bluuebunny/crossref_metadata_2025 huggingface dataset:
Physiological and symptomatic responses to cycling and walking in intermittent claudication
Authors: Askew C. D. , Green S. , Hou X. Y. , Walker P. J.
Published: March 2003

To shed light on the potential efficacy of cycling as a testing modality in the treatment of intermittent claudication (IC), this study compared physiological and symptomatic responses to graded walking and cycling tests in claudicants. Sixteen subjects with peripheral arterial disease (resting ankle:brachial index (ABI) < 0·9) and IC completed a maximal graded treadmill walking (T) and cycle (C) test after three familiarization tests on each mode. During each test, symptoms, oxygen uptake (VO2), minute ventilation (VE), respiratory exchange ratio (RER) and heart rate (HR) were measured, and for 10 min after each test the brachial and ankle systolic pressures were recorded. All but one subject experienced calf pain as the primary limiting symptom during T; whereas the symptoms were more varied during C and included thigh pain, calf pain and dyspnoea. Although maximal exercise time was significantly longer on C than T (690 ± 67 vs. 495 ± 57 s), peak VO2, peak VE and peak heart rate during C and T were not different; whereas peak RER was higher during C. These responses during C and T were also positively correlated (P<0·05) with each other, with the exception of RER. The postexercise systolic pressures were also not different between C and T. However, the peak decline in ankle pressures from resting values after C and T were not correlated with each other. These data demonstrate that cycling and walking induce a similar level of metabolic and cardiovascular strain, but that the primary limiting symptoms and haemodynamic response in an individual's extremity, measured after exercise, can differ substantially between these two modes.
Reference values for 99mTc‐MAG3 renography determined in healthy, potential renal donors
Authors: Clausen Thomas D. , Kanstrup Inge‐Lis , Iversen Jens
Published: March 2003

Background:  Reference values for 99mTc‐MAG3 renography were determined and the influence of sex and age (<50/≥50 years) was elucidated.

Methods:  Sixty‐eight potential renal donors were evaluated by renography among other tests. Through examination of their records 41 healthy subjects with a normal renal arteriography were included in this study and the reference values of the functional distribution (the split function, SF), the time to peak renal parenchymal activity (Tmax) and the residual activity (RA) were calculated.

Results:  For Tmax there was no significant influence of sex or age. Mean RA increased significantly with age (20·5 vs. 23·2%, P=0·03), but no difference was found between sexes. Mean SF (right kidney) was significantly higher among males.

Conclusions:  When a diuresis of at least 2 ml min−1 is demanded we found the following normal ranges: SF >41%, Tmax <4·3 min and RA <33·7%.
Portapres and differential oscillometric finger blood pressure changes during deep breathing test in the assessment of BRS index
Authors: Jagomägi Kersti , Raamat Rein , Talts Jaak , Länsimies Esko , Jurvelin Jukka
Published: March 2003

The aim of this study was to investigate changes in the finger blood pressure during a deep breathing test (DB) and to find out whether the mean blood pressure might be used as a substitute for the systolic pressure in calculations of baroreflex sensitivity from data derived from the DB test. Continuous beat‐to‐beat finger pressure was recorded by the volume clamp method (Portapres model 2 monitor). In addition, the mean arterial pressure was recorded by the modified oscillometric method (UT9201 beat‐to‐beat monitor, University of Tartu, Estonia). Fifteen healthy volunteers, aged 25–56 years, were studied. The amplitude of respiration‐linked oscillations in the Portapres systolic (Psyst) and mean blood pressure (Pmean) was 22·2 ± 8·8 and 16·6 ± 5·8 mmHg, respectively. There was no significant difference between the amplitudes of induced changes in Pmean recorded by the two devices: the amplitude of oscillations in the mean blood pressure recorded by the differential oscillometric monitor was 16·0 ± 5·9 mmHg. The amplitude of oscillations in Psyst correlated significantly with the amplitude of oscillations in Pmean recorded either by Portapres or by UT9201 (r=0·95 and 0·98, respectively). The high correlation between the amplitudes of oscillations in mean and systolic blood pressure allows to conclude that mean arterial pressure changes during a DB test might be used instead of systolic pressure changes in calculation of the ratio of changes in pulse interval to changes in blood pressure, which is considered to reflect baroreflex sensitivity.
Fragmentation of Phragmites Habitats, Minimum Viable Population Size, Habitat Suitability, and Local Extinction of Moths, Midges, Flies, Aphids, and Birds
Authors: Tscharntke Teja
Published: March 2003

Results from populations of insects and birds inhabiting Phragmites habitats were used to analyze effects of fragmentation. Flush‐crash cycles of the stem‐boring moth Archanara geminipuncta (Lepidoptera, Noctuidae) showed regionally concurrent, local extinctions despite an originally enormous population size (more than 180,000 adults), emphasizing the importance of metapopulation dynamics. Further, A. geminipuncta could be considered a keystone species, since shoot damage facilitated more than twenty species of herbivores, saprovores (of the caterpillars’ feces), and their parasitoids. The gall midge Lasioptera arundinis could survive only in side shoots induced by shoot damage of A. geminipuncta.

