bluuebunny/crossref_metadata_2025 huggingface dataset:
Relationship between exposure to zidovudine and decrease of P24 antigenemia in HIV‐infected patients in monotherapy
Authors: Sasomsin Patrinee , Mentré France , Diquet Bertrand , Simon François , Brun‐Vezinet Françoise
Published: March 2003

The link between virological response and exposure to zidovudine was studied in 40 HIV‐infected patients of the protocol ANRS 01. During this 45‐day trial, the patients received only oral zidovudine in six treatment groups. Our objectives were: to analyze and model the pharmacokinetics of zidovudine and the decrease of P24 antigenemia; to study the links between exposure and efficacy. For the pharmacokinetic study, 12 blood samples were collected from 0.16 to 24 h after the first dose and a compartmental model was used. For the pharmacodynamic study of P24 antigenemia, blood samples were collected before treatment and every 3 days until day 45; an exponantial decay model was used. The pharmacokinetic and pharmacodynamic parameters were estimated for each patient by nonlinear regression. The correlations between efficacy parameters and exposure parameters, were then studied in the 40 patients. The mean (± SD) apparent volume of distribution and clearance were 151 L (± 94) and 184 L/h (± 72), respectively. The mean initial antigen level was 472 pg/mL (± 409), the coefficient of reduction of antigenemia was 0.27 (± 0.21) and the rate of decrease was 0.27/day (± 0.16). The coefficient of P24 reduction was found to be significantly correlated to the daily area under the curve (P < 0.0014). This relationship was adequately described by an Imax model and the daily area under the curve, leading to 50% of antigenemia decrease, was estimated to be 2.32 mg.h/L (± 0.33). In conclusion, a significant relationship between exposure to zidovudine at day 1, and decrease of P24 antigenemia was found. It was estimated that the average steady‐state concentration, which corresponds to 70% of maximal efficacy, was 0.22 mg/L. Together with the large interpatient variability of zidovudine pharmacokinetics, these findings confirmed that zidovudine should be monitored and a clinical target concentration was defined.
Neurovascular responses to sequential deep inspirations assessed via laser‐Doppler perfusion changes in dorsal finger skin
Authors: Mayrovitz Harvey N. , Groseclose Edye E.
Published: March 2003

A vasomotor reflex triggered by a rapid and deep inspiration causes arteriolar vasoconstriction and a transient decrease in skin blood flow in most people. This is the inspiratory gasp vascular response (IGVR). The most common site of its measurement has been on the palmar or plantar aspect of the digits and little is known about its features in skin with few or any arterial venous anastomoses (AVAs). A basic aspect of this response that has not been systematically studied is its temporal pattern associated with multiple sequential inspiratory gasps (IG) in the same person. Such information would provide insight as to whether there is any form of adaptation or temporal dependence and may serve as a basis for judging response variability. Thus, the present study was undertaken to characterize the normal pattern of responses in finger dorsum skin in a group of 28 normal persons who performed 21 sequential, uniformly spaced IG, over an interval of 42 min. The results show that IGVR measured on the finger dorsum have a magnitude comparable with that obtained on finger pulp, in spite of the relative dearth of sympathetically controlled AVAs on the dorsum. It was also found that the magnitude of the IGVR displays little if any tendency for sequential adaptation or temporal trending. Finally, the results indicate that the largest component of response variability is associated with subject‐to‐subject differences as compared with sequential variability within subjects.
Neural networks – a diagnostic tool in acute myocardial infarction with concomitant left bundle branch block
Authors: Olsson Sven‐Erik , Ohlsson Mattias , Öhlin Hans , Edenbrandt Lars
Published: March 2003

