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Individual Species (individual + species)

Distribution by Scientific Domains
Life Sciences76%
Earth and Environmental Science9%
3 Other Domains15%
Distribution within Life Sciences
Ecology & Organismal Biology40%
Conservation Science19%
16 Other Subdomains41%

Terms modified by Individual Species

  • individual species distribution
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    Selected Abstracts

    The distribution and prevalence of sponges in relation to environmental gradients within a temperate sea lough: vertical cliff surfaces

    DIVERSITY AND DISTRIBUTIONS, Issue 6 2000
    James 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]

    Short and long term consequences of increases in exotic species richness on water filtration by marine invertebrates

    ECOLOGY LETTERS, Issue 8 2009
    Jarrett Byrnes
    Abstract Although recent research has considered the consequences of global declines in the number of species, less attention has focused on the aggregate effects of regional increases in species richness as a result of human-mediated introductions. Here we examine several potential ecosystem consequences of increasing exotic species diversity of suspension feeding marine invertebrates. First, we experimentally manipulated native and non-native suspension feeder richness and measured its effect on short-term phytoplankton clearance rates. Multispecies communities all performed similarly, regardless of whether they were dominated by natives, exotics, or an even mix of the two. Individual species varied considerably in filtration rates, but non-native species often filtered less than the most similar native. Second, we determined potential changes in integrated function over time by comparing seasonal patterns of recruitment as a proxy for the ability to quickly recover filtration capacity after a disturbance. We found that exotic species have complementary seasonal phenologies both to native species and each other. Our results suggest that the consequences of local increases in species richness due to invasions may be manifest over long (annual to interannual) time scales, even when short term changes in ecosystem function are negligible. [source]

    Landscape modification and habitat fragmentation: a synthesis

    GLOBAL ECOLOGY, Issue 3 2007
    Joern Fischer
    ABSTRACT Landscape modification and habitat fragmentation are key drivers of global species loss. Their effects may be understood by focusing on: (1) individual species and the processes threatening them, and (2) human-perceived landscape patterns and their correlation with species and assemblages. Individual species may decline as a result of interacting exogenous and endogenous threats, including habitat loss, habitat degradation, habitat isolation, changes in the biology, behaviour, and interactions of species, as well as additional, stochastic threats. Human-perceived landscape patterns that are frequently correlated with species assemblages include the amount and structure of native vegetation, the prevalence of anthropogenic edges, the degree of landscape connectivity, and the structure and heterogeneity of modified areas. Extinction cascades are particularly likely to occur in landscapes with low native vegetation cover, low landscape connectivity, degraded native vegetation and intensive land use in modified areas, especially if keystone species or entire functional groups of species are lost. This review (1) demonstrates that species-oriented and pattern-oriented approaches to understanding the ecology of modified landscapes are highly complementary, (2) clarifies the links between a wide range of interconnected themes, and (3) provides clear and consistent terminology. Tangible research and management priorities are outlined that are likely to benefit the conservation of native species in modified landscapes around the world. [source]

    Rodent assemblage in a habitat mosaic within the Valley Thicket vegetation of the Eastern Cape Province, South Africa

    AFRICAN JOURNAL OF ECOLOGY, Issue 1 2008
    Boris Kry, tufek
    Abstract We sampled small mammal assemblage in a mosaic of Valley Thicket vegetation in the Great Fish River Reserve during the summers of 2001 and 2002. Assemblage was dominated by seven rodent species with a single nonrodent species (Elephantulus edwardii) in the 357 trapped specimens. Rhabdomys dilectus was the most abundant in both years, followed by Mus minutoides (ranking 2nd in 2001) and Mastomys coucha (2nd in 2002). These three species, which are widespread generalists, made up 85.0% of the total rodent catch in 2001 and 74.3% in 2002. Individual species were captured on 2,14 sites of a total of 17 and M. minutoides was the most widespread. The majority of samples consisted of two (ten sites in a pooled sample for 2 years) or three species (ten sites). Significant morphological structuring was found only in two-species samples. Species turnover was high both among sites and between the 2 years. We found no evidence of significant nested structure which would suggest hierarchical sets of ecological relationships among the species. Vegetation structure explained better than species interactions, the population variables in the rodent assemblage. Résumé Nous avons échantillonné l'assemblage de petits mammifères dans une mosaïque végétale de Valley Thicket dans la Great Fish River Reserve au cours des étés de 2001 et 2002. L'assemblage des 357 spécimens attrapés était dominé par sept espèces de rongeurs et une autre espèce (Elephantulus edwardii). Rhabdomys dilectusétait l'espèce la plus abondante les deux années, suivie par Mus minutoides (classé 2ème en 2001) et par Mastomys coucha (2ème en 2002). Ces trois espèces, qui sont des espèces généralistes très répandues, représentaient 85,0% des prises totales de rongeurs en 2001 et 74,3% en 2002. Les espèces individuelles furent capturées sur deux à 14 sites sur un total de 17, et Mus minutoidesétait la plus répandue. La majorité des échantillons se composaient de deux (10 sites sur un échantillonnage groupé de deux ans) ou trois espèces (dix sites). On n'a découvert de structure morphologique significative que dans des échantillons de deux espèces. Le turnover des espèces était élevé entre les différents sites et entre les années. Nous n'avons trouvé aucune preuve d'une structure significative qui puisse suggérer l'existence de relations hiérarchiques écologiques entre les espèces. La structure de la végétation expliquait mieux que les interactions interspécifiques les variables des populations de l'assemblage des rongeurs. [source]

    Conservation Status as a Biodiversity Trend Indicator: Recommendations from a Decade of Listing Species at Risk in British Columbia

