X-ray crystal structure of the C4d fragment of human complement component C4

C4 fulfills a vital role in the propagation of the classical and lectin pathways of the complement system. Although there are no reports to date of a C4 functional activity that is mediated solely by the C4d region, evidence clearly points to it having a vital role in a number of the properties of native C4 and its major activation fragment, C4b. Contained within the C4d region are the thioester-forming residues, the four isotype-specific residues controlling the C4A/C4B transacylation preferences, a binding site for nascent C3b important in assembling the classical pathway C5 convertase and determinants for the Chido/Rodgers (Ch/Rg) blood group antigens. In view of its functional importance, we undertook to determine the three-dimensional structure of C4d by X-ray crystallography. Here we report the 2.3A resolution structure of C4Ad, the C4d fragment derived from the human C4A isotype. Although the approximately 30% sequence identity between C4Ad and the corresponding fragment of C3 might be expected to establish a general fold similarity between the two molecules, C4Ad in fact displays a fold that is essentially superimposable on the structure of C3d. By contrast, the electrostatic characteristics of the various faces of the C4Ad molecule show marked differences from the corresponding faces of C3d, likely reflecting the differences in function between C3 and C4. Residues previously predicted to form the major Ch/Rg epitopes were proximately located and accessible on the concave surface of C4Ad. In addition to providing further insights on the current models for the covalent binding reaction, the C4Ad structure allows one to rationalize why C4d is not a ligand for complement receptor 2. Finally the structure allows for the visualization of the face of the molecule containing the binding site for C3b utilized in the assembly of classical pathway C5 convertase.     

Effects of chilling temperature on photosynthetic rates, photosynthetic enzyme activities and metabolite levels in leaves of three sugarcane species

FBPase, fructose-1,6-bisphosphatase
NADP-MDH, NADP-malate dehydrogenase
NADP-ME, NADP-malic enzyme
OAA, oxaloacetic acid
PEP, phosphoenolpyruvate
PEPcase, phosphoenolpyruvate carboxylase
PPDK, pyruvate orthophosphate dikinase
Rubisco, ribulose-1,5-bisphosphate carboxylase/oxygenase

The aim of this study was to investigate the mechanism of photosynthetic changes in sugarcane leaves in response to chilling temperature by using three species ( Saccharum sinense R. cv. Yomitanzan, Saccharum sp. cv. NiF4 and Saccharum officinarum L. cv. Badira) differing in origin and cold sensitivity. Yomitanzan is native to subtropical areas, Badira is native to tropical areas and NiF4 is a hybrid species containing genes of both tropical and subtropical species. At exposure to chilling temperature (10 °C), the photosynthetic rate in the leaves at either 10 °C or 30 °C showed a greater decrease in Badira than in NiF4 and Yomitanzan. After 28 h exposure of plants to the chilling temperature, the extractable activities of pyruvate, orthophosphate dikinase (PPDK) and NADP-malate dehydrogenase (NADP-MDH) increased or were relatively stable in the leaves of NiF4 and Yomitanzan, but decreased substantially in Badira. Correspondingly, there was a substantial accumulation of aspartate, and the level of alanine increased in Badira leaves during the chilling treatment. It is suggested that NADP-MDH and PPDK are key enzymes which may determine the cold sensitivity in photosynthesis of sugarcane.     

Transit towards floristic homogenization on oceanic islands in the south-eastern Pacific: comparing pre-European and current floras

Aim  To quantify the occurrence of processes of homogenization or differentiation in the vascular flora of six oceanic islands.
Location  Six islands in the south-eastern Pacific drawn from the Desventuradas Archipelago, Easter Island and the Juan Fernández Archipelago.
Methods  Using published floristic studies, we determined the floristic composition of each island at two different stages: (1) pre-European colonization and (2) current flora. We compared changes in the number of shared plants and the floristic similarity among islands for each stage.
Results  The number of plant species doubled from 263 in pre-European flora to 531 species currently. Only three native species became extinct, four natives were translocated among the islands and 271 plant species were introduced from outside. The frequency of plant species shared by two or more islands is higher in the post-European floras than prior to European contact, and the level of floristic similarity between islands increased slightly.
Main conclusions  Considering the low naturalization rate of alien plants, the small number of extinctions and the meagre increase in floristic similarity, these islands are undergoing a slow process of floristic homogenization.     

