groups are defined for pines based on life history attributes important for invasion in the fire-prone mountain fynbos. The most successful invasive pines here (Pinus halepensis, P. pinaster and P. radiata) are fire-resilient and have small seeds, low seed-wing loadings, short juvenile periods, moderate to high degrees of serotiny and relatively poor fire-tolerance as adults. Other species with these attributes, especially from mediterranean-climate regions, wouldbe high-risk introductions. Taxa in other functional groups have not become major weeds even with widespread man-aided dissemination. Experience with pine invaders was used to define functional groups in western Australian Banksia species (Proteaceae), shrubs and trees which include taxa with similar attributes to fynbos invaders (e.g. Hakea and Pinus spp.). Banksias have only recently been introduced to the Cape, and are likely to be increasingly cultivated for the cut flower market. Tall serotinous shrubs with many small seeds per plant, short juvenile periods and low fire tolerance were identified as high risk introductions. This group includes thicket-forming species which maintain very large viable seed banks, e.g. Banksia burdettii, B. hookeriana and B. leptophylla. Low sprouting shrubs with few large seeds per plant and long juvenile periods are unlikely to become invasive in mountain fynbos. The approach of defining functional groups based on life history attributes and invasion windows is valuable for predicting the probability of invasive success. Chance interactions suchas an opportunistic dispersal mutualism between Pinus pinea and an introduced squirrel sometimes confound these predictions and underscore the idiosyncracies inherent in biological invasions.     

Determinants of the geographical extent of invasive plants in China: effects of biogeographical origin,life cycle and time since introduction

Plant invasions cause serious impacts to environment and human economy, and lots of researches have been paid to examine factors that determine the geographical extent of plant invaders. Many intrinsic species attributes, external environmental factors, and time since introduction have all been proposed to explain invasive success. Data on invasive plants distribution in province regions in China were collected, and species attributes and historical factors such as biogeographical origin, life cycle, and time since introduction were determined. While some annuals may eventually occupy the whole country area, perennials are unlikely to do so, particularly those from Central and South America. Time since introduction is significantly related to the number of provinces occupied by an invader; nevertheless after control of certain residence time, annuals are not likely to more provinces than the perennial herbs. High-impact invaders tend to spread faster than other invaders, but only when their life cycle is taken into account. This suggests that other plant traits, instead of life cycle, along with extrinsic factors, greatly contribute to invasive success and distribution area. Invasive plants in China are mainly distributed in human-made habitats, and their long-distance dispersal is primarily associated with human activities. Future studies need to consider interactions between species traits, environmental conditions, and human activities for further insights in researches alike.     

The nutritional status of plants from high altitudes

Summary Are plants at high altitudes short in nutrients? In order to answer this question the mineral nutrient content of leaves from over 150 plant species from 9 different mountain areas of all major climatic zones were analyzed (Kjeldahl nitrogen in all, phosphate in half of the samples, K, Mg, Mn, Ca in the Alps only). The majority of data are from herbaceous perennials, but shrubs and trees were studied as well. N-partitioning was studied in 45 herbaceous species from contrasting altitudes in the Alps. The survey falls into three categories: (1) comparisons of whole communities of species from contrasting altitudes, (2) analysis of altitudinal gradients, and (3) additional collections from high altitude sites alone. Unlike the other mineral nutrients, nitrogen content follows consistent altitudinal and latitudinal trends. The higher altitude sample always had higher N content per unit leaf area, irrespective of life form, wherever comparable plants (the same or related species) were investigated at contrasting altitudes. N content per unit dry weight (%) increased with altitude in herbaceous plants (in some species >4%), but was remarkably stable in evergreen woody plants (around 1%). The mean fraction of total plant N allocated to leaves of herbaceous plants in the Alps was the same at low and high altitude (1/3 of total). Leaf N (%) from the regional upper limits of higher plant life reveals a latitudinal decrease from subarctic to equatorial mountains, which may be related to the duration of annual leaf activity. Since mean N content per leaf area hardly differs between the uppermost sites, life span expectation (sink-duration) seems to control carbon investments rather than N input per leaf area. The growth of leaves at high altitude seems to be controlled in a way that leads to comparatively high nutrient contents, which in turn support high metabolic activity. Inherent developmental growth constraints inhibit nutrient dilution in the plant body and thus defy the application of classical concepts of plant-nutrient versus soil-nutrient relations developed for lowlands and in particular for cultivated plants. The results re-emphasize the global significance of links between nitrogen content, leaf sclerophylly, leaf longevity and photosynthetic capacity.Dedicated to Prof. Walter Larcher on the occasion of his 60th birthday, with thanks for leading me to comparative plant ecology     