    CONSERVATION BIOLOGY, Issue 4 2005
    JAMES F. QUAYLE
    especies amenazadas; especies en peligro; estado del ambiente Abstract:,Species conservation status is commonly used as a broad-scale indicator of the state of biological diversity. To learn about its value for tracking trends, we examined provincial lists of terrestrial vertebrate species and subspecies at risk in British Columbia, Canada, for 1992 and 2002 to see whether changes in these lists reflected changes in the status of the taxa they represent. Examination of the case histories of individual species and subspecies showed that 65% of additions and deletions to the British Columbia Red List were the result of improvement in knowledge of species status, changes in assessment procedures, and refinements in taxonomy rather than actual changes in a species' status. Comparison to an alternate set of rank scores provided by NatureServe for taxa that appeared on both 1992 and 2002 British Columbia Red Lists revealed changes in status that were not reflected by movement from the list. Estimates of historical conservation status for species on the 1992 British Columbia Red List demonstrated ambiguity around the natural baseline with regard to tracking changes in list composition over time. We discourage the continued use of indicators based solely on conservation status as a means of tracking biodiversity. Instead we recommend advancing strategic indicators around species at risk based on long-term monitoring data, deliberate and explicitly stated baselines, and consistent methods of conservation ranking. Resumen:,El estatus de conservación de las especies comúnmente es utilizado como un indicador de escala amplia del estado de la diversidad biológica. En un esfuerzo por aprender sobre su valor para el seguimiento de tendencias, examinamos listas provinciales, para 1992 y 2002, de especies y subespecies de vertebrados terrestres en riesgo en Columbia Británica, Canadá, para ver si los cambios en estas listas reflejaban cambios en el estatus de los taxa que representan. El examen de la historia del caso de especies y subespecies individuales mostró que 65% de las adiciones y supresiones en la Lista Roja de Columbia Británica fueron el resultado de avances en el conocimiento del estatus de la especie, de cambios en los procedimientos de evaluación y de refinamientos en la taxonomía y no de cambios en el estatus de una especie. La comparación con un conjunto alternativo de valores de clasificación proporcionado por NatureServe para taxa que aparecieron tanto en la Lista Roja de Columbia Británica de 1992 como de 2002 reveló cambios en el estatus que no se reflejaron en movimientos en la lista. Estimaciones del estatus de conservación histórico de especies en la Lista Roja de Columbia Británica de 1992 demostraron ambigüedad alrededor de la línea de base natural en relación con el seguimiento de cambios en el tiempo en la composición de la lista. Desalentamos el uso continuo de indicadores basados solamente en el estatus de conservación como un medio para el seguimiento de biodiversidad. En cambio, recomendamos avanzar con indicadores estratégicos en torno a especies en riesgo con base en datos de monitoreo de largo plazo, en líneas básicas puestas de manifiesto deliberada y explícitamente y en métodos consistentes para la clasificación de la conservación. [source]

    Influence of Temporal Scale of Sampling on Detection of Relationships between Invasive Plants and the Diversity Patterns of Plants and Butterflies

    CONSERVATION BIOLOGY, Issue 6 2004
    RALPH MAC NALLY
    But monitoring is often neglected because it can be expensive and time-consuming. Accordingly, it is valuable to determine whether the temporal extent of sampling alters the validity of inferences about the response of diversity measures to environmental variables affected by restoration actions. Non-native species alter ecosystems in undesirable ways, frequently homogenizing flora and fauna and extirpating local populations of native species. In the Mojave Desert, invasion of salt-cedar (Tamarix ramosissima Ledeb.) and human efforts to eradicate salt-cedar have altered vegetation structure, vegetation composition, and some measures of faunal diversity. We examined whether similar inferences about relationships between plants and butterflies in the Muddy River drainage (Nevada, U.S.A.) could have been obtained by sampling less intensively (fewer visits per site over the same period of time) or less extensively (equal frequency of visits but over a more limited period of time). We also tested whether rank order of butterfly species with respect to occurrence rate (proportion of sites occupied) would be reflected accurately in temporal subsamples. Temporal subsampling did not lead to erroneous inferences about the relative importance of six vegetation-based predictor variables on the species richness of butterflies. Regardless of the temporal scale of sampling, the species composition of butterflies was more similar in sites with similar species composition of plants. The rank order of occurrence of butterfly species in the temporal subsamples was highly correlated with the rank order of species occurrence in the full data set. Thus, similar inferences about associations between vegetation and butterflies and about relative occurrence rates of individual species of butterflies could be obtained by less intensive or extensive temporal sampling. If compromises between temporal intensity and extent of sampling must be made, our results suggest that maximizing temporal extent will better capture variation in biotic interactions and species occurrence. Resumen:,El monitoreo es un componente importante de los esfuerzos de restauración y de manejo adoptivo. Pero el monitoreo a menudo es desatendido porque puede ser costoso y consume tiempo. En consecuencia, es valioso determinar si la extensión temporal del muestreo altera la validez de inferencias sobre la respuesta de medidas de diversidad a variables ambientales afectadas por acciones de restauración. Las especies no nativas alteran a los ecosistemas de manera indeseable, frecuentemente homogenizan la flora y fauna y extirpan poblaciones locales de especies nativas. En el Desierto Mojave, la invasión de Tamarix ramosissima Ledeb. y los esfuerzos humanos para erradicarla han alterado la estructura y composición de la vegetación y algunas medidas de diversidad de fauna. Examinamos si se podían obtener inferencias similares sobre las relaciones entre plantas y mariposas en la cuenca Muddy River (Nevada, E.U.A.) muestreando menos intensivamente (menos visitas por sitio en el mismo período de tiempo) o menos extensivamente (igual frecuencia de visitas pero sobre un período de tiempo más limitado). También probamos si el orden jerárquico de especies de mariposas con respecto a la tasa de ocurrencia (proporción de sitios ocupados) se reflejaba con precisión en las submuestras temporales. El submuestreo temporal no condujo a inferencias erróneas acerca de la importancia relativa de seis variables predictivas basadas en vegetación sobre la riqueza de especies de mariposas. A pesar de la escala temporal del muestreo, la composición de especies de mariposas fue más similar en sitios con composición de especies de plantas similar. El orden jerárquico de ocurrencia de especies de mariposas en las muestras subtemporales estuvo muy correlacionado con el orden jerárquico de ocurrencia de especies en todo el conjunto de datos. Por lo tanto, se pudieron obtener inferencias similares de las asociaciones entre vegetación y mariposas y de las tasas de ocurrencia relativa de especies individuales de mariposas con muestreo temporal menos intensivo o extensivo. Si se deben hacer compromisos entre la intensidad y extensión de muestreo temporal, nuestros resultados sugieren que la maximización de la extensión temporal capturará la variación en interacciones bióticas y ocurrencia de especies más adecuadamente. [source]

    Genetic Identification of Pelagic Shark Body Parts for Conservation and Trade Monitoring