Small Phragmites stands had thinner shoots (due to a water or nutrient deficiency) and shoots with more leaves (due to a better light supply) than large stands, thereby influencing species‐specific demands for habitat suitability and nutritiousness of reed tissue. In other words significance of habitat fragmentation could not be assessed by area alone. For example, two chloropid flies depending on thin, yellowish shoots survived only in small habitats or in the unmown edges of large habitats.

Local persistence of Phragmites herbivores depended on much larger population sizes than could be expected from a population size sufficient to maintain genetic variation. At least 11,000 adults of the gall midge Giraudiella inclusa (or more than 84,000 galls) were necessary to avoid local extinction.

With regard to conservation management of reed habitats, nature reserves should consist of old and unmown reeds, have fewer disturbed (particularly, fewer mown) habitat edges, measure more than two hectares (priority should go to the largest remaining fragments), and be surrounded by nearby reed habitats providing reservoir populations and diverse shoot types.
The Role of Foreign Debt in Deforestation in Latin America
Authors: Gullison Raymond E. , Losos Elizabeth C.
Published: March 2003

Much current controversy exists about the role that foreign debt plays in deforestation in Latin America. In an attempt to familiarize concerned biologists with this issue, we present an overview of the proposed positive and negative effects that foreign debt has had on neotropical forest loss. From the literature, we identify three main hypotheses as to how the large external debts of developing Latin American countries may contribute to deforestation. We find that (1) countries have not increased exports of tropical timber and beef in response to rising debt; (2) external debts have contributed to economic stagnation and an associated increase in poverty in Latin America, which in turn has caused the degradation of marginal lands, but the role of debt in this process cannot be isolated from other important contributing factors; and (3) while debt payments have probably led to governmental budget cutbacks in environmental spending, historically spending in these areas has not been high. On the positive side, we found that (1) innovative debt‐for‐nature swaps have traded devalued debt for a commitment and funds to create and protect nature reserves; and (2) debt could be exchanged for forestry and agricultural sectoral reform, which would have very large positive effects on the conservation and management of forests.
A Population Viability Analysis for African Elephant (Loxodonta africana): How Big Should Reserves Be?
Authors: Armbruster Peter , Lande Russell
Published: March 2003

We present an age‐structured, density‐dependent model of elephant population dynamics in a fluctuating environment, drawing primarily upon the life history parameters obtained from studies in semi‐arid land at Tsavo National Park, Kenya. Density regulation occurs by changes in the age of first reproduction and calving interval. We model environmental stochasticity with drought events affecting sex‐ and age‐specific survivorships. Results indicate a maximum population growth rate of 3% per year and an equilibrium elephant density of 3.1/mile2. Analysis of the demographic results and their sensitivity to changes in juvenile survivorship and drought frequencies, supported by genetic considerations, suggests that in semi‐arid regions a minimum reserve size of 1000 mile2 is necessary to attain a 99% probability of population persistence for 1000 years. The effect of age‐independent culling on population viability is also analyzed.
Mitochondrial DNA Variation in Black Rhinoceros (Diceros bicornis): Conservation Management Implications
Authors: O'Ryan C. , Flamand J.R.B. , Harley E.H.
Published: March 2003

Cell cultures have been established from 33 individual black rhinoceroses. These were from wild populations from various localities in southern Africa and include representatives from three geographical regions (southwestern, south‐central, and eastern) corresponding to currently accepted conservation units, and include individuals previously attributed to one of the four subspecies, Diceros b. minor, D. b. bicornis, D. b. michaeli, and D. b. chobiensis (du Toit et al. 1987). Comparative mitochondrial DNA restriction maps were constructed using 16 restriction enzymes. These showed in each case two site differences between representative individuals from any two of the above geographical regions. Maps were monomorphic within geographical regions and, therefore, have the potential to provide diagnostic markers. The map from a single individual attributed to the D. b. chobiensis subspecies was identical to other individuals (attributed to D. b. minor) in the south‐central geographical region. The low amount of genetic diversity implied by these few differences renders it unlikely that problems with outbreeding depression will arise if, given the continuing decline in numbers of black rhinoceroses, it becomes necessary to supplement wild or captive populations with individuals from a different conservation unit in order to avoid inbreeding depression.
Lion‐Human Conflict in the Gir Forest, India
Authors: Saberwal Vasant K. , Gibbs James P. , Chellam Ravi , Johnsingh A.J.T.
Published: March 2003

