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Different Species (different + species)
Kinds of Different Species Selected AbstractsEVOLUTION OF CHARACTER DISPLACEMENT IN SPADEFOOT TOADS: DIFFERENT PROXIMATE MECHANISMS IN DIFFERENT SPECIESEVOLUTION, Issue 8 2010David W. Pfennig Character displacement occurs when two species compete, and those individuals most dissimilar from the average resource-use phenotypes of the other species are selectively favored. Few studies have explored the sequence of events by which such divergence comes about. We addressed this issue by studying two species of spadefoot toads that have undergone ecological character displacement with each other. Previous research revealed that phenotypic shifts between sympatric and allopatric populations of one species, Spea multiplicata, reflect a condition-dependent maternal effect. Here, we show that analogous shifts in the other species, S. bombifrons, cannot similarly be explained by such a maternal effect, and that these shifts instead appear to be underlain by allelic differences. We hypothesize that these two species have evolved different mechanisms of character displacement because they differ in duration in sympatry. Specifically, because they occur at the edge of a range expansion, populations of S. bombifrons have been exposed to S. multiplicata for a longer period. Consequently, S. bombifrons have likely had more time to accumulate genetic changes that promote character displacement. Generally, character displacement may often progress through an initial phase in which trait differences are environmentally induced to one in which they are constitutively expressed. [source] BIODIVERSITY RESEARCH: Genetic diversity in two introduced biofouling amphipods (Ampithoe valida & Jassa marmorata) along the Pacific North American coast: investigation into molecular identification and cryptic diversityDIVERSITY AND DISTRIBUTIONS, Issue 5 2010Erik M. Pilgrim Abstract Aim, We investigated patterns of genetic diversity among invasive populations of Ampithoe valida and Jassa marmorata from the Pacific North American coast to assess the accuracy of morphological identification and determine whether or not cryptic diversity and multiple introductions contribute to the contemporary distribution of these species in the region. Location, Native range: Atlantic North American coast; Invaded range: Pacific North American coast. Methods, We assessed indices of genetic diversity based on DNA sequence data from the mitochondrial cytochrome c oxidase subunit I (COI) gene, determined the distribution of COI haplotypes among populations in both the invasive and putative native ranges of A. valida and J. marmorata and reconstructed phylogenetic relationships among COI haplotypes using both maximum parsimony and Bayesian approaches. Results, Phylogenetic inference indicates that inaccurate species-level identifications by morphological criteria are common among Jassa specimens. In addition, our data reveal the presence of three well supported but previously unrecognized clades of A. valida among specimens in the north-eastern Pacific. Different species of Jassa and different genetic lineages of Ampithoe exhibit striking disparity in geographic distribution across the region as well as substantial differences in genetic diversity indices. Main conclusions, Molecular genetic methods greatly improve the accuracy and resolution of identifications for invasive benthic marine amphipods at the species level and below. Our data suggest that multiple cryptic introductions of Ampithoe have occurred in the north-eastern Pacific and highlight uncertainty regarding the origin and invasion histories of both Jassa and Ampithoe species. Additional morphological and genetic analyses are necessary to clarify the taxonomy and native biogeography of both amphipod genera. [source] The transferability of distribution models across regions: an amphibian case studyDIVERSITY AND DISTRIBUTIONS, Issue 3 2009Flavio Zanini ABSTRACT Aim, Predicting species distribution is of fundamental importance for ecology and conservation. However, distribution models are usually established for only one region and it is unknown whether they can be transferred to other geographical regions. We studied the distribution of six amphibian species in five regions to address the question of whether the effect of landscape variables varied among regions. We analysed the effect of 10 variables extracted in six concentric buffers (from 100 m to 3 km) describing landscape composition around breeding ponds at different spatial scales. We used data on the occurrence of amphibian species in a total of 655 breeding ponds. We accounted for proximity to neighbouring populations by including a connectivity index to our models. We used logistic regression and information-theoretic model selection to evaluate candidate models for each species. Location, Switzerland. Results, The explained deviance of each species' best models varied between 5% and 32%. Models that included interactions between a region and a landscape variable were always included in the most parsimonious models. For all species, models including region-by-landscape interactions had similar support (Akaike weights) as models that did not include interaction terms. The spatial scale at which landscape variables affected species distribution varied from 100 m to 1000 m, which was in agreement with several recent studies suggesting that land use far away from the ponds can affect pond occupancy. Main conclusions, Different species are affected by different landscape variables at different spatial scales and these effects may vary geographically, resulting in a generally low transferability of distribution models across regions. We also found that connectivity seems generally more important than landscape variables. This suggests that metapopulation processes may play a more important role in species distribution than habitat characteristics. [source] A review of relationships between interspecific competition and invasions in fruit flies (Diptera: Tephritidae)ECOLOGICAL ENTOMOLOGY, Issue 5 2004Pierre-Francois Duyck Abstract., 1. A number of invasions in the family Tephritidae (fruit flies) have been observed worldwide despite quarantine procedures. In this review, the potential importance of interspecific competition and competitive displacement among different tephritid species is evaluated in the context of recent invasions. 