    CONSERVATION BIOLOGY, Issue 4 2002
    Mahmood Shivji
    Difficulties with the identification of many commonly fished sharks and their body parts has resulted in a global dearth of catch and trade information, making reliable assessment of exploitation effects and conservation needs for individual species nearly impossible. We developed and tested a highly streamlined molecular genetic approach based on species-specific, polymerase-chain-reaction primers in an eight-primer multiplex format to discriminate simultaneously between body parts from six shark species common in worldwide pelagic fisheries. The species-specific primers are based on DNA sequence differences among species in the nuclear ribosomal internal transcribed spacer 2 locus. The primers and multiplex format accurately and sensitively distinguished samples from each of three lamnid ( Isurus oxyrinchus, Isurus paucus, and Lamna nasus) and three carcharhinid ( Prionace glauca, Carcharhinus obscurus, and Carcharhinus falciformis) species from all but one other shark species encountered in the North Atlantic fishery. Furthermore, the three lamnid primers were robust enough in their discriminatory power to be useful for species diagnosis on a global scale. Preliminary testing of dried fins from Asian and Mediterranean commercial markets suggests that our genetic approach will be useful for determining the species of origin of detached fins, thus allowing the monitoring of trade in shark fins for conservation assessment. Our approach will also facilitate detection of products from protected and other at-risk shark species and may prove useful as a model for development of the high-throughput, genetic, species-diagnosis methods typically required in conservation and management contexts. Resumen: La conservación y manejo de tiburones fundamentado a nivel de especie es una necesidad imperativa debido a la creciente demanda de aletas de tiburón y el reconocimiento de que las especies individuales de tiburones responden de manera distinta a la explotación. Las dificultades para la identificación de muchos tiburones capturados comúnmente, así como de partes de su cuerpo, han resultado en una escasez global de información sobre capturas y comercialización, haciendo casi imposible el poder realizar evaluaciones de los efectos de la explotación y de las necesidades de conservación. Desarrollamos y evaluamos un método altamente estilizado de genética molecular basado en detonadores de la reacción en cadena de la polimerasa, especie-específicos, en un formato múltiple de ocho detonadores para discriminar simultáneamente entre las partes del cuerpo de seis especies de tiburones provenientes de pesquerías pelágicas mundiales comunes. Los detonadores especie-específicos están basados en diferencias en las secuencias de ADN entre especies del locus espaciador 2 nuclear, ribosomal, transcrito. Los detonadores y el formato múltiple distinguen muestras con precisión y sensitividad de cada uno de los tres lámnidos ( Isurus oxyrinchus, Isurus paucus y Lamna nasus) y tres especies de carcarínidos ( Prionace glauca, Carcharhinus obscurus y Carcharhinus falciformis) especies todas encontradas en las pesquerías de Norteamérica, excepto una. Mas aún, los detonadores de los tres lamnidos fueron lo suficientemente robustos en su poder discriminante como para ser usados para el diagnóstico de especies a escala mundial. Las pruebas preliminares de aletas secas de los mercados comerciales de Asia y el Mediterráneo sugieren que nuestro método genético puede ser útil para determinar la especie de origen de las aletas separadas, permitiendo así usar el monitoreo de las aletas de tiburón para evaluaciones de conservación. Nuestro método también podría facilitar la detección de productos provenientes de especies protegidas o en riesgo y podría resultar útil como un modelo para el desarrollo de métodos genéticos de alto rendimiento para el diagnóstico de especies, métodos típicamente requeridos en los contextos de conservación y manejo. [source]

    Bushmeat Markets on Bioko Island as a Measure of Hunting Pressure

    CONSERVATION BIOLOGY, Issue 6 2000
    John E. Fa
    Comparisons of the availability and abundance of individual species between years showed that more species and more carcasses appeared in 1996 than in 1991. In biomass terms, the increase was significantly less, only 12.5%, when compared with almost 60% more carcasses entering the market in 1996. A larger number of carcasses of the smaller-bodied species (i.e., rodents and the blue duiker [Cephalophus monticola] ) were recorded in 1996 than in 1991. Although an additional four species of birds and one squirrel were recorded in 1996, these were less important in terms of their contribution to biomass or carcass numbers. Concurrently, there was a dramatic reduction in the larger-bodied species, Ogilby's duiker (C. ogilbyi) and seven diurnal primates. We examined these changes, especially the drop in the number of larger animals. We considered the possible following explanations: (1) the number of hunters dropped either because of enforced legislation or scarcity of larger prey; (2) a shift in the use of hunting techniques occurred ( from shotguns to snares); or (3) consumer demand for primate and duiker meat dropped, which increased demand for smaller game. Our results suggest that the situation in Bioko may be alarmingly close to a catastrophe in which primate populations of international conservation significance are being hunted to dangerously low numbers. Although there is still a need for surveys of actual densities of prey populations throughout the island, working with the human population on Bioko to find alternatives to bushmeat is an urgent priority. Resumen: Realizamos conteos de los cuerpos de animales llevados al mercado de Malabo, en la Isla Bioko, Guinea Ecuatorial, durante dos periodos de estudio de ocho meses cada uno en 1991 y 1996. Las comparaciones realizadas de la disponibilidad y abundancia de especies individuales entre estos años mostró que más especies y más cuerpos aparecieron en 1996 que en 1991. En términos de biomasa, el incremento fue significativamente menor, solo 12.5% cuando se comparó con un incremento de casi un 60% más de cuerpos que llegaron al mercado en 1996. Se observó un mayor número de cuerpos de especies de tamaño pequeño ( por ejemplo roedores, y el duiker azul, Cephalophus monticola) en 1996 que en 1991. A pesar de que hubo una adición de cuatro especies de aves y una especie de ardilla en 1996, estas fueron menos importantes en cuanto a su contribución a la biomasa o el número de cuerpos. Al mismo tiempo, hubo una reducción dramática de especies de cuerpo grande, el duiker de Ogilby (C. ogilbyi) y siete primates diurnos. Examinamos estos cambios, especialmente la caída en el número de animales grandes y consideramos las siguientes posibles explicaciones: (1) hubo una caída significativa en el número de cazadores debido a la posible ejecución de la legislación o debido a una escasez de presas grandes; (2) hubo un cambio en el uso de técnicas de caza ( por ejemplo, el reemplazo de armas de fuego por trampas); o (3) la demanda del consumidor por carne de primates y duikers disminuyó, incrementándose la demanda por animales pequeños. Nuestros resultados sugieren que la situación en Bioko puede estar alarmantemente cerca de una catástrofe en la cual las poblaciones de primates, que son de gran significado para la conservación internacional, han sido reducidas a niveles peligrosamente bajos. A pesar de que aún se necesita llevar a cabo estudios de las densidades existentes de poblaciones de presas a lo largo de la isla, es urgente trabajar con la población humana de Bioko para encontrar alternativas a la venta de carne silvestre. [source]

    Using multi-scale species distribution data to infer drivers of biological invasion in riparian wetlands

