Natural Colonization Research Articles

Trout (Salmo trutta) mitochondrial DNA polymorphism in the centre of the marble trout distribution area

The marble trout, a lineage of the Salmo trutta complex, is endemic to the Southern Alpine region. Although it is endangered throughout its entire distribution range, population genetic data were lacking for the central area, including the upper Etsch/Adige River system (South Tyrol, Northern Italy). A total of 672 Salmo trutta specimens, comprising phenotypic marble trout and phenotypic brown trout, from 20 sampling sites throughout South Tyrol were analysed by sequencing the complete mitochondrial DNA control region. Thirteen distinct haplotypes were identified, which clustered within three major genetic lineages: the Marmoratus (MA), the Atlantic (AT) and the Danubian (DA) lineage. 41.7% of the investigated individuals carried haplotypes of the MA lineage, 47.9% of the AT lineage and 10.4% of the DA lineage. It is noticeable that AT haplotypes were present at all sampling sites and no “pure” marble trout population with exclusively MA haplotypes was found. This points to a considerable impact of stocking with allochthonous brown trout, given that there is no evidence for natural colonisation by individuals of the AT lineage. However, our data indicate, for at least four localities, a limited gene flow between the native marble trout and hatchery-reared strains. Future conservation and rehabilitation measures will thus have to concentrate on the identification of remnant pure marble trout individuals from such mixed populations.

Live yeasts in the gut: Natural occurrence, dietary introduction, and their effects on fish health and development

This minireview summarises the present state of knowledge concerning the importance of yeasts in fish gut. Yeasts have been commonly isolated in the gastrointestinal tract, and high population densities were sometimes noted in healthy fish, but the data were quite variable in terms of colony counts and taxonomical diversity. Rhodotorula sp. seemed relatively frequent in both marine and freshwater fish, and Debaryomyces hansenii has been found to be dominant in rainbow trout. Some other dominant strains have been described, such as Metschnikowia zobelii, Trichosporon cutaneum, and Candida tropicalis in marine fish, and Candida sp., Saccharomyces cerevisiae, and Leucosporidium sp. in rainbow trout. The natural proliferation of yeasts in fish mucus may be generally considered as commensalism, in spite of a few cases of pathological infections mainly due to opportunistic strains. Several strains were documented to settle and grow in fish intestine after experimental introduction, particularly S. cerevisiae and D. hansenii in rainbow trout. There have been a few instances of competition among yeasts in fish intestine, while the effect of yeast on associated bacteria is still unclear. Yeasts can stimulate the immune response in fish. β-glucans are likely the most important compounds in this regard, but some other cell-wall components or soluble factors may also play a role. Both cellular and humoral responses have been educed by dietary yeast, depending on the experimental conditions. Other benefits may be expected for the host, especially the intestinal colonisation of early feeding fry with yeast, which may have some effect on development, e.g. by accelerating the maturation of the digestive system. In older fish, dietary yeast may stimulate metabolism and growth. Such beneficial effects need to be further investigated, either in cases of natural colonisation or after dietary introduction, while trying to elucidate the mode of action, and determine whether cellular viability is a prerequisite for efficacy.

Evaluation of the efficiency of water-repellent and biocide compounds against microbial colonization of mortars

Abstract Mortars are building material with a high primary bioreceptivity and thus, they are easily colonized by different microorganisms. To reduce this problem, especially if it concerns restoration and conservation of works of art, water repellents and biocides can be applied alone or in combination. This paper describes experimental data carried out in laboratory conditions as well as outdoors with artificially infected mortars to reproduce natural colonization. The effects of three hydrophobic compounds (RHODORSIL RC80, HYDROPHASE SUPERFICI and HYDROPHASE MALTE) applied alone or in combination with the biocide ALGOPHASE and with the new water miscible formulation (ALGOPHASE PH025/d) were studied. Effectiveness was compared with the behavior of untreated mortars. In both types of experiments, it was clearly shown that water repellents alone do not stop microbial colonization, while water repellents plus biocides prevent microbial growth. In addition, it was shown under indoor and outdoor conditions that fungi are able to colonize untreated mortars as well as those treated only with hydrophobic compounds before phototrophic microorganisms. No significant differences were observed among the compounds tested in their efficacy in preventing colonization.

