Home About us Contact
|
Home About us Contact | ||
|
|
||
Species Accumulation (species + accumulation)
Terms modified by Species Accumulation Selected AbstractsSpatial and temporal variation of abundance, biomass and diversity within marine reserves in the PhilippinesDIVERSITY AND DISTRIBUTIONS, Issue 4 2010Jonathan A. Anticamara Abstract Aim, The objective of this study was to investigate the influence of protection duration (years of fishing closure) and location (distance from shore) on reef fish diversity. Location, Danajon Double Barrier Reef, Bohol, Philippines. Methods, Reef fish abundance and size structure, by species, were obtained monthly using replicated underwater visual belt transects (n = 8; 70 × 5-m belt transects) over 3 years (2002,2005) at eight sites that included six marine reserves and two unprotected reef areas. We analysed species accumulation curves, diversity indices and abundance,biomass comparison (ABC) curves within and across the study sites to assess the influence of protection duration and location. Results, Analyses showed that longer protection duration impacted reef fish diversity at both inshore and offshore sites by shifting ABC curves from higher abundance than biomass curves at fished sites to higher biomass than abundance curves at most of the protected sites. Protection duration did not significantly influence either the rate of species accumulation within sites or the 12 diversity indices measured across the study sites. The offshore sites consistently showed higher rates of species accumulation and diversity indices values than inshore sites with similar protection duration. One protected offshore young marine reserve site that has been assessed as the least well-managed showed patterns more consistent with the fished sites. Main conclusions, Analyses showed that protection duration mainly impacted diversity by increasing the dominance of large-bodied species and enhancing total biomass. Besides protection duration, reserve location influenced species accumulation curves and diversity indices. [source] On the estimation of species richness based on the accumulation of previously unrecorded speciesECOGRAPHY, Issue 1 2002Emmanuelle Cam Estimation of species richness of local communities has become an important topic in community ecology and monitoring. Investigators can seldom enumerate all the species present in the area of interest during sampling sessions. If the location of interest is sampled repeatedly within a short time period, the number of new species recorded is typically largest in the initial sample and decreases as sampling proceeds, but new species may be detected if sampling sessions are added. The question is how to estimate the total number of species. The data collected by sampling the area of interest repeatedly can be used to build species accumulation curves: the cumulative number of species recorded as a function of the number of sampling sessions (which we refer to as "species accumulation data"). A classic approach used to compute total species richness is to fit curves to the data on species accumulation with sampling effort. This approach does not rest on direct estimation of the probability of detecting species during sampling sessions and has no underlying basis regarding the sampling process that gave rise to the data. Here we recommend a probabilistic, nonparametric estimator for species richness for use with species accumulation data. We use estimators of population size that were developed for capture-recapture data, but that can be used to estimate the size of species assemblages using species accumulation data. Models of detection probability account for the underlying sampling process. They permit variation in detection probability among species. We illustrate this approach using data from the North American Breeding Bird Survey (BBS). We describe other situations where species accumulation data are collected under different designs (e.g., over longer periods of time, or over spatial replicates) and that lend themselves to of use capture-recapture models for estimating the size of the community of interest. We discuss the assumptions and interpretations corresponding to each situation. [source] The myth of plant species saturationECOLOGY LETTERS, Issue 4 2008Thomas J. Stohlgren Abstract Plant species assemblages, communities or regional floras might be termed ,saturated' when additional immigrant species are unsuccessful at establishing due to competitive exclusion or other inter-specific interactions, or when the immigration of species is off-set by extirpation of species. This is clearly not the case for state, regional or national floras in the USA where colonization (i.e. invasion by exotic species) exceeds extirpation by roughly a 24 to 1 margin. We report an alarming temporal trend in plant invasions in the Pacific Northwest over the past 100 years whereby counties highest in native species richness appear increasingly invaded over time. Despite the possibility of some increased awareness and reporting of native and exotic plant species in recent decades, historical records