2. Where polyphagous tephritid species have been introduced in areas already occupied by a polyphagous tephritid, interspecific competition has resulted in a decrease in number and niche shift of the pre-established species. No reciprocal invasions have been observed. 3. The data on tephritid invasions seem to support a hierarchical mode of competition; however, complete exclusion usually did not occur. Indeed, tephritid distribution and abundance are markedly structured by various abiotic (mostly climatic) and biotic (host plants) factors. 4. The primary determinant of competitive interactions in near-optimal conditions, such as lowlands with abundant fruit plantations, is probably the life-history strategy. The r,K gradient could be used as a predictor of potential invaders, because K traits (such as large adult size) may favour both exploitation and interference competition. 5. For future research, a better understanding of competition mechanisms seems essential. Different species competing in the same area should be compared with respect to: (i) demographic parameters, (ii) the outcome of experimental co-infestations on the same fruit, and (iii) behavioural and chemical interference mechanisms. [source] Genetic variability in a population of arbuscular mycorrhizal fungi causes variation in plant growthECOLOGY LETTERS, Issue 2 2006Alexander M. Koch Abstract Different species of arbuscular mycorrhizal fungi (AMF) alter plant growth and affect plant coexistence and diversity. Effects of within-AMF species or within-population variation on plant growth have received less attention. High genetic variation exists within AMF populations. However, it is unknown whether genetic variation contributes to differences in plant growth. In our study, a population of AMF was cultivated under identical conditions for several generations prior to the experiments thus avoiding environmental maternal effects. We show that genetically different Glomus intraradices isolates from one AMF population significantly alter plant growth in an axenic system and in greenhouse experiments. Isolates increased or reduced plant growth meaning that plants potentially receive benefits or are subject to costs by forming associations with different individuals in the AMF population. This shows that genetic variability in AMF populations could affect host-plant fitness and should be considered in future research to understand these important soil organisms. [source] Synergistic Effects of Subsistence Hunting and Habitat Fragmentation on Amazonian Forest VertebratesCONSERVATION BIOLOGY, Issue 6 2001Carlos A. Peres These effects are likely to be considerably aggravated by forest fragmentation because fragments are more accessible to hunters, allow no (or very low rates of ,) recolonization from nonharvested source populations, and may provide a lower-quality resource base for the frugivore-granivore vertebrate fauna. I examined the likelihood of midsized to large-bodied bird and mammal populations persisting in Amazonian forest fragments of variable sizes whenever they continue to be harvested by subsistence hunters in the aftermath of isolation. I used data from a comprehensive compilation of game-harvest studies throughout Neotropical forests to estimate the degree to which different species and populations have been overharvested and then calculated the range of minimum forest areas required to maintain a sustainable harvest. The size distribution of 5564 Amazonian forest fragments,estimated from Landsat images of six regions of southern and eastern Brazilian Amazonia,clearly shows that these are predominantly small and rarely exceed 10 ha, suggesting that persistent overhunting is likely to drive most midsized to large vertebrate populations to local extinction in fragmented forest landscapes. Although experimental studies on this negative synergism remain largely unavailable, the prospect that increasingly fragmented Neotropical forest regions can retain their full assemblages of avian and mammalian species is unlikely. Resumen: La cacería de subsistencia tiene efectos negativos profundos sobre la diversidad de especies, la biomasa y estructura de las comunidades de vertebrados en bosques de la Amazonía que de otra forma están poco perturbadas. Estos efectos se agravan considerablemente por la fragmentación del bosque porque los fragmentos son más accesibles a los cazadores, no permiten la recolonización por poblaciones no cazadas o disminuyen las tasas de recolonizacíon y pueden proporcionar una base de recursos de menor calidad para la fauna de vertebrados frugívoro-granívoros. Examiné la posibilidad de persistencia de poblaciones de aves y mamíferos medianos a grandes en fragmentos de bosque de tamaño variable si continúan sujetos a la cacería de subsistencia como una consecuencia del aislamiento. Utilicé datos de una compilación extensiva de estudios de cacería en bosques neotropicales para estimar el grado en que diferentes especies y poblaciones han sido sobre explotadas y calculé el área de bosque minima requerida para mantener una cosecha sostensible. La distribucíon de tamaños de 5564 fragmentos de bosque amazónica, estimado a partir de imágues de Landsat de seis regiones del sur y del esté de la Amazonía brasileña indica claramente que estos fragmentós son principalmente pegueños y que rara vez exceden las lolta, lo que sugiere que la sobre cacería persistente probablemente lleve a la extincíon local de poblaciones de vertebrados de tamaño mediano a grande en paisajes boscosos fragmentados. Aunque estudios experimentales de este sinergismo negativo no están disponibles, la perspectiva de que las regiones neotropicales cada vez más fragmentadas, puedan retener las comunidades completas de aves y mamíferos poco es probable. [source] The distribution and prevalence of sponges in relation to environmental gradients within a temperate sea lough: vertical cliff surfacesDIVERSITY AND DISTRIBUTIONS, Issue 6 2000James J. Bell Abstract. The prevalence and distribution of sponges was surveyed on vertical cliff surfaces at Lough Hyne Marine Nature Reserve, Co. Cork, Ireland. The number of sponge species was recorded at 6-metre depth intervals at four sites within Lough Hyne, and at one site on the adjacent Atlantic coastline to examine differences in abundance and zonation patterns. Sites ranged from an exposed turbulent regime to sheltered, sedimented environments. Individual species showed different distributions and prevalence between