Asiatic lions (Panthera leo persica) now occur in the wild only as a small population (about 250 animals) within a single reserve, the Gir forest in Gujarat state in western India. Persistent attacks by lions on humans hinder support among local peoples for lion conservation. We analyzed 193 attacks by lions on humans and conducted interviews with 73 villagers to identify the spatial, temporal, and social factors associated with lion‐human conflict in the region. An average of 14.8 attacks by lions and 2.2 lion‐caused deaths occurred annually between 1978 and 1991, and most attacks (82%) occurred on private lands outside the forest reserve. A drought in 1987–1988 precipitated an increase in rates of conflicts (from 7.3 to 40.0 attacks/year) and in the proportion of attacks that occurred outside the reserve (from 75% to 87%). The spatial pattern of lion attacks could not be distinguished from random before the drought, whereas attacks were clustered after the drought in village subdistricts with a higher ratio of revenue land to forest edge and those closer to sites where lions were formerly baited for tourist shows. Subadult lions were involved in conflicts in disproportion to their relative abundance. A majority of villagers interviewed expressed hostile attitudes toward lions owing to the threat of personal injury and economic hardship (mainly livestock damage) posed by lions. The escalation in lion‐human conflict following the drought probably resulted from a combination of increased aggressiveness in lions and a tendency for villagers to bring their surviving livestock into their dwellings. Dissatisfaction with the government’s compensation system for lion‐depredated livestock was reported widely. The current strategy for coping with problem lions—that is, returning them to areas in the Gir forest already saturated with lions—is inadequate, as indicated by the sharp increase in lion‐human conflict since 1988. Prohibiting lion baiting for tourist shows, consolidation of reserve boundaries, and implementation of a more equitable and simpler system for compensating villagers for livestock destroyed by lions could provide short‐term alleviation of lion‐human conflict in the region. Long‐term alleviation may entail reducing the lion population by relocating or culling lions.
Vegetation Responses along Edge‐to‐Interior Gradients in the Mixed Hardwood Forests of the Roanoke River Basin, North Carolina
Authors: Fraver Shawn
Published: March 2003

Compared with forest interiors, forest edges typically have a different plant species composition and community structure, a phenomenon known as “edge effect.” Edge effects make the functional interior area of a forest smaller than its actual area. The objective of this study was to estimate how far the effects of agriculturally maintained edges penetrate the mixed hardwood forests of the Roanoke River Basin, North Carolina. I determined percentage cover for all vascular plant species in 10‐by‐100‐meter belt transects on north‐facing or south‐facing edges of four relatively undisturbed forests. Changes in the percentage cover of individual species, the relative cover of exotic species, and species richness all indicated that edge effects penetrate deeper on south‐facing edges (to 60 meters) than on north‐facing edges (to 20 meters). Analyses of species responses to the edge showed a number of species to be edge oriented, but no species was found to be interior oriented. The results of multivariate analyses (ordination and cluster analysis) suggested that edge effects could be detected to 50 meters on south‐facing edges and 10–30 meters on north‐facing edges. These results allow us to better understand the difference between a forest’s actual area and its functional interior area.
Free Trade Is Green, Protectionism Is Not
Authors: Yu Douglas
Published: March 2003

Many writers argue that free trade will lead to environmental degradation. Most environmentally pernicious public policies, however, such as subsidies of timber extraction and ranching, are also trade protectionist policies. To the extent that free trade treaties, such as the General Agreement on Tariffs and Trade, do away with such trade protectionism, free trade instead could be viewed as a major pathway to environmental reform. Furthermore, trade liberalization is associated with urbanization and industrialization, both of which reduce population growth rates and the pressures of colonization. I suggest that we, as environmentalists, can ally ourselves with free traders.
Relationships Between Developmental Stability and Fitness: Application for Conservation Biology
Authors: Clarke Geoffrey M.
Published: March 2003

One of the most difficult tasks in conservation biology is identifying populations subject to stress before such stress has a detrimental impact on the population, thus allowing conservation and remedial action to be undertaken. Measuring fitness (fecundity, survival, etc.) changes directly is often difficult, expensive, or impractical. The ability of an organism to buffer its development against disturbances (developmental stability) is often considered an integral component of an individual’s fitness. Data are presented from a number of studies that establish a clear relationship between developmental stability and fitness in response to both genetic and environmental stress. Consequently, I suggest that developmental stability may be used as a surrogate for more direct fitness estimation for use in conservation biology and biomonitoring programs and that is has widespread application as an early warning system for monitoring the effect of genetic and environmental stresses on natural populations.
Reproductive Success of Migratory Birds in Habitat Sources and Sinks
Authors: Donovan Therese M. , Thompson Frank R. , Faaborg John , Probst John R.
Published: March 2003