The Spindle Tree, <em>Euonymus europaea</em> L. (Celastraceae): A Newly Naturalized Shrub in Nova Scotia

Over 100 plants, including over 750 individual shoots, of Euonymus europaea L. are reported from the Town of Antigonish in northern Nova Scotia. Plants were found in five discrete areas separated by 200-1000 m. A few individuals at one site may represent human planting; however, over 90% of plants occur on waste ground or in dense shrubbery where natural colonization has occurred. Many individuals were observed in fruit in the fall of 2005, and over 95% of the plants had well developed buds and flowers in May and early June 2006. Euonymus europaea is considered a newly naturalized species for the flora of Nova Scotia.

The bark and ambrosia beetles (Curculionidae, Scolytinae) of Cocos Island, Costa Rica and the role of mating systems in island zoogeography

Cocos Island is a small oceanic island midway between Costa Rica and the Galápagos Archipelago; about 2 Myr in age, it is the only tropical oceanic island in the eastern Pacific with tropical wet forest. We identified several hundred bark beetle specimens collected during recent expeditions by INBio, the National Biodiversity Institute of Costa Rica, and re-examined all specimens from earlier collections. We report 19 species in ten genera, seven or eight of which are endemic, making scolytines the largest group of beetles known from the island. We describe as new Pycnarthrum pseudoinsulare, Xyleborinus cocoensis, and Xyleborus sparsegranulosus, resurrect Xyleborus bispinatus as separate from X. ferrugineus, and report six other species as new to Cocos Island. Three-quarters of the scolytines reproduce by brother–sister mating, and we argue that inbreeders are superior island colonists because they are less affected than are outbreeders by problems of mate location and inbreeding depression. The fauna and flora of Cocos Island arrived by dispersal and human transport. We examine natural colonization patterns for the fauna, using the distributions of the relatives of island endemics: most colonization came from the Americas, but the closest relatives to some endemics are found on Caribbean or Galápagos islands. © 2006 The Linnean Society of London, Biological Journal of the Linnean Society, 2006, 89, 729–743.

Dynamics of immature stages of Anopheles arabiensis and other mosquito species (Diptera: Culicidae) in relation to rice cropping in a rice agro-ecosystem in Kenya

We determined changes in species composition and densities of immature stages of Anopheles arabiensis mosquitoes in relation to rice growth cycle in order to generate data for developing larval control strategies in rice ecosystems. Experimental rice paddies (6.3m x 3.15m) exposed to natural colonization of mosquitoes were sampled weekly for two rice growing cycles between February 2004 and March 2005. Overall, 21,325 Anopheles larvae were collected, of which 91.9% were 1st and 2nd instars and 8.1% were 3rd and 4th instars. An. arabiensis was the predominant species (84.1%) with other species, An. pharoensis (13.5%), An. funestus (2.1%), An. coustani (0.3%), and An. maculipalpis (0.1%) accounting for only a small proportion of the anophelines collected. Culex quinquefasciatus (65.7%) was the predominant species among the non-anopheline species. Others species collected included: C. annulioris (9.9%), C. poicilipes (7.3%), C. tigripes (7.2%), C. duttoni (0.6%), Aedes aegypti (5.3%), Ae. cumminsii (3.5%), and Ae. vittatus (0.7%). The densities of the major anopheline species were closely related to rice stage and condition of the rice field. An. arabiensis, the predominant species, was most abundant over a three-week period after transplanting. Low densities of larvae were collected during the late vegetative, reproductive, and ripening phases of rice. An increase in larval density ten days post-transplanting was found to correlate with the application of fertilizer (sulphate of ammonia). Culicine and aedine species densities were significantly higher during the post-harvesting period. Our results suggest that the transplanting stage is favorable for the growth of immature stages of An. arabiensis and provides a narrow window for targeted larval intervention in rice.