sites and with increasing depth. Greatest differences were observed between the most- and least-disturbed sites. Distinct sponge zonation patterns were evident at all sites sampled. Twenty-five species were considered dominant at all five sites with the remaining 48 species considered rare. Only four of the 25 most-dominant species occurred at the site experiencing the most turbulent flow conditions, whereas 12 species were found at the site of unidirectional fast flow. At sites of moderate to slight water movement and high sedimentation, between 18 and 24 of the most dominant species were present. Encrusting forms constituted high proportions of sponge communities at all five sites sampled (although consisting of different species). At sites of turbulent and unidirectional fast flow massive forms also dominated whereas at the least turbulent sites, where sedimentation was high, arborescent sponges were abundant. Few species showed exclusive distribution to a single depth and site, but there was some degree of correlation between species distributions and abiotic factors such as sedimentation rate and flow regimes. Sponge distributions and densities are discussed with respect to the suitability of species' morphologies to particular environments, intra-specific and inter-specific competition and physiological adaptations that enable them to survive in different habitats. [source] Spatial variation in population density across the geographical range in helminth parasites of yellow perch Perca flavescensECOGRAPHY, Issue 5 2007Robert Poulin The abundance of a species is not constant across its geographical range; it has often been assumed to decrease from the centre of a species' range toward its margins. The central assumption of this "favourable centre" model is tested for the first time with parasites, using different species of helminth parasites exploiting fish as definitive hosts. Data on prevalence (percentage of hosts that are infected) and abundance (mean no. parasites per host) were compiled for 8 helminth species occurring in 23 populations of yellow perch Perca flavescens, from continental North America. For each parasite species, correlations were computed between latitude and both local prevalence and abundance values. In addition, the relationships between the relative prevalence or abundance in one locality and the distance between that locality and the one where the maximum value was reported, were assessed separately for each species to determine whether abundance tends to decrease away from the presumed centre of the range, where it peaks. For both the cestode Proteocephalus pearsei and the acanthocephalan Leptorhynchoides thecatus, there was a positive relationship between prevalence or abundance and the latitude of the sampled population. There was also a significant negative relationship between relative prevalence and the distance from the locality showing the maximum value in P. pearsei, but no such pattern was observed for the other 7 parasite species. Since this single significant decrease in prevalence with increasing distance from the peak value may be confounded by a latitudinal gradient, it appears that the distribution of abundance in parasites of perch does not follow the favourable centre model. This means that the environmental variables affecting the density of parasites (host availability, abiotic conditions) do not show pronounced spatial autocorrelation, with nearby sites not necessarily providing more similar conditions for the growth of parasite populations than distant sites. [source] Distribution, abundance, and individual strategies: a multi-scale analysis of dasyurid marsupials in arid central AustraliaECOGRAPHY, Issue 3 2006Adele S. Haythornthwaite We investigated the effects of different environmental factors on the distribution and abundance of 6 species of dasyurid marsupials using a multiple-scale analysis. Data collected in the spinifex dunefields of the Simpson Desert, Australia, were analysed at 3 spatial scales spanning more than 5 orders of magnitude: "metasite" (covering an area of 1000,2000 km2), site (2,12 km2) and grid (0.01 km2). Temporal variability was also investigated, using data collected in March, April, and May in 4 consecutive years from 1997 to 2000. Both abiotic and biotic factors influenced the capture rates of different species at different times and spatial scales. At the coarsest spatial scale, Dasycercus cristicauda (mulgara) was consistently limited in its distribution by the intensity of rainfall, probably as an indirect result of increased grazing pressure from pastoral activity and a higher density of feral predators in high rainfall areas. However, at the finest spatial scale, this partly carnivorous species was scarce in areas of dense spinifex, perhaps because such habitats yield lowest returns during foraging, and was more common in areas where small invertebrate prey were abundant. Factors affecting the distribution of the most abundant dasyurid species in the study area, Sminthopsis youngsoni (lesser hairy-footed dunnart), could not be identified at any scale; we conclude that this reflects the opportunistic foraging strategies and flexible habitat requirements of this insectivorous species. Both Ningaui ridei (wongai ningaui) and Sminthopsis hirtipes (hairy-footed dunnart) were less abundant throughout the study region. For N. ridei, a spinifex specialist, predictors of occurrence could be identified only at the finest scale of analysis; at the grid level, a close positive association was detected in 2 of the 4 study years between capture rate and spinifex cover. For S. hirtipes, all 3 levels of spatial analysis revealed a negative association between capture rate and both rainfall and spinifex density. For the rarely-caught S. crassicaudata (fat-tailed dunnart) and Planigale tenuirostris (narrow-nosed planigale), no clear results were obtained at any spatial scale, and we interpret this to indicate that the study region represents sub-optimal habitat for these species. Given that different factors affected the distribution and abundance of dasyurids at different spatial scales over time, we conclude that a multiple-scale approach to population and community analysis is vital to accurately identify which environmental processes shape population and community dynamics. Understanding the interplay between regional and local processes will be crucial for management of existing species populations and for prediction