The prognosis of acute myocardial infarction (AMI) improves by early revascularization. However the presence of left bundle branch block (LBBB) in the electrocardiogram (ECG) increases the difficulty in recognizing an AMI and different ECG criteria for the diagnosis of AMI have proved to be of limited value. The purpose of this study was to detect AMI in ECGs with LBBB using artificial neural networks and to compare the performance of the networks to that of six sets of conventional ECG criteria and two experienced cardiologists. A total of 518 ECGs, recorded at an emergency department, with a QRS duration >120 ms and an LBBB configuration, were selected from the clinical ECG database. Of this sample 120 ECGs were recorded on patients with AMI, the remaining 398 ECGs being used as a control group. Artificial neural networks of feed‐forward type were trained to classify the ECGs as AMI or not AMI. The neural network showed higher sensitivities than both the cardiologists and the criteria when compared at the same levels of specificity. The sensitivity of the neural network was 12% (P = 0·02) and 19% (P = 0·001) higher than that of the cardiologists. Artificial neural networks can be trained to detect AMI in ECGs with concomitant LBBB more effectively than conventional ECG criteria or experienced cardiologists.
Can Large‐Scale Climatic Models Be Linked with Multiscale Ecological Studies?*
Authors: Root Terry L. , Schneider Stephen H.
Published: March 2003

On a global scale climatic changes driven by human activities are typically projected to increase from 1° C to 5° C per 100 years a rate of change that is an order of magnitude greater than that typically experienced naturally. Such a potentially dramatic change in climate could easily cause dramatic biological responses including extinction. Species show a wide range of responses to climate and consequently the response of different species of plants and animals to climatic change will be quite variable. This implies a likelihood for a disassembling of natural communities and for transient, nonequivalent restructuring of habitats as climatic change unfolds. Validated models that help forecast these events are needed to aid scientists in better understanding the ecological ramifications of global climatic change. Also, and perhaps more important for conservation biology, such validated models can help provide probabilities for the occurrence of these events, which will allow policy makers to make better, informed decisions. Typically, the study plots of most ecological field work are telecommunications, while the smallest resolved scales in global climatic models are about 500 × 500 km. Computer limitations preclude significant reduction in scales of climatic models. Consequently, more multi‐species ecological studies are needed over broad geographic and long temporal scales. We provide an example of large‐scale ecological response studies, namely the case of wintering North American birds. We also provide an example of attempts to translate results of large‐scale climatic models (at a 500 × 500 km scale) to a mesoscale (50 × 50 km). Participation of climatologists with ecologists at early stages in research planning can help bridge the scale mismatch between climatic and ecological measurement, and provide more reliable estimates of community responses to century‐long, time‐evolving patterns of climatic change. We are convinced that many more such interdisciplinary research attempts are urgently needed if the scientific community is to produce information useful to the development of conservation strategies. Such strategies might help to mitigate potential negative consequences of global climatic changes before they manifest themselves irreversibly in nature.
Geographic Range Fragmentation and Abundance in Neotropical Migratory Birds
Authors: Maurer Brian A. , Heywood S. Greg
Published: March 2003

Populations of neotropical migrant landbirds have experienced significant declines in recent years. We investigated potential consequences of these declines by examining the relationship between abundance and fragmentation of geographic ranges of species on the North American breeding grounds. We estimated areograpbic fragmentation using the box dimension of a species’ geographic range and demographic fragmentation using the fractal dimension of the semivariance function calculated from samples of population abundance across species’ geographic ranges. We found a negative relationship between average abundance and demographic fragmentation for neotropical migrants, but not for residents. We also showed that demographic fragmentation and areographic fragmentation are inversely related for residents, but not for neotropical migrants. These results imply that neotropical migrants may be more sensitive to extinction than are residents.
Aquatic Mammal Conservation in Latin America: Problems and Perspectives
Authors: VIDAL OMAR
Published: March 2003