    DIVERSITY AND DISTRIBUTIONS, Issue 1 2010
    Jane A. Catford
    Abstract Aim, Biological invasion is a major conservation problem that is of interest to ecological science. Understanding mechanisms of invasion is a high priority, heightened by the management imperative of acting quickly after species introduction. While information about invading species' ecology is often unavailable, species distribution data can be collected near the onset of invasion. By examining distribution patterns of exotic and native plant species at multiple spatial scales, we aim to identify the scale (of those studied) that accounts for most variability in exotic species abundance, and infer likely drivers of invasion. Location, River Murray wetlands, south-eastern Australia. Methods, A nested, crossed survey design was used to determine the extent of variation in wetland plant abundance, grazing intensity and water depth at four spatial scales (reaches, wetland clumps, wetlands, wetland sections), and among three Depth-strata. We examined responses of exotic and native species groups (grouped into terrestrial and amphibious taxa), native weeds and 10 individual species using hierarchical ANOVA. Results, As a group dominated by terrestrial taxa, exotic species cover varied at reach-, wetland- and section-scales. This likely reflects differences in abiotic characteristics and propagule pressure at these scales. Groups based on native species did not vary at any scale examined. Cover of 10 species mostly varied among and within wetlands (patterns unrelated to species' origin or functional group), but species' responses differed, despite individual plants being similar in size. While flora mostly varied among wetlands, exotic cover varied most among reaches (26%), which was attributed to hydrological modification and human activities. Main conclusions, Multi-scale surveys can rapidly identify factors likely to affect species' distributions and can indicate where future research should be directed. By highlighting disproportionate variation in exotic cover among reaches, this study suggests that flow regulation and human-mediated dispersal facilitate exotic plant invasion in River Murray wetlands. [source]

    Potential impacts of climate change on Sub-Saharan African plant priority area selection

    DIVERSITY AND DISTRIBUTIONS, Issue 6 2006
    Colin J. McClean
    ABSTRACT The Global Strategy for Plant Conservation (GSPC) aims to protect 50% of the most important areas for plant diversity by 2010. This study selects sets of 1-degree grid cells for 37 sub-Saharan African countries on the basis of a large database of plant species distributions. We use two reserve selection algorithms that attempt to satisfy two of the criteria set by the GSPC. The grid cells selected as important plant cells (IPCs) are compared between algorithms and in terms of country and continental rankings between cells. The conservation value of the selected grid cells are then considered in relation to their future species complement given the predicted climate change in three future periods (2025, 2055, and 2085). This analysis uses predicted climate suitability for individual species from a previous modelling exercise. We find that a country-by-country conservation approach is suitable for capturing most, but not all, continentally IPCs. The complementarity-based reserve selection algorithms suggest conservation of a similar set of grid cells, suggesting that areas of high plant diversity and rarity may be well protected by a single pattern of conservation activity. Although climatic conditions are predicted to deteriorate for many species under predicted climate change, the cells selected by the algorithms are less affected by climate change predictions than non-selected cells. For the plant species that maintain areas of climatic suitability in the future, the selected set will include cells with climate that is highly suitable for the species in the future. The selected cells are also predicted to conserve a large proportion of the species richness remaining across the continent under climate change, despite the network of cells being less optimal in terms of future predicted distributions. Limitations to the modelling are discussed in relation to the policy implications for those implementing the GSPC. [source]

    The effect of short fire cycles on the cover and density of understorey sprouting species in South African mountain fynbos

    DIVERSITY AND DISTRIBUTIONS, Issue 5 2000
    J. H. J. Vlok
    Abstract. Two South African mountain fynbos sites were studied to determine the effect of short fire cycles on the cover and density of understorey sprouting species and their subsequent effect on plant-species richness. Frequent fires (4,6 years between burns) increased the cover of sprouting species by 32% when compared to an adjacent site where the penultimate fire was 28 years previously. There was little or no effect of fire frequency on the densities of understorey sprouters; however, individuals were larger at sites with short fire cycles. The response of individual species of sprouters was variable with one species, Hypodiscus striatus, showing no response to fire frequency. The impact of sprouting species on the species richness of the plant community was great. The mean number of species recorded in quadrats with a high cover of sprouters was 60% lower in comparison to quadrats with low covers or under the burned skeletons of overstorey proteas. The effect of sprouters was consistent for all functional groups of species (i.e. sprouters, non-sprouters, short-lived and long-lived species), in each case reducing the number of species present. [source]

    Fragmentation, habitat composition and the dispersal/predation balance in interactions between the Mediterranean myrtle and avian frugivores

    ECOGRAPHY, Issue 1 2010
    Juan P. González-Varo
    Human-induced fragmentation and disturbance of natural habitats can shift abundance and composition of frugivore assemblages, which may alter patterns of frugivory and seed dispersal. However, despite their relevance to the functioning of ecosystems, plant-frugivore interactions in fragmented areas have been to date poorly studied. I investigated spatial variation of avian frugivore assemblages and fruit removal by dispersers and predators from Mediterranean myrtle shrubs (Myrtus communis) in relation to the degree of fragmentation and habitat features of nine woodland patches (72 plants). The study was conducted within the chronically fragmented landscape of the Guadalquivir Valley (SW Spain), characterized by ~1% of woodland cover. Results showed that the abundance and composition of the disperser guild was not affected by fragmentation, habitat features or geographical location. However, individual species and groups of resident/migrant birds responded differently: whereas resident dispersers were more abundant in large patches, wintering dispersers were more abundant in fruit-rich patches. Predator abundances were similar between patches, although the guild composition shifted with fragmentation. The proportion of myrtle fruits consumed by dispersers and predators varied greatly between patches, but did not depend on bird abundances. The geographical location of patches determined the presence or absence of interactions between myrtles and seed predators (six predated and three non-predated patches), a fact that greatly influenced fruit dispersal success. Moreover, predation rates were lower (and dispersal rates higher) in large patches with fruit-poor heterospecific environments (i.e. dominated by myrtle). Predator satiation and a higher preference for heterospecific fruits by dispersers may explain these patterns. These results show that 1) the frugivore assemblage in warm Mediterranean lowlands is mostly composed of fragmentation-tolerant species that respond differently to landscape changes; and 2) that the feeding behaviour of both dispersers and predators influenced by local fruit availability may be of great importance for interpreting patterns of frugivory throughout the study area. [source]