of their distributions and abundances in future. [source] The influence of scale and patchiness on spider diversity in a semi-arid environmentECOGRAPHY, Issue 4 2002Mary E. A. Whitehouse Semi-arid scrubland in the Middle East consists of a soil crust matrix overlain with patches of perennial shrubs. To understand factors influencing biodiversity in this vulnerable landscape we need to understand how this mosaic of habitats influences associated fauna. Spiders are particularly abundant in this habitat so we asked if spider diversity differed between habitat patches and if different patch types contained either a subset of the regional species pool or specific species guilds. We also asked whether changes in the fractal nature of the microphytic and macrophytic patch mosaic altered spider diversity in this habitat. We found that the semi-arid scrubland at Sayeret Shaked Park (Israel) contains different spider communities that require patches of a certain quality to develop fully. Different patch types contain communities of different species, but the community structure of the patches is similar. We suggest that large-scale environmental factors typical of the site as a whole influence coarse-grained community structure, while small-scale differences between patch types result in the specialisation of species to different patch types. [source] Effects of environmental perturbations on abundance of subarctic plants after three, seven and ten years of treatmentsECOGRAPHY, Issue 1 2001Enrico Graglia Analyses of changes in vegetation were carried out after three, seven and ten years of fertilizer addition, warming and light attenuation in two subarctic, alpine dwarf shrub heaths. One site was just above the tree line, at ca 450 m a.s.l., and the other at a much colder fell-field at ca 1150 m altitude. The aim was to investigate how the treatments affected the abundance of different species and growth forms over time, including examinations of transient changes. Grasses, which increased in abundance by fertilizer addition, and cryptogams, which, by contrast, decreased by fertilizer addition and warming, were the most sensitive functional groups to the treatments at both sites. Nutrient addition exerted a stronger and more consistent effect than both shading and warming. Warming at the fell-field had slightly greater effect than at the warmer tree line with an increase in deciduous shrubs. The decreased abundance of mosses and lichens to fertilizer addition and/or warming was most likely an indirect treatment effect, caused by competition through increased abundance and overgrowth of grasses. Such changes in species composition are likely to alter decomposition rates and the water and energy exchange at the soil surface. We observed few, if any, transient effects of declining responses during the 10 yr of treatments. Instead, there were many cumulative effects of the treatments for all functional groups and many interactions between time and treatment, suggesting that once a change in community composition is triggered, it will continue with unchanged or accelerated rate for a long period of time. [source] Host plant specificity in several species of generalist mite predatorsECOLOGICAL ENTOMOLOGY, Issue 6 2001J. J. Beard Summary 1. Species in the genus Neoseiulus are considered to be generalist predators, with some species used in biological control programmes against phytophagous mites and insects. 2. A general survey of Neoseiulus species in inland Australia indicated that different species are associated with particular tree species. This pattern of host plant use was investigated for four Neoseiulus species (N. buxeus, N. cappari, N. brigarinus, N. eremitus) by means of a sampling programme through time and across space. 3. Each species of Neoseiulus was collected entirely or mostly from one species of tree; little or no overlap was detected despite the tree species growing in well-mixed stands. Host plant specificity thus appears to be strong in this genus. 4. Species in two other genera (Pholaseius and Australiseiulus), also considered to be predatory, showed a similar association with particular tree species. 5. The implications for the use of these predators in biological control are considerable. In particular, phytoseiid species with specific needs in terms of host plants may not be suitable for use as general purpose predators. Meeting the needs of phytoseiids through the modification of host plant attributes may be a step towards enhancing their efficacy as biological control agents. [source] When random sampling does not work: standard design falsely indicates maladaptive host preferences in a butterflyECOLOGY LETTERS, Issue 1 2002Michael C. Singer In experiments that investigate species' interactions, individuals are often chosen at random to represent their populations. However, this practice can generate misleading results when individuals of different species do not interact at random. We illustrate this effect by examining oviposition preferences of Euphydryas aurinia butterflies from three populations using three different plant genera. We first offered each insect a randomly chosen member of its own host population and a foreign host (Succisa pratensis) not present in the insect's habitat. The butterflies uniformly preferred the foreign Succisa over their own hosts. Preferences were apparently maladaptive because insects wasted time searching for a nonexistent plant. We repeated the experiment using individual hosts that had naturally received eggs in the field. The overall preference for Succisa and the appearance of maladaptation both disappeared. In the original experiments, our random choice of experimental host individuals had combined with strong within-species discrimination by the butterflies and with overlap of acceptability between host species to obscure the true nature of host preference. [source] Parental care in response to natural variation in nest predation pressure in six sunfish (Centrarchidae: Teleostei) speciesECOLOGY OF FRESHWATER FISH, Issue 4 2008S. J. Cooke Abstract,,, Parental care is an important, energetically costly component of the life history of many fishes. Despite this importance, little is known about how different species of fish vary parental care in response to natural nest predator burdens. In this study, underwater videography was used to quantify parental care activity of six species of syntopic nesting male centrarchid fishes in Lake