Competition for nitrogen between Australian native grasses and the introduced weed Nassella trichotoma

BACKGROUND: and Aims Nassella trichotoma is an unpalatable perennial grass weed that invades disturbed native grasslands in temperate regions of south-eastern Australia. This experiment investigated whether elevated N levels, often associated with disturbance, increases the competitiveness of N. trichotoma relative to C3 and C4 native Australian grasses. METHODS: A pot experiment investigated competitive interactions between four native grasses, two C3 species (Microlaena stipoides and Austrodanthonia racemosa) and two C4 species (Themeda australis and Bothriochloa macra), and N. trichotoma at three different N levels (equivalent to 0, 60 and 120 kg ha-1) and three competing densities (zero, one and eight neighbouring plants), using an additive design. KEY RESULTS: All native grasses were competitive with N. trichotoma at low N levels, but only M. stipoides was competitive at high N. High densities of native grasses (8:1) had a major competitive effect on N. trichotoma at all N levels. The competitive ranking of native grasses, across all N levels, on N. trichotoma was: M. stipoides>A. racemosa>B. macra>T. australis. The C3 species were generally more competitive than the C4 species and C4 grasses were not inherently more productive at low N levels, in contrast to the results of other studies. CONCLUSION: To resist invasion from N. trichotoma, these native grasses need to be maintained at a high density and/or biomass. The results do not support the theory that species such as N. trichotoma, with high tissues density, are always less competitive than those of low tissue density; in this case competitiveness depended on N levels. The ability of N. trichotoma to accumulate biomass at a higher rate than these native grasses, helps to explain why it is a major weed in disturbed Australian native grasslands.     

Effect of temperature on the microbial flora of herring fillets stored in air or carbon dioxide

The microbial development on fillets of herring from the Baltic Sea was studied at temperatures from 0-15 C in air or 100% carbon dioxide (96-100% CO2). The shelf-life of the fillets , defined as the time for the 'total aerobic count' to reach 1 X 10(7) c.f.u./g increased with decreased temperature from 1 d at 15 degrees C to 7 d at 0 degrees C (air). The corresponding values in CO2 were 3 d and 33 d, respectively. The initial flora of the herring fillets was dominated by Alteromonas putrefaciens and Pseudomonas spp. and so was the spoilage flora after storage in air (together 62-95% of the flora: all temperatures). Alteromonas putrefaciens predominated slightly at 2 degrees C to 15 degrees C, while Pseudomonas spp. dominated at 0 degrees C. The Pseudomonas flora was mainly split between Ps. fragi , Ps. fluorescens and a heterogenous group of unidentified Pseudomonas spp. The proportions were not influenced by temperature. In 100% CO2 at the time of spoilage the flora consisted of a significant number of Lactobacillus spp. Below 4 C the domination was almost complete while at 10 degrees C and 15 degrees C. Enterobacteriaceae, Vibrionaceae and Alt. putrefaciens was also found. It was concluded that the microbiological shelf-life of herring fillets is improved by refrigeration storage in 100% CO2 but for good results the temperature should not exceed 2 degrees C.     

Factors affecting the diversity of flora and vegetation in central European settlements

Published data on the number of plant species and/or communities were gathered for 77 European cities and 85 villages. The relationships between the floristic and vegetation diversity and some environmental variables were analysed. Species number in cities showed log linear increase with city size (expressed as the population size or city area). A linear increase in the species number with size was found in the village flora. The richness of both city and village flora was not significantly related to any climatic variable. On the contrary, the number of communities in both villages and cities was correlated not only with settlement size but also with altitude and mean annual temperature. The diversity of village vegetation was closely related to the climax type of the respective region. The features of human settlements that make it possible to consider them as landscape islands are discussed.     

The Australasian grass flora in a global context

Australia's flora and fauna have long been considered unique, but whether this applies to its grasses is less known. This study characterises the Australasian grass flora biogeographically. We investigate the distribution of C₃ and C₄ grass genera across four continents and construct broad profiles of their grass flora. We use endemism to examine global patterns of specialisation, and inter-continental distributions as indicators of dispersal, using databases constructed over twenty years. We examined Australasian patterns with regard to endemicity and shared groups and categorised all of the region's genera into four age classes, from Australia's separation from Gondwana to the present. Globally, each continent presented a unique profile and C₄ grasses were more widely shared than C₃. Australasia's grasses equally comprise C₃ and C₄ genera; it shared two thirds of its C₄ types with other continents, whereas C₃ types split evenly between shared and endemic. Australasia shared relatively few genera with just one neighbour (7% C₃, 13% C₄), primarily with EurAsia. Australasian grass genera and species were either endemic or globally widespread, and 88% of C₃ and 93% of C₄ species were derived from lineages that originated elsewhere. We conclude Southeast Asia was the gateway for dispersal into Australasia, akin to rainforest taxa exchanges which increased from c12 Ma, with about 65% of Australasia's grass genera arriving in the past 3.5 Ma. The strong presence of C₄ grasses in Australasia implies they have infiltrated a wide range of ecosystems, many probably occupied by ancient taxa with which they had not co-evolved.     