Effect of legume species introduction to early abandoned field on vegetation development

One of the most important areas in ecology is to elucidate the factors that drive succession in ecosystems. The purpose of our study was to assess the effects of legume species (Medicago sativa, Melilotus suaveolens and Astragalus adsurgens) introduction to abandoned arable land on vegetation development in the Loess Plateau, China. Results from our study showed that addition of legume species strongly affected the composition of recently abandoned-field vegetation. Legume species were effective at reducing the number and dominance of natural colonizers (mainly weeds from the seed bank). The introduction of legume species into newly abandoned fields maintained high total cover and above-ground biomass and could improve soil organic carbon and total nitrogen. However, the effects of the treatments were species-specific. Melilotus suaveolens turned out to be severely suppressive to natural colonizers (weed species). Also, Melilotus suaveolens-adding maintained the highest cover and above-ground biomass and was helpful to improve later succession species, e.g. Stipa breviflora and Astragalus polycladus, to invade and establish. Medicago sativa-adding was superior in enhancing the soil organic carbon and total nitrogen. The present results suggested that addition of legume species with greater cover and biomass strongly suppressed the dominance of the weedy species in early succession and the course of old-field succession may be accelerated by introduction of legume species at least temporarily. However, the experimental period was too short to assess to what extent succession may be affected in the longer term.

Island Populations, Human Introductions and the Limitations of Genetic Analyses: the Case of the Sardinian Red Deer (Cervus elaphus corsicanus)

The Corsican red deer (Cervus elaphus corsicanus) is endemic to the Tyrrhenian islands of Corsica and Sardinia. It has been regarded as an introduced species and has allegedly been present on the islands since the beginning of the Neolithic culture some 8,000 years ago. In this review, we present the results of relevant genetic analyses and discuss their implications for the origin of C. e. corsicanus. Different genetic studies hypothesize that the most probable ancestral populations for Sardianian red deer were alternatively, the Near East, North Africa, or mainland Italy. These respective scenarios are evaluated and it is concluded that geneticists have not yet been unable to definitively solve the problem. However, a natural colonization of the Tyrrhenian islands from mainland Italy via the Tuscan archipelago is not only in accordance with palaeontological findings but also with at least some of the genetic data.

Floristic composition of gold and uranium tailings dams, and adja­cent polluted areas, on South Africa’s deep-level mines

Gold and uranium tailings (‘slimes’) dams and the adjacent polluted soils in the deep-level mining regions of South Africa (Carletonville, Klerksdorp and Welkom) were surveyed for the frequency of occurrence of naturally colonizing, actively introduced and persisting plant species. Fifty-six tailings dams with a combined area of 5864 ha. and a similar area o f tail- ings-polluted soils, were surveyed between July 1996 and March 1997. During the survey, 376 plant species and subspecies were recorded from the dams and adjacent polluted soils, with an additional 8 6 records obtained between 1998 and 2003 (i.e. a total of 462 taxa: species and infraspecific species). Overall, the most commonly represented families were the Poaceae (107 species and subspecies), Asteraceae (81). Fabaceae (55) and Anacardiaceae (16). with other families represented by just one to 14 species. Only 60 species were common to all three regions, and of these 24 had been introduced during rehabilitation attempts. Most of the species found on tailings were persisters or natural colonizers (53-88%, depending on substrate), with the vast majority being indigenous and perennial taxa (76% and 85% respectively), with semi-woody to woody growth forms (6 6% being resprouters, forbs, shrubs and trees). Less than 4% of the naturally-colonizing taxa found during the survey had also been introduced by vegetation practitioners. The majority of introduced plants were alien herbaceous taxa. The number and frequency of annuals was only high on recently vegetated sites, whereas annuals were rarely present on old-vegetated and never-vegetated dams. This list includes a wide range of indigenous plant species that may be suitable for phytoremediation of tailings dams and polluted soils due to their apparent tolerance of acid mine drainage and salinity.

Soil Formation and Vegetation Establishment on the Cliff Face of Abandoned Quarries in the Early Stages of Natural Colonization

Abstract The large number of abandoned quarries in many countries presents challenges for restoration of these extremely degraded habitats. To understand soil and plant development in these extreme habitats at a most critical stage of restoration, we evaluated the edaphic conditions and natural vegetation of three large quarries in southern China 3, 5, and 7 years following abandonment. Although soil fertility (organic matter, and N, P, K concentrations) did not differ significantly over a few years, it was much higher than would be expected from newly weathered soil and was comparable to that of the adjacent garden soil on level ground with no slope. This suggests that soil formation on the steep slopes of quarry cliffs is a secondary migration process rather than a primary weathering process. Vegetation cover increased from 10.6 to 18.6 and 23.4%, and species abundance increased from 8 to 11 and 12 species, and from 3 to 6 and 7 families. Plant species composition changed from predominantly annual and perennial herbaceous species to a more diverse community with drought‐tolerant and heliophilous shrubs. The vegetation cover was highly positively correlated with soil depth and soil volume (p < 0.001), and also significantly correlated with soil organic matter, total N, and available N and P concentrations (p < 0.05). This suggests that vegetation succession is more limited by available soil volume than by soil fertility during the early stages of quarry restoration.