Opinicon, Ontario, in response to natural predators. This approach was used to test the hypothesis that as offspring develop from eggs to wrigglers, parental care activity should decrease or remain static for fish guarding nests with low predator burden and increase for those with high predator burden, reflecting different external risks. Principal components analysis (PCA) was used to derive common aeration and nest defence variables. Aeration and predator defence activity of the fish varied extensively among species. Parental care behaviours indicative of defence and vigilance (e.g., turning, departures, time away from nest, displays) tended to be highest for species that had the most predation attempts, although this was not entirely consistent. There was also a positive relationship between the defence PCA metric and attempted predation. Defence did not vary with stage of offspring development, although interactions between defence and developmental stage were noted for several species. A trade-off between aeration and defence was not observed. In fact, species that provide high levels of aeration also simultaneously provide high levels of defence. Stage-specific patterns of defence in this study were less apparent than those documented by studies using responses to staged predator intrusions making it unclear as to the extent that fish were responding to the level of the risk to offspring than to the value of the brood. Therefore, combined use of observational and experimental assessments of parental care investment may be most appropriate for refining current theoretical paradigms. [source] Capillary electrophoresis of liposomes functionalized for protein bindingELECTROPHORESIS, Issue 20 2006Gerhard Bilek Abstract CE enabled assessing the attachment of hexa-histidine-tagged proteins to functionalized phospholipid liposomes. The liposomes were made of 1-palmitoyl-2-oleoyl- sn -glycero-3-phosphocholine, phosphatidyl-ethanolamine, cholesterol and distearoyl-glycero-3-phosphoethanolamine- N -methoxy(polyethylene glycol) in a molar ratio of 29:26:40:5. The unilamellar vesicles, which had an average diameter of 170,nm, were labelled by inclusion of FITC-dextran for fluorescence detection. CE was carried out in poly(vinyl alcohol) (PVA)-coated capillaries at 25°C with a BGE consisting of Tris-HCl (50,mM, pH,8.0). For conjugation of the liposomes with the proteins (soluble synthetic receptor fragments with molecular mass of 60 and 70,kDa, respectively), Ni2+ was implanted into the vesicle surface by an anchor lipid containing a nitrilotriacetate acid (NTA) group as complexation agent for the metal ions. The difference in surface charge enabled the separation of the different species of interest by CE: plain vesicles, vesicles functionalised with Ni-NTA, vesicle,protein complexes and the species formed upon removal of the Ni-ions by complexation with EDTA. Loss of the Ni-ions resulted in the release of the proteins and the reappearance of the plain Ni-free NTA-liposome species in the electropherograms. [source] Cross-reactivity of antibodies to actin- depolymerizing factor/cofilin family proteins and identification of the major epitope recognized by a mammalian actin-depolymerizing factor/cofilin antibodyELECTROPHORESIS, Issue 15 2004Alisa E. Shaw Abstract Members of the actin-depolymerizing factor (ADF)/cofilin family of proteins are expressed in all eukaryotic cells. In higher vertebrates, cells often express as many as three different ADF/cofilin genes and each of these proteins may be phosphorylated on serine 3, giving rise to up to six different species. Also, many avian, amphibian, and invertebrate systems have been useful in studying different aspects of ADF/cofilin function. Antibodies have been prepared against different members of the ADF/cofilin family, but no systematic examination of their cross-reactivity has been reported. Although ADF and cofilins within a single vertebrate species have about a 70% sequence homology, antibodies often differentiate between these proteins. Here, Western blotting was used with chemiluminescence substrates of different sensitivities to determine the relative immunoreactivities of different polyclonal rabbit antibodies and a mouse monoclonal antibody to purified ADF/cofilins from plants, protists, nematodes, insects, echinoderms, birds, and mammals. From immunocross-reactivities and sequence alignments, the principal epitope in mammalian ADF and cofilin-1 recognized by an antibody raised against avian ADF was identified. The specificity of an antibody to the phosphopeptide epitope of metazoan ADF/cofilins was confirmed by two-dimensional (2-D) immunoblot analysis. Futhermore, this bank of antibodies was used to identify by Western blotting a putative member of the ADF/cofilin family in the sea slug, Aplysia californica. [source] Larval pupation site preference on fruit in different species of DrosophilaENTOMOLOGICAL RESEARCH, Issue 3 2008Nakul B. VANDAL Abstract Larval pupation site preference (PSP) of different species of Drosophila was analyzed on fruit in the laboratory. The larvae of D. melanogaster, D. ananassae, D. virilis, D. novamexicana and D. hydei pupated on the surface of glass vials; D. simulans, D. yakuba, D. mauritiana and D. malerkotliana pupated in/on fruit; and D. rajasekari pupated on cotton plugs in all experiments. D. bipectinata larvae changed their preference from fruit in the control to glass surface for all of the fruits tested. The statistical analysis of PSP (glass and fruit) found a significant result in that compared to other species, D. mauritiana and D. ananassae preferred to pupate on cotton compared to the control. [source] Antimutagenicity of green tea polyphenols in the liver of transgenic medakaENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 2 2005Richard N. Winn Abstract We examined the ability of a mixture of the predominant green tea polyphenolic compounds (GTP) to reduce benzo[a]pyrene (B[a]P)-induced mutations in the cII gene of the , transgenic medaka. Fish were treated with 50 ppb B[a]P for 24 hr, followed by exposure to 2 ppm or 10 ppm GTP for 28 days. cII mutations in livers of fish exposed to B[a]P were increased significantly, 2.6-fold above controls. In contrast, the addition of GTP significantly reduced the frequency of cII mutants by 84%, comparable to that of controls. The frequencies of mutations at G:C basepairs, mutations that are highly characteristic of B[a]P exposure, were elevated significantly