Assignment, by proton magnetic resonance, of histidines of dihydrofolate reductase from chicken liver

The effects of pH and temperature upon C epsilon 1 H resonances of the four histidyl residues of chicken liver dihydrofolate reductase in binary complex with methotrexate were studied by 500-MHz 1H NMR spectroscopy. The four histidines labelled a, b, c, d are distinguishable by their pK values and the chemical shifts of their C epsilon 1H protons. The local electromagnetic environment as deduced from X-ray studies at 2.9 A resolution was used as a basis for proposed assignment of the four histidines. The assignments were a: H42, b: H140, c: H131, d: H87. Furthermore the histidyl residue labelled c was shown to be upfield shifted in its C epsilon 1H proton in the enzyme-methotrexate complex compared to the native enzyme. The hypothesis of a conformational change of the protein is discussed.     

世界上已知维管植物有多少种? 基于多个全球植物数据库的整合

维管植物是地球上生物多样性的重要组成部分, 拥有超过200年的研究历史。然而, 世界上有多少种维管植物, 其中有多少种已被发现和描述等问题迄今仍未很好回答。本文整合分析了全球4个主要植物数据库, 以期回答全球已发现和描述了多少物种的问题。结果表明, 全球已发现和描述的维管植物有376,366种(包括自然杂交种)。排除自然杂交种后, 全球共包含369,054种维管植物, 其中广义蕨类植物13,810种, 裸子植物1,172种, 被子植物354,072种。我们的结果比已有的4个数据库中的任何一个的物种数都至少要多17,700种。     

Predicting plant invasiveness from native range size: clues from the Kashmir Himalaya

Aims In view of the growing interest in modelling the potential spread of invasive species, prediction of plant invasiveness on the basis of native range size holds considerable promise. Our objective was to use a simple model to evaluate whether a wider native range predisposes plant species to become invasive in non-native regions and to easily identify potential invaders on this basis. The Kashmir Himalayan alien flora, of which a large proportion is native to Europe, was used to test this model.Methods The Kashmir Himalayan alien flora comprises 436 species of vascular plants at different stages of invasion. We focussed on plant species at two critical invasion stages (sensu Colautti and MacIsaac 2004), i.e. Stage II (species that are just at the earliest phase of introduction) and Stage V (species that are widespread and dominant in the invaded region and are thus considered invasive). We used the territorial distribution in Europe (number of countries) as a surrogate for the native range size of plants of European origin.Important findings Using a subset of 88 species, for which information on the native European range was available, we showed that a large proportion (68%) of Stage II species growing in the Kashmir Valley had a relatively restricted European range (present in ≤20 countries); on the other hand, 77% of Stage V species had an extensive native range (present in>20 countries). We consequently hypothesized that 14 Kashmir Himalayan Stage II species of European origin that are distributed in>20 European countries are at risk of becoming future invaders in Kashmir. On the other hand, those Kashmir Himalayan Stage II species of European origin distributed in ≤20 European countries are less likely to become invasive. Although this analysis is quite simple, the data suggest that a wider native range is a good predictor of plant invasiveness and could be used as a simple and low-cost early warning tool in predicting potential invasive species.     

黄河干流河岸带C4植物群落特征及其对水库生态效应的指示

于2008年9月16日至10月31日对黄河干流河岸带植物群落开展了系统调查。共采集高等植物124种,分属于32科、97属,其中C4植物9科、24属、34种,占科、属、种总数的28%、25%和27%。对该区域的研究结果还表明：（1）C4植物主要分布于单子叶植物纲的禾本科和莎草科,两者共占C4植物总种数的61%。（2）从上游到下游C4植物种数递增,但中游C4/C3比、C4植物密度和生物量要明显高于上游和下游。（3）C4植物种数及C4/C3比与海拔、年均气温、年均降水量及年均流量均有相关关系,C4植物生物量仅和年均降水量显著相关。（4）水库位置的C4/C3比要明显高于其临近样区,说明C4植物对水库干扰下河岸带植被的动态变化具有一定的指示作用。     

Is there a massive glacial–Holocene flora continuity in Central Europe?