Long-term effects of sowing high or low diverse seed mixtures on plant and gastropod diversity

A number of studies have reported that consumers affect a range of community-level processes, and in turn their diversity and abundance is influenced by the structure and diversity of the plant community. Although gastropods are important generalist herbivores in many environments, few studies have examined the effects of plant species richness and plant community structure on gastropods. This study investigated gastropod species richness and interactions with various above-ground parameters of the vegetation on an experimental field with four plant treatments: low and high diversity of sown later succession plant species, natural colonization at the start of the experiment and natural colonization after 3 years of continued agricultural practice. The investigated gastropod assemblage contained only seven species and was highly dominated by two of them. Both in pitfalls and with hand-sorting the number of species collected per plot was highest in plots with natural plant colonization. Multivariate analysis revealed that overall gastropod abundance was positively associated with plant height and percentage cover of plants, and negatively with percentage grass cover. The same pattern holds for one of the dominant species-complex (Cochlicopa lubrica/lubricella). The other dominant gastropod species (Deroceras reticulatum) was more abundant in samples with higher percentages of moss cover and higher plant diversity, while less abundant at samples with higher plant cover, indicating that the gastropod species preferences may matter more than just their response to plant diversity. Two plant–gastropod species-level associations were observed: Senecio jacobaea with D. reticulatum and Tanacetum vulgare with Cochlicopa spp. The present study also demonstrated that pitfall-traps are suitable for collecting terrestrial gastropods, at least for species-poor grassland habitats. [KEYWORDS: Cochlicopa spp. ; Deroceras reticulatum ; Plant diversity ; Plant–gastropod interactions ; Terrestrial gastropod diversity ; Vegetation structure]

English

Soil and water contaminated with metals and arsenic as a result of resource extraction and ore smelting comprise significant environmental and human health problems throughout all regions of the world. In Montana's Upper Clark Fork River Basin, hundreds of square kilometers of land are impacted by metal mine wastes and/or smelter emissions. Contaminated soils are often of low pH and highly metalliferous. Natural plant colonization is often impaired, as evidenced by barren areas where phytotoxic rootzones preclude any vegetation establishment. Rehabilitation of these lands can be done in situ using limestone as an amendment to raise pH, thus immobilizing metals and making them less bioavailable. Since contaminants are not removed from soils through in situ treatment, there is concern about the plant communities that can be established on these amended soils. Several areas within the Basin that received lime treatment support plant communities of limited diversity, and seeded species often fail to establish. Sensitivity or tolerance of reclamation plant species to arsenic, cadmium, copper, zinc and lead was explored in a replicated-dose-response greenhouse study designed to test the hypothesis that metals and arsenic in lime- amended soils were impairing plant performance. Two sets of contaminated and reference soils from within the Basin were collected and mixed to obtain metal and arsenic concentration gradients from 240 to 5700 mg/kg and 250 to 7500mg/kg for the two sets of soils, respectively. Different plant species were tested, including Leymus cinerus and Elymus trachycaulus. Response variables included germination, plant height and biomass, root length and root biomass. Some species demonstrated tolerance to higher levels of metals and arsenic in the amended soils, while others exhibited sensitivity at similar concentrations. This greenhouse study may be extended to field settings where more realistic evaluations of establishment and persistence can be made.