    Patterns of abundance of fire ants and native ants in a native ecosystem

    ECOLOGICAL ENTOMOLOGY, Issue 4 2009
    KATHARINE L. STUBLE
    Abstract 1.,This correlational study examines the relationship between the red imported fire ant (Solenopsis invicta) and native ants in a longleaf pine savanna. Fire ants are frequently associated with a decline in native ants throughout the invaded range, but fire ant invasion is often coupled with habitat disturbance. Invasion of fire ants into the longleaf pine savanna provides an opportunity to examine the structure of the ant community in the absence of habitat disturbance. 2.,Pitfall trapping was conducted within the longleaf pine savanna as well as across a naturally occurring soil moisture gradient, in plots that had been artificially watered. 3.,Species richness did not vary as a function of fire ant density. There was an inverse relationship between native ant density and fire ant density, but this abundance pattern does not necessarily imply a causal link between fire ant invasion and native ant decline. For individual species, fire ant densities were negatively correlated with the densities of only two native ant species, including Solenopsis carolinensis, a native species that potentially limits the invasion of fire ants. Additionally, fire ants and native ants respond differently to soil moisture, with native ants favouring drier conditions than fire ants. 4.,The possible exclusion of fire ants by some native ants, as well as differences in habitat preferences, provide alternative explanations for the frequently observed negative correlation between fire ants and native ants. [source]

    A practical protocol to assess impacts of unplanned disturbance: a case study in Tuggerah Lakes Estuary, NSW

    ECOLOGICAL MANAGEMENT & RESTORATION, Issue 2003
    A. J. Underwood
    Summary Environmental managers are often confronted with unplanned or accidental disturbances that may lead to environmental impacts. Procedures for detecting or measuring the size of such impacts are complicated because of the lack of data available before the disturbance and because of the intrinsic variability of most natural measures. Here, a protocol for detecting impacts is illustrated for single-measure variables (numbers of individual species) and multivariate measures (relative abundances of invertebrates in assemblages). The present paper describes a case concerning drainage of acidified water into an estuary due to construction of a drainage channel in an area of wetland for which there had been no prior investigations (i.e. no ,before' data). The spatial extent of any impact was also unknowable. Sampling was, therefore, designed to allow for impacts of only a few tens of metres (using control sites 50 m from the mouth of the channel) and impacts covering much larger areas (500 m and 1 km from the mouth of the channel). Invertebrates in the mud around the channel and in control sites were sampled in replicated cores and the amount of seagrass in each core was weighed. Average abundances of invertebrate animals and weights of seagrass were compared, as was variation among samples in potentially impacted and control sites (using univariate analyses of variance). Sets of species were compared using multivariate methods to test the hypothesis that there was an impact at one of the scales examined. In fact, there was no evidence for any sort of impact on the fauna or seagrasses; the disturbance was a short-term pulse without any obvious or sustained ecological response. One consequence of the study was that the local council was able to demonstrate no impact requiring remediation and no penalties were imposed for the unapproved construction of the channel. The implications of this type of study after an environmental disturbance are discussed. The present study identifies the need for clear definition of relevant hypotheses, coupled with rigorous planning of sampling and analyses, so that reliable answers are available to regulators and managers. [source]

    Predictions and tests of climate-based hypotheses of broad-scale variation in taxonomic richness

    ECOLOGY LETTERS, Issue 12 2004
    David J. Currie
    Abstract Broad-scale variation in taxonomic richness is strongly correlated with climate. Many mechanisms have been hypothesized to explain these patterns; however, testable predictions that would distinguish among them have rarely been derived. Here, we examine several prominent hypotheses for climate,richness relationships, deriving and testing predictions based on their hypothesized mechanisms. The ,energy,richness hypothesis' (also called the ,more individuals hypothesis') postulates that more productive areas have more individuals and therefore more species. More productive areas do often have more species, but extant data are not consistent with the expected causal relationship from energy to numbers of individuals to numbers of species. We reject the energy,richness hypothesis in its standard form and consider some proposed modifications. The ,physiological tolerance hypothesis' postulates that richness varies according to the tolerances of individual species for different sets of climatic conditions. This hypothesis predicts that more combinations of physiological parameters can survive under warm and wet than cold or dry conditions. Data are qualitatively consistent with this prediction, but are inconsistent with the prediction that species should fill climatically suitable areas. Finally, the ,speciation rate hypothesis' postulates that speciation rates should vary with climate, due either to faster evolutionary rates or stronger biotic interactions increasing the opportunity for evolutionary diversification in some regions. The biotic interactions mechanism also has the potential to amplify shallower, underlying gradients in richness. Tests of speciation rate hypotheses are few (to date), and their results are mixed. [source]

    Invasion impacts local species turnover in a successional system

    ECOLOGY LETTERS, Issue 9 2004
    Kathryn A. Yurkonis
    Abstract Exotic plant invasions are often associated with declines in diversity within invaded communities. However, few studies have examined the local community dynamics underlying these impacts. Changes in species richness associated with plant invasions must occur through local changes in extinction and/or colonization rates within the community. We used long-term, permanent plot data to evaluate the impacts of the exotic vine Lonicera japonica. Over time, species richness declined with increasing L. japonica cover. L. japonica reduced local colonization rates but had no effect on extinction rates. Furthermore, we detected significant reductions in the immigration of individual species as invasion severity increased, showing that some species are more susceptible to invasion than others. These findings suggest that declines in species richness associated with L. japonica invasion resulted from effects on local colonization rates only and not through the competitive displacement of established species. [source]

    Contribution of rarity and commonness to patterns of species richness

    ECOLOGY LETTERS, Issue 2 2004
    Jack J. Lennon
    Abstract There is little understanding in ecology as to how biodiversity patterns emerge from the distribution patterns of individual species. Here we consider the question of the contributions of rare (restricted range) and common (widespread) species to richness patterns. Considering a species richness pattern, is most of the spatial structure, in terms of where the peaks and troughs of diversity lie, caused by the common species or the rare species (or neither)? Using southern African and British bird richness patterns, we show here that commoner species are most responsible for richness patterns. While rare and common species show markedly different species richness patterns, most spatial patterning in richness is caused by relatively few, more common, species. The level of redundancy we found suggests that a broad understanding of what determines the majority of spatial variation in biodiversity may be had by considering only a minority of species. [source]

    Detection of bacteria associated with harmful algal blooms from coastal and microcosm environments using electronic microarrays