The prevailing paradigm about the Quaternary ecological and evolutionary history of Central European ecosystems is that they were repeatedly impoverished by regional extinctions of most species during the glacial periods, followed by massive recolonizations from southern and eastern refugia during interglacial periods. Recent literature partially contradicts this view and provides evidence to re-evaluate this Postglacial Recolonization Hypothesis and develop an alternative one. We examined the long-term history of the flora of the Carpathian (Pannonian) Basin by synthesising recent advances in ecological, phylogeographical, palaeoecological and palaeoclimatological research, and analysing the cold tolerance of the native flora of a test area (Hungary, the central part of the Carpathian Basin). We found that (1) many species have likely occurred there continuously since before the Last Glacial Maximum (LGM); (2) most of the present-day native flora (1404 species, about 80%) can occur in climates as cold as or colder than the LGM (mean annual temperature ≤+3.5°C); and (3) grasslands and forests can be species-rich under an LGM-like cold climate. These arguments support an alternative hypothesis, which we call the Flora Continuity Hypothesis. It states that long-term continuity of much of the flora in the Carpathian Basin is more plausible than regional extinctions during the LGM followed by massive postglacial recolonizations. The long-term continuity of the region's flora may have fundamental implications not only for understanding local biogeography and ecology (e.g. the temporal scale of processes), but also for conservation strategies focusing on protecting ancient species-rich ecosystems and local gene pools.     

Do non‐native fish as prey favour the conservation of the threatened indigenous Eurasian otter?

1. Biological invasions are considered a major threat to biodiversity. Most research has focused on the distribution, biology and impacts of non‐native species on native fauna and flora. However, few studies have explored their role as prey for native predators of conservation concern. 2. To assess the incidence and intensity of predation by the Eurasian otter Lutra lutra on established non‐native fish species, data were collated from the published literature. To be selected, studies had to cover at least 1 year, analyse more than 100 spraints and report the study period and percentage relative frequency (%RF) of all prey fish species. 3. To permit reliable, time‐related comparisons with %RF of non‐native fishes in otter diet, we also reviewed available information about both the distribution of non‐native fishes and history of their introductions to European countries, revealing a decrease with longitude in the number of naturalised non‐native fishes taken (ranging between 5 and 34) and their percentage in each fish assemblage. 4. Our selective criteria were met by 30 dietary studies from 44 study areas in 15 European countries during 1970–2010. The extent to which otters rely on non‐native fishes was almost negligible (mean %RF = 4.8), with the number of non‐native fishes preyed upon by otters decreasing with both latitude and longitude. 5. The %RF of non‐native fish in the diet increased slightly with time, with otters preying significantly more on non‐native fish in study areas where alterations of the fish assemblage had been highlighted in the reference papers. No relationship was found between otter diet breadth and the occurrence of non‐native fishes in their diet. 6. The current role of non‐native species in otter diet suggests that effective otter conservation management plans should focus on the maintenance and/or enhancement of native fish assemblages.     

Native and alien floras in urban habitats: a comparison across 32 cities of central Europe

Aim To determine relative effects of habitat type, climate and spatial pattern on species richness and composition of native and alien plant assemblages in central European cities. Location Central Europe, Belgium and the Netherlands. Methods The diversity of native and alien flora was analysed in 32 cities. In each city, plant species were recorded in seven 1‐ha plots that represented seven urban habitat types with specific disturbance regimes. Plants were classified into native species, archaeophytes (introduced before ad 1500) and neophytes (introduced later). Two sets of explanatory variables were obtained for each city: climatic data and all‐scale spatial variables generated by analysis of principal coordinates of neighbour matrices. For each group of species, the effect of habitat type, climate and spatial variables on variation in species composition was determined by variation partitioning. Responses of individual plant species to climatic variables were tested using a set of binomial regression models. Effects of climatic variables on the proportion of alien species were determined by linear regression. Results In all cities, 562 native plant species, 188 archaeophytes and 386 neophytes were recorded. Proportions of alien species varied among urban habitats. The proportion of native species decreased with increasing range and mean annual temperature, and increased with increasing precipitation. In contrast, proportions of archaeophytes and neophytes increased with mean annual temperature. However, spatial pattern explained a larger proportion of variation in species composition of the urban flora than climate. Archaeophytes were more uniformly distributed across the studied cities than the native species and neophytes. Urban habitats rich in native species also tended to be rich in archaeophytes and neophytes. Main conclusions Species richness and composition of central European urban floras are significantly affected by urban habitat types, climate and spatial pattern. Native species, archaeophytes and neophytes differ in their response to these factors.     

