JOURNAL OF PETROLEUM GEOLOGY, Issue 2 2000
K. H. James
Venezuela's most important hydrocarbon reserves occur in the intermontane Maracaibo Basin and in the Eastern Venezuela foreland basin. Seeps are abundant in these areas. Lesser volumes occur in the Barinas-Apure foreland basin. Most of the oil in these basins was derived from the Upper Cretaceous La Luna Formation in the west and its equivalent, the Querecual Formation, in the east. Minor volumes of oil derived from Tertiary source rocks occur in the Maracaibo and Eastern Venezuela Basins and in the Falcdn area. Offshore, several TCF of methane with some associated condensate are present in the Cadpano Basin, and gas is also present in the Columbus Basin. Oil reserves are present in La Vela Bay and in the Gulf of Paria, and oil has been encountered in the Cariaco Basin. The Gulf of Venezuela remains undrilled. The basins between the Netherlands and Venezuelan Antillian Islands seem to lack reservoirs. Tertiary sandstones provide the most important reservoirs, but production comes also from fractured basement (igneous and metamorphic rocks), from basal Cretaceous sandstones and from fractured Cretaceous limestones. Seals are provided by encasing shales, unconformities, faults and tar plugs. There is a wide variety of structural and stratigraphic traps. The Orinoco Heavy Oil Belt of the Eastern Venezuela Basin, one of the world's largest accumulations (1.2 times 1012 brl) involves stratigraphic trapping provided by onlap and by tar plugging. Stratigraphic trapping involving unconformities and tar plugging also plays a major role also in the Bolivar Coastal complex of fields along the NE margin of Lake Maracaibo. Many of the traps elsewhere in the Maracaibo Basin were influenced by faulting. The faults played an extensional role during Jurassic rifting and subsequently suffered inversion and strike-slip reactivation. This created anticlines as well as fracture porosity and permeability, and influenced the distribution of sandstone reservoirs, unconformities and related truncation traps. The faults probably also provided migration paths as well as lateral seals. This is very likely the case also in the large, thrust-related traps of the Furrial Trend in Eastern Venezuela. Normal faults, many antithetic to basement dip, provide important traps in the Las Mercedes, Oficina and Emblador complexes on the southern flanks of the Eastern Venezuela Basin. Similar faults seem to control the Sinco-Silvestre complex of the Barinas-Apure Basin. Much of VenezuelaS crude (around 1.5 trillion brls original STOIIP) has been degraded and is heavy, Perhaps two to three trillion brls of precursor, lighter oil existed. While the known Upper Cretaceous La Luna and Querecual Formations are known to include prolific source rocks, a reasonable generation/accumulation efficiency of 10% implies volumes too large to have come from the reported kitchens. The country's vast reserves are perhaps better explained by recognizing that the present-day basins are remnants of much broader sedimentary areas. The source rocks originally had a much more regional distribution. They suffered widespread, earlier phases of generation that probably charged early-formed traps on a regional scale. These, together with more recent kitchens, provided oil to the present-day accumulations. This history involved long-distance migration and remigration. [source]

THE GEOLOGY AND HYDROCARBON HABITAT OF THE SARIR SANDSTONE, SE SIRT BASIN, LIBYA

JOURNAL OF PETROLEUM GEOLOGY, Issue 2 2000
G. Ambrose
The Jurassic , Lower Cretaceous Sarir Sandstone Cformerly known as the Nubian Sandstone) in the SE Sirt Basin is composed of four members which can be correlated regionally using a lithostratigraphic framework. These synrift sandstones unconformably overlie a little known pre-rift succession, and are in turn unconformably overlain by post-rift marine shales of Late Cretaceous age. Within the Sarir Sandstone are two sandstone-dominated members, each reflecting a rapid drop in base level, which are important oil reservoirs in the study area. Between these sandstones are thick shales of continental origin which define the architecture of the reservoir units. This four-fold lithostratigraphic subdivision of the Sarir Sandstone contrasts with previous schemes which generally only recognised three members. The sandstones below the top-Sarir unconformity host in excess of 20 billion barrels of oil in-place. The dominant traps are structural (e.g. Sarir C field), stratigraphic (e.g. Messla field), hanging-wall fault plays (e.g. UU1,65 field) and horst-block plays (e.g. Calanscio field). Three Sarir petroleum systems are recognised in the SE Sirt Basin. The most significant relies on post-rift (Upper Cretaceous) shales, which act as both source and seal. The Variegated Shale Member of the Sarir Sandstone may also provide source and seal; while a third, conceptual petroleum system requires generation of non-marine oils from pre-rift (?Triassic) source rocks in the axis of the Sarir Trough. The intrabasinal Messla High forms a relatively rigid block at the intersection of two rift trends, around which stress vectors were deflected during deposition of the syn-rift Sarir Sandstone. Adjacent troughs accommodated thick, post-rift shale successions which comprise excellent source rocks. Palaeogene subsidence facilitated oil generation, and the Messla High was a focus for oil migration. Wrenching on master faults with associated shale smear has facilitated fault seal and the retention of hydrocarbons. In the Calanscio area, transpressional faulting has resulted in structural inversion with oil entrapment in "pop-up" horst blocks. Elsewhere, transtensional faulting has resulted in numerous fault-dependent traps which, in combination with stratigraphic and truncation plays, will provide the focus for future exploration. [source]

INFLUENCES OF WATERSHED URBANIZATION AND INSTREAM HABITAT ON MACROINVERTEBRATES IN COLD WATER STREAMS,

JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 5 2003
Lizhu Wang
ABSTRACT: We analyzed data from riffle and snag habitats for 39 small cold water streams with different levels of watershed urbanization in Wisconsin and Minnesota to evaluate the influences of urban land use and instream habitat on macroinvertebrate communities. Multivariate analysis indicated that stream temperature and amount of urban land use in the watersheds were the most influential factors determining macroinvertebrate assemblages. The amount of watershed urbanization was nonlinearly and negatively correlated with percentages of Ephemeroptera-Plecoptera-Trichoptera (EPT) abundance, EPT taxa, filterers, and scrapers and positively correlated with Hilsenhoff biotic index. High quality macroinvertebrate index values were possible if effective imperviousness was less than 7 percent of the watershed area. Beyond this level of imperviousness, index values tended to be consistently poor. Land uses in the riparian area were equal or more influential relative to land use elsewhere in the watershed, although riparian area consisted of only a small portion of the entire watershed area. Our study implies that it is extremely important to restrict watershed impervious land use and protect stream riparian areas for reducing human degradation on stream quality in low level urbanizing watersheds. Stream temperature may be one of the major factors through which human activities degrade cold-water streams, and management efforts that can maintain a natural thermal regime will help preserve stream quality. [source]

CHARACTERIZATION OF BEAKED WHALE (ZIPHIIDAE) AND SPERM WHALE (PHYSETER MACROCEPHALUS) SUMMER HABITAT IN SHELF-EDGE AND DEEPER WATERS OFF THE NORTHEAST U. S.