Fragmentation of breeding habitat in North America has been implicated in the decline of forestnesting, Neotropical migrant birds. We used a comparative approach to examine the effects of fragmentation on three forest‐nesting migrants: Ovenbird (Seiurus aurocapillus), Red‐eyed Vireo (Vireo olivaceus), and Wood Thrush (Hylocichla mustelina). We surveyed birds and monitored reproductive success on 28 study plots in fragmented and contiguous forests in two midwestern regions. Distribution of individuals between fragmented and contiguous forests appeared to vary among species and regions, but total nest failure was significantly higher infragments than contiguous forests in both regions for all species (p = 0.053). We attributed greater nest failure to increased nest predation (p = 0.093) and increased brood parasitism by the Brown‐headed Cowbird (Molothrus ater, p= 0.009). In addition to greater total nest failure, partial nest failure due to cowbird parasitism led to a reduction in the number of host fledglings. Although the causes of nest mortality appeared to be species specific, total nest failure and partial nest failure acted in concert to reduce the number of offspring per adult for all three species on fragments. We used simple population growth models to assess the viability of the three species infragmented and contiguous habitats in both regions. In general, populations on fragments appeared to be population sinks and populations on continguous forests appeared to be population sources. Assuming constant mortality during winter, projected growth indicated that without immigration Ovenbird and Red‐eyed Vireo populations should become extinct on fragments in both regions and Wood Thrush populations should be maintained or slightly decline on fragments. Populations of all three species should increase in contiguous habitats in both regions without emigration. We suggest that habitat fragmentation reduces local reproduction and may have ramifications for the entire population. A clear understanding of population demography depends on examination of demographic dynamics within and among sources and sinks. We emphasize that the long‐term viability of these species depends on maintaining large tracts of forest throughout the breeding range until the spatial scale at which source and sink populations interact can be determined.
Ecological Risk Assessment of Pesticides for Terrestrial Vertebrates: Evaluation and Application of the U.S. Environmental Protection Agency’s Quotient Model
Authors: Tiebout Harry M. , Brugger Kristin E.
Published: March 2003

The ecological risks of pesticides to wildlife are assessed by the United States Environmental Protection Agency with a simple quotient model. A risk factor is calculated by dividing the estimated dietary concentration by the chemical’s dietary toxicity. The risk factor, which can be used to predict population mortality, serves as a regulatory criterion to identify compounds that could pose unacceptable risk. Under the “New Paradigm,” the Environmental Protection Agency recently cut by 50% the critical risk factor, yielding more‐rigorous decision‐making criteria by decreasing acceptable wildlife mortality from 50 to 8.8% following one pesticide application and by increasing the number of pesticides that pose unacceptable risk to wildlife. The quotient model depends on at least one implicit and approximately 11 explicit assumptions; deviations from these assumptions may bias outputs and consequent regulatory decisions. To correct error‐prone assumptions we present three modifications that improve ecological risk estimates. We used the agency’s quotient model to survey risks to a regional avifauna (Florida birds) in relation to mosquito pesticide exposure (fenthion, malathion, and naled). Certain groups (small‐bodied, insectivorous passerines) were predicted to face the highest ecological risk due to taxonomy, diet, and body mass. Finally, we performed a risk assessment for Black‐whiskered Vireos (Vireo altiloquus barbatulus) exposed to fenthion. The results revealed that this species could potentially suffer 42% mortality in a population exposed to one application of fenthion. Ecological risk assessments increasingly will be based on mathematical models. To improve predictions of the effects of xenobiotic compounds on wildlife, biologists‐especially conservationists‐should work with ecotoxicologists to improve current models, develop new models, and provide data to parameterize models. Equally important, conservationists should participate in defining regulatory levels of ecological risk for wildlife.
The Challenge and Opportunity of Recovering Wolf Populations
Authors: Mech L. David
Published: March 2003

The gray wolf once inhabited a wide variety of habitats throughout most of the northern hemisphere north of 20°N latitude. Because the animal preyed on livestock and competed with humans for wild prey, it was extirpated from much of its range outside of wilderness areas. Environmental awareness in the late 1960s brought for the wolf legal protection, increased research, and favorable media coverage. The species has increased in both Europe and North America, is beginning to reoccupy semiwilderness and agricultural land, and is causing increased damage to livestock. Because of the wolf's high reproductive rate and long dispersal tendencies, the animal can recolonize many more areas. In most such areas control will be necessary, but the same public sentiments that promoted wolf recovery reject control. If wolf advocates could accept control by the public rather than by the government, wolves could live in far more places. Insistence on government control discourages some officials and government agencies from promoting recovery. The use of large‐ or small‐scale zoning for wolf management may help resolve the issue. Public education is probably the most effective way to minimize the problem and maximize wolf recovery, but the effort must begin immediately.
Human Culture and Large Carnivore Conservation in North America
Authors: Kellert Stephen R. , Black Matthew , Rush Colleen Reid , Bath Alistair J.
Published: March 2003

We examined and compared human attitudes toward wolves (Canis lupus), grizzly bears (Ursus arctos horribilis), and mountain lions (Puma concolor) in North America, with an emphasis on the Rocky Mountains of the United States and Canada. Primary research, literature review, and secondary data were included in the analysis. Wolves were historically persecuted by Euro‐American settlers, but they have been the focus of a significant attitudinal transformation during the latter half of this century. Many now view the wolf in positive and protective ways. Considerable variation remains, however, in contemporary attitudes. Attitudes toward mountain lions have been highly ambivalent, never assuming the prominence or clarity of views on wolves. The behavior and physiology of the species, along with human psychological factors, are important reasons for the difference in human perceptions of wolves and mountain lions. We also examined attitudes toward grizzly bears. Many indigenous cultures revered grizzly bears, although European settlers were interested in exploiting and eliminating them. Today, perceptions of grizzly bears range from positive to negative. Our recommendations include targeting key groups with education programs, building support through the use of spokespeople within the target groups, integrating human and ecological concerns, and designing species‐specific education initiatives in some cases.
Cross‐Boundary Management of Algonquin Park Wolves
Authors: Forbes Graham J. , Theberge John B.
Published: March 2003