Does detritus quality predict the effect of native and non‐native plants on the performance of larval amphibians?

1. The lack of consistent differences between the traits of native and non‐native plant species makes it difficult to make general predictions about the ecological impact of invasive plants; however, the increasing number of non‐native plants in many habitats makes the assessment of the impact of each individual species impracticable. General knowledge about how specific plant traits are linked to their effects on communities or ecosystems may be more useful for predicting the effect of plant invasions. Specifically, we hypothesised that higher carbon‐to‐nitrogen ratio (C:N) and percent lignin in plant detritus would reduce the rate of development and total mass at metamorphosis of tadpoles, resulting in lower metamorph production (total fresh biomass) and amphibian species richness. 2. To test these hypotheses, we raised five species of tadpoles in mesocosms containing senescent leaves of three common native and three common non‐native wetland plants that varied in C:N ratio and % lignin. 3. Leaf mass loss, total metamorph production and the number of species that metamorphosed declined as a function of increasing C:N ratio of plant leaves. Plant lignin content was not related to the production of metamorphs or the number of species that metamorphosed. The percentage of wood frog (Lithobates sylvaticus) and American toad (Anaxyrus americanus) tadpoles reaching metamorphosis declined as a function of increasing plant C:N ratio. Mean time to metamorphosis increased and mean mass at metamorphosis declined as a function of increasing plant C:N ratio. Tadpole performance and metamorph diversity and production (biomass) were similar between native and non‐native plant species with similar C:N ratio in leaves. Percent lignin was not a significant predictor of tadpole performance. 4. Our results show that the impact of a plant invasion on tadpole performance could depend on differences between the quality of the detritus produced by the invading species and that of the native species it replaces. We suggest that plant community changes that lead to dominance by more recalcitrant plant species (those with higher leaf C:N ratio) may negatively affect amphibian populations.     

Phytogeography of Italian deciduous oak woods based on numerical classification of plant distribution ranges

Abstract. 358 vascular plant species occurring in the deciduous oak woods of Italy were subdivided into 18 phytogeographical groups (chorotypes) through a numerical classification of their total ranges. The distribution patterns of the chorotypes are illustrated by chorograms, i.e. isopleth maps showing the joint distribution of species in Europe and surroundings regions. Except for Mediterranean species, which occur only occasionally in deciduous forests, the oak-wood flora of Italy consists of four main phytogeographical elements, which have a similar incidence (ca. 25 % each): (a) narrow-ranging, southern European species, (b) southeastern European species of submediterranean woodlands, (c) central-European species, (d) widely distributed European species. The oak woods of Italy differ from their central-European counterparts as to the relatively high floristic diversity, and in the presence of several narrow-ranging taxa, centred in different refugial areas for forest vegetation during the glacial period. There is a relation between the distribution patterns of the chorotypes and their relative frequencies in different communities; the latitudinal and longitudinal extensions of the ranges reflect the thermic and hygric conditions of the communities. The oak woods of northern and southern Italy are phytogeographically well-characterized; the former have a maximum of wide-ranging, central European species, the latter host several narrow-ranging taxa. The woodlands of central Italy have intermediate phytogeographical features, which is one of the main reasons for the difficulties in their syntaxonomical arrangement.     

Alien and native species in Central European urban floras: a quantitative comparison

The paper provides quantitative information on the occurrence of alien species in Central European cities and analyses factors determining the richness of alien and native floras in this habitat type. Data for 54 cities (25 Polish, 24 German, 4 Czech and 1 Austrian) were gathered, and the representation of archaeophytes (i.e. aliens introduced before 1500 ad ), neophytes (introduced after that date) and native species was expressed. In an average city there were 87.4 archaeophytes (15.2% of the city flora) and 172.4 neophytes (25.2%) giving a total of 259.7 for alien species (40.3%). The number of native species averaged 386.5. The numbers of species in each category of immigration status increased significantly with city size. For neophytes, the species-area relationship showed a higher slope (0.49) on log–log axes than for both archaeophytes (0.16) and native species (0.30). Not only the number, but also the relative contribution of neophytes to the total flora, increased with city size, indicating that neophytes are the group which are most closely associated with human activity. On the other hand, archaeophytes were better represented in smaller cities, as they were confined to rural environment. A step-wise multiple regression was used to test for environmental variables acting as significant predictors, and explained between 40 and 65% of variation in the species numbers for particular categories of immigration status, providing the best fit for neophytes. City size was the best predictor for each characteristic, except of the proportion of total aliens, where the percentage of explained variability was low (8.2%), with latitude being the only significant predictor. Temperature was another highly significant predictor for the number of archaeophytes and total aliens, reflecting the origin of aliens in warmer areas. There was an effect of region on some flora characteristics. Polish cities had significantly higher proportion of archaeophytes and of total aliens than German cities. It is concluded that the occurrence of native and alien species in urban floras follows rather different pattern.     