MARINE MAMMAL SCIENCE, Issue 4 2001
G. T. Waring
Abstract Sperm whales (Physeter macrocephalus) and beaked whales (Mesoplodon spp. and Ziphius cavirostris) are deep-diving cetaceans that frequent shelf-edge and Gulf Stream waters off the northeast U. S. coast. Sighting data collected during seven summer (1990, 1991, 1993, and 1995,1998) shipboard surveys were analyzed using a geographic information system to determine habitat use based on bathymetric and oceanographic features. Although sighting rates were lower for beaked whales, both taxa occupied similar habitats. Beaked whales were concentrated at the colder shelf edge, whereas sperm whales were associated with warmer off-shelf water. Mean sighting rates for both taxa were higher in canyon features, but only beaked whale sighting rates were significantly different between canyon and non-canyon habitat (Wilcoxon signed rank test P= 0.007). Within the shared habitat, the two taxa were separated at fine-scale based on oceanographic features. [source]

EVOLUTION ON A LOCAL SCALE: DEVELOPMENTAL, FUNCTIONAL, AND GENETIC BASES OF DIVERGENCE IN BILL FORM AND ASSOCIATED CHANGES IN SONG STRUCTURE BETWEEN ADJACENT HABITATS

EVOLUTION, Issue 8 2008
Alexander V. Badyaev
Divergent selection on traits involved in both local adaptation and the production of mating signals can strongly facilitate population differentiation. Because of its links to foraging morphologies and cultural inheritance song of birds can contribute particularly strongly to maintenance of local adaptations. In two adjacent habitats,native Sonoran desert and urban areas,house finches (Carpodacus mexicanus) forage on seeds that are highly distinct in size and shell hardness and require different bite forces and bill morphologies. Here, we first document strong and habitat-specific natural selection on bill traits linked to bite force and find adaptive modifications of bite force and bill morphology and associated divergence in courtship song between the two habitats. Second, we investigate the developmental basis of this divergence and find that early ontogenetic tissue transformation in bill, but not skeletal traits, is accelerated in the urban population and that the mandibular primordia of the large-beaked urban finches express bone morphogenetic proteins (BMP) earlier and at higher level than those of the desert finches. Further, we show that despite being geographically adjacent, urban and desert populations are nevertheless genetically distinct corroborating findings of early developmental divergence between them. Taken together, these results suggest that divergent selection on function and development of traits involved in production of mating signals, in combination with localized learning of such signals, can be very effective at maintaining local adaptations, even at small spatial scales and in highly mobile animals. [source]

REPRODUCTIVE ISOLATION CAUSED BY NATURAL SELECTION AGAINST IMMIGRANTS FROM DIVERGENT HABITATS

EVOLUTION, Issue 4 2005
Patrik Nosil
Abstract The classification of reproductive isolating barriers laid out by Dobzhansky and Mayr has motivated and structured decades of research on speciation. We argue, however, that this classification is incomplete and that the unique contributions of a major source of reproductive isolation have often been overlooked. Here, we describe reproductive barriers that derive from the reduced survival of immigrants upon reaching foreign habitats that are ecologically divergent from their native habitat. This selection against immigrants reduces encounters and thus mating opportunities between individuals from divergently adapted populations. It also reduces the likelihood that successfully mated immigrant females will survive long enough to produce their hybrid offspring. Thus, natural selection against immigrants results in distinctive elements of premating and postmating reproductive isolation that we hereby dub "immigrant inviability". We quantify the contributions of immigrant inviability to total reproductive isolation by examining study systems where multiple components of reproductive isolation have been measured and demonstrate that these contributions are frequently greater than those of traditionally recognized reproductive barriers. The relevance of immigrant inviability is further illustrated by a consideration of population-genetic theory, a review of selection against immigrant alleles in hybrid zone studies, and an examination of its participation in feedback loops that influence the evolution of additional reproductive barriers. Because some degree of immigrant inviability will commonly exist between populations that exhibit adaptive ecological divergence, we emphasize that these barriers play critical roles in ecological modes of speciation. We hope that the formal recognition of immigrant inviability and our demonstration of its evolutionary importance will stimulate more explicit empirical studies of its contributions to speciation. [source]

DUSKY DOLPHIN (LAGENORHYNCHUS OBSCURUS) FORAGING IN TWO DIFFERENT HABITATS: ACTIVE ACOUSTIC DETECTION OF DOLPHINS AND THEIR PREY

MARINE MAMMAL SCIENCE, Issue 2 2004
Kelly J. Benoit-Bird
Abstract Active-acoustic surveys were used to determine the distribution of dusky dolphins and potential prey in two different New Zealand locations. During seven survey days off Kaikoura Canyon, dusky dolphins were found within the DeepScattering Layer (DSL) at 2000 when it rose to within 125 m of the surface. As the DSL rose to 30 m at 0100, the observed depth of dolphins decreased, presumably as the dolphins followed the vertical migration of their prey. Acoustically identified subgroups of coordinated animals ranged from one to five dolphins. Time, depth of layer, and layer variance contributed significantly to predicting foraging dusky dolphin subgroup size. In the much shallower and more enclosed Admiralty Bay, dolphins noted at the surface as foraging were always detected with the sonar, but were never observed in coordinated subgroups during the brief (two-day) study there. In Admiralty Bay dolphin abundance was correlated with mean volume scattering from potential prey in the water column; and when volume scattering, an index of prey density, was low, dolphins were rarely present. Ecological differences between the deep waters of Kaikoura Canyon and the shallow nearshore waters of Admiralty Bay may result in differences in how, when, and in what social groupings dusky dolphins forage. [source]

Bayesian Networks and Adaptive Management of Wildlife Habitat

CONSERVATION BIOLOGY, Issue 4 2010
ALISON L. HOWES
herramientas para la toma de decisiones; incertidumbre ecológica; pastoreo feral; regímenes de quema; validación de modelos Abstract:,Adaptive management is an iterative process of gathering new knowledge regarding a system's behavior and monitoring the ecological consequences of management actions to improve management decisions. Although the concept originated in the 1970s, it is rarely actively incorporated into ecological restoration. Bayesian networks (BNs) are emerging as efficient ecological decision-support tools well suited to adaptive management, but examples of their application in this capacity are few. We developed a BN within an adaptive-management framework that focuses on managing the effects of feral grazing and prescribed burning regimes on avian diversity within woodlands of subtropical eastern Australia. We constructed the BN with baseline data to predict bird abundance as a function of habitat structure, grazing pressure, and prescribed burning. Results of sensitivity analyses suggested that grazing pressure increased the abundance of aggressive honeyeaters, which in turn had a strong negative effect on small passerines. Management interventions to reduce pressure of feral grazing and prescribed burning were then conducted, after which we collected a second set of field data to test the response of small passerines to these measures. We used these data, which incorporated ecological changes that may have resulted from the management interventions, to validate and update the BN. The network predictions of small passerine abundance under the new habitat and management conditions were very accurate. The updated BN concluded the first iteration of adaptive management and will be used in planning the next round of management interventions. The unique belief-updating feature of BNs provides land managers with the flexibility to predict outcomes and evaluate the effectiveness of management interventions. Resumen:,El manejo adaptativo es un proceso interactivo de recopilación de conocimiento nuevo relacionado con el comportamiento de un sistema y el monitoreo de las consecuencias ecológicas de las acciones de manejo para refinar las opciones de manejo. Aunque el concepto se originó en la década de los 1970s, rara vez es incorporado activamente en la restauración ecológica. Las redes Bayesianas (RBs) están emergiendo como herramientas eficientes para la toma de decisiones ecológicas en el contexto del manejo adaptativo, pero los ejemplos de su aplicación en este sentido son escasos. Desarrollamos una RB en el marco del manejo adaptativo que se centra en el manejo de los efectos del pastoreo feral y los regímenes de quemas prescritas sobre la diversidad de aves en bosques subtropicales del este de Australia. Construimos la RB con datos para predecir la abundancia de aves como una función de la estructura del hábitat, la presión de pastoreo y las quemas prescritas. Los resultados del análisis de sensibilidad sugieren que la presión de pastoreo incrementó la abundancia de melífagos agresivos, que a su vez tuvieron un fuerte efecto negativo sobre paserinos pequeños. Posteriormente se llevaron a cabo intervenciones de manejo para reducir la presión del pastoreo feral y quemas prescritas, después de las cuales recolectamos un segundo conjunto de datos de campo para probar la respuesta de paserinos pequeños a estas medidas. Utilizamos estos datos, que incorporaron cambios ecológicos que pueden haber resultado de la intervención de manejo, para validar y actualizar la RB. Las predicciones de la abundancia de paserinos pequeños bajo las nuevas condiciones de hábitat y manejo fueron muy precisas. La RB actualizada concluyó la primera iteración de manejo adaptativo y será utilizada para la planificación de la siguiente ronda de intervenciones de manejo. La característica única de actualización de la RBs permite que los manejadores tengan flexibilidad para predecir los resultados y evaluar la efectividad de las intervenciones de manejo. [source]