Abstract: Management of renewable natural resources in developing countries has been hampered by a mix of socio‐economic and political difficulties that in turn have resulted in insufficient scientific knowledge, limited environmental awareness and education, and limited commitment to conservation. Aquatic mammals provide good examples. Despite the fact that about 65% of all known living species of aquatic mammals are found in Latin America (including 19 species found nowhere else), local and regional conservation efforts have developed only recently and are isolated. While management of the commercial exploitation of most baleen whales and pinnipeds has been more or less successfully achieved, the lack of comprehensive policies and conservation strategies for small cetaceans, manatees, and otters has allowed several species or populations to become threatened or even endangered. Threats include incidental mortality in fisheries, direct exploitation for human consumption or for use as bait in other fisheries, and habitat loss and degradation. To illustrate these problems, several cases are briefly discussed: (1) the endangered vaquita (Phocoena sinus) in México; (2) the tuna‐dolphin problem in the eastern tropical Pacific; (3) the small cetacean fishery in Perú; and (4) the Amazon river dolphin (Inia geoffrensis). Because many aquatic mammal populations are shared by Latin American countries, international cooperation is critical to ensuring their long‐term conservation.
Conservation of Fragmented Populations
Authors: Fahrig Lenore , Merriam Gray
Published: March 2003

In this paper we argue that landscape spatial structure is of central importance in understanding the effects of fragmentation on population survival. Landscape spatial structure is the spatial relationships among habitat patches and the matrix in which they are embedded. Many general models of subdivided populations make the assumptions that (1) all habitat patches are equivalent in size and quality and (2) all local populations (in the patches) are equally accessible by dispersers. Models that gloss over spatial details of landscape structure can be useful for theoretical developments but will almost always be misleading when applied to real‐world conservation problems. We show that local extinctions of fragmented populations are common. From this it follows that recolonization of local extinctions is critical for regional survival of fragmented populations. The probability of recolonization depends on (1) spatial relationships among landscape elements used by the population, including habitat patches for breeding and elements of the inter‐patch matrix through which dispersers move, (2) dispersal characteristics of the organism of interest, and (3) temporal changes in the landscape structure. For endangered species, which are typically restricted in their dispersal range and in the kinds of habitat through which they can disperse, these factors are of primary importance and must be explicitly considered in management decisions.
Reserve Design for Territorial Species: The Effects of Patch Size and Spacing on the Viability of the Northern Spotted Owl*
Authors: Lamberson Roland H. , Noon Barry R. , Voss Curtis , McKelvey Kevin S.
Published: March 2003

Designing a reserve system for a threatened territorial species such as the Northern Spotted Owl requires the balancing of biological necessity against economic reality. The Spotted Owl conservation plan and the Pacific Northwest timber industry are in conflict because both demand large areas of mature and old‐growth coniferous forests. The primary focus of this paper is the efficient design of a reserve system for territorial species with obligate juvenile dispersal. We examine the relationship between the degree of aggregation of suitable owl habitat, the level of occupancy of that habitat by pairs of Spotted Owls, and the likelihood of owl persistence given different amounts and spatial arrangements of suitable habitat across the landscape. We develop a population model for Spotted Owls that includes an abstracted forest landscape where suitable owl habitat is arrayed in clusters embedded in a matrix not suitable for owl habitation. We conclude from our study of this model that, for any given fraction of the landscape set aside in reserves, the level of occupancy (efficiency of use) of that area will increase as the aggregation of suitable habitat increases. After the reserves reach a size that includes territories for 20 to 25 owl pairs, however, there are diminishing returns from further increases. Preserving connectivity and increasing the geographical extent of the reserve begin to outweigh increased size in importance in insuring the long‐term viability of the species.
Variation among Desert Topminnows in Their Susceptibility to Attack by Exotic Parasites
Authors: Leberg Paul L. , Vrijenhoek Robert C.
Published: March 2003