    ENVIRONMENTAL MICROBIOLOGY, Issue 3 2007
    Edward A. Barlaan
    Summary With the global expansion of harmful algal blooms (HABs), several measures, including molecular approaches, have been undertaken to monitor its occurrence. Many reports have indicated the significant roles of bacteria in controlling algal bloom dynamics. Attempts have been made to utilize the bacteria/harmful algae relationship in HAB monitoring. In this study, bacterial assemblages monitored during coastal HABs and bacterial communities in induced microcosm blooms were investigated. Samples were analysed using denaturing gradient gel electrophoresis (DGGE) of the 16S rRNA gene. DGGE bands with peculiar patterns before, during, and after algal blooms were isolated and identified. Probes for six ribotypes representing organisms associated with Chatonella spp., Heterocapsa circularisquama, or Heterosigma akashiwo were used for analysis on NanoChip electronic microarray. In addition, a new approach using cultured bacteria species was developed to detect longer (533 bp) polymerase chain reaction-amplified products on the electronic microarray. The use of fluorescently labelled primers allowed the detection of individual species in single or mixed DNA conditions. The developed approach enabled the detection of the presence or absence and relative abundance of the HAB-related ribotypes in coastal and microcosm blooms. This study indicates the ability of electronic microarray platform to detect or monitor bacteria in natural and induced environments. [source]

    Uncertainty analysis of single-concentration exposure data for risk assessment,introducing the species effect distribution approach

    ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 11 2006
    Janeck J. Scott-fordsmand
    Abstract In recent years, the inclusion of uncertainty analysis in risk assessment has been much debated. One pertinent issue is the translation of the effects observed with a limited number of test species to a general protection level for most or all species present in the environment. In a number of cases, toxicity data may consist of data from tests employing only a control and one treatment. Given that more species (or processes) have been tested with the same treatment, the treatment can be considered as fixed, and the effect level of the individual species (or processes) can be considered as variable. The distribution of effects can be viewed as a species effect distribution for that treatment. The distribution will represent all organisms and may be used to predict the maximum impact on any fraction of all organisms (e.g., 95% of all species). Hence, it is possible to predict the maximum effect level, with a selected certainty, for a given fraction of all species. [source]

    Relative sensitivity distribution of aquatic invertebrates to organic and metal compounds

    ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2004
    Peter Carsten von der Ohe
    Abstract In the field, a multitude of species can be exposed to numerous toxicants; thus, the sensitivity of individual species to particular toxicants must be known to predict effects and to analyze changes in species composition. For most species, no information about their toxicant sensitivity is available. To address this limitation, we have grouped the available information to assign sensitivities to aquatic invertebrate taxa relative to Daphnia magna. With respect to organic compounds, most taxa of the orders Anisoptera, Basommatophora, Coleoptera, Decapoda, Diptera, Ephemeroptera, Eulamellibranchiata, Heteroptera, Hirudinea, Isopoda, Oligochaeta, Prosobranchia, Trichoptera, Tricladida, and Zygoptera are less sensitive than D. magna. Some taxa of the Amphipoda, Plecoptera, and Cladocera (other than D. magna) are significantly more sensitive. For organic compounds, approximately 22% of the investigated taxa were more sensitive than D. magna. Most taxa of the orders Amphipoda, Basommatophora, Diptera, Ephemeroptera, Eulamellibranchiata, Heteroptera, Isopoda, Oligochaeta, and Tricladida are significantly less sensitive than D. magna to metal compounds. The taxa belonging to the Crustacea, with the exception of the order Isopoda, are much more sensitive. For metal compounds, approximately 30% of the investigated taxa were more sensitive than D. magna. Hence, D. magna is among the most sensitive taxa regarding both groups of toxicants. The sensitivities for several taxa are listed, and use of the relative sensitivity distribution to link toxicant effects in mesocosm studies and field investigations is discussed. [source]

    Technical basis for narcotic chemicals and polycyclic aromatic hydrocarbon criteria.

    ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2000

    Abstract A method is presented for developing water quality criteria (WQC) for type I narcotic chemicals in general and PAHs in particular. The criteria can be applied to any individual or mixture of narcotic chemicals using only the chemical's octanol-water partition coefficient KOW. It is derived from a database of LC50s comprising 156 chemicals and 33 species, including fish, amphibians, arthropods, mollusks, polychaetes, coelenterates, and protozoans. A target lipid model is proposed that accounts for variations in toxicity due to differing species sensitivities and chemical differences. The model is based on the idea that a target lipid is the site of action in the organism. Further, it is assumed that target lipid has the same lipid-octanol linear free energy relationship for all species. This implies that the slope of the log(LC50),log(KOW) relationship is the same for all species. However, individual species may have varying target lipid body burdens that cause toxicity. The target lipid LC50 body burdens derived from concentration data in the water only are compared to measured total lipid LC50 body burdens for five species. They are essentially equal, indicating that the target lipid concentration is equal to the total extracted lipid concentration. The precise relationship between partitioning in target lipid and octanol is established. The species-specific body burdens are used to determine the WQC final acute value, i.e., the 95-percentile level of protection. An acute-to-chronic ratio is used to compute the body burden corresponding to the WQC final chronic value, which is the procedure used to derive the U.S. Environmental Protection Agency water quality criteria. The criteria are expressed either as dissolved concentrations in the water column or as tissue concentrations. [source]

    Improvements for comparative analysis of changes in diversity of microbial communities using internal standards in PCR-DGGE

    FEMS MICROBIOLOGY ECOLOGY, Issue 3 2005
    Dorthe Groth Petersen
    Abstract The use of internal standards both during DNA extraction and PCR-DGGE procedure gives the opportunity to analyse the relative abundance of individual species back to the original sample, thereby facilitating relative comparative analysis of diversity. Internal standards were used throughout the DNA extraction and PCR-DGGE to compensate for experimental variability. Such variability causes decreased reproducibility among replicate samples as well as compromise comparisons between samples, since experimental errors cannot be differentiated from actual changes in the community abundance and structure. The use of internal standards during DNA extraction and PCR-DGGE is suitable for ecological and ecotoxicological experiments with microbial communities, where relative changes in the community abundance and structure are studied. We have developed a protocol Internal Standards in Molecular Analysis of Diversity (ISMAD) that is simple to use, inexpensive, rapid to perform and it does not require additional samples to be processed. The internal standard for DNA extraction (ExtrIS) is a fluorescent 510-basepair PCR product which is added to the samples prior to DNA extraction, recovered together with the extracted DNA from the samples and analysed with fluorescence spectrophotometry. The use of ExtrIS during isolation of sample DNA significantly reduced variation among replicate samples. The PCR internal standard (PCRIS) originates from the Drosophila melanogaster genome and is a 140-basepair long PCR product, which is amplified by non-competitive primers in the same PCR reaction tubes as the target DNA and analysed together with the target PCR product on the same DGGE gel. The use of PCRIS during PCR significantly reduced variation among replicate samples both when assessing total PCR product and when comparing bands representing species on a DGGE gel. The entire ISMAD protocol was shown to accurately describe changes in relative abundance in an environmental sample using PCR-DGGE. It should, however, be mentioned that despite the use of ISMAD some inherent biases still exist in DNA extraction and PCR-DGGE and these should be taken into consideration when interpreting the diversity in a sample based on a DGGE gel. [source]