Gastrointestinal Bacterial Transmission among Humans, Mountain Gorillas, and Livestock in Bwindi Impenetrable National Park, Uganda

CONSERVATION BIOLOGY, Issue 6 2008
INNOCENT B. RWEGO
ecología de enfermedades; Escherichia coli; primates; salud del ecosistema; zoonosis Abstract:,Habitat overlap can increase the risks of anthroponotic and zoonotic pathogen transmission between humans, livestock, and wild apes. We collected Escherichia coli bacteria from humans, livestock, and mountain gorillas (Gorilla gorilla beringei) in Bwindi Impenetrable National Park, Uganda, from May to August 2005 to examine whether habitat overlap influences rates and patterns of pathogen transmission between humans and apes and whether livestock might facilitate transmission. We genotyped 496 E. coli isolates with repetitive extragenic palindromic polymerase chain reaction fingerprinting and measured susceptibility to 11 antibiotics with the disc-diffusion method. We conducted population genetic analyses to examine genetic differences among populations of bacteria from different hosts and locations. Gorilla populations that overlapped in their use of habitat at high rates with people and livestock harbored E. coli that were genetically similar to E. coli from those people and livestock, whereas E. coli from gorillas that did not overlap in their use of habitats with people and livestock were more distantly related to human or livestock bacteria. Thirty-five percent of isolates from humans, 27% of isolates from livestock, and 17% of isolates from gorillas were clinically resistant to at least one antibiotic used by local people, and the proportion of individual gorillas harboring resistant isolates declined across populations in proportion to decreasing degrees of habitat overlap with humans. These patterns of genetic similarity and antibiotic resistance among E. coli from populations of apes, humans, and livestock indicate that habitat overlap between species affects the dynamics of gastrointestinal bacterial transmission, perhaps through domestic animal intermediates and the physical environment. Limiting such transmission would benefit human and domestic animal health and ape conservation. Resumen:,El traslape de hábitats puede incrementar los riesgos de transmisión de patógenos antroponótica y zoonótica entre humanos, ganado y simios silvestres. Recolectamos bacterias Escherichia coli de humanos, ganado y gorilas de montaña (Gorilla gorilla beringei) en el Parque Nacional Bwindi Impenetrable, Uganda, de mayo a agosto 2005 para examinar sí el traslape de hábitat influye en las tasas y patrones de transmisión de patógenos entre humanos y simios y sí el ganado facilita esa transmisión. Determinamos el genotipo de 496 aislados de E. coli con marcaje de reacción en cadena de polimerasa palindrómica extragénica (rep-PCR) y medimos la susceptibilidad a 11 antibióticos con el método de difusión de disco. Realizamos análisis de genética poblacional para examinar las diferencias genéticas entre poblaciones de bacterias de huéspedes y localidades diferentes. Las poblaciones de gorilas con alto grado de traslape en el uso de hábitat con humanos y ganado presentaron E. coli genéticamente similar a E. coli de humanos y ganado, mientras que E. coli de gorilas sin traslape en el uso hábitat con humanos y ganado tuvo relación lejana con las bacterias de humanos y ganado. Treinta y cinco porciento de los aislados de humanos, 27% de los aislados de ganado y 17% de los aislados de gorilas fueron clínicamente resistentes a por lo menos un antibiótico utilizado por habitantes locales, y la proporción de gorilas individuales con presencia de aislados resistentes declinó en las poblaciones proporcionalmente con la disminución en el grado de traslape con humanos. Estos de patrones de similitud genética y resistencia a antibióticos entre E. coli de poblaciones de simios, humanos y ganado indican que el traslape de hábitat entre especies afecta la dinámica de transmisión de bacterias gastrointestinales, probablemente a través de animales domésticos intermediarios y el ambiente físico. La limitación de esa transmisión beneficiaría a la salud de humanos y animales domésticos y a la conservación de simios. [source]

One Hundred Fifty Years of Change in Forest Bird Breeding Habitat: Estimates of Species Distributions

CONSERVATION BIOLOGY, Issue 6 2005
LISA A. SCHULTE
aptitud del hábitat; ecología aviar; ecología de paisaje; planificación de conservación Abstract:,Evaluating bird population trends requires baseline data. In North America the earliest population data available are those from the late 1960s. Forest conditions in the northern Great Lake states (U.S.A.), however, have undergone succession since the region was originally cut over around the turn of the twentieth century, and it is expected that bird populations have undergone concomitant change. We propose pre-Euro-American settlement as an alternative baseline for assessing changes in bird populations. We evaluated the amount, quality, and distribution of breeding bird habitat during the mid-1800s and early 1990s for three forest birds: the Pine Warbler (Dendroica pinus), Blackburnian Warbler (D. fusca), and Black-throated Green Warbler (D. virens). We constructed models of bird and habitat relationships based on literature review and regional data sets of bird abundance and applied these models to widely available vegetation data. Original public-land survey records represented historical habitat conditions, and a combination of forest inventory and national land-cover data represented current conditions. We assessed model robustness by comparing current habitat distribution to actual breeding bird locations from the Wisconsin Breeding Bird Atlas. The model showed little change in the overall amount of Pine Warbler habitat, whereas both the Blackburnian Warber and the Black-throated Green Warbler have experienced substantial habitat losses. For the species we examined, habitat quality has degraded since presettlement and the spatial distribution of habitat shifted among ecoregions, with range expansion accompanying forest incursion into previously open habitats or the replacement of native forests with pine plantations. Sources of habitat loss and degradation include loss of conifers and loss of large trees. Using widely available data sources in a habitat suitability model framework, our method provides a long-term analysis of change in bird habitat and a presettlement baseline for assessing current conservation priority. Resumen:,La evaluación de tendencias de las poblaciones de aves requiere de datos de referencia. En Norte América, los primeros datos disponibles de poblaciones son del final de la década de 1960. Sin embargo, las condiciones de los bosques en los estados de los Grandes Lagos (E.U.A.) han experimentado sucesión desde que la región fue talada en los inicios del siglo veinte, y se espera que las poblaciones de aves hayan experimentado cambios concomitantes. Proponemos que se considere al período previo a la colonización euro americana como referencia alternativa para evaluar los cambios en las poblaciones de aves. Evaluamos la cantidad, calidad y distribución del hábitat para reproducción de tres especies de aves de bosque (Dendroica pinus, D. fusca y D. virens) a mediados del siglo XIX e inicios del XX. Construimos modelos de las relaciones entre las aves y el hábitat con base en la literatura y conjuntos de datos de abundancia de aves y los aplicamos a los datos de vegetación ampliamente disponibles. Los registros topográficos de tierras públicas originales representaron las condiciones históricas del hábitat, y una combinación de datos del inventario forestal y de cobertura de suelo representaron las condiciones actuales. Evaluamos la robustez del modelo mediante la comparación de la distribución de hábitat actual con sitios de reproducción de aves registrados en el Wisconsin Breeding Bird Atlas. El modelo mostró poco cambio en la cantidad total de hábitat de Dendroica pinus, mientras que tanto D. fusca como D. virens han experimentado pérdidas sustanciales de hábitat. Para las especies examinadas, la calidad del hábitat se ha degradado desde antes de la colonización y la distribución espacial del hábitat cambió entre ecoregiones, con la expansión del rango acompañando la incursión de bosques en hábitats anteriormente abiertos o el reemplazo de bosques nativos con plantaciones de pinos. Las fuentes de pérdida y degradación de hábitats incluyen la pérdida de coníferas y de árboles grandes. Mediante la utilización de fuentes de datos ampliamente disponibles en un modelo de aptitud de hábitat, nuestro método proporciona un análisis a largo plazo de los cambios en el hábitat de aves y una referencia precolonización para evaluar prioridades de conservación actuales. [source]