in treated fish. By comparison, B[a]P-exposed fish also treated with GTP showed reductions in these mutations, demonstrating a protective effect of GTP against B[a]P-induced mutagenesis. The antioxidant mechanism of GTP possibly played an important role in the reduction of B[a]P mutagenicity. These results corroborate findings from rodent models, showing that the protective effects of green tea extend to different species, and suggesting that similar mechanisms of B[a]P mutagenesis and GTP antimutagenesis are shared among the models. These studies illustrate the utility of , transgenic medaka for in vivo mutation analyses and suggest that this fish may be a valuable model in chemoprevention studies. Environ. Mol. Mutagen., 2005. © 2005 Wiley-Liss, Inc. [source] Niche separation of ammonia-oxidizing bacteria across a tidal freshwater marshENVIRONMENTAL MICROBIOLOGY, Issue 11 2008Hendrikus J. Laanbroek Summary Like many functional groups or guilds of microorganisms, the group of ammonia-oxidizing bacteria (AOB) consists of a number of physiologically different species or lineages. These physiological differences suggest niche differentiation among these bacteria depending on the environmental conditions. Species of AOB might be adapted to different zones in the flooding gradient of a tidal marsh. This issue has been studied by sampling sediments from different sites and depths within a tidal freshwater marsh along the river Scheldt near the village of Appels in Belgium. Samples were taken in February, April, July and October 1998. Communities of AOB in the sediment were analysed on the basis of the 16S rRNA gene by application of polymerase chain reaction in combination with denaturing gradient gel electrophoresis (DGGE). In addition, moisture content and concentrations of ammonium and nitrate were determined as well as the potential ammonia-oxidizing activities. Six different DGGE bands belonging to the ,-subclass of the Proteobacteria were observed across the marsh. The community composition of AOB was determined by the elevation in the flooding gradient as well as by the sampling depth. The presence of plants was less important for the community composition of AOB. DGGE bands affiliated with the Nitrosospira lineage were mostly found in the upper part of the marsh and in the deeper layers of the sediment. Two of the three DGGE bands related to the Nitrosomonas oligotropha lineage were more broadly distributed over the marsh, but were predominantly found in the upper layers of the sediment. Members of the environmental Nitrosomonas lineage 5 were predominantly detected in the deeper layers in the lower parts of the marsh. Potential driving factors for niche differentiation are discussed. [source] Seasonal and substrate preferences of fungi colonizing leaves in streams: traditional versus molecular evidenceENVIRONMENTAL MICROBIOLOGY, Issue 2 2005Liliya G. Nikolcheva Summary Aquatic hyphomycetes are the main fungal decomposers of plant litter in streams. We compared the importance of substrate (three leaf species, wood) and season on fungal colonization. Substrates were exposed for 12 4-week periods. After recovery, mass loss, fungal biomass and release of conidia by aquatic hyphomycetes were measured. Fungal communities were characterized by counting and identifying released conidia and by extracting and amplifying fungal DNA (ITS2), which was subdivided into phylotypes by denaturing gradient gel electrophoresis (DGGE) and terminal-restriction fragment length polymorphism (T-RFLP). Mass loss, fungal biomass and reproduction were positively correlated with stream temperature. Conidial diversity was highest between May and September. Numbers of different phylotypes were more stable. Principal coordinate analyses (PCO) and canonical analyses of principal coordinates (CAP) of presence/absence data (DGGE bands, T-RFLP peaks and conidial species) showed a clear seasonal trend (P, 0.002) but no substrate effect (P, 0.88). Season was also a significant factor when proportional similarities of conidial communities or relative intensities of DGGE bands were evaluated (P, 0.003). Substrate was a significant factor determining DGGE band intensities (P = 0.002), but did not significantly affect conidial communities (P = 0.50). Both traditional and molecular techniques suggest that strict exclusion of fungi by substrate type is rare, and that presence of different species or phylotypes is governed by season. Biomasses of the various taxa (based on DGGE band intensities) were related to substrate type. [source] Multiple species of the dinophagous dinoflagellate genus Amoebophrya infect the same host speciesENVIRONMENTAL MICROBIOLOGY, Issue 11 2003Paulo S. Salomon Summary Populations of the dinoflagellate Dinophysis norvegica in the Baltic Sea and in the adjacent North Sea are infected by the endoparasite Amoebophrya sp. The high diversity recently unveiled within the genus Amoebophrya brings uncertainty about their identities. We applied molecular biology techniques , 18S rDNA sequencing and fluorescent in situ hybridization (FISH) , to compare this host,parasite system from both environments. The North Sea Amoebophrya sp. 18S rDNA sequence was 89% identical to the previously described Baltic Sea Amoebophrya sp. sequence, suggesting they are different species. In spite of that, a phylogenetical analysis placed the North Sea parasite sequence in a well-supported cluster with other Amoebophrya sp. sequences. The D. norvegica 18S rDNA sequences from both environments were 100% identical, indicating that the hosts have not evolved independently. A DNA probe designed for the Baltic Sea Amoebophrya sp. 18S rRNA was used in FISH assays on infected D. norvegica populations from both environments. The probe stained all infected cells from the Baltic sample, whereas none from the North Sea were stained. The results indicate that D. norvegica is released from one parasite when entering the Baltic Sea, and become less infected by an alternative parasite species. [source] Summer changes in cyanobacterial bloom composition and microcystin concentration in eutrophic Czech reservoirsENVIRONMENTAL TOXICOLOGY, Issue 3 2006Petr Znachor Abstract In mid-July and August 2003 and 2004, 18 reservoirs in the Czech Republic were sampled for phytoplankton species composition and concentration of intracellular microcystins (MCs). As a consequence of high nutrient loading, most of the reservoirs experienced cyanobacterial blooms of