show a significant, consistent long-term increase in exotic species (number and frequency) at county, state and regional scales in the Pacific Northwest. Here, as in other regions of the country, colonization rates by exotic species are high and extirpation rates are negligible. The rates of species accumulation in space in multi-scale vegetation plots may provide some clues to the mechanisms of the invasion process from local to national scales. [source] PHYLOGENETIC ANALYSIS OF ECOMORPHOLOGICAL DIVERGENCE, COMMUNITY STRUCTURE, AND DIVERSIFICATION RATES IN DUSKY SALAMANDERS (PLETHODONTIDAE: DESMOGNATHUS)EVOLUTION, Issue 9 2005Kenneth H. Kozak Abstract An important dimension of adaptive radiation is the degree to which diversification rates fluctuate or remain constant through time. Focusing on plethodontid salamanders of the genus Desmognathus, we present a novel synthetic analysis of phylogeographic history, rates of ecomorphological evolution and species accumulation, and community assembly in an adaptive radiation. Dusky salamanders are highly variable in life history, body size, and ecology, with many endemic lineages in the southern Appalachian Highlands of eastern North America. Our results show that lifehistory evolution had important consequences for the buildup of plethodontid-salamander species richness and phenotypic disparity in eastern North America, a global hot spot of salamander biodiversity. The origin of Desmognathus species with aquatic larvae was followed by a high rate of lineage accumulation, which then gradually decreased toward the present time. The peak period of lineage accumulation in the group coincides with evolutionary partitioning of lineages with aquatic larvae into seepage, stream-edge, and stream microhabitats. Phylogenetic simulations demonstrate a strong correlation between morphology and microhabitat ecology independent of phylogenetic effects and suggest that ecomorphological changes are concentrated early in the radiation of Desmognathus. Deep phylogeographic fragmentation within many codistributed ecomorph clades suggests long-term persistence of ecomorphological features and stability of endemic lineages and communities through multiple climatic cycles. Phylogenetic analyses of community structure show that ecomorphological divergence promotes the coexistence of lineages and that repeated, independent evolution of microhabitat-associated ecomorphs has a limited role in the evolutionary assembly of Desmognathus communities. Comparing and contrasting our results to other adaptive radiations having different biogeographic histories, our results suggest that rates of diversification during adaptive radiation are intimately linked to the degree to which community structure persists over evolutionary time. [source] Beta diversity of frogs in the forests of New Guinea, Amazonia and Europe: contrasting tropical and temperate communitiesJOURNAL OF BIOGEOGRAPHY, Issue 5 2009Chris Dahl Abstract Aim, To test the hypothesis that animal communities within environmentally relatively uniform lowland forests are characterized by low beta diversity, both in tropical and in temperate areas. Location, Lowland forests in the basins of the Sepik and Ramu rivers in New Guinea, the Amazon river in Bolivia, and the Elbe and Dyje rivers in the Czech Republic. Methods, A network of 5,6 study sites spanning distances from 20,80 to 300,500 km in each study area was systematically surveyed for all frogs, using visual detection and call tracking. The community data were analysed for alpha and beta diversity. Results, Local (alpha) diversity of frog communities was similar in the two tropical areas, New Guinea (mean ± SE of 22 ± 1.4 species per site) and Amazonia (24 ± 1.7 species), but was significantly lower in Europe (8 ± 0.8 species). In Amazonia, 36 of the total of 70 species were recorded from single sites. In contrast, widespread species dominated in Europe, whereas New Guinea exhibited an intermediate pattern with both local and widespread species well represented. The rate of species accumulation across different sites was lowest in Europe, intermediate in New Guinea and highest in Amazonia. The regional species diversity, expressed as the combined number of species from five study sites, was 1.5 times higher than the local species diversity at a single site in Europe, 2.0 times higher in New Guinea and 2.7 times higher in Amazonia. The proportion of species shared between communities decreased with geographic distance in New Guinea and Europe, but not in Amazonia. Main conclusions, Frog communities in the lowland tropical rain forests of New Guinea and Amazonia had similar numbers of species, but differed in their beta diversity. More species in Amazonia had restricted distributions than in New Guinea. Both tropical areas had markedly higher alpha and beta diversity than the temperate area in Europe. [source] Forest plant species richness in small, fragmented mixed deciduous forest patches: the role of area, time and dispersal limitationJOURNAL OF BIOGEOGRAPHY, Issue 6 2001Hans Jacquemyn Aim The research aimed to investigate how plant