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Similar Species (similar + species)
Selected AbstractsCorrelative and mechanistic models of species distribution provide congruent forecasts under climate changeCONSERVATION LETTERS, Issue 3 2010Michael R. Kearney Abstract Good forecasts of climate change impacts on extinction risks are critical for effective conservation management responses. Species distribution models (SDMs) are central to extinction risk analyses. The reliability of predictions of SDMs has been questioned because models often lack a mechanistic underpinning and rely on assumptions that are untenable under climate change. We show how integrating predictions from fundamentally different modeling strategies produces robust forecasts of climate change impacts on habitat and population parameters. We illustrate the principle by applying mechanistic (Niche Mapper) and correlative (Maxent, Bioclim) SDMs to predict current and future distributions and fertility of an Australian gliding possum. The two approaches make congruent, accurate predictions of current distribution and similar, dire predictions about the impact of a warming scenario, supporting previous correlative-only predictions for similar species. We argue that convergent lines of independent evidence provide a robust basis for predicting and managing extinctions risks under climate change. [source] Impacts of Dreissena invasions on benthic macroinvertebrate communities: a meta-analysisDIVERSITY AND DISTRIBUTIONS, Issue 2 2007Jessica M. Ward ABSTRACT Dreissenid mussels (the zebra mussel Dreissena polymorpha and the quagga mussel Dreissena bugensis) have invaded lakes and rivers throughout North America and Europe, where they have been linked to dramatic changes in benthic invertebrate community diversity and abundance. Through a meta-analysis of published data from 47 sites, we developed statistical models of Dreissena impact on benthic macroinvertebrates across a broad range of habitats and environmental conditions. The introduction of Dreissena was generally associated with increased benthic macroinvertebrate density and taxonomic richness, and with decreased community evenness (of taxa excluding Dreissena). However, the strength of these effects varied with sediment particle size across sites. The effects of Dreissena differed among taxonomic and functional groups of macroinvertebrates, with positive effects on the densities of scrapers and predators, particularly leeches (Hirudinea), flatworms (Turbellaria), and mayflies (Ephemeroptera). Gastropod densities increased in the presence of Dreissena, but large-bodied snail taxa tended to decline. Dreissena was associated with declines in the densities sphaeriid clams and other large filter-feeding taxa, as well as burrowing amphipods (Diporeia spp.), but had strong positive effects on gammarid amphipods. These patterns are robust to variation in the methodology of primary studies. The effects of Dreissena are remarkably concordant with those of ecologically similar species, suggesting universality in the interactions between introduced byssally attached mussels and other macroinvertebrates. [source] Long-term effects of ungulates on phytophagous insectsECOLOGICAL ENTOMOLOGY, Issue 2 2007JOSÉ M. GÓMEZ Abstract 1.,Most plants interact with a diverse suite of herbivores, allowing the opportunity for the existence of positive and negative interactions between highly dissimilar organisms. However, most studies on herbivorous interactions have been performed under the assumption that they occur mainly between similar species. Consequently, ecologists are still far from a full understanding of the ecological factors that determine insect population dynamics. 2.,In this study, a 7-year field experiment was conducted that manipulated the presence of ungulates to evaluate their effects on the abundance, attack rate, and survival of four guilds of co-occurring herbivorous insects living on the same host plant: seed predators, stem borers, gall makers and sap suckers. These four guilds differed in habits and behaviour, the first three being sessile and endophytic and the last being free-living. 3.,This study shows that the abundance of all four guilds was negatively affected by ungulates. However, the effect on attack rate differed among guilds, as mammals do not affect the seed predator attack rate. Ungulates also differentially affected insect survival, ingesting only seed predators and gall makers. 4.,In summary, this study suggests that diverse mechanisms may affect different insect guilds in different ways. Therefore, competition between disparate herbivores appears to be complex and can be provoked by multiple mechanisms. [source] Demographics of the spawning aggregations of four catostomid species in the Savannah River, South Carolina and Georgia, USAECOLOGY OF FRESHWATER FISH, Issue 2 2008T. B. Grabowski Abstract,,, Differences in the life history strategies employed by otherwise ecologically similar species of a fish assemblage may be an important factor in the coexistence of these species and is an essential consideration in the conservation and management of these assemblages. We collected scales to determine age and growth of four species of the catostomid assemblage (northern hogsucker Hypentelium nigricans, spotted sucker Minytrema melanops, notchlip redhorse Moxostoma collapsum and robust redhorse Moxostoma robustum) of the Savannah River, Georgia,South Carolina in spring 2004 and 2005. Robust redhorse was the largest species; reaching sexual maturity at an older age and growing faster as a juvenile than the other species. Spotted sucker did not achieve the same size as robust redhorse, but reached sexual maturity at younger ages. Notchlip redhorse was intermediate between the abovementioned two species in age at maturity and size. Northern hogsucker was the smallest species of the assemblage and reached the sexual maturity at the age of three. Both robust redhorse and spotted sucker were sexually dimorphic in size-at-age. The range of life history strategies employed by Savannah River catostomids encompasses the range of life history strategies exhibited within the family as a whole. [source] TESTING THE ROLE OF INTERSPECIFIC COMPETITION IN THE EVOLUTIONARY ORIGIN OF ELEVATIONAL ZONATION: AN EXAMPLE WITH BUARREMON BRUSH-FINCHES (AVES, EMBERIZIDAE) IN THE NEOTROPICAL MOUNTAINSEVOLUTION, Issue 5 2007Carlos Daniel Cadena Interspecific competition might drive the evolution of ecological niches and result in pairs of formerly competing species segregating along ecological gradients following a process of character displacement. This mechanism has been proposed to account for replacement of related species along gradients of elevation in many areas of the world, but the fundamental issue of whether competition is responsible for the origin of elevational replacements has not been tested. To test hypotheses about the role of interspecific competition in the origin of complementary elevational ranges, I combined