various intensities, with the prevalence of cyanobacteria increasing markedly in August, along with a conspicuous shift in species composition toward dominance of Microcystis spp. Microcystins were detected in 90% of the samples, and their amount also increased considerably in August, reflecting the cyanobacterial biomass. In Microcystis -dominated samples, a significantly higher amount of MCs (p < 0.001) occurred than in samples in which other taxa prevailed. Microcystins were positively correlated with chlorophyll a and cyanobacterial biovolume (p < 0.05, R2 = 0.61 and 0.66, respectively), with the strongest correlation found for Microcystis spp. biovolume (p < 0.001, R2 = 0.87). This taxon was the most important producer of MCs in Czech reservoirs. The main structural variants of MCs were MC-LR, MC-RR, and MC-YR. This study's data also indicate that the relative share of MC variants (MC-LR and MC-RR) varies considerably with time, most likely as a consequence of different species and strain compositions during the summer. This study clearly demonstrates a high prevalence of MC-producing cyanobacteria in Czech reservoirs. Therefore, regular monitoring of these reservoirs is highly desirable in an effort to minimize potential health risks to the human population. © 2006 Wiley Periodicals, Inc. Environ Toxicol 21: 236,243, 2006. [source] Development and application of a species sensitivity distribution for temperature-induced mortality in the aquatic environmentENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2008Pepijn de Vries Abstract Current European legislation has static water quality objectives for temperature effects, based on the most sensitive species. In the present study a species sensitivity distribution (SSD) for elevated temperatures is developed on the basis of temperature sensitivity data (mortality) of 50 aquatic species. The SSD applies to risk assessment of heat discharges that are localized in space or time. As collected median lethal temperatures (LT50 values) for different species depend on the acclimation temperature, the SSD is also a function of the acclimation temperature. Data from a thermal discharge in The Netherlands are used to show the applicability of the developed SSD in environmental risk assessment. Although restrictions exist in the application of the developed SSD, it is concluded that the SSD approach can be applied to assess the effects of elevated temperature. Application of the concept of SSD to temperature changes allows harmonization of environmental risk assessment for stressors in the aquatic environment. When a synchronization of the assessment methods is achieved, the steps to integration of risks from toxic and nontoxic stressors can be made. [source] Influence of feeding ecology on blood mercury concentrations in four species of turtlesENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2007Christine M. Bergeron Abstract Mercury is a relatively well-studied pollutant because of its global distribution, toxicity, and ability to bioaccumulate and biomagnify in food webs; however, little is known about bioaccumulation and toxicity of Hg in turtles. Total Hg (THg) concentrations in blood were determined for 552 turtles representing four different species (Chelydra serpentina, Sternotherus odoratus, Chrysemys picta, and Pseudemys rubriventris) from a Hg-contaminated site on the South River (VA, USA) and upstream reference sites. Methylmercury and Se concentrations also were determined in a subset of samples. Because the feeding ecology of these species differs drastically, stable isotopes of carbon (,13C) and nitrogen (,15N) were employed to infer the relationship between relative trophic position and Hg concentrations. Significant differences were found among sites and species, suggesting that blood can be used as a bioindicator of Hg exposure in turtles. We found differences in THg concentrations in turtles from the contaminated site that were consistent with their known feeding ecology: C. serpentina , S. odoratus > C. picta > P. rubriventris. This trend was generally supported by the isotope data, which suggested that individual turtles were feeding at more than one trophic level. Methylmercury followed similar spatial patterns as THg and was the predominant Hg species in blood for all turtles. Blood Se concentrations were low in the system, but a marginally positive relationship was found between THg and Se when species were pooled. The blood THg concentrations for the turtles in the present study are some of the highest reported in reptiles, necessitating further studies to investigate potential adverse effects of these high concentrations. [source] Alteration of normal cellular profiles in the scleractinian coral (Pocillopora damicornis) following laboratory exposure to fuel oilENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2006Luc Rougée Abstract Petroleum contamination from oil spills is a continuing threat to our ocean's fragile ecosystems. Herein, we explored the effects of the water-soluble fraction of crude oil on a stony coral, Pocillopora damicornis (Linneaeus 1758). We developed methods for exposing corals to various concentrations of crude oil and for assessing the potential molecular responses of the corals. Corals were exposed to water-accommodated fraction solutions, and appropriate cellular biomarkers were quantified. When compared to the "healthy" control specimens, exposed corals exhibited shifts in biomarker concentrations that were indicative of a shift from homeostasis. Significant changes were seen in cytochrome P450 1-class, cytochrome P450 2-class, glutathione- S -transferase-pi, and cnidarian multixenobiotic resistance protein-1 biomarkers, which are involved the cellular response to, and manipulation and excretion of, toxic compounds, including polycyclic aromatic hydrocarbons. A shift in biomarkers necessary for porphyrin production (e.g., protoporphyrinogen oxidase IX and ferrochelatase) and porphyrin destruction (e.g., heme oxygenase-1 and invertebrate neuroglobin homologue) illustrates only one of the cellular protective mechanisms. The response to oxidative stress was evaluated through measurements of copper/zinc superoxide dismutase-1 and DNA glycosylase MutY homologue-1 concentrations. Likewise, changes in heat shock protein 70 and small heat shock proteins indicated an adjustment in the cellular production of proteins. Finally, the results of this laboratory study were nearly identical to