Immigration of Phytoseiid Mites from Surrounding Uncultivated Areas into a Newly Planted Vineyard

This study reports (1) a faunistic survey of phytoseiid mites observed inside a vine plot and in neighbouring vegetation (other vine plots and uncultivated areas) and (2) dispersal of phytoseiid mites into the plot studied. These data aim to raise some hypotheses concerning natural colonisation of a vineyard by predatory mites. The study was carried out over 3 years (1999, 2000 and 2001) in an experimental plot planted with two cultivars (Grenache and Syrah) and with Sorbus domestica in a framework of agroforestry investigations. Phytoseiid mites were collected in both cultivated and uncultivated areas surrounding the experimental plot, and their dispersal into the plot studied using "aerial" traps. Densities remained quite low compared to previous studies. The main species encountered in the uncultivated areas and in the traps was Typhlodromus phialatus. Despite the low numbers of phytoseiid mites trapped, densities of phytoseiid mites into the vine field increased during 3 years. Typhlodromus phialatus, the species mainly found in the neighbouring uncultivated areas, was rarely found in vineyards. Another morphologically close species was predominant on vines: Typhlodromus exhilaratus. However, Kampimodromus aberrans the main phytoseiid mite species in vineyards of Southern France was not found in the present survey. Hypotheses for this colonisation process are discussed.

Realistic Variation in Species Composition Affects Grassland Production, Resource Use and Invasion Resistance

We investigated the effects of realistic variation in plant species and functional group composition, with species occurring at realistic abundances, on ecosystem processes in exotic-dominated California grassland communities. Progressive species removals from microcosm communities, designed to mimic nested variation in diversity observed in the field, reduced grassland production, resistance to intentional invasions, and resistance to natural colonization by new species. Three lines of evidence point to the particular importance of intensified competition within a single functional group—late-active forbs—in explaining the observed effects of realistic species loss order on community resistance. First, reduced success of naturally colonizing species in more diverse assemblages was dominated by declining colonization by late-active forbs. Second, increasing late-active forb biomass appeared to reduce the biomass of intentionally introduced yellow starthistle (Centaurea solstitialis, a late-season forb) both within and across diversity levels. Finally, starthistle addition reduced biomass of resident late-season forbs but not of any other functional group. Increasing diversity increased light levels and soil moisture availability in spring and summer, providing a proximate mechanism linking our realistic species loss order to decreased community resistance. Starthistle addition reduced light and soil moisture availability but not N across richness levels, mirroring the apparent effects of the additional late-active forb species present in higher diversity treatments. Species losses that entail the early loss of whole or key functional groups could, through mechanisms like those we explore, have greater ecosystem consequences than those suggested by randomized-loss experiments.

Multilocus Sequence Typing Reveals Intrafamilial Transmission and Microevolutions of Candida albicans Isolates from the Human Digestive Tract

Candida albicans is a human commensal that is also responsible for superficial and systemic infections. Little is known about the carriage of C. albicans in the digestive tract and the genome dynamics that occur during commensalisms of this diploid species. The aim of this study was to evaluate the prevalence, diversity, and genetic relationships among C. albicans isolates recovered during natural colonization of the digestive tract of humans, with emphasis on Crohn's disease patients who produce anti-yeast antibodies and may have altered Candida sp. carriage. Candida sp. isolates were recovered from 234 subjects within 25 families with multiple cases of Crohn's disease and 10 control families, sampled at the oral and fecal sites. Prevalences of Candida sp. and C. albicans carriage were 53.4% and 46.5%, respectively, indicating frequent commensal carriage. No differences in prevalence of carriage could be observed between Crohn's disease patients and healthy subjects. Multilocus sequence typing (MLST) of C. albicans isolates revealed frequent colonization of a subject or several members of the same family by genetically indistinguishable or genetically close isolates. These latter isolates differed by loss-of-heterozygosity events at one or several of the MLST loci. These loss-of-heterozygosity events could be due to either chromosome loss followed by duplication or large mitotic recombination events between complementary chromosomes. This study was the first to jointly assess commensal carriage of C. albicans, intrafamilial transmission, and microevolution. The high frequency of each of these events suggests that the digestive tract provides an important and natural niche for microevolutions of diploid C. albicans through the loss of heterozygosity.