molecular phylogenetics, phylogeography, and population genetic analyses on Buarremon torquatus and B. brunneinucha (Aves, Emberizidae), whose patterns of elevational distribution suggest character displacement or ecological release. The hypothesis that elevational distributions in these species changed in opposite directions as a result of competition is untenable because: (1) a historical expansion of the range of B. brunneinucha into areas occupied by B. torquatus was not accompanied by a shift in the elevational range of the former species; (2) when B. brunneinucha colonized the range of B. torquatus, lineages of the latter distributions had already diverged; and (3) historical trends in effective population size do not suggest populations with elevational ranges abutting those of putative competitors have declined as would be expected if competition caused range contractions. However, owing to uncertainty in coalescent estimates of historical population sizes, the hypothesis that some populations of B. torquatus have declined cannot be confidently rejected, which suggests asymmetric character displacement might have occurred. I suggest that the main role of competition in elevational zonation may be to act as a sorting mechanism that allows the coexistence along mountain slopes only of ecologically similar species that differ in elevational distributions prior to attaining sympatry. The contrasting biogeographic histories of B. brunneinucha and B. torquatus illustrate how present-day ecological interactions can have recent origins, and highlights important challenges for testing the hypothesis of character displacement in the absence of data on population history and robust reconstructions of the evolution of traits and geographic ranges. [source] COLONY SEX RATIOS IN THE FACULTATIVELY POLYGYNOUS ANT PHEIDOLE PALLIDULA: A REANALYSIS WITH NEW DATAEVOLUTION, Issue 5 2004Ken R. Helms Abstract A recent study by Fournier et al. (2003) provides important new information on sex allocation in the ant Pheidole pallidula, and proposes a new scenario for sex-ratio evolution in P. pallidula and similar species. However, Helms proposed to the authors that two important conclusions of the study were questionable because of potential problems with the analyses. Here we provide new data and a reanalysis that strengthens the conclusion that colony sex ratio is associated with breeding system (i.e., polygyny or monogyny). However, the proposal that colonies shift from monogyny to polygyny when they become larger and more productive is weakened because there is substantial overlap in productivity between monogynous and polygynous colonies. [source] Vier neue Arten aus den Gattungen Leucoagaricus und Leucocoprinus mit bräunlichen bis rußfarbigen Tönungen in den Hutfarben,FEDDES REPERTORIUM, Issue 1-2 2004P. Mohr Vier neue Arten aus den Gattungen Leucoagaricus und Leucocoprinus werden beschrieben und gegen bekannte ähnliche Arten abgegrenzt. Leucoagaricus fuligineodiscusP.Mohr & E.Ludwig sp. nova stammt aus Brandenburg im östlichen Teil Deutschlands. Die anderen drei Arten, Leucoagaricus atroalbusP.Mohr & R.M.Dähncke sp. nova, L. brunneosquamulosusP.Mohr & R.M.Dähncke sp. nova und Leucocoprinus canariensisP.Mohr & R.M.Dähncke sp. nova, wurden auf La Palma, Kanarische Inseln (Spanien) gefunden. Leucocoprinus mauritianus(Henn.) P.Mohr wird neu kombiniert, Leucocoprinus heinemanniiMigliozzi var. melanotrichoides P.Mohr neu aufgestellt. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) Four new species of Leucoagaricus and Leucocoprinus with brownish to fuliginous hues of the pileus Four new species of Leucoagaricus and Leucocoprinus are described and delineated against other similar species. Leucoagaricus fuligineodiscusP.Mohr & E.Ludwig sp. nova was found in Brandenburg in East Germany. The other three species Leucoagaricus atroalbusP.Mohr & R.M.Dähncke sp. nova, L. brunneosquamulosusP.Mohr & R.M.Dähncke sp. nova and Leucocoprinus canariensisP.Mohr & R.M.Dähncke sp. nova were collected in La Palma, Canary Islands (Spain). Leucocoprinus mauritianus(Henn.) P.Mohr is newly combined, Leucocoprinus heinemanniiMigliozzi var. melanotrichoidesP.Mohr is a new variety. [source] Ecological effects of regime shifts in the Bering Sea and eastern North Pacific OceanFISH AND FISHERIES, Issue 2 2002Ashleen J Benson Abstract Large-scale shifts occurred in climatic and oceanic conditions in 1925, 1947, 1977, 1989 and possibly 1998. These shifts affected the mix and abundance of suites of coexisting species during each period of relative environmental stability,from primary producers to apex predators. However, the 1989 regime shift was not a simple reversal of the 1977 shift. The regime shifts occurred abruptly and were neither random variations nor simple reversals to the previous conditions. Timing of these anomalous environmental events in the North Pacific Ocean appears to be linked to physical and biological responses in other oceanic regions of the world. Changes in the atmospheric pressure can alter wind patterns that affect oceanic circulation and physical properties such as salinity and depth of the thermocline. This, in turn, affects primary and secondary production. Data from the North Pacific indicate that regime shifts can have opposite effects on species living in different domains, or can affect similar species living within a single domain in opposite ways. Climatic forcing appears to indirectly affect fish and marine mammal populations through changes in the distribution and abundance of their predators and prey. Effects of regime shifts on marine ecosystems are also manifested faster at lower trophic levels. Natural variability in the productivity of fish stocks in association with regime shifts indicates that new approaches to managing fisheries should incorporate climatic as well as fisheries effects. [source] Convergence of fish communities from the littoral zone of reservoirsFRESHWATER BIOLOGY, Issue 6 2009KEITH B. GIDO Summary 1.,Understanding factors that regulate the assembly of communities is a main focus of ecology. Human-engineered habitats, such as reservoirs, may provide insight into these assembly processes because they represent novel habitats that are subjected to colonization by fishes from the surrounding river basin or transported by humans. By contrasting community similarity within and among reservoirs from different drainage basins to nearby stream communities, we can test the relative constraints of reservoir habitats and regional species pools in determining species composition of reservoirs. 2.,We used a large spatial database that included intensive collections from 143 stream and 28 reservoir sites within three major river basins in the Great Plains, U.S.A., to compare patterns of species diversity and community structure between streams and reservoirs and to characterize variation in fish community structure within and among major drainage basins. We expected reservoir fish faunas to reflect the regional species pool, but would be more homogeneous that stream communities because similar species are stocked and thrive in reservoirs (e.g. planktivores and piscivores), and they lack obligate stream organisms that are not shared among regional species pools. 