Cross‐boundary management issues concerning the spatial requirements of large predators and the inadequate size of protected areas are exemplified by the movements of gray wolf (Canis lupus) in and out of Algonquin Park, Canada. From 1987 to 1993, 65 juvenile and adult wolves from 22 packs inside Algonquin were radio‐tagged and regularly monitored by aerial and ground telemetry. Of the 41 wolves that died during the 6‐year study, mortality caused by humans was the highest single source, at 56%. Most mortality (68%) occurred outside the park, of which almost half (48%) was related to the seasonal movements by wolves out of the park in response to migrating white‐tailed deer (Odocoileus virginianus). In 1993 the provincial government banned the killing of wolves in a 200‐km2 deer wintering area adjacent to the park. The ban was considered necessary because (1) a high proportion (82%) of packs from the eastern half of the park was traveling to the deer area; (2) outside the park killing of wolves by hunting or trapping was uncontrolled; and (3) much of the mortality comprised adult, non‐dispersing wolves. Public response to the ban was hostile initially, but apart from some flagrant violations the protective measures appear to have been successful. Only 2 radio‐collared wolves were killed in 1993 and 1994 combined, compared with 10 in 1992 alone. Controversy over management decisions led us to conclude that cross‐boundary problems associated with this controversial species necessitate complete, partial, or emergency protection. Complete protection requires protection beyond the existing park boundary, either through buffer zones or increased regulation. Partial and emergency protection strategies rely on effective monitoring, an important factor if public cooperation is limited. At Algonquin the magnitude of wolf killing, the importance of the wolf in interpretive programs, and the difficulties in regulating partial protection because of unreported kills and damage to radio collars makes complete protection the prudent choice.
The Role of Local Government in the Conservation of Rare Species
Authors: Press Daniel , Doak Daniel F. , Steinberg Paul
Published: March 2003

In the U.S. rare and endangered species protection is a public policy responsibility commonly ascribed to the federal or state governments. We make three related claims: 1) the scale of local and regional land use control and open‐space acquisitions matches the range sizes of many rare, endemic species, 2) land acquisition is the most attractive approach to conserving many rare taxa, especially endangered flora, and 3) at least some local governments and non‐governmental organizations have the policy capacity necessary to identify, acquire, and manage critical habitats for endangered species. Although local involvement can have conservation payoffs throughout the United States, we focus on California in general and, in particular, use as a case study the biology and political resources of four adjoining counties in the central coast region of the state: San Mateo, Santa Cruz, Santa Clara, and Monterey. We close with a discussion of policy implications for coordinating local, state, and federal conservation efforts. These include 1) brokering land acquisition deals with input from public land managers and private owners, 2) shifting funding priorities for rare, well‐known species away from research to habitat acquisition and management, and 3) encouraging biologists to invest more effort in local land use regulations so that they may make more effective use of local land management and conservation opportunities.
Extinction Debts and Risks Faced by Abundant Species
Authors: McCarthy Michael A. , Lindenmayer David B. , Drechsler Martin
Published: March 2003

A recent model indicating that good competitiors and abundant species face the greatest risk of extinction from habitat destruction is critically examined. The conclusions drawn from the model are shown to rely on a number of assumptions regarding the mechanism of species coexistence, the relationship between abundance and competitive ability, and spatial characteristics of habitat destruction. The generality of these assumptions is questioned. Of particular concern are the assumptions that good competitors are poor dispersers, and that good competitors are the most abundant species. Furthermore, we suggest that the spatial scale of metapopulation dynamics in the model may not be appropriate for representing impacts of habitat destrustion. Empirical evidence is discussed indicating the limited applicability of the model for describing effects of habitat destruction on risks of species extinctions. Examples from a number of fragmented systems demonstrate that poor competitors and rare species are vulnerable to habitat destruction.
Effects of Habitat Fragmentation on the Abundance of Two Species of Leptodactylid Frogs in an Andean Montane Forest
Authors: Marsh David M. , Pearman Peter B.
Published: March 2003

We used visual transect surveys to study the effects of forest fragmentation on abundance of two species of Leptodactylid frogs in an Andean forest of northern Ecuador. We measured the abundances of Eleutherodactylus chloronatus and E. trepidotus at various distances from the forest edge in one large forest patch (200 ha) and four adjacent forest fragments (0.25–5.3 ha). We also collected data on forest characteristics ( leaf litter thickness, understory density, and number and size of canopy trees) at each site. Abundance of E. chloronatus and E. trepidotus were respectively 3.5 and 2.1 times higher at sites in the large forest patch than at sites in the small fragments. Abundance of E. chloronatus was positively correlated with the log of patch size and inversely correlated with understory density. E. trepidotus abundance was not correlated with either patch size or understory density, but was inversely correlated with distance from the site to the large forest patch. The two species thus both appear to be affected by habitat fragmentation, but through different processes.