A template for the future: digitizing and databasing a taxonomic illustration collection

This is the first iconographic taxonomic database intended as an everyday tool for the practising taxonomist, that allows access to the original drawings used to describe species. We demonstrate the system with water mites (Acari, Parasitengona, Hydrachnidia) but it may be used with any other plant or animal group. Query by genus or species leads to the original drawings and any additional images associated to that particular name. At present, the database includes images from more than 4,000 species (around 38,000 illustrations) and is easily expandable. Copyright does not allow the database to be used in an open WWW context, but it can be an extremely useful tool in private taxonomic applications.     

Adaptation of ecological systems: compositional patterns of species and morphological and functional traits

Abstract. The species composition and morphological and functional traits of ecological systems are compared. The significance of the resulting relationship is interpreted considering the underlying spatial environmental variation. Using 60 morphological and functional traits, a gradient of ecological persistence was detected in Mediterranean grasslands along an altitudinal range of ca. 1200 m. This pattern coincides with the one expressed by its taxonomic composition and thus permits ‘styles of adaptation’ of ecological systems to be recognized. Species composition may represent one of the possible combinations which optimises its environmental fit. The relevance to ecological theory of this pattern of grassland organization is discussed in the context of a hypothetical model of evolution.     

Floristic composition and floral phenology of the Mediterranean batha of Ariel,Samaria

Field observations over a three-year period were used to document the floristic composition, flowering and fruiting sequences of the Sarcopoterium spinosa Mediterranean batha of Ariel. This plant community was found to be species-rich, with high percentages of annuals, bushes and geophytes, low percentages of herbaceous plants, climbers and trees, and ten species considered rare in Israel. Typical Mediterranean characteristics were observed in the S. spinosa batha: spring flowering reaching a peak in April, small between-year variation in flowering and fruiting, most species having Mediterranean distribution, and partial resistance to fire.     

Liverworts of southwest Ethiopian montane forests: ecological and biogeographical notes

Abstract

Ethiopia has diverse topographic features and climatic conditions with a diverse flora. The liverwort flora of southwest Ethiopia is practically unknown, despite a favourable climate and the occurrence of suitable ecosystems such as montane rainforests. During an ecological study of diversity patterns of bryophytes and vascular plants in relation to land use, we recorded many bryophyte species. In this paper we report the finding of 89 species of liverworts, and give short ecological notes and describe the distribution (locally and in Africa) for each species. Of these, 51 species are newly reported from Ethiopia. It is thus obvious that Ethiopia is considerably richer in liverworts than might be expected from previous checklists.     

Sauropod dinosaurs from the Lower Cretaceous of eastern Asia: taxonomic and biogeographical implications

Sauropod dinosaurs are poorly represented in the Lower Cretaceous of eastern Asia. Here, we describe a number of isolated sauropod teeth from the Kuwajima Formation (?Berriasian–?Hauterivian) of Shiramine, Japan. The mosaic of shared derived characters and symplesiomorphies displayed by the teeth indicate that they are referable to a basal member of the titanosauriform radiation. A taxonomic review of previously described sauropod specimens from eastern and south–eastern Asia reveals that a diversity of sauropods (including a titanosaurian, a basal titanosauriform and a ?euhelopodid, as well as several forms of indeterminate systematic position) was present in this region in the Early Cretaceous. This diversity conflicts with previous suggestions that eastern Asia was biogeographically isolated from the rest of Laurasia until the late Early Cretaceous and that the sauropod fauna was limited to the endemic East Asian clade Euhelopodidae. The presence of titanosauriform sauropods in the basal Cretaceous of Japan and Thailand indicate that the proposed faunal isolation of eastern Asia ended approximately 20 myr earlier than usually suggested.     