    Concurrent assessment of fish and habitat in warmwater streams in Wyoming

    FISHERIES MANAGEMENT & ECOLOGY, Issue 1 2006
    M. C. QUIST
    Abstract, Fisheries research and management in North America have focused largely on sport fishes, but native non-game fishes have attracted increased attention due to their declines. The Warmwater Stream Assessment (WSA) was developed to evaluate simultaneously both fish and habitat in Wyoming streams by a process that includes three major components: (1) stream-reach selection and accumulation of existing information, (2) fish and habitat sampling and (3) summarisation and evaluation of fish and habitat information. Fish are sampled by electric fishing or seining and habitat is measured at reach and channel-unit (i.e. pool, run, riffle, side channel, or backwater) scales. Fish and habitat data are subsequently summarised using a data-matrix approach. Hierarchical decision trees are used to assess critical habitat requirements for each fish species expected or found in the reach. Combined measurements of available habitat and the ecology of individual species contribute to the evaluation of the observed fish assemblage. The WSA incorporates knowledge of the fish assemblage and habitat features to enable inferences of factors likely influencing both the fish assemblage and their habitat. The WSA was developed for warmwater streams in Wyoming, but its philosophy, process and conceptual basis may be applied to environmental assessments in other geographical areas. [source]

    Temporal changes in replicated experimental stream fish assemblages: predictable or not?

    FRESHWATER BIOLOGY, Issue 9 2006
    WILLIAMJ.
    Summary 1.,Natural aquatic communities or habitats cannot be fully replicated in the wild, so little is known about how initially identical communities might change over time, or the extent to which observed changes in community structure are caused by internal factors (such as interspecific interactions or traits of individual species) versus factors external to the local community (such as abiotic disturbances or invasions of new species). 2.,We quantified changes in seven initially identical fish assemblages, in habitats that were as similar as possible, in seminatural artificial streams in a 388-day trial (May 1998 to May 1999), and compared the change to that in fish assemblages in small pools of a natural stream during a year. The experimental design excluded floods, droughts, immigration or emigration. The experimental fish communities diverged significantly in composition and exhibited dissimilar trajectories in multivariate species space. Divergence among the assemblages increased from May through August, but not thereafter. 3.,Differences among the experimental assemblages were influenced by differences that developed during the year in algae cover and in potential predation (due to differential survival of sunfish among units). 4.,In the natural stream, fish assemblages in small pools changed more than those in the experimental units, suggesting that in natural assemblages external factors exacerbated temporal variation. 5.,Our finding that initially identical assemblages, isolated from most external factors, would diverge in the structure of fish assemblages over time suggests a lack of strong internal, deterministic controls in the assemblages, and that idiosyncratic or stochastic components (chance encounters among species; vagaries in changes in the local habitat) even within habitat patches can play an important role in assemblage structure in natural systems. [source]

    Variation in leaf functional trait values within and across individuals and species: an example from a Costa Rican dry forest

    FUNCTIONAL ECOLOGY, Issue 1 2010
    Catherine M. Hulshof
    Summary 1.,Patterns of species co-existence and species diversity in plant communities remain an important research area despite over a century of intensive scrutiny. To provide mechanistic insight into the rules governing plant species co-existence and diversity, plant community ecologists are increasingly quantifying functional trait values for the species found in a wide range of communities. 2.,Despite the promise of a quantitative functional trait approach to plant community ecology, we suggest that, along with examining trait variation across species, an assessment of trait variation within species should also be a key component of a trait-based approach to community ecology. Variability within and between individuals and populations is likely widespread due to plastic responses to highly localized abiotic and biotic interactions. 3.,In this study, we quantify leaf trait variation within and across ten co-existing tree species in a dry tropical forest in Costa Rica to ask: (i) whether the majority of trait variation is located between species, within species, within individuals or within the leaves themselves; (ii) whether trait values collected using standardized methods correlate with those collected using unstandardized methods; and (iii) to what extent can we differentiate plant species on the basis of their traits? 4.,We find that the majority of variation in traits was often explained by between species differences; however, between leaflet trait variation was very high for compound-leaved species. We also show that many species are difficult to reliably differentiate on the basis of functional traits even when sampling many individuals. 5.,We suggest an ideal sample size of at least 10, and ideally 20, individuals be used when calculating mean trait values for individual species for entire communities, though even at large sample sizes, it remains unclear if community level trait values will allow comparisons on a larger geographic scale or if species traits are generally similar across scales. It will thus be critical to account for intraspecific variation by comparing species mean trait values across space in multiple microclimatic environments within local communities and along environmental gradients. Further, quantifying trait variability due to plasticity and inheritance will provide a better understanding of the underlying patterns and drivers of trait variation as well as the application of functional traits in outlining mechanisms of species co-existence. [source]

    The evolution of senescence from a comparative perspective

    FUNCTIONAL ECOLOGY, Issue 3 2008
    R. E. Ricklefs
    Summary 1Comparative studies of ageing address the evolutionary lability of the rate of ageing as an indication of potential for, and constraints on, the extension of life span. 2Experimental studies on ageing have focused on damage induced by reactive oxygen species (ROS) and other stresses, and on the mechanisms to prevent or repair this damage. Research on animal models has revealed genes with large effects on life span. However, the relevance of some animal models to human ageing is unclear and it is not known whether evolved differences in ageing involve such major gene effects. 3Studies on the demography of populations of vertebrates in the wild show that animals suffer from senescence in nature. Variation in the rate of ageing is consistent with evolutionary theory in that senescence is delayed in populations that suffer relatively low extrinsic mortality. 4Populations of longer-lived individuals suffer a higher proportion of ageing-related mortality, and thus stronger selection against early ageing. The presence of ageing-related deaths in these populations suggests a lack of suitable mechanisms that would further extend life span. 5Similar patterns of ageing-related mortality in wild and captive or domesticated populations indicate that most ageing-related death is caused by intrinsic factors, such as tumours and cardiovascular failure, rather than increasing vulnerability to extrinsic causes of mortality. 6Studies of several wild populations of long-lived birds suggest that ageing-related mortality is often catastrophic, with individuals maintaining high levels of condition until shortly before their demise. 7Comparative studies of many species suggest connections between early development and the pattern of ageing later in life, consistent with laboratory studies on variation within individual species. The physiological connections across the life span are not well understood. 8Comparative studies have provided important insights into the ageing process. However, we still lack information on important issues, including the causes of death in natural populations, the relationship of within- and between-population variation in the rate of ageing, the genetic basis of variation in rate of ageing in natural populations, and detailed longitudinal studies of individual health and reproductive success in relation to age at death. [source]