Reproductive Investment of a Lacertid Lizard in Fragmented Habitat

CONSERVATION BIOLOGY, Issue 5 2005
JOSÉ A. DÍAZ
calidad de hábitat; fragmentación de bosque; Psammodromus; tamaño de puesta; tamaño de huevo Abstract:,We studied the effect of habitat fragmentation on female reproductive investment in a widespread lacertid lizard ( Psammodromus algirus) in a mixed-forest archipelago of deciduous and evergreen oak woods in northern Spain. We captured gravid females in fragments (,10 ha) and forests (, 200 ha) and brought them to the laboratory, where they laid their eggs. We incubated the eggs and released the first cohort of juveniles into the wild to monitor their survival. Females from fragments produced a smaller clutch mass and laid fewer eggs (relative to mean egg mass) than females of similar body size from forests. Lizards did not trade larger clutches for larger offspring, however, because females from fragments did not lay larger eggs (relative to their number) than females from forests. Among the first cohort of juveniles, larger egg mass and body size increased the probability of recapture the next year. Thus, fragmentation decreased the relative fecundity of lizards without increasing the quality of their offspring. Reduced energy availability, increased predation risk, and demographic stochasticity could decrease the fitness of lizards in fragmented habitats, which could contribute to the regional scarcity of this species in agricultural areas sprinkled with small patches of otherwise suitable forest. Our results show that predictable reduction of reproductive output with decreasing size of habitat patches can be added to the already known processes that cause inverse density dependence at low population numbers. Resumen:,Estudiamos el efecto de la fragmentación sobre la inversión reproductiva de hembras en una lagartija lacértida ( Psammodromus algirus) ampliamente distribuida en un archipiélago mixto de bosques deciduos y siempre verdes de roble en el norte de España. Capturamos hembras grávidas en fragmentos (, 10 ha) y en bosques (, 200 ha) y las trasladamos al laboratorio, donde pusieron sus huevos. Incubamos los huevos y liberamos a la primera cohorte de juveniles para monitorear su supervivencia. Las hembras de fragmentos produjeron una puesta de menor masa y pusieron menos huevos (en relación con la masa promedio de los huevos) que hembras con talla corporal similar provenientes de bosques. Sin embargo, las lagartijas no cambiaron puestas mayores por crías más grandes porque las hembras de fragmentos no pusieron huevos más grandes (en relación con su número) que las hembras de bosques. Entre las primeras cohortes de juveniles, la mayor masa de los huevos incrementó la probabilidad de recaptura en el siguiente año. Por lo tanto, la fragmentación redujo la fecundidad relativa de las lagartijas sin aumentar la calidad de sus crías. La disponibilidad reducida de energía, el incremento en el riesgo de depredación y la estocasticidad demográfica podrían disminuir la adaptabilidad de lagartijas en hábitats fragmentados, lo que podría contribuir a la escasez regional de esta especie en áreas agrícolas salpicadas de pequeños parches de bosque por lo demás adecuado. Nuestros resultados muestran que la reducción predecible en la reproducción al disminuir el tamaño de los parches de hábitat se puede agregar a los procesos ya conocidos que causan la inversión de la denso dependencia en tamaños poblacionales pequeños. [source]

A spatial model of bird abundance as adjusted for detection probability

ECOGRAPHY, Issue 2 2009
P. Marcos Gorresen
Modeling the spatial distribution of animals can be complicated by spatial and temporal effects (i.e. spatial autocorrelation and trends in abundance over time) and other factors such as imperfect detection probabilities and observation-related nuisance variables. Recent advances in modeling have demonstrated various approaches that handle most of these factors but which require a degree of sampling effort (e.g. replication) not available to many field studies. We present a two-step approach that addresses these challenges to spatially model species abundance. Habitat, spatial and temporal variables were handled with a Bayesian approach which facilitated modeling hierarchically structured data. Predicted abundance was subsequently adjusted to account for imperfect detection and the area effectively sampled for each species. We provide examples of our modeling approach for two endemic Hawaiian nectarivorous honeycreepers: ,i,iwi Vestiaria coccinea and ,apapane Himatione sanguinea. [source]

Habitat and food choice of Arctic charr in Linnévatn on Spitsbergen, Svalbard: the first year-round investigation in a High Arctic lake

ECOLOGY OF FRESHWATER FISH, Issue 1 2007
M.-A. Svenning
Abstract,,, Habitat and diet of Arctic charr Salvelinus alpinus (L.) were studied by monthly sampling from late autumn to early summer in Linnévatn, Svalbard (78°3,N, 13°50,E). This is the first year-round study of a population of charr in the High Arctic, with samples being taken every 5,7 weeks. The ice cover lasted for more than 9 months, from mid-October to late July, with the greatest thickness in mid-May. Although most charr occupied the littoral zone during winter, the highest densities in April and October were found in the deeper areas (20 m) of the lake. The fish fed at all times of the year, but the number of stomachs with food and the stomach-filling indices were lowest during the darkest part of the season. The diet of smaller charr (<15 cm) varied strongly with season, showing a dominance of zooplankton in late autumn and chironomids in winter (larvae) and summer (pupae). The food choice was in accordance with the density of food items available. Larger fish (,15 cm) were mostly cannibalistic during the entire year. [source]