what we observed previously among corals of a different species, Porites lobata, exposed to an oil spill in the field after the grounding of the Merchant Vessel Kyowa Violet. [source] Comparison of Cd, Cu, and Zn toxic effects on four marine phytoplankton by pulse-amplitude-modulated fluorometryENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2005Ai-Jun Miao Abstract The toxic effects of Cd, Cu, and Zn on four different marine phytoplankton, Dunaliella tertiolecta, Prorocentrum minimum, Synechococcus sp., and Thalassiosira weissflogii, were examined by comparing the cell-specific growth rate, pulse-amplitude-modulated (PAM) parameters (maximum photosystem II quantum yield ,M and operational quantum yield ,'M), chlorophyll a content, and cellular metal concentration, over a 96-h period. The calculated no-observed-effect concentration (NOEC) based on both cell-specific growth rate and two PAM parameters (,M and ,'M) were mostly identical. Thus, these PAM parameters and cell-specific growth rate were comparable in their sensitivities as the biomarkers for trace metal toxicity to marine phytoplankton. The cyanobacteria Synechococcus sp. was the most sensitive species among the four algal species tested because of its higher cell surface to volume ratio. The toxicity of the three tested metals followed the order of Cd > Cu > Zn based on the cellular metal concentration of the four algae at the NOEC. The cellular metal bioaccumulation followed the same Freundlich isotherm for each metal regardless of the algal species, indicating that the metal accumulation was a nonmetabolic process under high ambient metal concentrations and that the cell surface metal binding was comparable among the different species. For all the algae examined in our study, the bioaccumulation potentials of Cu and Zn were similar to each other, while the Cd bioaccumulation was much lower under environmentally realistic metal concentration. [source] An empirical method for inferring species richness from samplesENVIRONMETRICS, Issue 2 2006Paul A. Murtaugh Abstract We introduce an empirical method of estimating the number of species in a community based on a random sample. The numbers of sampled individuals of different species are modeled as a multinomial random vector, with cell probabilities estimated by the relative abundances of species in the sample and, for hypothetical species missing from the sample, by linear extrapolation from the abundance of the rarest observed species. Inference is then based on likelihoods derived from the multinomial distribution, conditioning on a range of possible values of the true richness in the community. The method is shown to work well in simulations based on a variety of real data sets. Copyright © 2005 John Wiley & Sons, Ltd. [source] Bayesian hierarchical generalized linear models for a geographical subset of recovery dataENVIRONMETRICS, Issue 2 2002Daniela Cocchi Abstract The aim of this work is to check whether modifications in the length of the hunting seasons had an effect on the chance of reproduction of different species of ringed birds. We start from a national data set of ringing-recovered data on three species of game birds. Only data on birds recovered as juveniles are used. Data on recoveries are organized in a 4-way contingency table. Several generalized linear models are proposed for the counts of recovered birds. Bayesian hierarchical modeling is particularly suitable for this kind of data, for which an over-dispersion parameter can be introduced at the second level of the hierarchy. Maximum Likelihood and Bayesian solutions are computed for the different models: the Bayesian framework, in particular under an individual modeling of over-dispersion, exhibits the best fit in terms of Bayesian p -value. The results show that the modification in the length of the hunting seasons does not produce equal benefits for the three species considered. Copyright © 2002 John Wiley & Sons, Ltd. [source] Different methods of monitoring susceptibility of oilseed rape beetles to insecticidesEPPO BULLETIN, Issue 1 2008T. Thieme The resistance of oilseed rape pollen beetles to lambda-cyhalothrin has increased in Germany over the period 2002 to 2007. Oilseed rape pollen beetles are very good at dispersing, therefore field results should always be compared with those of laboratory experiments. The response of oilseed rape pollen beetles to active substances may not be the same as that to formulated products. Bioassays in which beetles are exposed to insecticides on either complete inflorescences or flower buds give different results. It is evident that samples of the genus Meligethes collected in the field can include several different species. Monitoring for insecticide resistance should be done using only the true oilseed rape pollen beetle. [source] Locomotion and Escape Modes in Rodents of the Monte Desert (Argentina)ETHOLOGY, Issue 6 2003Paula Taraborelli Modes of locomotion and escape tactics are attributes that affect the structure of animal communities, promoting exploitation of different microhabitats and the coexistence of different species. Bipedal locomotion is considered to be more effective than a quadrupedal gait in escaping attacks by predators because it allows for higher speed, a faster response to attack, sudden changes of direction and better detection of aerial raptors. The aim of this study was to determine the type of locomotion used at the moment of escape by three rodent species of the Monte desert ,Eligmodontia typus, Akodon molinae and Graomys griseoflavus. The study was carried out in three plant communities of the Ñacuñán Reserve (Mendoza). All three species showed differences in both mode of escape and locomotory pattern. Graomys griseoflavus exhibited the highest proportion of escapes using quadrupedal saltation. The mode of locomotion employed by E. typus varied according to the type of plant communities it inhabited. Those occurring at open sites (Medanal community) exhibited a greater propensity to jump during escapes than those from more sheltered habitats (Algarrobal community). Akodon molinae relied primarily on a quadrupedal gait when fleeing from predators, which would explain its greater dependence on plant cover. Therefore, the morphological and behavioural characteristics of these species are related to their mode of locomotion and the strategies they employ to diminish the risk of predation. [source] | ||||||||||||||||||||||||||||||||||||||||||||||