Efectos de la Fragmentación del Hábitat en la Abundancia de dos Especies de Ranas Leptodactílidas en un Bosque de Montaña de los Andes

Utilizamos datos de transectos lineales para estudiar los efectos de la fragmentación del bosque sobre dos especies de ranas en los Andes del norte de Ecuador. Medimos la abundancia de Eleutherodactylus chloronatus y E. trepidotus en sitios a distancias determinadas del horde del hosque en un fragmento grande (200 ha) y cuatro fragmentos menores adyacentes (0.25–5.3 ha). Obtuvimos dates sobre las características del bosque (espesor de la hojarasca, densidad del sotobosque, número de árboles en el dosel) en cada sitio. La abundancia de E. chloronatus y E. trepidotus fue 3.5 y 2. 1 veces mas alta en los sitios del fragmento grande one en los sitios de los fragmentos menores. La abundancia de E. chloronatus estuvo correlacionada con el logaritmo del tamaño del fragmento e inversamente correlacionada con la densidad del sotobosque. La abundancia de E. trepidotus no estuvo correlacionada con el tamaño del fragmento, ni con la densidad del sotobosque, pero sí con la distancia del sitio hasta el fragmento grande. Po lo tanto, las dos especies aparentemente son sustancialmente impactadas por la fragmentación del hábitat, pero a través de procesos diferentes.
Impact of Hunting on Large Vertebrates in the Mbaracayu Reserve, Paraguay
Authors: Hill Kim , Padwe Jonathan , Bejyvagi Carlos , Bepurangi Ambrosio , Jakugi Felipe , Tykuarangi Roberto , Tykuarangi Tito
Published: March 2003

Over 1,400,000 m of line transect data were collected in collaboration with Ache Indians to determine encounter rates with all large vertebrates in the Mbaracayu Reserve Paraguay. The data were analyzed using logistic regression in order to determine the impact of human hunting on animal encounter rates in the reserve. The method controlled for effects of season, weather, time of day, and habitat in order to statistically isolate the human predation effect. Encounters with the animals themselves as well as fresh signs of their activity allowed us to determine whether lower encounter rates in hunted zones are simply due to increased wariness by target species. Our results show that areas near hunters are hunted more frequently, and that Dasypus novemcinctus, Cebus apella, Tapirus terrestris, and Mazama spp. are all encountered at lower rates in those areas than in unhunted zones. We were unable to show that encounter rates with other important game species have been affected by human hunting. Demonstration of local depletion by central place foragers is expected, however, and cannot be used to conclude that prey species are in danger of regional extirpation.

Impacto de la Captura de Vertebrados Mayores en la Reserva de Mbaracayu, Paraguay

Datos de mas de 1,400,000 m de transectos en linea fueron colectados en colaboración con los indios Ache para determinar las tasas de encuentro con vertebrados mayores en la reserva Mbaracayu del Paraguay. Los datos fueron analizados usando regresión logística para determinar el impacto de la cazería sobre la tasa de encuentros en la reserva. El método fue controlado para aislar el efecto de la depredación humana de los efectos de la estación, el clima, la hora del día y el tipo de habitat. Los encuentros con animales, así como marcas frescas de su actividad nos permitieron determinar si las tasas bajas de encuentros en las zonas de caza son simplemente debidas al incremento en la alerta de las especies blanco. Nuestros resultados muestran que las áreas cercanas a los cazadores son utilizadas mas frecuentemente y que Dasypus novemcinctus, Cebus apella, tapirus terrestris y Mazama spp. se encuentran todos en menor proporción que en las áreas no utilizadas para la cazería. No pudimos demostrar que las tasas de encuentros con otras especies de caza importantes han sido afectadas por la caza humana. Esperamos una disminución local debida a la presencia de forrajeros centrales, aunque esto no puede ser utilizado para concluir que las especies de presas se encuentran en peligro de una extirpación regional.
Comparisons of Related Rare and Common Species in the Study of Plant Rarity
Authors: Bevill R. L. , Louda S. M.
Published: March 2003

Abstract:Conservation of rare plant populations is an important dimension of the preservation of biodiversity. Yet the database underlying both the theoretical understanding and management of rare—in contrast to common—plant species is scattered, unfocused, and conceptually weak. Our review of studies comparing attributes of rare vascular plants with those of closely related, more common relatives found fewer studies than expected (n= 38) and no consistency in the attributes measured, which precluded further assessment of pattern. Only 10% of 71 response variables compared were reported in more than four studies, and most of the traits ( 79%) were compared in only one or two studies. Improvement of comparisons of rare and common species requires standardization of attributes measured among studies. Although experiments evaluating hypothesized limiting factors are desirable, at a minimum all studies should include population densities and life table schedules. Demographic parameters provide detailed data, required for scientific management of specific rare plants, and extensive data, required for meta‐analyses and detection of general patterns in rarity.
Three Faces of Ecosystem Management
Authors: Yaffee Steven L.
Published: March 2003