The Influence of Google on Urban Policy in Developing Countries

INTERNATIONAL JOURNAL OF URBAN AND REGIONAL RESEARCH, Issue 1 2010
RICHARD TOMLINSON
Abstract ,Google's mission is to organize the world's information and make it universally accessible and useful.' In the case of urban policy in developing countries, Google not only provides information, e.g. the size of a city's population, but also knowledge, e.g. analyses of urban issues and policies. Based on research conducted between January and May 2008, we argue that googling urban policy issues contributes to hegemonic policy perspectives; that the manner in which Google organizes knowledge limits access to alternative policy perspectives and debate; and that this is not in the public interest. We make three claims. The first is that the World Bank, the Cities Alliance and UN Habitat together dominate explanations of urban issues and appropriate policies. The second is that googling policy issues contributes to this dominance. The third claim is that Google especially serves this purpose when the query ,keywords' can be used as labels whose conceptualization can be ,owned'. These claims are demonstrated through explaining how the Google search engine works and creates ,biases'; and then through googling ,city development strategy', ,slum upgrading', and ,municipal services, finances and capacity building in developing countries'. We further demonstrate that finding potential alternative policies requires perseverance and time and pre-existing knowledge of what the policy issues might be. Résumé ,Google a pour mission d'organiser les informations à l'échelle mondiale dans le but de les rendre accessibles et utiles à tous.' En matière de politique urbaine dans les pays en développement, Google fournit des informations (chiffres de la population d'une ville, par exemple), mais aussi du savoir (comme les analyses des enjeux et des politiques de la ville). Une étude menée entre janvier et mai 2008 permet de montrer que les recherches via Google sur les questions de politique urbaine contribuent à des approches politiques hégémoniques, que le mode d'organisation du savoir par Google limite l'accès à des points de vue et débats alternatifs, et que cette situation ne répond pas à l'intérêt public. Trois observations sont formulées: d'abord, la Banque mondiale, l'Alliance des villes et l'ONU-Habitat monopolisent les explications sur les questions urbaines et les politiques appropriées; ensuite, interroger Google sur les enjeux de politique publique contribue à cette hégémonie; enfin, Google va dans ce sens lorsque les ,mots clés' de recherche peuvent servir de ,dénominations' pour des concepts renvoyant à des ,propriétaires'. À l'appui de ces affirmations, nous expliquons comment le moteur de recherche de Google fonctionne et crée des ,distorsions', puis nous présentons les résultats d'interrogations sur ,city development strategy', ,slum upgrading' et ,municipal services, finances and capacity building in developing countries'. Nous montrons également que trouver des politiques alternatives potentielles exige persévérance et temps, ainsi qu'une connaissance préalable des enjeux de politique publique. [source]

Habitat and abundance of Balitoridae in small rivers of central Thailand

JOURNAL OF FISH BIOLOGY, Issue 10 2008
F. W. H. Beamish
Balitorids were collected, by electrofishing, from small rivers across central Thailand between October 2000 and March 2004. Total balitorid abundance for the 18 species averaged 3·8% of the cumulative total for all fishes. Balitorid species numbers and abundance varied directly with elevation to c. 400 m, substratum particle size and ambient silica concentration. Species numbers at stations were modest and few species were widely distributed. Species associations related significantly with elevation, temperature and ambient concentrations of dissolved oxygen and silica. Turbidity was also significant but probably an artefact. Habitat separation clearly occurs among some balitorids, particularly the less common species, and probably represents species-specific direct and indirect habitat effects. The more common balitorid species tended to occur in similar habitats where the significant factors approximated average values. For these species, coexistence is suggested to occur through food resource sharing possibly facilitated through adaptations. Balitorid distributions in low-order rivers are attributed to the direct and indirect influences of the environment on energy available for the performance of essential activities. [source]

An Evaluation of Qualitative Indexes of Physical Habitat Applied to Agricultural Streams in Ten U.S. States,

JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 4 2010
Robert M. Hughes
Hughes, Robert M., Alan T. Herlihy, and Philip R. Kaufmann, 2010. An Evaluation of Qualitative Indexes of Physical Habitat Applied to Agricultural Streams in Ten U.S. States. Journal of the American Water Resources Association (JAWRA) 46(4): 792-806. DOI: 10.1111/j.1752-1688.2010.00455.x Abstract:, Assessment of stream physical habitat condition is important for evaluating stream quality globally. However, the diversity of metrics and methods for assessing physical habitat condition confounds comparisons among practitioners. We surveyed 51 previously sampled stream sites (0.0-6.3 m wide) located in regions of row-crop agriculture in Oregon, California, North Dakota, South Dakota, Nebraska, Iowa, Minnesota, Pennsylvania, Maryland, and West Virginia to evaluate the comparability of four indexes of physical habitat condition relative to each other. We also compared the indexes to previously calculated indexes of fish and macroinvertebrate condition. The physical habitat indexes included the Stream Visual Assessment Protocol Version 2 of the Natural Resources Conservation Service, the qualitative habitat evaluation index of the Ohio Environmental Protection Agency, the rapid bioassessment protocol of the United States Environmental Protection Agency (USEPA), and a qualitative physical habitat index based on USEPA quantitative physical habitat measurements. All four indexes were highly correlated with each other, but low-to-moderately correlated with biotic index scores for fish and macroinvertebrate assemblages. Moderately high correlations occurred between some macroinvertebrate biotic index scores and quantitative metrics. We conclude that additional research is needed to increase the predictive and diagnostic capabilities of qualitative physical habitat indexes. [source]

Habitat For Humanity: Building Social Capital Through Faith Based Service

JOURNAL OF URBAN AFFAIRS, Issue 3 2002
R. Allen Hays
This essay examines citizen involvement in community housing issues through Habitat for Humanity as a faith, based expansion of social capital in urban communities. This article expands Putnam's model of social capital to include criteria for evaluating the conditions under which social capital formation has a positive impact on the larger community. Using a representative sample of nine cities from various regions of the US, it examines the functioning of the Habitat affiliate in each of these cities and the attitudes and motivations of their most active volunteers. Habitat has emerged as a highly effective volunteer, non, profit producer of housing for lower income persons, yet the nature of the social capital created by this organization also reflects the contradictions raised by such an undertaking in a complex urban environment characterized by deep social divisions. [source]

Molecular phylogeny of Enchytraeidae (Oligochaeta) indicates separate invasions of the terrestrial environment