3.,We found that fish communities from reservoirs were a subset of fishes collected from streams and dominant taxa had ecological traits that would be favoured in lentic environments. Although there were regional differences in reservoir fish communities, species richness, patterns of rank abundance and community structure in reservoir communities were more homogonous across three major drainage basins than for stream communities. 4.,The general pattern of convergence of reservoir fish community structure suggests their assembly is constrained by local factors such as habitat and biotic interactions, and facilitated by the introduction of species among basins. Because there is a reciprocal transfer of biota between reservoirs and streams, understanding factors structuring both habitats is necessary to evaluate the long-term dynamics of impounded river networks. [source] Ostracode faunas of bottom sediments from the continental shelf, south Marmara Sea, NW Turkey, and their comparison with other shelf environments in the Mediterranean and Aegean regionsGEOLOGICAL JOURNAL, Issue 2 2001Atike Nazik Abstract This study describes the ostracode faunal composition and distribution on the continental shelf of the southern Marmara Sea in Turkey. Twenty-three bottom samples were collected from the shelf. These samples are characterized by silt-clay (mud), sand and gravel in the studied area. A total of 46 species belonging to 32 genera were determined from these samples. Seven species were dominant from 46 ostracode species. Three assemblages were identified by their dominant species. These are characterized by: Costa edwardsii (Roemer); a mixed assemblage which consists of Cytheridea neapolitana Kollmann, Pterygocythereis ceratoptera (Bosquet), Tegmenia rugosa (Costa), Acanthocythereis hystrix (Reuss) and Xestoleberis communis (G.W. Müller); and Aurila convexa (Baird). The relations between the dominant species, lithology and CaCO3 concentration have been investigated, and the results are compared with other shelf environments within the Mediterranean and Aegean regions. Pterygocythereis, Costa, Tegmenia and Cytheridea are abundant in muddy substrates; Aurila and Acanthocythereis are abundant in sandy substrates. Acanthocythereis hystrix (Reuss), Aurila convexa (Baird), Buntonia subulata Ruggieri, Carinocythereis antiquata (Baird), Carinocythereis carinata (Roemer), Costa batei (Brady), Costa edwardsii (Roemer), Cytheridea neapolitana Kollmann, Celtia quadridentata (Baird), Loxoconcha rhomboidea (Fischer), Pterygocythereis jonesii (Baird) and Semicytherura acuticostata (Sars) are common, and similar species are recorded from other continental shelves of the Mediterranean. Copyright © 2001 John Wiley & Sons, Ltd. [source] Using presence signs to discriminate between similar speciesINTEGRATIVE ZOOLOGY (ELECTRONIC), Issue 3 2009Sara M. SANTOS Abstract The Lusitanian and the Mediterranean pine voles (Microtus lusitanicus Gerbe, 1879 and Microtus duodecimcostatus de Selys-Longchamps, 1839) are fossorial sister species and have an allopatric pattern of distribution in Portugal, which includes a potential sympatry area in the centre of the country. The present study aimed to determine the validity of using presence signs in the field for discrimination of the two species in an area of sympatry (Northern Alentejo) and the characteristics that achieve the best classification accuracy. A total of 175 trapping plots were sampled across the study area. Prior to the set up of traps, ten presence signs were randomly selected for measurements of four variables: proportion of soil mounds, mean diameter of mounds, proportion of burrow openings and mean diameter of burrow openings. On the basis of a classification tree analysis, results showed that presence signs can be used to discriminate plots inhabited by one or the other species in the studied sympatry area. The characteristic that most accurately enables species identification is the proportion of burrow openings: for every ten presence signs found in a plot, if more than eight have an opening, then it is inhabited by M. lusitanicus (i.e. mostly burrow openings with few or no mounds present); if eight or fewer have an opening, M. duodecimcostatus is present (i.e. mostly mounds with few or no burrow openings). [source] Spatial abundance structures in an assemblage of gall-forming sawfliesJOURNAL OF ANIMAL ECOLOGY, Issue 3 2004M. A. McGeoch Summary 1Examination of the fine-scale internal structure of species geographical ranges, and interspecific variation therein across landscapes, contributes to a more comprehensive understanding of the structure of geographical ranges. Two components of this internal structure that require further examination are the occurrence, extent and position of spatial autocorrelation, and relationships between the spatial abundance structures of closely related, ecologically similar species. 2Here we compare the abundance structures of an assemblage of gall-forming sawflies (Tenthredinidae) across a landscape. We identify the relative roles of spatial and non-spatial factors in explaining their abundance structures and test the hypothesis that sawfly density is explained by host plant quality, as has been demonstrated repeatedly at finer scales. We use these results to distinguish between alternative sets of mechanisms that may be operating at the landscape scale. 3Species densities were mainly multimodal across the landscape and significantly spatially structured, with patch, periodic and trend components. The abundance structures thus mimic those found generally for species across the full extent of their geographical ranges. 4Many abundance structure characteristics were unique to species, with differences in their correlogram profiles, distances over which densities were positively autocorrelated, and the absence of significant spatial structure in one species. 5In contrast to previous, fine-scale studies, host plant quality explained little of the variation in sawfly gall density across the landscape, whereas unexplained spatial structure contributed between 30% and 50%. Based on knowledge of the biology of these species and the absence of competitive interactions, species dispersal characteristics and the Moran effect are suggested as probable alternative hypotheses at this scale. 