    Soil animals influence microbial abundance, but not plant,microbial competition for soil organic nitrogen

    FUNCTIONAL ECOLOGY, Issue 5 2004
    L. COLE
    Summary 1In a microcosm experiment we examined the effects of individual species of microarthropods, and variations in microarthropod diversity of up to eight species, on soil microbial properties and the short-term partitioning of a dual-labelled organic nitrogen source (glycine-2- 13C- 15N) between a grassland plant, Agrostis capillaris, and the soil microbial biomass, to determine how soil fauna and their diversity influence plant,microbial competition for organic N. 2We hypothesized that variations in the diversity of animals would influence the partitioning of 15N inputs between plants and the microbial biomass, due to the effect of animal grazing on the microbial biomass, and hence its ability to sequester N. 3Certain individual species of Collembola influenced the microbial community of the soil. Folsomia quadrioculata reduced microbial biomass, whereas Mesaphorura macrochaeta enhanced arbuscular mycorrhizal (AM) colonization of A. capillaris roots. Effects of increasing species richness of microarthropods on microbial biomass and AM colonization were detected, but these effects could be interpreted in relation to the presence or absence of individual species. 4Microbial uptake of added 15N was not affected by the presence of any of the individual species of animal in the monoculture treatments. Similarly, increasing diversity of microarthropods had no detectable effect on microbial 15N. 5Root and shoot uptake of 15N was also largely unaffected by both single species and variations in diversity of microarthropods. However, one collembolan species, Ceratophysella denticulata, reduced root 15N capture when present in monoculture. We did not detect 13C in plant tissue under any experimental treatments, indicating that all N was taken up by plants after mineralization. 6Our data suggest that, while single species and variations in diversity of microarthropods influence microbial abundance in soil, there is no effect on microbial or plant uptake of N. Overall, these data provide little support for the notion that microbial-feeding soil animals are regulators of microbial,plant competition for N. [source]

    Species-level effects more important than functional group-level responses to elevated CO2: evidence from simulated turves

    FUNCTIONAL ECOLOGY, Issue 3 2004
    M. E. HANLEY
    Summary 1Using mixtures of 14 calcareous grassland plant species drawn from three functional groups, we looked at the effects of elevated atmospheric CO2 on contrasting levels of ecosystem performance (species, functional group and community). Experimental communities were subjected to ambient (,350 µmol mol,1) or elevated CO2 (,600 µmol mol,1) in controlled environments, with grazing simulated by clipping at monthly intervals for 546 days. 2We assessed the effect of elevated CO2 on plant performance by quantifying the productivity (biomass) and cover of component species. We also examined the effect of elevated CO2 on the vertical structure of the plant canopy. Elevated CO2 resulted in a significant increase in total community biomass only following nutrient addition. Within functional groups, non-leguminous forb species had significantly greater biomass and cover in elevated CO2 both before and after nutrient addition, although the effect was mainly due to the influence of one species (Centaurea nigra). Grasses, in contrast, responded negatively to elevated CO2, although again significant reductions in biomass and cover could mainly be ascribed to a single species (Brachypodium pinnatum). Legumes exhibited increased biomass and cover in elevated CO2 (the effects being particularly marked for Anthyllis vulneraria and Lotus corniculatus), but this response disappeared following nutrient addition. Vertical structure was little affected by CO2 treatment. 3We conclude that due to the idiosyncratic responses of individual species, the categorization of plants into broad functional groups is of limited use in guiding our understanding of the impacts of elevated atmospheric CO2 on plant communities. [source]

    Contemporary climate change in the Sonoran Desert favors cold-adapted species

    GLOBAL CHANGE BIOLOGY, Issue 5 2010
    SARAH KIMBALL
    Abstract Impacts of long-term climate shifts on the dynamics of intact communities within species ranges are not well understood. Here, we show that warming and drying of the Southwestern United States over the last 25 years has corresponded to a shift in the species composition of Sonoran Desert winter annuals, paradoxically favoring species that germinate and grow best in cold temperatures. Winter rains have been arriving later in the season, during December rather than October, leading to the unexpected result that plants are germinating under colder temperatures, shifting community composition to favor slow growing, water-use efficient, cold-adapted species. Our results demonstrate how detailed ecophysiological knowledge of individual species, combined with long-term demographic data, can reveal complex and sometimes unexpected shifts in community composition in response to climate change. Further, these results highlight the potentially overwhelming impact of changes in phenology on the response of biota to a changing climate. [source]

    Body size-dependent responses of a marine fish assemblage to climate change and fishing over a century-long scale

    GLOBAL CHANGE BIOLOGY, Issue 2 2010
    MARTIN J. GENNER
    Abstract Commercial fishing and climate change have influenced the composition of marine fish assemblages worldwide, but we require a better understanding of their relative influence on long-term changes in species abundance and body-size distributions. In this study, we investigated long-term (1911,2007) variability within a demersal fish assemblage in the western English Channel. The region has been subject to commercial fisheries throughout most of the past century, and has undergone interannual changes in sea temperature of over 2.0 °C. We focussed on a core 30 species that comprised 99% of total individuals sampled in the assemblage. Analyses showed that temporal trends in the abundance of smaller multispecies size classes followed thermal regime changes, but that there were persistent declines in abundance of larger size classes. Consistent with these results, larger-growing individual species had the greatest declines in body size, and the most constant declines in abundance, while abundance changes of smaller-growing species were more closely linked to preceding sea temperatures. Together these analyses are suggestive of dichotomous size-dependent responses of species to long-term climate change and commercial fishing over a century scale. Small species had rapid responses to the prevailing thermal environment, suggesting their life history traits predisposed populations to respond quickly to changing climates. Larger species declined in abundance and size, reflecting expectations from sustained size-selective overharvesting. These results demonstrate the importance of considering species traits when developing indicators of human and climatic impacts on marine fauna. [source]