JOURNAL OF ZOOLOGICAL SYSTEMATICS AND EVOLUTIONARY RESEARCH, Issue 3 2010
Bent Christensen
Abstract Enchytraeidae is a family of soil inhabiting small- to medium-sized oligochaete worms using degradable plant material as a food source and primarily adapted to terrestrial or semi-terrestrial environments. The molecular phylogeny based upon both mitochondrial and nuclear genes indicates early segregations of the two genera Enchytraeus and Lumbricillus leaving the remaining genera included in this study as a later segregated major monophyletic branch. Extant members of the two former genera dominate in decaying seaweed in the littoral zone along the sea although members of in particular the genus Enchytraeus have also invaded other habitats. Historically the littoral zone of the sea is undoubtedly the first terrestrial or semi-terrestrial habitat where dead plant material accumulates to any greater extent and Enchytraeus and Lumbricillus may represent early successful attempts to exploit this resource. Inland soils probably had to await the emergence of land plants in order to provide a similar food resource and here the major branch of enchytraeid genera diversified into a high number of species in the numerous decomposer networks of this varied environment. A subdivision into the genera Enchytraeus and Lumbricillus on the one hand and a branch of mainly inland genera on the other is supported by differences in two somewhat neglected morphological features. Firstly, in Enchytraeus and Lumbricillus the testes are enclosed in a testis sac within which the male cells mature, by one possible exception a unique feature among Oligochaeta, The other enchytraeid genera studied and Oligochaeta in general lack this sac and the male cells mature directly in the cavity of the testicular segment. Secondly, species of Enchytraeus and Lumbricillus generally have a higher reproductive output than species of the inland terrestrial branch and this may represent an adaptation to the unpredictable littoral zone compared to the more stable nature of inland habitats. In the older literature the genus Mesenchytraeus is considered to have a basic position within the entire family but our molecular data do not support this expectation. In Enchytraeidae the nephridia are elaborate organs of a characteristic and constant shape covering species from different genera in a pattern following the molecular phylogeny. Other much used morphological features such as shape of setae, anteclitellar origin of the dorsal vessel and various modifications of the intestine have arisen more than once. Zusammenfassung Enchytraeidae sind eine Familie kleiner bis mittelgroßer edaphischer Oligochaeten, welche abbaubares Pflanzenmaterial als Nahrungsquelle nutzen und primär an terrestrische oder semiterrestrische Lebensräume angepaßt sind. Die hier vorgestellte, auf mitochondrialen und nukleären Genen beruhende molekulare Phylogenie indiziert eine frühe Abtrennung der beiden Gattungen Enchytraeus und Lumbricillus und beläßt die übrigen der in dieser Studie untersuchten Gattungen als eine später abgezweigte monophyletische Großgruppe. Rezente Glieder der beiden erwähnten Gattungen dominieren in verrottendem Strandanwurf des Meereslitorals, obwohl Arten insbesondere der Gattung Enchytraeus auch andere Lebensräume erobert haben. Historisch gesehen ist das Meereslitoral zweifelsohne das erste terrestrische oder semiterrestrische Habitat, in dem totes Pflanzenmaterial in größerem Ausmaß akkumulierte, und Enchytraeus und Lumbricillus könnten frühe erfolgreiche Versuche der Nutzung dieser Ressource darstellen. Festlandsböden dagegen bedurften wahrscheinlich der Entwicklung von Landpflanzen, um eine vergleichbare Nahrungsquelle zur Verfügung zu stellen, und hier diversifizierte sich der Hauptzweig der Enchytraeidengattungen in viele Arten in den diversen Zersetzernetzen dieses vielgestaltigen Lebensraums. Eine Unterteilung in die Gattungen Enchytraeus und Lumbricillus auf der einen Seite und einen Zweig mit vorwiegend terrestrischen Gattungen auf der anderen wird durch zwei bislang eher vernachlässigte morphologische Merkmale gestützt. Erstens, bei Enchytraeus und Lumbricillus wird der Hoden von einem Testis-Sack, in dem die männlichen Zellen reifen, umschlossen. Dies ist mit einer möglichen Ausnahme einzigartig bei Oligochaeten. Bei den übrigen untersuchten Enchytraeidengattungen und bei Oligochaeten generell fehlt dieser Sack, und die männlichen Zellen reifen unmittelbar in der Körperhöhle des Hodensegmentes. Zweitens, die Reproduktionsrate von Enchytraeus und Lumbricillus ist generell höher als die der Arten des Festlandszweigs. Dies könnte eine Anpassung an die im Vergleich zu Festlandsböden instabileren Bedingungen des Meereslitorals bedeuten. In der älteren Literatur wird der Gattung Mesenchytraeus eine basale Position innerhalb der gesamten Familie zugewiesen, aber unsere molekularen Daten stützen diese Annahme nicht. Die Nephridien der Enchytraeiden sind komplexe Organe mit einer charakteristischen und artübergreifend konstanten Form, deren gattungsmäßige Abwandlungen der molekularen Phylogenie entsprechen. Andere oft verwendete morphologische Merkmale wie Borstenform, anteclitellarer Ursprung des Dorsalgefäßes und verschiedene Darmmodifikationen sind mehr als einmal entstanden. [source]

Habitat selection and habitat-specific survival of fledgling ovenbirds (Seiurus aurocapilla)

JOURNAL OF ZOOLOGY, Issue 4 2006
D. I. King
Abstract Patterns of habitat use by some passerines change after the young leave the nest, and thus our understanding of habitat selection derived from counts of singing males earlier in the nesting cycle may not adequately represent the breeding habitat requirements of these species. Post-fledging changes in habitat use may have important conservation implications if the survival of fledglings is affected by characteristics of the habitat; however, there have been relatively few systematic studies of the post-fledging ecology of forest passerines and, of these, even fewer have incorporated analyses of the relationship between habitat characteristics and fledgling survival. We studied the post-fledging habitat selection and survival of ovenbirds Seiurus aurocapilla in northern New Hampshire, USA during two breeding seasons using radio telemetry. Habitat at sites used by radio-marked fledgling ovenbirds was characterized by fewer large trees and greater vertical structure 0,3 m above ground than ovenbird nest sites. Similarly, habitat at sites used by fledgling ovenbirds was characterized by fewer large trees and greater vertical structure than unused sites. Most (80%) of the 15 mortalities that we observed were due to predation. Nine (70%) of these occurred within the first 3 days of fledging, resulting in a significant drop in survival during this period. Fledgling survival increased significantly with increased vegetation structure. Our observations that fledgling ovenbirds are selective in their habitat use, that they select different habitat features than adult ovenbirds select for nesting and that fledgling survival is positively associated with these habitat features suggest that the use of habitat models based on counts of singing males before fledging does not adequately represent the habitat needs of this species. Conceivably, mortality during the post-fledging period could limit recruitment to levels insufficient to maintain the viability of ovenbird population even if adequate nesting habitat were available. [source]

The Chalan beel in Bangladesh: Habitat and biodiversity degradation, and implications for future management

LAKES & RESERVOIRS: RESEARCH AND MANAGEMENT, Issue 1 2009
Mostafa A. R. Hossain
Abstract This study provides an overview of the current resources and fisheries status of the Chalan beel, and identifies the scope of opportunities to evolve existing fisheries management strategies, focusing on fish biodiversity conservation. Chalan beel is the largest, most important watershed in the North Central Bangladesh, and covers an area of about 375 km2 during the monsoon season. The watershed serves about 5 million people, predominantly through fisheries and agricultural activities. Although considerably degraded over time, Chalan beel still supports a diverse ichthyofauna of major importance to the local economy and people's livelihoods. The Chalan beel area incorporates 21 rivers and 93 smaller seasonal beels of varying size. Most of the rivers and beels are at risk of partial or total degradation, as a result of agricultural encroachment, siltation and other anthropogenic activities. During the study, , 83% of the rivers, and 68% of the beels in the lean season, shrunk to 0,5% of their maximum (monsoon) water-spread area during the dry season (i.e. critical levels for survival of many fish species). A fish catch survey was carried out in the main fishing season (July to December) over two successive years in the three most important catchment areas; namely, the Gumani, Baral and Katagang Rivers. A total of 72 sampling episodes yielded 9818 individuals, representing 114 fish species. The most abundant fish species during the 2-year study period were punti (Puntius sophore and Puntius ticto), followed by chanda (Chanda nama and Parambassis ranga), chapila (Gudusia chapra) and tengra (Mystus vittatus). The study results indicate at least 19 fish species once considered abundant can now be classified as threatened, with a possibility of local extinction. The mean fish catch was 2.08 ± 0.49 kg, and 1.29 ± 0.32 kg per hour per person, by suti jal (set bag net , the most common gear used in the beel) in 2005 and 2006, respectively, with a significant (P < 0.05) variation among catches in months and years at all three sample sites. In 2005,2006, the annual fish production in Chalan beel was 12 217 tonnes, being less than half of the production observed in 1982. The stakeholders identified several major causes they thought were directly responsible for the continued decrease in fish production and biodiversity of the beel area. Several management strategies were suggested by the same stakeholders, and the findings are discussed in the context of overall developments in the Chalan beel fisheries related to habitat and biodiversity management. [source]

Experimental evidence of habitat provision by aggregations of Riftia pachyptila at hydrothermal vents on the East Pacific Rise