Cross effects of the strain of dietary Saccharomyces cerevisiae and rearing conditions on the onset of intestinal microbiota and digestive enzymes in rainbow trout, Onchorhynchus mykiss, fry

Two strains of Saccharomyces cerevisiae were tested as probiotics for rainbow trout fry, during the first month of feeding. Each strain was introduced into separate diets, at the rate of 10 6 CFU g − 1 and their effects were compared with those of a control diet. Two rearing conditions were simultaneously compared, to test the adaptability of the probiotic treatment. From start feeding onwards, the water supply came from either spring or river, resulting in two different temperature ranges, 11–11.5 and 7–8 °C respectively. Growth and development were optimal in spring water, while some delay was observed with colder river water. A slight but significant increase in mortality was also observed in the river group. In all groups, the counts of bacteria associated with trout intestine were maximum 10 days post start feeding (dpsf; 10 7 CFU g − 1 ). The counts of probiotic yeast were also maximum at 10 dpsf (10 4–10 5 CFU g − 1 ), but the decrease was slower in river than in spring water. An autochthonous yeast, Debaryomyces hansenii, was also retrieved associated to the intestine of the control group in high numbers after 240 degree days of experiment (10 4–10 5 CFU g − 1 ), while the colonization level was significantly less in trout fed the probiotic diets. The effect of the dietary yeast was observed by assaying the activity of three enzymes in the brush border membrane of the enterocytes: alkaline phosphatase (AP), γ-glutamyl-transpeptidase (GGT), and leucine-amino-peptidase N (LAP). At 10 and 20 dpsf, the trout reared in spring water had higher activities of the three enzymes when they were fed the strain S. cerevisiae var. boulardii, suggesting an earlier maturation of the digestive system in this group, compared with trout fed either the other strain of S. cerevisiae or the control diet. The effect was not observed in trout reared in river water with slower growth. Both S. boulardii and D. hansenii seemed to stimulate digestive maturation in fish, but the natural colonization by D. hansenii was likely too late for trout reared at optimal temperature. The supplementation of trout starter diet with S. boulardii may be particularly useful in fast growing conditions.

Interactions between arbuscular mycorrhizal fungi and intraspecific competition affect size, and size inequality, of Plantago lanceolata L.

Summary 1 Intraspecific competition causes decreases in plant size and increases in size inequality. Arbuscular mycorrhizas usually increase the size and inequality of non-competing plants, but mycorrhizal effects often disappear when plants begin competing. We hypothesized that mycorrhizal effects on size inequality would be determined by the experimental conditions, and conducted simultaneous field and glasshouse experiments to investigate how AM fungi and intraspecific competition determine size inequality in Plantago lanceolata . 2 As predicted, plant size was reduced when plants were competing, in both field and controlled conditions. However, size inequality was unexpectedly reduced by competition. Plants may have competed in a symmetric fashion, probably for nutrients, rather than the more common situation, in which plant competition is strongly asymmetric. 3 Mycorrhizas had no effect on plant size or size inequality in competing plants in either field or controlled conditions, possibly because competition for nutrients was intense and negated any benefit the fungi could provide. 4 The effects of mycorrhizas on non-competing plants were also unexpected. In field-grown plants, AM fungi increased plant size, but decreased size inequality: mycorrhizal plants were more even in size, with few very small individuals. In glasshouse conditions, mycorrhizal colonization was extremely high, and was generally antagonistic, causing a reduction in plant size. Here, however, mycorrhizas caused an increase in size inequality, supporting our original hypothesis. This was because most plants were heavily colonized and small, but a few had low levels of colonization and grew relatively large. 5 This study has important implications for understanding the forces that structure plant communities. AM fungi can have a variety of effects on size inequality and thus potentially important influences on long-term plant population dynamics, by affecting the genetic contribution of individuals to the next generation. However, these effects differ, depending on whether plants are competing or not, the degree of mycorrhizal colonization and the responsiveness of the plant to different colonization densities.

Evaluating Children in the Ukraine for Colonization With the Intestinal Bacterium Oxalobacter formigenes, Using a Polymerase Chain Reaction-based Detection System.