Biosecurity Implications of New Technology and Discovery in Plant Virus Research

Human activity is causing new encounters between viruses and plants. Anthropogenic interventions include changing land use, decreasing biodiversity, trade, the introduction of new plant and vector species to native landscapes, and changing atmospheric and climatic conditions. The discovery of thousands of new viruses, especially those associated with healthy-appearing native plants, is shifting the paradigm for their role within the ecosystem from foe to friend. The cost of new plant virus incursions can be high and result in the loss of trade and/or production for short or extended periods. We present and justify three recommendations for plant biosecurity to improve communication about plant viruses, assist with the identification of viruses and their impacts, and protect the high economic, social, environmental, and cultural value of our respective nations'' unique flora: 1) As part of the burden of proof, countries and jurisdictions should identify what pests already exist in, and which pests pose a risk to, their native flora; 2) Plant virus sequences not associated with a recognized virus infection are designated as “uncultured virus” and tentatively named using the host plant species of greatest known prevalence, the word “virus,” a general location identifier, and a serial number; and 3) Invest in basic research to determine the ecology of known and new viruses with existing and potential new plant hosts and vectors and develop host-virus pathogenicity prediction tools. These recommendations have implications for researchers, risk analysts, biosecurity authorities, and policy makers at both a national and an international level.     

Seasonal water availability predicts the relative abundance of C3 and C4 grasses in Australia

Aim Numerous studies have examined the climatic factors that influence the abundance of C₄ species within the grass flora (C₄ relative species richness) in various regions throughout the world, but very few have examined the relative abundance of C₄ vs. C₃ grasses (C₄ relative abundance). We sought to determine the climatic factors that influence C₄ relative abundance throughout Australia. Location Australia (including Tasmania). Methods We measured C₄ relative abundance at 168 locations and measured δ¹³C (the abundance of ¹³C relative to ¹²C) of the bone collagen of 779 kangaroos collected throughout Australia, as bone collagen δ¹³C was assumed to be proportional to the relative abundance of C₄ grasses in the diet. Results Both C₄ relative abundance and kangaroo bone collagen δ¹³C were found to have a strong positive relationship with seasonal water availability, i.e. the distribution of rainfall in the C₄ vs. C₃ growing seasons (76% and 69% of deviance explained, respectively). There was clear evidence that seasonal water availability was a better predictor of both C₄ relative abundance and bone collagen δ¹³C than other climate variables such as mean annual temperature and January daily minimum temperature. However, seasonal water availability appeared to be a relatively poor predictor of C₄ relative species richness, which was most closely related to January daily minimum temperature (90% of deviance explained). Main conclusions Our results highlight the relatively poor relationship between C₄ relative abundance and C₄ relative species richness, and suggest that these two variables may be related to different climatic factors. They also suggest that caution is required when using C₄ relative species richness to infer the relative biomass and productivity of C₄ grasses on a global scale.     

Do arbuscular mycorrhizal fungi recolonize revegetated grasslands?

Fifteen native and common exotic herbaceous species from four functional groups (C4 grass, C3 grass, chamaephyte and hemicryptophyte) occurring within remnant and revegetated grassland and grassy woodlands were sampled for evidence of structures associated with functioning arbuscular mycorrhizal fungi (AMF) from across a broad geographical range of central and south‐western Victoria, Australia. Revegetated communities had been established on ex‐agricultural land by direct seeding. They included sites that had been kept fallow with herbicide for up to 3 years prior to seeding and those from which topsoil had been removed (scalped) to a depth of 100 mm prior to seeding. Structures associated with AMF (external and internal aseptate hyphae, arbuscules and vesicles) were observed in root samples from all native and exotic species, regardless of site history (remnant or revegetated; fallowed or scalped). These findings indicate that AMF are ubiquitous in the herbaceous flora of this region (native and exotic), even in situations where sites had been intensively disturbed prior to revegetation treatment. However, while there was evidence of AMF in all revegetated communities, only sites which had been scalped prior to direct seeding supported species‐rich native herbaceous communities.