6Therefore, a spatial approach has identified the hierarchical nature of mechanisms underlying the population dynamics of this sawfly assemblage for the first time. Furthermore, it has highlighted the importance of spatial processes in explaining the densities of species at the landscape scale, as well as the individualistic nature of their abundance structures. [source] A test of methods for estimating population size of the invasive land snail Achatina fulica in dense vegetationJOURNAL OF APPLIED ECOLOGY, Issue 4 2002Paul G. Craze Summary 1Physical inaccessibility often complicates censuses of poorly mobile organisms. We therefore assessed the effectiveness of using a sample of quadrat counts to generate a population estimate corrected for inaccessible areas. The result is directly applicable to management of the introduced snail Achatina fulica on Ile aux Aigrettes, a small island off Mauritius, but also has implications for counting this and similar species elsewhere. Accurate counting of A. fulica is important given that this species is such a widespread and serious pest. 2Counts were made in 17 quadrats taken from a grid covering the island. These were used to produce one population estimate by interpolating for the rest of the grid using GIS software (method 1). A second estimate assumed equal density of snails in accessible and inaccessible parts of the 17 quadrats, again with the population estimate interpolated (method 2). 3Four further quadrats were cleared of vegetation and, by comparison of counts before and after clearance, the relationship between initial count and true snail number was estimated. This resulted in two further population estimates, with the relationship used to adjust counts in the 17 experimental quadrats before interpolation (methods 3 and 4). 4All four estimates were tested using 35 additional quadrats of two types. Type 1 quadrats were physically cleared of vegetation; type 2 quadrats were fully accessible without clearance. Predicted counts in these quadrats were assessed for accuracy by comparison with actual counts. 5The method 1 estimate was clearly inadequate; method 4 gave a consistent overestimate; method 2 gave the smallest error in both quadrat types. In type 1 quadrats, method 2 and 3 estimates were not significantly different and method 2 had a slight tendency to underestimate. Overall, for studies of A. fulica, method 2 is recommended. However, it should be noted that the study took place towards the end of the wet season. In the dry season, damp refuges under inaccessible vegetation may be more important and methods 3 and 4 may then give a better estimate. 6The population of A. fulica with shell length > 10 mm on Ile aux Aigrettes near the end of the wet season in 2000 was between 37 300 and 45 100, with 39 700 being the best estimate. 7The results underline the importance of considering inaccessible areas when accurate counts of species are needed, and a method is suggested by which a simple census technique can be adjusted. In the case of A. fulica, more accurate estimates of population size and distribution are invaluable in the management, monitoring and eradication of this invasive species. [source] Kinetic and heat transfer modeling of rubber blends' sulfur vulcanization with N - t -butylbenzothiazole-sulfenamide and N,N -di- t -butylbenzothiazole-sulfenamideJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007Likozar Abstract Vulcanization kinetics and heat transfer for various blends of natural (NR) and polybutadiene (BR) rubber were studied simultaneously using a mechanistic approach when developing vulcanization model kinetics. Rubber process analyzer (RPA), dynamic scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR) methods were used for the study. The model reaction scheme was based on one of the best possible proposed individual reaction mechanisms. Molecular modeling was applied to distinguish between the reactivity of chemically similar species. The kinetics of N - t -butylbenzothiazole-sulfenamide (TBBS) and N,N -di- t -butylbenzothiazole-sulfenamide (TBSI) were treated separately using FTIR experiment data, and then incorporated in a model suitable for two-accelerator vulcanization. The proposed model quite well describes the thermal equilibration during the induction period despite a few simplifications. During cure and over-cure periods the course of vulcanization was described using a rigorous kinetic model. Physical and chemical model parameters were calculated from experimental data. Average heat transfer coefficient minimum during induction period was found to be at a weight ratio of BR and NR 1 : 1. The activation energy of significant reactions between rubber and other species was found to vary linearly with vulcanization compound composition. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 293,307, 2007 [source] Species,area relationships in Mediterranean-climate plant communitiesJOURNAL OF BIOGEOGRAPHY, Issue 11 2003Jon E. Keeley Abstract Aim To determine the best-fit model of species,area relationships for Mediterranean-type plant communities and evaluate how community structure affects these species,area models. Location Data were collected from California shrublands and woodlands and compared with literature reports for other Mediterranean-climate regions. Methods The number of species was recorded from 1, 100 and 1000 m2 nested plots. Best fit to the power model or exponential model was determined by comparing adjusted r2 values from the least squares regression, pattern of residuals, homoscedasticity across scales, and semi-log slopes at 1,100 m2 and 100,1000 m2. Dominance,diversity curves were tested for fit to the lognormal model, MacArthur's broken stick model, and the geometric and harmonic series. Results Early successional Western Australia and California shrublands represented the extremes and provide an interesting contrast as the exponential model was the best fit for the former, and the power model for the latter, despite similar total species richness. We hypothesize that structural differences in these communities account for the different species,area curves and are tied to patterns of dominance, equitability and life form distribution. Dominance,diversity relationships for Western Australian heathlands exhibited a close fit to MacArthur's broken stick model, indicating more equitable distribution of species. In contrast, Californian shrublands, both postfire and mature stands, were best fit by the geometric model indicating strong dominance and many minor subordinate species. These regions differ in life form distribution, with annuals being a major component of diversity in early successional Californian shrublands although they are largely lacking in mature stands. Both young and old Australian heathlands are dominated by perennials, and annuals are largely absent. Inherent in all of these ecosystems is cyclical disequilibrium caused by periodic fires. The potential for community reassembly is greater in Californian shrublands where only a quarter of the flora resprout, whereas three quarters resprout in Australian heathlands. Other Californian vegetation types sampled include coniferous forests, oak savannas and desert scrub, and demonstrate that different community structures may lead to a similar species,area relationship. Dominance,diversity relationships for coniferous forests closely follow a geometric model whereas associated oak savannas show a close fit to the lognormal