MARINE ECOLOGY, Issue 1 2007
Breea Govenar
Abstract Habitat created or modified by the physical architecture of large or spatially dominant species plays an important role in structuring communities in a variety of terrestrial, aquatic, and marine habitats. At hydrothermal vents, the giant tubeworm Riftia pachyptila forms large and dense aggregations in a spatially and temporally variable environment. The density and diversity of smaller invertebrates is higher in association with aggregations of R. pachyptila than on the surrounding basalt rock seafloor. Artificial substrata designed to mimic R. pachyptila aggregations were deployed along a gradient of productivity to test the hypothesis that high local species diversity is maintained by the provision of complex physical structure in areas of diffuse hydrothermal flow. After 1 year, species assemblages were compared among artificial aggregations in low-, intermediate-, and high-productivity zones and compared to natural aggregations of R. pachyptila from the same site. Hydrothermal vent fauna colonized every artificial aggregation, and both epifaunal density and species richness were highest in areas of high chemosynthetic primary production. The species richness was also similar between natural aggregations of R. pachyptila and artificial aggregations in intermediate- and high-productivity zones, suggesting that complex physical structure alone can support local species diversity in areas of chemosynthetic primary production. Differences in the community composition between natural and artificial aggregations reflect the variability in microhabitat conditions and biological interactions associated with hydrothermal fluid flux at low-temperature hydrothermal vents. Moreover, these local ecological factors may further contribute to the maintenance of regional species diversity in hydrothermal vent communities on the East Pacific Rise. [source]

Habitat and Microhabitat of Mediterranean Clingfishes (Teleostei: Gobiesociformes: Gobiesocidae)

MARINE ECOLOGY, Issue 1 2000
Robert Hofrichter
Abstract. This study addresses the habitat and microhabitat of the seven species of gobiesocid fish in the Mediterranean Sea. It is shown that Lepadogaster lepadogaster is closely adapted to large pebbles and boulder fields of rounded stones with a smooth surface. L. candollei is more euryecious and, in addition to inhabiting boulder fields also, occurs close to seagrass meadows, in small cavities and in association with sea urchins. Diplecogaster bimaculata is also euryecious and extends to greater depths. It lives on sand and muddy bottoms as well as on coralline grounds. At some locations this species is found in high abundance during the spawning season under empty bivalve shells or flat stones. Apletodon dentatus is the rarest species of Gobiesocidae in the Mediterranean Sea. It has a close association with seagrass or large brown algae (Cystoseira). Juveniles of A. incognitus are either associated with sea urchins or inhabit Posidonia meadows. Adults prefer the vicinity of seagrass meadows under empty bivalve shells and stones overgrown with red algae. Gouania wildenowi is stenoecious and is restricted to the interstices of roundish coarse gravel near the waterline. Opeatogenys gracilis is also stenoecious and lives only on the leaves of Posidonia and Cymodocea seagrass. The colourations of the different species and their variations are described and discussed. [source]

EFFECTS OF AN OFFSHORE OIL DEVELOPMENT ON LOCAL ABUNDANCE AND DISTRIBUTION OF RINGED SEALS (PHOCA HISPIDA) OF THE ALASKAN BEAUFORT SEA,

MARINE MAMMAL SCIENCE, Issue 2 2005
Valerie D. Moulton
Abstract This study investigates how densities of ringed seals were affected by construction and oil production activities at Northstar, an artificial island built in the nearshore Alaskan Beaufort Sea. Intensive and replicated aerial surveys of seals on landfast ice were conducted during six spring seasons: for three seasons before island construction began (1997,1999); after a winter of intensive island construction (2000); and after more limited construction plus drilling (2001) and drilling plus oil production (2002). A Poisson regression model was used to examine seal densities relative to distance from Northstar after allowance for environmental covariates. Post hoc power analysis indicated that the study design and Poisson regression approach had high power to detect small-scale changes in seal densities near Northstar if such changes had occurred. However, seal densities during spring were not significantly affected by proximity to Northstar in 2000,2002. Habitat, temporal, and weather factors did have significant effects on seal densities. This study shows that effects of the Northstar oil development on local distribution of basking ringed seals are no more than slight, and are small relative to the effects of natural environmental factors. An understanding of environmental effects is essential when assessing potential impacts of industrial activity on ringed seals. [source]

The Genus Chelipoda Macquart (Diptera, Empididae, Hemerodromiinae) in Chile

MITTEILUNGEN AUS DEM MUSEUM FUER NATURKUNDE IN BERLIN-DEUTSCHE ENTOMOLOGISCHE ZEITSCHRIFT, Issue 1 2009
Adrian R. Plant
Abstract Chilean species of Chelipoda Macquart, 1823 (Diptera, Empididae, Hemerodromiinae) are reviewed and a key provided to all known species. Six new species are described; Chelipoda ceraphoron sp. n., C. deletrix sp. n., C. interfectrix sp. n., C. kolua sp. n., C. lentiginosa sp. n. and C. perditrix sp. n. Lectotypes and paralectotypes are designated for C. fimbriata Collin, 1933, C. obtusipennis Collin, 1933 and C. remissa Collin, 1933 and a lectotype is designated for C. subflava Collin, 1933. Cladistic analysis resolved two distinct clades defined largely on male genitalic characters. Habitat, biogeography and occurrence of secondary sexual characters are briefly discussed. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Ecological stress and linear enamel hypoplasia in Cebus

AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 1 2010
Madeleine B. Chollet
Abstract Although it is assumed that monkeys in some environments experience more nutritional or physiological stress than others, little research has been conducted on this topic. This study examines the relationship between linear enamel hypoplasia (LEH) frequency, a physiological indicator of stress, and environmental stressors. To test this relationship, LEH frequencies were calculated for 144 Cebus from 54 locations in Brazil. Habitat, temperature range, and annual rainfall were compared between individuals with and without LEH. The LEH frequency for Cebus from semideciduous forests was significantly higher than that for monkeys from coastal areas, the rainforest, and the savanna (,2 = 9.97, df = 1; P = 0.0016). A significantly higher LEH frequency was also found for monkeys living in environments with the mean annual temperature between 15 and 18°C than for those in environments greater than 18°C (,2 = 7.74, df = 1, P = 0.0054). However, no significant difference was found between LEH frequency and annual rainfall (t = 1.22, P = 0.23) or the average difference in rainfall between the driest and wettest months (t = 0.77, P = 0.44). These results indicate that levels of physiological stress can differ among environments and that habitat and temperature, but not precipitation, may be driving the difference in stress levels among environments. Am J Phys Anthropol, 2010. © 2009 Wiley-Liss, Inc. [source]

Habitat Overlap and Facilitation in Tamarisk and Box Elder Stands: Implications for Tamarisk Control Using Native Plants

RESTORATION ECOLOGY, Issue 3 2010
John M. DeWine
Invasive plants are typically managed using top-down control techniques that focus on the removal of the target organism. Bottom-up control limits the resources available to the undesired species by manipulating disturbance, competition, and successional processes, and thus may prevent reinvasion. Tamarisk species (Tamarix sp.) have invaded riparian areas throughout western North America, resulting in expansive control efforts. A companion study has shown that a native competitor, Box elder (Acer negundo), is capable of outcompeting and killing established Tamarisk through light interception in canyons of Dinosaur National Monument (DNM), Colorado. The goal of this study was to determine the feasibility of using Box elder as a bottom-up control agent by (1) determining the distributional overlap of the two species in DNM; (2) determining if Tamarisk facilitates Box elder establishment; and (3) analyzing Box elder seedling survival across a range of physical gradients. The distribution of Tamarisk and Box elder overlapped considerably throughout the study area. Box elder seedlings were planted under Tamarisk canopies or areas with the canopy removed. Survival was significantly higher under Tamarisk canopies, indicating that Tamarisk facilitates Box elder seedling survival. Box elder seedling survival was tested across soil texture, litter depth, groundwater depth, and shade intensities indicative of conditions found in the canyons of DNM, and survival was high for all treatments. The manipulation of competitive and successional processes through the promotion of Box elder and other native tree establishment is suggested as a means of bottom-up Tamarisk control to complement traditional control techniques. [source]