species richness of small, fragmented forest patches changes over time. Also interactions between time and area were studied in relation to species richness. Finally, the relative importance of plant dispersal limitation on the process of species accumulation was examined by investigating how species were distributed within a regional landscape. Location Mixed deciduous forest patches in central Belgium. Methods The land use history of a region of 80 km2 was reconstructed using nine historical maps dating from 1775 to 1991. Within a central area of 42 km2, 241 forest patches were surveyed for presence/absence of 203 species predominantly occurring in forests. Aggregation of species within this region was estimated using a Monte Carlo simulation. Spatial and temporal patterns of species richness were investigated by both regression and analysis of variance (ANOVA). Results Fifty-one of 103 species showed significant spatial aggregation patterns, suggesting severe dispersal limitation. Species richness significantly increased with age. However, the effects of time on species richness could not be separated from area and area and time clearly interacted. Slopes of regression equations for species number on area and patch age were shown to be significantly interrelated. Main conclusions Area and time cannot be treated independently as predictors of plant species richness. Dispersal proved to be important in structuring local forest plant community composition, contrary to most other studies that have investigated local forest plant community structure. The processes of forest succession and species accumulation are controlled by both local and regional processes. More studies focusing on the regional factors determining local community composition are needed in order to fully understand the process of forest plant community assembly. [source] Nicotinamide phosphoribosyltransferase imparts human endothelial cells with extended replicative lifespan and enhanced angiogenic capacity in a high glucose environmentAGING CELL, Issue 2 2009Nica M. Borradaile Summary Endothelial dysfunction is a characteristic of aging-related vascular disease and is worsened during diabetes. High glucose can impair endothelial cell (EC) function through cellular accumulation of reactive oxygen species, an insult that can also limit replicative lifespan. Nicotinamide phosphoribosyltransferase (Nampt), also known as PBEF and visfatin, is rate-limiting for NAD+ salvage from nicotinamide and confers resistance to oxidative stress via SIRT1. We therefore sought to determine if Nampt expression could resist the detrimental effects of high glucose and confer a survival advantage to human vascular EC in this pathologic environment. Human aortic EC were infected with retrovirus encoding eGFP or eGFP-Nampt, and FACS-selected to yield populations with similar, modest transgene expression. Using a chronic glucose exposure model we tracked EC populations to senescence, assessed cellular metabolism, and determined in vitro angiogenic function. Overexpression of Nampt increased proliferation and extended replicative lifespan, and did so preferentially during glucose overload. Nampt expression delayed markers of senescence and limited reactive oxygen species accumulation in high glucose through a modest increase in aerobic glycolysis. Furthermore, tube networks formed by Nampt-overexpressing EC were more extensive and glucose-resistant, in accordance with SIRT1-mediated repression of the anti-angiogenic transcription factor, FoxO1. We conclude that Nampt enables proliferating human EC to resist the oxidative stress of aging and of high glucose, and to productively use excess glucose to support replicative longevity and angiogenic activity. Enhancing endothelial Nampt activity may thus be beneficial in scenarios requiring EC-based vascular repair and regeneration during aging and hyperglycemia, such as atherosclerosis and diabetes-related vascular disease. [source] Development of an in vitro cell culture model of hepatic steatosis using hepatocyte-derived reporter cells,BIOTECHNOLOGY & BIOENGINEERING, Issue 5 2009Amol V. Janorkar Abstract Fatty liver disease is a problem of growing clinical importance due to its association with the increasingly prevalent conditions of obesity and diabetes. While steatosis represents a reversible state of excess intrahepatic lipid, it is also associated with increased susceptibility to oxidative and cytokine stresses and progression to irreversible hepatic injury characterized by steatohepatitis, cirrhosis, and malignancy. Currently, the molecular mechanisms underlying progression of this dynamic disease remain poorly understood, particularly at the level of transcriptional regulation. We recently constructed a library of stable monoclonal green fluorescent protein (GFP) reporter cells that enable transcriptional regulation to be studied dynamically in living cells. Here, we adapt the reporter cells to create a model of steatosis that will allow investigation of transcriptional dynamics associated with the development of steatosis and the response to subsequent "second