model. However, for both communities, species,area curves fit a power model. The primary driver appears to be the presence of annuals. Desert scrub communities illustrate dramatic changes in both species diversity and dominance,diversity relationships in high and low rainfall years, because of the disappearance of annuals in drought years. Main conclusions Species,area curves for immature shrublands in California and the majority of Mediterranean plant communities fit a power function model. Exceptions that fit the exponential model are not because of sampling error or scaling effects, rather structural differences in these communities provide plausible explanations. The exponential species,area model may arise in more than one way. In the highly diverse Australian heathlands it results from a rapid increase in species richness at small scales. In mature California shrublands it results from very depauperate richness at the community scale. In both instances the exponential model is tied to a preponderance of perennials and paucity of annuals. For communities fit by a power model, coefficients z and log c exhibit a number of significant correlations with other diversity parameters, suggesting that they have some predictive value in ecological communities. [source] Inhibitory effects of Cu, Zn, Ni and Co on nitrification and relevance of speciationJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 4 2010Ferhan Çeçen Abstract BACKGROUND: The speciation of metals is often overlooked in understanding their observed inhibitory effect in biological systems, in particular in nitrification systems. This study examines the effects of Cu, Zn, Ni and Co on a nitrifying sludge, where the aim is to relate inhibition to speciation. RESULTS: Nitrification inhibition was monitored by O2 and CO2 measurements, an approach rarely followed to date. The IC50 value of each metal was expressed in terms of total, free and labile metal. Zn and Cu formed similar species, but had different free and labile fractions. Although free and labile fractions of Cu were much lower than the others, it was the most inhibitory metal. Ni and Co exhibited quite different inhibitory effects on nitrification despite the formation of similar metal species. Co was the least inhibitory metal and exhibited its effect very slowly. CONCLUSION: The study is among the few which examine inhibition and speciation of several metals in a comparative way. In the same nitrification medium each metal formed different species, which is a factor to be considered in interpretation of inhibition. The results may be projected to nitrifying systems to clarify the underlying factors in inhibition. Copyright © 2009 Society of Chemical Industry [source] A precise water displacement method for estimating egg volumeJOURNAL OF FIELD ORNITHOLOGY, Issue 2 2009Scott A. Rush ABSTRACT Relationships between egg volume and an array of life-history traits have been identified for many bird species. Despite the importance of egg volume and the need for precise and accurate measurements, egg volume is usually estimated using a mathematical model that incorporates length and width measurements along with a shape variable. We developed an instrument that provides precise estimates of egg volume and can be easily used in the field. Using Clapper Rail (Rallus longirostris) eggs, we compared egg volumes measured using our instrument with estimates based on linear measurements. We found our instrument to be both precise and accurate. Compared with a method based on linear measurements of eggs, use of our instrument reduced variation in egg volume estimates by 1.6 cm3, approximately 8% of the volume of a Clapper Rail's egg. Further advantages of our technique include ease of use, increased accuracy of field-based volume estimates, and increased resolution of variation in egg volume estimates. In addition, our technique does not require postdata collection processing time and did not influence hatching success. Also, for Clapper Rails and similar species, our technique can be combined with other techniques (e.g., egg flotation) so that both egg volume and embryonic stage can be estimated at the same time. SINOPSIS Las relaciones entre el volumen del huevo y una gran cantidad de caracteres en las historias de vida han sido identificadas para muchas especies de aves. A pesar de la importancia del volumen del huevo y la necesidad de medidas más precisas, el volumen del huevo es comúnmente estimado usando modelos matemáticos que incorporan medidas del largo, ancho y forma del huevo. Nosotros creamos un instrumento que proporciona estimativos precisos del volumen del huevo y puede ser fácilmente usado en el campo. Usando huevos de Rallus longirostris comparamos las medidas de los volúmenes de los huevos usando nuestro instrumento con estimados obtenidos mediante mediadas lineales. Encontramos que nuestro instrumento fue preciso. Comparado con métodos que se basan en medidas lineales de los huevos, el uso de nuestro instrumento reduce la variación de los estimativos del volumen de los huevos en 1.6 cm3, aproximadamente 8% del volumen de los huevos de Rallus longirostris. Ventajas adicionales de nuestra técnica incluye facilidades de uso, incremento en la precisión en los estimativos de volumen realizados en el campo y un incremento en la disminución de la variación de los estimativos del volumen del huevo. Adicionalmente, nuestra técnica no requiere tiempo de manejo después de la colección de los datos, y no afecta el éxito de eclosión. También, para Rallus longirostris y especies similares, nuestra técnica puede ser combinada con otras técnicas (e. g., flotación de los huevos) de tal forma que simultáneamente se puedan estimar el volumen del huevo y el estadio embrionario. [source] Distinguishing between two sympatric Acanthopagrus species from Dapeng Bay, Taiwan, using morphometric and genetic charactersJOURNAL OF FISH BIOLOGY, Issue 2 2009M. C. Tseng Morphometric and genetic data were used to compare two sympatric and morphologically similar species, Acanthopagrus berda and Acanthopagrus taiwanensis, in Dapeng Bay, South-western Taiwan. A principle component analysis of morphological data indicated a distinction between the two species, with pectoral fin length and eye diameter accounting for 32·27% of the variation. Interspecific sequence divergence, based on mtDNA cytochrome b (0·118 ± 0·01), was larger than intraspecific divergences between haplotypes (0·007 for A. taiwanensis and 0·003 for A. berda). Individuals of the two species clustered into different groups in three phylogenetic trees with 100% bootstrap support. The mean observed heterozygosity for eight microsatellite loci was 0·471 ± 0·202 for A. taiwanensis and 0·637 ± 0·145 for A. berda. Nei's unbiased measure of interspecific genetic distance (DS) was 1·334. FST (0·134) and RST (0·404) values indicated significant differentiation between species. An unrooted neighbour-joining tree was constructed by allele-sharing distances and the factorial correspondence