Exposure of native species to novel disease organisms is a major threat posed by introduced exotic species. The genetic background of a native population should affect its response to an exotic disease. We evaluate the susceptibility of sexually and asexually reproducing lineages of fish (genus Poeciliopsis) to infection by a novel trematode parasite (Gyrodactylus turnbulli). The parasite commonly infects guppies (Poecilia reticulata), which have obtained a worldwide distribution as a consequence of their value in the pet trade. We examined two sexual species and two related clonal (nonrecombinant) lineages of Poeciliopsis that coexist naturally in Sonora, Mexico. One sexual species (P. monacha) and one clone (ML/VIII) were completely refractory to infection by G. turnbulli. The other sexual species (P. lucida) was relatively resistant. The second clone (ML/VII) was susceptible, however, and infections led to increased mortality. Chance fixations of alleles that occurred during the hybrid origins of these clonal lineages probably were responsible for the differences in susceptibility between lineages. Lack of heritable genetic diversity within a clonal lineage would hamper its ability to quickly evolve a suitable response to an exotic parasite and would make it particularly vulnerable to extinction.
Mammal Diversity and Conservation in the Selva Lacandona, Chiapas, Mexico
Authors: Medellín Rodrigo A.
Published: March 2003

The Selva Lacandona region of Chiapas, Mexico, has high biodiversity, represents the last large portion of tropical rainforest in México, and faces imminent destruction. Through fieldwork and literature searches I found a total of 112 mammal species (including 17 Middle‐American endemics) on the Lacandona’s 331,200 ha Montes Azules Biosphere Reserve. This inventory plus those from eight additional Neotropical localities show local mammal species richness in the Neotropics to be in the range of 70–116 species. Richness is primarily correlated with the amount of annual rainfall, but within rainforest areas species richness is probably not correlated with rainfall, latitude, altitude, or area size. Rather, above a certain limit of rainfall and below a critical level of latitude and altitude, mammal species richness seem to reach an asymptotic maximum. Areas covered with tropical rainforest and with a well‐known, relatively intact fauna have about 112–116 mammal species. In the Montes Azules Reserve most mammals (57%) are bats. The most heavily occupied feeding guilds are frugivores/herbivores and insectivores/omnivores. Large species and carnivores appear most vulnerable to local extinction. Montes Azules (and thus the Selva Lacandona) is especially noteworthy because (1) it contains a greater proportion of species facing conservation problems than expected from a random draw of Mexican mammals; (2) it is probably the most diverse ecosystem in Mexico; (3) many species sustain their only Mexican populations in this area; and (4) it is the largest remnant of tropical rainforest in Mexico and is part of the largest expanse of that vegetation type in Central America.
Recovery of the Kakerori: An Endangered Forest Bird of the Cook Islands
Authors: Robertson Hugh A. , Hay J. Rod , Saul Edward K. , Mccormack Gerald V.
Published: March 2003

The Kakerori, or Rarotonga Flycatcher (Pomarea dimidiata), is an endangered monarch flycatcher endemic to the island of Rarotonga, Cook Islands. This bird was reported to be common until the middle of the nineteenth century, but it declined before 1885 and was thought to be extinct early this century. A small population persisted in the rugged interior of Rarotonga; in 1987 the population stood at 38 birds but was in decline. We determined that introduced predators, especially ship rats (Rattus rattus), were affecting breeding success. Through a program of experimental management, aimed mainly at rodent control, the population increased from a low of 29 birds in Spring 1989 to 60 birds in Spring 1993. The recovery can be attributed to both improved breeding success and increased adult survivorship.
New Approaches Toward a Better Understanding of the Decline of Takahe (Porphyrio mantelli) in New Zealand
Authors: Bunin Judah S. , Jamieson Ian G.
Published: March 2003