Abstract: The debate over the objectives and methods of ecosystem management has been confusing, in part because people truly mean different things when they use the term ecosystem management. These different meanings reflect differences in interests, values, and knowledge. I organized these meanings into three sets: “environmentally sensitive multiple use,” an “ecosystem approach to resource management,” and “ecoregional management.” Environmentally sensitive multiple use takes an anthropocentric perspective that seeks to foster multiple human uses subject to an understanding of environmental constraints that goes beyond that considered in traditional multiple‐use management. An ecosystem approach incorporates a biocentric view in which ecosystems are understood as a metaphor for holistic thinking requiring an expanded consideration of the dynamism and complexity of ecological systems, scale phenomena, and the need for management across ownership boundaries. Ecoregional management takes an ecocentric perspective that focuses on the management of specific landscape ecosystems defined as real geographic spaces and that shifts management focus toward ecosystem processes and away from biota. Understanding these three conceptualizations as different points along a continuum of resource management paradigms helps clarify the different visions of ecosystem management held by different groups. Because different places and groups are at various points on the continuum, progress comes from moving along the continuum and not necessarily by seeking a single state called “ecosystem management.” Policy prescriptions, such as changes in law, incentives, and information provision, can be targeted more effectively to the realities of different settings. Ultimately, the conceptualization suggests that heterogeneity of ecosystem management approaches is desirable, as long as we learn from the diverse experiences that result.
Effects of Elevated Atmospheric Carbon Dioxide on Insect‐Plant Interactions
Authors: Coviella Carlos E. , Trumble John T.
Published: March 2003

Abstract: In the enriched carbon dioxide atmosphere expected in the next century, many species of herbivorous insects will confront less nutritious host plants that will induce both lengthened larval developmental times and greater mortality. The limited data currently available suggest that the effect of increased atmospheric CO2 on herbivory will be not only highly species‐specific but also specific to each insect‐plant system. Several scenarios can be predicted, however: (1) local extinctions will occur; (2) the endangered species status as well as the pest status of some insect species will change; (3) geographic distributions for some insect species will shift with host‐plant ranges; and (4) changes in the population dynamics of affected insect species will influence their interactions with other insects and plants. For insect conservation purposes, it is critical to begin long‐term studies on the effects of enhanced CO2 levels on insect populations. An analysis of the available literature indicates that many orders containing insect species important for ecosystem conservation, and even those important as agricultural or medical pests, have not been examined. Without a major increase in research on this topic, we will be unprepared for the species changes that will occur, we will lose the opportunity to document just how some insects adapt to elevated CO2 levels, and we will lack the information necessary for effective conservation efforts.
Ethnobotany of Woody Species in Second‐Growth, Old‐Growth, and Selectively Logged Forests of Northeastern Costa Rica
Authors: Chazdon Robin L. , Coe Felix G.
Published: March 2003

Abstract: We assessed quantitatively the woody species used for timber, medicine, and other products in 10 tropical wet‐forest stands with different land‐use histories in the Atlantic lowlands of northeastern Costa Rica. Species were classified into 20 use categories based on regional ethnobotanical studies. Three size classes of woody vegetation were sampled in nested, contiguous plots along transects: trees (≥5 cm diameter at breast height [dbh]), saplings (>1 m high, <5 cm dbh), and seedlings (>20 cm high, <1 m high). Our study included five second‐growth stands, three old‐growth stands, and two selectively logged stands. Of the 459 woody species surveyed, 70% of the species and 86% of the total number of individuals had at least one use. Overall, species richness was highest for medicinal species (167 species). Absolute and relative abundance of medicinal and timber trees was significantly higher in second‐growth stands than in old‐growth and selectively logged stands. For 8 of the 15 use categories examined statistically, stem density showed no significant differences across forest types for any stem size class. Young, tropical, second‐growth forests and selectively logged forests have high utilitarian as well as conservation value and will likely become important sources of forest products. The success of secondary forest regeneration, however, depends critically upon conservation of genetically diverse source populations in forest fragments and protected old‐growth stands.
Priority‐Setting Tool Applied to Canada's Landbirds Based on Concern and Responsibility for Species
Authors: Dunn Erica H. , Hussell David J.T. , Welsh Daniel A.
Published: March 2003