analysis split all specimens into two distinct clusters. The results of morphometric, mtDNA and microsatellite analyses indicated the presence of two species, A. taiwanensis and A. berda. [source] Behavioural interactions between native smokey dace and introduced yellowfin shiner: implications from habitat selection theory for an ongoing invasionJOURNAL OF FISH BIOLOGY, Issue 2003C. M. Wagner The occupation of adjacent, non-overlapping positions along environmental gradients by closely related and ecologically similar species has drawn considerable attention from ecologists over the past decades. Condition-specific competition, wherein competitive superiority varies with the abiotic environmental gradient, has been proposed as the major structuring force behind such distributions. These concepts, however, are generally applied to explain the contemporary distribution of organisms that share an evolutionary history. Our aim was to apply these concepts to the naive interactions between native and introduced fishes. In 1990 yellowfin shiner (Notropis lutipinnis) were introduced into the headwaters of the Little Tennessee River of western North Carolina, U.S.A. where it exhibits microhabitat preferences that overlap significantly with those of a threatened native minnow, the smokey dace (Clinostomus funduloides raneyi). Previous research has established that these drift-feeding minnows: (1) differ in their average ability to intercept drifting prey as a function of water velocity; (2) generally occupy focal-point velocities that maximize the rate of prey capture; and, (3) occasionally defend the forward positions in foraging aggregations that form in high quality patches. We present the results of a series of experiments designed to: (1) evaluate the role of aggression in the establishment and maintenance of preferred foraging positions in drift-feeding minnows; (2) test the effects of prey availability, group size, and velocity on dominance rank, spatial position in groups, and feeding rates of individuals; and, (3) evaluate the potential for condition-specific competition to establish competitive refugia for the native within the natural heterogeneity of mountain streams. [source] PHYLOGENETIC RELATIONSHIPS WITHIN THE GENUS HYPNEA (GIGARTINALES, RHODOPHYTA), WITH A DESCRIPTION OF H. CAESPITOSA SP.JOURNAL OF PHYCOLOGY, Issue 2 2010Species discrimination within the gigartinalean red algal genus Hypnea has been controversial. To help resolve the controversy and explore phylogeny within the genus, we determined rbcL sequences from 30 specimens of 23 species within the genus, cox1 from 22 specimens of 10 species, and psaA from 16 species. We describe H. caespitosa as a new species characterized by a relatively slender main axis; a pulvinate growth habit with entangled, anastomosing, and subulate uppermost branches; and unilaterally borne tetrasporangial sori. The new species occurs in the warm waters of Malaysia, the Philippines, and Singapore. The phylogenetic trees of rbcL, psaA, and cox1 sequences showed a distant relationship of H. caespitosa to H. pannosa J. Agardh from Baja California and the marked differentiation from other similar species. The rbcL + psaA tree supported monophyly of the genus with high bootstrap values and posterior probabilities. The analysis revealed three clades within the genus, corresponding to three sections, namely, Virgatae, Spinuligerae, and Pulvinatae first recognized by J. G. Agardh. Exceptions were H. japonica T. Tanaka in Pulvinatae and H. spinella (C. Agardh) Kütz. in Spinuligerae. [source] Disturbance dynamics of old-growth Picea rubens forests of northern MaineJOURNAL OF VEGETATION SCIENCE, Issue 5 2005Shawn Fraver Abstract Question: How have the spatial and temporal aspects of past disturbance shaped the current structure and composition of old-growth Picea rubens forests? Location: Northern Maine, USA. Methods: We established three 50 m × 50 m plots in old-growth Picea rubens forests and mapped the location of trees and saplings. We extracted increment cores from canopy trees, and recorded growth releases indicating past disturbance. By linking spatial data (tree positions) and temporal data (dated growth releases), we reconstructed the location and size of former canopy gaps back to 1920, and determined a more general disturbance chronology extending as far back as 1740. Results: We found no evidence of stand-replacing disturbances. The disturbance dynamic includes pulses of moderate-severity disturbances caused by wind storms and host-specific disturbance agents (spruce budworm, spruce bark beetle) interposed upon a background of scattered smaller canopy gaps. Consequently, rates of disturbance fluctuated considerably over time. Reconstructed canopy gaps were temporally and spatially scattered; during disturbance peaks, they were both larger and more numerous. Conclusions: Despite peaks in disturbance, several of which created relatively large gaps, this system has experienced no significant change in species composition. Instead, the shade-tolerant Picea rubens has maintained canopy dominance. The patch dynamics described here consist of dramatic structural, not compositional, changes to the forest. The persistence of Picea rubens is attributed to a combination of traits: (1) abundance of advance regeneration; (2) ability to endure suppression and respond favourably to release; and (3) longevity relative to ecologically similar species. [source] Genetic effective size, Ne, tracks density in a small freshwater cyprinid, Pecos bluntnose shiner (Notropis simus pecosensis)MOLECULAR ECOLOGY, Issue 14 2010MEGAN J. OSBORNE Abstract Genetic monitoring tracks changes in measures of diversity including allelic richness, heterozygosity and genetic effective size over time, and has emerged as an important tool for understanding evolutionary consequences of population management. One proposed application of genetic monitoring has been to estimate abundance and its trajectory through time. Here, genetic monitoring was conducted across five consecutive year for the Pecos bluntnose shiner, a federally threatened minnow. Temporal changes in allele frequencies at seven microsatellite DNA loci were used to estimate variance effective size (NeV) across adjacent years in the time series. Likewise, effective size was computed using the linkage disequilibrium method (NeD) for each sample. Estimates of Ne were then compared to estimates of adult fish density obtained from traditional demographic monitoring. For Pecos bluntnose shiner, density (catch-per-unit-effort), NeV and NeD were positively associated across this time series. Results for Pecos bluntnose shiner were compared to a related and ecologically similar species, the Rio Grande silvery minnow. In this species, density and NeV were negatively associated, which suggested decoupling of abundance and effective size trajectories. Conversely, density and NeD were positively associated. For Rio Grande silvery minnow, discrepancies among estimates of Ne and