hit" stresses. The reporter model recapitulates many cellular features of the human disease, including fatty acid uptake, intracellular triglyceride accumulation, increased reactive oxygen species accumulation, decreased mitochondrial membrane potential, increased susceptibility to apoptotic cytokine stresses, and decreased proliferation. Finally, to demonstrate the utility of the reporter cells for studying transcriptional regulation, we compared the transcriptional dynamics of nuclear factor ,B (NF,B), heat shock response element (HSE), and glucocorticoid response element (GRE) in response to their classical inducers under lean and fatty conditions and found that intracellular lipid accumulation was associated with dose-dependent impairment of NF,B and HSE but not GRE activation. Thus, steatotic reporter cells represent an efficient model for studying transcriptional responses and have the potential to provide important insights into the progression of fatty liver disease. Biotechnol. Bioeng. 2009;102: 1466,1474. © 2008 Wiley Periodicals, Inc. [source] Herpetofaunal Diversity and Abundance in Tropical Upland Forests of Cameroon and Panama,BIOTROPICA, Issue 1 2001Ulrich Hofer ABSTRACT Two tropical upland forests, Mount Kupe in Cameroon and Bosque Protector Palo Seco in Panama, were compared in terms of herpetofaunal species richness and density of individuals. Based on rarefaction, whereby samples are standardized for abundance, Palo Seco had significantly more species of frogs and lizards. Extrapolations to total local species richness, by fitting the Michaelis,Menten equation to the species accumulation curves and by using Chao's estimator, yielded divergent results: more lizard species on Mount Kupe, and an equal number of frogs at both sites. These disparities can be accounted for by differences in evenness, which was higher in Palo Seco. Frog density was significantly higher on Mount Kupe, snake density significantly higher in Palo Seco, and lizards exhibited no density difference. Overall, the results revealed a less consistent pattern and more moderate differences than what is known from southeast Asian,-Central American comparisons. This outcome is discussed in the light of available knowledge, but quantitative data from African forests are too sparse to allow general conclusions. Se comparó la herpetofauna de dos bosques tropicales húmedos ubicados en las montañas, Mount Kupe en Camerún y Bosque Protector Palo Seco en Panamá, en relación a la riqueza especifica y la densidad de individuos. Con base en el método de rarefacción, en el cual los muestreos se estandarizan en base a su abudancia, Palo Seco presenta significativamente mas especies de anuros y lagartos. Extrapolaciones con respecto a la riqueza especifica total de los sitios, mediante un ajuste de la ecuación de Michaelis-Menten a las curvas de acumulación de especies, y utilizando el índice de Chao, produjeron resultados divergentes: más especies de lagartos en Mount Kupe, y el mismo número de especies de anuros en ambos sitios. Dichas diferencias pueden resultar de una equitatividad más alta en Palo Seco. La densidad de anuros resultó significativamente más alta en Mount Kupe, mientras que la densidad de serpientes fue significativamente más alta en Palo Seco, y no se encontró una diferencia entre k densidad de lagartos en ambos sitios. En general los resultados muestran patrones menos consistentes y diferencias mis moderadas de las que se conocen entre el Sureste de Asia y Centroamerica. Se discuten los resultados con base en la información disponible, sin embargo, la existencia de datos cuantitativos para bosques africanos es demasiado escaza como para permitir conclusiones generales. RESUMES Se comparó la herpetofauna de dos bosques tropicales húmedos ubicados en las montañas, Mount Kupe en Camerún y Bosque Protector Palo Seco en Panamá, en relación a la riqueza especifica y la densidad de individuos. Con base en el método de rarefacción, en el cual los muestreos se estandarizan en base a su abudancia, Palo Seco presenta significativamente mas especies de anuros y lagartos. Extrapolaciones con respecto a la riqueza especifica total de los sitios, mediante un ajuste de la ecuación de Michaelis-Menten a las curvas de acumulación de especies, y utilizando el índice de Chao, produjeron resultados divergentes: más especies de lagartos en Mount Kupe, y el mismo número de especies de anuros en ambos sitios. Dichas diferencias pueden resultar de una equitatividad más alta en Palo Seco. La densidad de anuros resultó significativamente más alta en Mount Kupe, mientras que la densidad de serpientes fue significativamente más alta en Palo Seco, y no se encontró una diferencia entre k densidad de lagartos en ambos sitios. En general los resultados muestran patrones menos consistentes y diferencias mis moderadas de las que se conocen entre el Sureste de Asia y Centroamerica. Se discuten los resultados con base en la información disponible, sin embargo, la existencia de datos cuantitativos para bosques africanos es demasiado escaza como para permitir conclusiones generales. [source] | ||||||||||