Abstract: As a contribution to Partners in Flight–Canada, the Canadian Wildlife Service developed a ranking system to help set priorities for landbird species. Two complementary species lists were generated: one with scores for “concern” representing vulnerability and population trend, and one for “responsibility” for regionally characteristic fauna. The concern score gave equal weight to vulnerability, a composite score based on abundance and breadth of range, and population trend, because its purpose was to give early warning of potential problems. Responsibility scores were scale‐free and were assigned for the season in which the species is most abundant. Other systems for identifying species of concern may be more appropriate for other jurisdictions or organisms, but the responsibility ranking is widely applicable. This system is a coarse filter that generates preliminary ranks; additional information should be considered in deciding how to allocate scarce resources for conservation. Unrefined results are nonetheless useful for a variety of purposes, as illustrated by the scores for Canadian landbirds. About 25% of Canada's high‐responsibility species are also of high concern. These high‐concern species are not associated with specific habitats or migration patterns. Conservation of species ranking high on concern and responsibility merits cooperation with the United States and Mexico in particular. The scores identified improved monitoring as a priority conservation activity for Canada.
Cars, Cows, and Checkerspot Butterflies: Nitrogen Deposition and Management of Nutrient‐Poor Grasslands for a Threatened Species
Authors: Weiss Stuart B.
Published: March 2003

Abstract:Nutrient‐poor, serpentinitic soils in the San Francisco Bay area sustain a native grassland that supports many rare species, including the Bay checkerspot butterfly ( Euphydryas editha bayensis). Nitrogen (N) deposition from air pollution threatens biodiversity in these grasslands because N is the primary limiting nutrient for plant growth on serpentinitic soils. I investigated the role of N deposition through surveys of butterfly and plant populations across different grazing regimes, by literature review, and with estimates of N deposition in the region. Several populations of the butterfly in south San Jose crashed following the cessation of cattle grazing. Nearby populations under continued grazing did not suffer similar declines. The immediate cause of the population crashes was rapid invasion by introduced annual grasses that crowded out the larval host plants of the butterfly. Ungrazed serpentinitic grasslands on the San Francisco Peninsula have largely resisted grass invasions for nearly four decades. Several lines of evidence indicate that dry N deposition from smog is responsible for the observed grass invasion. Fertilization experiments have shown that soil N limits grass invasion in serpentinitic soils. Estimated N deposition rates in south San Jose grasslands are 10–15 kg  N/ha/year; Peninsula sites have lower deposition, 4–6 kg N/ha/year. Grazing cattle select grasses over forbs, and grazing leads to a net export of N as cattle are removed for slaughter. Although poorly managed cattle grazing can significantly disrupt native ecosystems, in this case moderate, well‐managed grazing is essential for maintaining native biodiversity in the face of invasive species and exogenous inputs of N from nearby urban areas.
Molecular Systematics, Ethics, and Biological Decision Making under Uncertainty
Authors: Shrader‐Frechette Kristin , McCoy Earl D.
Published: March 2003

Abstract: The controversy among
Karl and Bowen (1999),
Pritchard (1999), and
Grady and Quattro (1999) over scientific uncertainties and the ethical and political consequences of the black turtle's taxonomic status is caused by incomplete and uncertain scientific knowledge. When faced with cases of uncertainty, conservation biologists need to use ethical rationality, not merely scientific rationality. They should follow three general ethical principles: (1) perform and present unbiased research, (2) promote use of unbiased research by others, and (3) protect human and environmental welfare. Adhering to these principles is difficult because they can conflict, are too general to provide specific guidance in a particular situation, and are not ranked according to which ought to take priority in different situations. One way to deal with these difficulties is to employ a two‐stage ethical analysis. This analysis develops general principles (first stage) and then investigates the consequences of adopting each of the principles (second stage). A two‐stage ethical analysis applied to the controversy over the black turtle's taxonomic status suggests that even if there are some grounds for expanding conservation biologists' responsibilities to human and environmental welfare, they are not ethically justified in using any means whatsoever to achieve desirable consequences when the public has rights to full information. Conservation biologists do not appear to have grounds for paternalism in this case because it involves value judgments, not merely professional expertise.
Comparative Effects of Ambient Ultraviolet‐B Radiation on Two Sympatric Species of Australian Frogs
Authors: Broomhall Sara D. , Osborne William S. , Cunningham Ross B.
Published: March 2003

Abstract: Declines have been observed in a number of Australian frog species, many of these at high elevations. Alpine regions in Australia are likely to be particularly subject to increases in ultraviolet‐B radiation ( UV‐B, 280–320 nm) because UV‐B levels increase with elevation and because anthropogenic depletion of ozone has been particularly severe in the southern hemisphere. We compared survivorship of embryos and tadpoles of a declining species of frog, Litoria verreauxii alpina, with those of a sympatric nondeclining species, Crinia signifera, under three ambient UV‐B treatments, unshielded, control, and UV‐B–excluding. Experiments were conducted in artificial water bodies established at three different elevations (1365, 1600, and 1930 m) in the Snowy Mountains of southeastern Australia. The exclusion of UV‐B significantly enhanced survival of L. v. alpina (declining species) at all elevations. Overall, the probability of dying was highest in the unshielded treatments and lowest under the UV‐B–excluding treatment for both species over all elevations. The probability of dying was significantly higher in L. v. alpina than in C. signifera for a given UV‐B treatment at the two highest elevations. Our results support the hypothesis that ultraviolet radiation is likely to be a contributing factor in the disappearance of L. v. alpina at high elevations in southern Australia.