Fruit size and shape: Allometry at different taxonomic levels in bird-dispersed plants

Summary The likelihood that a plant's seeds will be dispersed by fruit-eating birds may depend upon the size and shape of its fruits. Assuming that elongate fruits can be swallowed more easily than spherical fruits of equal volume and that plant fitness is enhanced by seed dispersal by many individuals and species of birds, natural selection should favour increasing fruit elongation with increasing fruit size in bird-dispersed plants. According to this view, this allometric pattern would be adaptive. Alternatively, fruit shape in bird-dispersed plants may be constrained by development or phylogeny. To determine whether there was any evidence to support the adaptive allometry hypothesis, we examined allometric relationships between length and diameter in fruits and seeds in a group of neotropical bird-dispersed plant species. Using the major axis technique, we regressed ln(diameter) on ln(length) for fruits and seeds at various taxonomic levels: (1) within individual trees ofOcotea tenera (Lauraceae) (2) among 19 trees within a population ofO. tenera, as well as among pooled fruits from multiple trees within 20 other species in the Lauraceae, (3) among 25 sympatric species within a plant family (Lauraceae) and (4) among 167 species representing 63 angiosperm families within a plant community in Monteverde, Costa Rica. At most taxonomic levels, a tendency for fruit length to increase more rapidly than fruit diameter among fruits (negative allometry) occurred more frequently than expected by chance. Estimated slopes of the regressions of fruit length on fruit diameter were < 1 within 15 of the 19 individualO. tenera trees, among tree means withinO. tenera, among pooled fruits within 16 of the 20 other species in the Lauraceae, among species means within the Lauraceae and among means of all bird-dispersed species in the lower montane forests of Monteverde. Seed allometry showed similar patterns, although for both fruits and seeds the broad confidence intervals of the slopes estimated by major axis regression overlapped 1 in many cases. Among the 63 Monteverde family means, fruit length and diameter scaled isometrically. Based on measurements of ontogenetic changes in fruit shape in a single species,O. viridifolia, we found no evidence that negative allometry in fruit shape within the Lauraceae was an inevitable consequence of developmental constraints. Instead, increasing elongation of fruits and seeds in certain plant taxa is consistent with adaptation to gape-limited avian seed dispersers. Contrary results from vertebrate-dispersed species from Malawi and Spain may reflect differences between the New and Old World in plant taxa, seed dispersers or evolutionary history.     

Partially hydrated pollen: taxonomic distribution, ecological and evolutionary significance

 The problem of the water content of pollen is reconsidered, especially the distinction between “partially hydrated pollen” (PH pollen), pollen with a water content greater than 30%, and “partially dehydrated pollen” (PD pollen), which has a water content of less than 30%. Both types have been found even in systematically contiguous groups or the same genus. Partially hydrated pollen, encountered in at least 40 families of angiosperms, has the advantage of germinating quickly, normally in a few minutes to less than an hour. Dispersal of highly hydrated pollen also occurs in orchids but for a different reason, i.e. to enable packaging of massulae. The disadvantage of pollen dispersed with a high water content is that water is readily lost and the pollen may desiccate and die unless it has biochemical or anatomical devices to retain water or phenological strategies, such as flowering when temperatures are not too high and when relative humidity is high. Most pollen of Gymnosperms and Angiosperms studied has, however, been found partially dehydrated. Received March 8, 2002; accepted April 8, 2002 Published online: November 14, 2002 Addresses of the authors: G.G. Franchi (e-mail: franchi@unisi.it), Department of Pharmacology, Università di Siena, Via delle Scotte 6, I-53100 Siena, Italy; M. Nepi (e-mail: nepim@unisi.it) and E. Pacini (e-mail: pacini@unisi.it), Department of Environmental Sciences, Università di Siena, Via P.A. Mattioli 4, I-53100 Siena, Italy; A. Dafni (e-mail: adafni@research.haifa.ac.il), Laboratory of Pollination Ecology, Institute of Evolution, University of Haifa, 31905 Israel.