Background: Oxalobacter formigenes is a recently discovered anaerobic bacterium residing in the gastrointestinal tracts of most vertebrates, including humans. Evidence suggests that this bacterium plays an important symbiotic relationship with its hosts by regulating oxalic acid homeostasis. Oxalic acid is a ubiquitous toxic by-product of metabolism associated with numerous pathologic conditions, including hyperoxaluia, cardiac myopathy and conductance disorders, kidney stones, and even death. Despite the potential importance of O. formigenes in several major health disorders, the difficulty in culturing, isolating, and identifying this fastidious anaerobe has limited research of its disease associations. Because O. formigenes must use two unique enzymes to catabolize oxalic acid, this bacterium appeared to be a suitable model for DNA-based identification, thereby circumventing the labor-intensive procedures currently used. Methods and Results: In this study, genus- and group-specific oligonucleotide sequences were designed corresponding to homologous regions residing in the oxc gene that enodes for oxalyl-coenzyme A decarboxylase. A polymerase chain reaction (PCR)-based amplification of the 5'end of this gene directly from genomic DNA isolated from various strains of O. formigenes was used to show that the genus- and group-specific oligonucleotide probes could identify and subgroup the bacterium. Field testing of this PCR-based detection system with 100 fecal cultures collected from children aged 0-12 years demonstrated the ease and efficacy with which O. formigenes can now be identified. Furthermore, these latter data provide a profile for the natural colonization of a human population with this intestinal bacterium. Conclusions: Development and use of this PCR-based detection system permit the rapid identification and classification of the gut-associated bacterium O. formigenes, thereby circumventing the need for the more labor-intensive and lengthy method currently used. The first field test of this detection system indicates that humans apparently do not become colonized with O. formigenes until they begin crawling about in the environment. Furthermore, studies investigating the association between several disorders (eg, kidney stones, irritable bowel syndrome, and hyperoxaluria) and the absence of the bacterium from the gut will now prove far easier.

FIRST ANALYSIS OF GENETIC VARIABILITY IN CARINTHIAN POPULATIONS OF THE WHITE-CLAWED CRAYFISH AUSTROPOTAMOBIUS PALLIPES

Several authors have speculated about the nativeness of the white-clawed crayfish (Austropotamobius pallipes) in the Austrian province of Carinthia, since this is the only occurrence of the species within the Danube river system. Phylogeographic analyses based on mitochondrial DNA sequences showed that Carinthian A. pallipes are closely related to specimens from Slovenia, Croatia and north-eastern Italy. These analyses additionally pointed to an absence of variability among populations in Carinthia. In the present study a larger number of individuals sampled from three different brooks in western Carinthia was investigated by analysing sequences of the mtDNA cytochrome c oxidase gene (COI), microsatellite DNA and microsatellite length variation in the nuclear ribosomal DNA internal transcribed spacer region (ITS1). Not only COI sequences revealed low degrees of genetic variability, but also microsatellite loci displayed low allelic diversity and low heterozygosity. Analysis of ITS1 microsatellite length variation in turn showed high levels of intragenomic variability, since single individuals manifested up to seven distinct fragments. Microsatellite data and ITS1 microsatellite length variation analyses also revealed significant differentiation among some population pairs. Since genetic divergence was mainly based on differences in allele frequencies and not on the occurrence of alternative alleles, we assume that Carinthian populations became isolated rather recently and that the occurrence of this species in this region is more likely to be a result of human introduction than of natural postglacial colonisation.

Seed and (micro)site limitation in ditch banks: Germination, establishment and survival under different management regimes

Summary Although maintenance of species-rich plant communities in ditch banks seems possible with agri-environment schemes, in general these schemes have not delivered an increase in species richness in these habitats. This could be related to an emphasis in the existing management guidelines on preventing extinction of desirable plant species as opposed to encouraging their colonisation. We investigated germination, establishment, survival and reproduction of nine target species on ditch banks and determined how differences in vegetation productivity (biomass) and management regime affect the outcome of these processes. Our results suggest that ditch bank target species are more limited by colonisation (seed and microsite limitation) than by extinction (site limitation). Since target species are often lacking from the soil seed bank, restoration of populations of these species in ditch banks should focus on improving colonisation opportunities and promoting dispersal from nearby sources. Introduction by the sowing of seeds could be considered, especially in instances where natural colonisation appears unlikely. Although microsite limitation is always a limiting factor, the relative importance of microsite limitation compared to seed and site limitations greater in high-productivity ditch banks. This provides support for the ‘shifting limitation hypothesis’ postulating that the major factor regulating species richness shifts from regional to local processes under increasing productivity. For effective ditch bank restoration, it is essential to improve the conditions for germination and establishment, particularly at high-productivity ditch banks. We conclude that extensive management strategies advocating late first cuts appear suboptimal, regardless of the productivity of ditch bank systems. Current management recommendations in agri-environment schemes need to be revised and defined separately for low- and high-productivity situations in order to achieve largest conservation gain. Continuous monitoring and adaptation of the implemented management to fit individual circumstances will be required.