their relationships with adult fish density could be related to effects of high variance in reproductive success in the wild and/or effects of supplementation of the wild population with captive-bred and reared fish. The efficacy of Ne as a predictor of density and abundance may depend on intrinsic population dynamics of the species and how these dynamics are influenced by the landscape features, management protocols and other factors. [source] Up against the edge: invasive species as testbeds for basic questions about evolution in heterogeneous environmentsMOLECULAR ECOLOGY, Issue 21 2009ROBERT D. HOLT Yogi Berra is often credited, with having opined that ,prediction is very difficult, especially about the future'. There is no discipline for which this statement holds with more force than invasion biology, where it has been historically very challenging to predict the fate of introduced species (Williamson 2006). Some species after introduction quickly go extinct. Other relatively similar species may persist, but with little spread from their initial beachheads. Yet others can become aggressive invaders, with devastating consequences for native communities and ecosystems. This lack of predictability may of course sometimes reflect a simple lack of knowledge, both about key features of a species' basic biology, and about the environmental and community milieu in which invasion occurs (Williamson 2006). However, unpredictability may also arise from a fundamental fact about populations of living organisms , they almost always contain genetic variation, and so are not fixed entities responding to an environmental template, but instead labile in how they cope with the environment, over many spatial and temporal scales. Chance vicissitudes in the origination, maintenance and spatial organization of genetic variation could play a large role in generating the observed unpredictability in the fates of introduced species. The degree to which a particular introduced species becomes ,invasive', to the extent of coming to the attention of worried land managers, governmental officials and the public , may reflect in part its capacity for adaptive evolution across a wide range of environmental conditions. [source] Evolution on oceanic islands: molecular phylogenetic approaches to understanding pattern and processMOLECULAR ECOLOGY, Issue 6 2002B. C. Emerson Abstract By their very nature oceanic island ecosystems offer great opportunities for the study of evolution and have for a long time been recognized as natural laboratories for studying evolution owing to their discrete geographical nature and diversity of species and habitats. The development of molecular genetic methods for phylogenetic reconstruction has been a significant advance for evolutionary biologists, providing a tool for answering questions about the diversity among the flora and fauna on such islands. These questions relate to both the origin and causes of species diversity both within an archipelago and on individual islands. Within a phylogenetic framework one can answer fundamental questions such as whether ecologically and/or morphologically similar species on different islands are the result of island colonization or convergent evolution. Testing hypotheses about ages of the individual species groups or entire community assemblages is also possible within a phylogenetic framework. Evolutionary biologists and ecologists are increasingly turning to molecular phylogenetics for studying oceanic island plant and animal communities and it is important to review what has been attempted and achieved so far, with some cautionary notes about interpreting phylogeographical pattern on oceanic islands. [source] On Hieracium incurrens (Asteraceae) and similar species in central SwedenNORDIC JOURNAL OF BOTANY, Issue 3-4 2007Torbjörn Tyler Hieracium incurrens Saelan ex Norrl., originally described from Finland, has been reported from Sweden several times and independently by different authors. Still, however, its presence in Sweden has remained dubious and it has become obvious that the different reports are referable to different taxa and the name has thus been, at least partially, misapplied. In the present study, all Swedish material and putative taxa that have been suggested to belong to H. incurrens, as well as some additional closely similar taxa, is critically compared with authentic material of the latter from Finland. It is concluded that H. incurrens do indeed occur in central Sweden, namely in the eastern coastal provinces closest to Finland. However, the relevant material has mostly been referred to H. longilingua Johanss., which is here considered to be a later synonym of H. incurrens. Material previously referred to H. incurrens from other parts of Sweden does, however, represent other taxa. Five accepted species of this affinity are described and discussed in some detail and one species, viz. H. oestmanii T. Tyler is described anew. In addition, the unrelated species H. arnoldii T. Tyler is described anew based on material from the provinces of Hälsingland and Medelpad. [source] Impact of released Eurasian otters on a population of American mink: a test using an experimental approachOIKOS, Issue 1 2004L. Bonesi Competition is considered to be a major evolutionary driving force within assemblages of related and morphologically similar species, but it is notoriously difficult to test and quantify especially amongst species that cannot be easily manipulated in a laboratory or in the field. By exploiting a re-introduction of Eurasian otters (Lutra lutra) in the Upper Thames catchment (UK) in 1999 we performed an experiment to test whether there was evidence of competition between otters and American mink (Mustela vison). Mink and otters are semi-aquatic mustelids belonging to the same guild. Otters are expected to be the dominant competitor because they are larger and better adapted at exploiting aquatic resources. Our hypothesis was that mink declines when the density of otters increases. We measured the effect of competition at the population level, by observing whether mink distribution and densities changed in an area of 1353 km2 in association with the arrival of its putative competitor. We estimated distribution and densities by means of sign surveys and trapping. The results showed that otters were associated with a significant and rapid reduction in the densities of mink, while mink occupancy remained approximately the same in an area of 2464 km2 that was used as a control. We observed that the spatial distribution of the mink population throughout its decline was influenced by the yearly cycle of mink activities, with areas being temporarily re-colonized during the dispersal season. Mink is an invasive species in the UK threatening the survival of some native species. Our findings suggest that the re-establishment of otter populations is likely to lead to a decline of mink that may, in turn, be beneficial to native species threatened by this invasive. [source] A NEW