Restoring Forbs for Sage Grouse Habitat: Fire, Microsites, and Establishment Methods

RESTORATION ECOLOGY, Issue 3 2003
Troy A. Wirth
Abstract The decline and range reduction of sage grouse populations are primarily due to permanent loss and degradation of sagebrush,grassland habitat. Several studies have shown that sage grouse productivity may be limited by the availability of certain preferred highly nutritious forb species that have also declined within sagebrush ecosystems of the Intermountain West, U.S.A. The purpose of this study was to determine the suitability of three species of forbs for revegetation projects where improving sage grouse habitat is a goal. Species suitability was determined by evaluating the emergence, survival, and reproduction of Crepis modocensis, C. occidentalis, and Astragalus purshii in response to method of establishment (seeding or transplanting), site preparation treatment (burned or unburned), and microsite (mound or interspace) in an Artemisia tridentata ssp. wyomingensis vegetation association in south central Oregon. For seeded plants A. purshii had the lowest emergence (8%) of all three species. Both seeded Crepis species had similar overall emergence (38%). Significantly more Crepis seedlings emerged from shrub mounds in unburned areas (50%) than in any other fire-by-microsite treatment (33 to 36%). Approximately 10% more Crepis seedlings survived in mounds compared with interspaces. Nearly twice as many emerging Crepis seedlings survived in the burned areas as opposed to unburned areas (p < 0.01). This resulted in more plant establishment in burned mounds despite higher emergence in unburned mounds. Astragalus purshii seedlings also survived better in burned areas (p = 0.06) but had no differential response to microsite. Fire enhanced survival of both Crepis and A. purshii transplants (p = 0.08 and p = 0.001). We believe additional research is needed to improve A. purshii emergence before it will become an effective plant for restoring sage grouse habitat. Conversely, we conclude that these Crepis species provide a viable revegetation option for improving sage grouse habitat in south central Oregon. [source]

Contrasting Functional Performance of Juvenile Salmon Habitat in Recovering Wetlands of the Salmon River Estuary, Oregon, U.S.A.

RESTORATION ECOLOGY, Issue 3 2002
Ayesha Gray
Abstract For an estuarine restoration project to be successful it must reverse anthropogenic effects and restore lost ecosystem functions. Restoration projects that aim to rehabilitate endangered species populations make project success even more important, because if misjudged damage to already weakened populations may result. Determining project success depends on our ability to assess the functional state or "performance" and the trajectory of ecosystem development. Mature system structure is often the desired "end point" of restoration and is assumed to provide maximum benefit for target species; however, few studies have measured linkages between structure and function and possible benefits available from early recovery stages. The Salmon River estuary, Oregon, U.S.A., offers a unique opportunity to simultaneously evaluate several estuarine restoration projects and the response of the marsh community while making comparisons with a concurring undiked portion of the estuary. Dikes installed in three locations in the estuary during the early 1960s were removed in 1978, 1987, and 1996, creating a "space-for-time substitution" chronosequence. Analysis of the marsh community responses enables us to use the development state of the three recovering marshes to determine a trajectory of estuarine recovery over 23 years and to make comparisons with a reference marsh. We assessed the rate and pattern of juvenile salmon habitat development in terms of fish density, available prey resources, and diet composition of wild juvenile Oncorhynchus tshawytscha (chinook salmon). Results from the outmigration of 1998 and 1999 show differences in fish densities, prey resources, and diet composition among the four sites. Peaks in chinook salmon densities were greatest in the reference site in 1998 and in the youngest (1996) site in 1999. The 1996 marsh had higher densities of chironomids (insects; average 864/m2) and lower densities of amphipods (crustaceans; average 8/m3) when compared with the other sites. Fauna differences were reflected in the diets of juvenile chinook with those occupying the 1978 and 1996 marshes based on insects (especially chironomids), whereas those from the 1987 and reference marshes were based on crustaceans (especially amphipods). Tracking the development of recovering emergent marsh ecosystems in the Salmon River estuary reveals significant fish and invertebrate response in the first 2 to 3 years after marsh restoration. This pulse of productivity in newly restored systems is part of the trajectory of development and indicates some level of early functionality and the efficacy of restoring estuarine marshes for juvenile salmon habitat. However, to truly know the benefits consumers experience in recovering systems requires further analysis that we will present in forthcoming publications. [source]

Dry season habitat use by critically endangered white-shouldered ibis in northern Cambodia

ANIMAL CONSERVATION, Issue 1 2010
H. L. Wright
Abstract We present the first scientific study of white-shouldered ibis Pseudibis davisoni habitat preferences in dry dipterocarp forest. Foraging sites included seasonal pools, forest understorey grasslands and fallow rice fields, with terrestrial sites used more following rainfall. Habitat and anthropogenic effects in logistic models of foraging site selection were examined by multimodel inference and model averaging. White-shouldered ibis preferred pools with greater cover of short vegetation (<25 cm) and less of the boundary enclosed, and forest sites with greater cover of bare substrate and lower people encounter rate. At forest sites, livestock density was positively related to bare substrate extent and thus may improve suitability for foraging ibis. At pools, livestock removed tall vegetation between the early and late dry season indicating their importance in opening up foraging habitats after wet season growth. However, by the late dry season, pools with greater livestock density had less short vegetation, the habitat favoured by ibis. Conservation strategies for white-shouldered ibis must consider a range of habitats, not just seasonal wetlands, and should incorporate extensive grazing and associated burning practises of local communities. Further understanding of the effects of these practices on vegetation, prey abundance and prey availability are therefore needed for effective conservation of this species. This will also develop our understanding of potentially beneficial anthropogenic influences in tropical environments. [source]

Rangeland degradation is poised to cause Africa's first recorded avian extinction

ANIMAL CONSERVATION, Issue 3 2009
C. N. Spottiswoode
Abstract Rangeland degradation by livestock threatens several restricted-range species, but is largely overlooked by conservation biologists. The Sidamo lark Heteromirafra sidamoensis, confined to the Liben Plain grassland in southern Ethiopia, is critically endangered by bush encroachment, permanent settlement and agricultural conversion. Its global range was previously estimated at 760 km2, but in 2007,2008 available habitat covered<35 km2. Density estimates from multi-model inference analysis of distance transect data provided a global population estimate of 90,256 adults (possibly with a serious sex-ratio bias towards males). Logistic regression models of habitat selection showed that males preferentially occurred in areas of grassland with greater cover of medium-length grass (5,15 cm), less cover of bare ground and fewer bushes. Habitat transects extending outward from its core range revealed massive and rapid bush encroachment, corroborating information from semi-structured interviews. The survival of both local Borana pastoralism and this species , mainland Africa's likeliest first avian extinction , depends on restoring seasonal patterns of grazing, resisting agricultural conversion of grasslands, reversing fire suppression policies and clearing bush. [source]