MICROCHOERINE OMOMYID (PRIMATES, MAMMALIA) FROM THE ENGLISH EARLY EOCENE AND ITS PALAEOBIOGEOGRAPHICAL IMPLICATIONSPALAEONTOLOGY, Issue 3 2007J. J. HOOKER Abstract:, A new genus and species of omomyid primate, Melaneremia bryanti, is described from the Early Eocene Blackheath Beds of Abbey Wood, London, UK. It shares unique derived characters with the European subfamily Microchoerinae and is its most primitive member. It is nevertheless more derived than the primitive omomyid Teilhardina belgica from the beginning of the European Eocene. Cladistic analysis shows that the Microchoerinae are sister group to a clade comprising subfamilies Omomyinae and Anaptomorphinae, but excluding Teilhardina belgica and T. asiatica, which are stem omomyids. The Mammalian Dispersal Event (MDE), which marks the beginning of the Eocene (55·8 Ma), saw the dispersal of primates, perissodactyls and artiodactyls into the Northern Hemisphere. At this time similar species of Teilhardina lived in Europe, Asia and North America. The Abbey Wood microchoerine lived about 1 million years later. It co-occurs with non-primate species identical or very similar to those that lived in North America. The latter were ground-dwellers, whereas the microchoerine and others that show distinct differences from North American relatives were tree-dwellers. Land-bridges connected North America and Europe via Greenland at the beginning of the Eocene, but 2 million years later these had been severed by submarine rifting. North American species at Abbey Wood indicate that a land connection still remained at c. 55 Ma. However, the forest belt that must have been continuous during the MDE to allow tree-dwellers to disperse between the continents is likely by this time to have been disrupted, perhaps by volcanic eruption. [source] Microcostatus schoemanii sp. nov., M. cholnokyi sp. nov. and M. angloensis sp. nov. three new terrestrial diatoms (Bacillariophyceae) from South AfricaPHYCOLOGICAL RESEARCH, Issue 3 2010Jonathan C. Taylor SUMMARY The terrestrial diatom Microcostatus schoemanii sp. nov. is described from dry soils of the Faan Meintjies Nature Reserve (North-West Province, South Africa). Microcostatus cholnokyi sp. nov. and Microcostatus angloensis sp. nov. are described from sandy soils at a colliery near the town of Kriel (Mpumalanga Province, South Africa). The morphology of these taxa is examined using both light and scanning electron microscopy and new taxa are compared with similar species. In M. schoemanii the density of the striae combined with the valve outline and the distance between the central raphe endings are the main distinguishing morphological features. M. cholnokyi is differentiated by the presence of a conopeum and the distinct structure of the microcostae. M. angloensis is similar to M. schoemanii but differentiated by the shape of the cell and the apices, the angle of striation and the distance in between the proximal raphe endings. [source] Oxytocin and vasopressin receptor distributions in a solitary and a social species of tuco-tuco (Ctenomys haigi and Ctenomys sociabilis)THE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 6 2008Annaliese K. Beery Abstract The neuropeptides oxytocin and vasopressin and their receptors have been implicated in elements of mammalian social behavior such as attachment to mates and offspring, but their potential role in mediating other types of social relationships remains largely unknown. We performed receptor autoradiography to assess whether forebrain oxytocin receptor (OTR) or vasopressin V1a receptor (V1aR) distributions differed with social structure in two closely related and ecologically similar species of South American rodents, the colonial tuco-tuco (Ctenomys sociabilis) and the Patagonian tuco-tuco (Ctenomys haigi). Long-term field studies have revealed that C. haigi is solitary, whereas C. sociabilis is social and provides a model of female-based group living. Our analyses revealed marked differences in OTR and V1aR distributions between these species. For example, only C. sociabilis had OTR binding in the piriform cortex and thalamus and V1aR binding in the olfactory bulbs. In contrast, C. haigi exhibited dramatically higher levels of OTR binding throughout the lateral septum and hippocampus. More generally, the group-living C. sociabilis exhibited a pattern of nucleus accumbens OTR and ventral pallidum V1aR binding different from that associated with the formation of opposite-sex pair bonds in microtine rodents. Higher binding in the central nucleus of the amygdala of C. sociabilis was consistent with the hypothesis that formation of social groups in C. sociabilis may be facilitated by reduced social anxiety. Low OTR binding in the lateral septum might also be a permissive factor for group living in C. sociabilis. Future studies will expand on these analyses to explore interspecific differences in ctenomyid receptor binding patterns in a phylogenetic context. J. Comp. Neurol. 507:1847,1859, 2008. © 2008 Wiley-Liss, Inc. [source] Modelling species distribution at multiple spatial scales: gibbon habitat preferences in a fragmented landscapeANIMAL CONSERVATION, Issue 3 2010T. N. E. Gray Abstract Conservation of Indochinese primates is hampered by a lack of knowledge of species ecology, habitat preferences and, locally, distribution. Predictive distribution and habitat suitability models, using predictors known to affect the distribution of similar species elsewhere, may, therefore be of great benefit to conservationists within the region. Yellow-cheeked crested gibbon Nomascus gabriellae is an IUCN-listed endangered primate distributed east of the Mekong River in Cambodia, southern Vietnam, and possibly southern Lao PDR. Within Cambodia, yellow-cheeked crested gibbon are naturally restricted to evergreen forest fragments within a landscape matrix of deciduous dipterocarp and semi-evergreen forests. During the 2008 dry season, auditory surveys for yellow-cheeked crested gibbon were conducted within Phnom Prich Wildlife Sanctuary, Mondulkiri province, Cambodia. Predictive distribution models, in which variables were included at the scale at which they best explained gibbon occurrence (multi-grain models), were constructed to examine the species' habitat associations and tolerance of habitat fragmentation within the wildlife sanctuary. Gibbon occupancy (,) was higher in evergreen (0.43±0.26,0.62) than in semi-evergreen forest (0.21±0.09,0.4), with gibbon presence constrained by a critical amount of evergreen forest within 5 km radius of listening posts. Three patches of optimal habitat within Phnom Prich Wildlife Sanctuary were identified. These, and connecting habitats, should be the target of increased enforcement effort to limit hunting and habitat conversion. Similar multi-grain models are likely to be valuable for conservationists within mosaic habitats as they can facilitate identification of the minimum suitable fragment size for species of conservation concern. [source] | ||||||||||||||||||||||||||||||||||