Island populations of endemic birds are known to be particularly susceptible to extinction. This paper focuses on factors behind past and present declines of the highly endangered Takahe (Porphyrio mantelli), a flightless rail endemic to New Zealand. Subfossil evidence indicates that Takahe were once found throughout this island nation, being most abundant along forest margins and streams in lowland regions. Their numbers have declined dramatically since human colonization about 800–1000 years ago, probably due to a combination of habitat destruction and hunting by early Polynesian settlers. Today, the wild Takahe population consists of about 100 adult birds in an isolated alpine habitat and approximately 30 individuals recently released on several small offshore islands. Despite protection and intensive management, including removal of an introduced competitor (red deer, Cervus elaphus), the alpine population has continued to decline. In contrast, the Takahe’s nearest relative, the Pukeko (Porphyrio porphyrio) has expanded its range across New Zealand despite heavy hunting pressure since its colonization from Australia less than 1000 years ago. We suggest that, unlike Pukeko, Takahe lack appropriate behavioral responses to cope with mammalian predators such as stoats (Mustela erminea), which have been introduced relatively recently by European colonists. A study comparing predator defense behavior between these two closely related species is currently underway.
Recovery Plans and the Endangered Species Act: Are Criticisms Supported by Data?
Authors: Tear Timothy H. , Scott J. Michael , Hayward Patricia H. , Griffith Brad
Published: March 2003

To address recent criticisms of the recovery process of the U.S. Endangered Species Act and to search for ways to improve recovery efforts, we evaluated all recovery plans approved by the U.S. Fish and Wildlife Service and the National Marine Fisheries Service as of August 1991. As expected with rare species, we found an overall lack of detailed biological information presented in recovery plans. Information on species’ distributions was most common, being mentioned in 88% of the original recovery plans, while information on species’ abundance, population demographics, and dynamics (in descending order) was much less available. Biological information tended to be sparsely distributed among taxonomic groups. We found that threatened and endangered species were at risk of extinction, yet differentiation between threatened and endangered species’ status in the wild and their recovery goals was not evident. Based on criteria developed by Mace and Lande (1991) (and depending on choice of minimum criteria), population‐based recovery goals set in recovery plans, if achieved, would not improve the level of endangerment for 60–73% of vertebrate species. With few exceptions, a taxonomic bias was detected in the recovery process that favored animals over plants, vertebrates over invertebrates, and birds and mammals over fish and herpetofauna. The average time in years between listing and original recovery plan approval, however, was significantly shorter for plants (4.1) than animals (11.3), and for invertebrates (6.3) than vertebrates (9.4). It took an average of at least five years between each step in the recovery plan process (from listing to recovery plan approval and subsequent revision). Only 3.5% of the species in recovery plans were identified as keystones, and little recent emphasis has been placed on recovery plans covering multiple species. Finally, though public education was recommended frequently (92%) in recovery plans, public attitude assessment was virtually ignored (<2%). We suggest possible explanations for some of these findings, discuss the implications in light of the Endangered Species Act reauthorization, and present recommendations for future recovery plans and conservation strategies.
Helping a Species Go Extinct: The Sumatran Rhino in Borneo
Authors: Rabinowitz Alan
Published: March 2003

The Sumatran rhinoceros has been declining in numbers for more than a century, primarily due to bunting and to loss of its habitat as land is converted to other uses. Only in the last quarter century has the international community made concerted efforts to reverse this decline. However, government officials, international funding agencies, and conservation organizations, while paying lip service to the need for strong action, have often taken the path of least resistance in helping this species. Much of the money and effort put toward Sumatran rhino conservation has focused on new technologies or politically expedient strategies that have little to do with the real reasons behind the rhino’s decline. The primary means of Sumatran rhino conservation in Indonesia and Malaysia, where viable populations might still exist, is still the capture and attempted breeding of this species‐which, until now, has failed. I examined the history of the Sumatran rhino in Borneo and the recent situation in Sabah, where at least two important populations of this species might still survive. Sabah is presented as a case study that is indicative of the plight of the Sumatran rhino throughout its present range.
The Effects of Blister Rust on Post‐Fire Regeneration of Whitebark Pine: The Sundance Burn of Northern Idaho (U.S.A.)
Authors: Tomback Diana F. , Clary Jane Kees , Koehler James , Hoff Raymond J. , Arno Stephen F.
Published: March 2003

In the northern Rocky Mountains, whitebark pine (Pinus albicaulis) is rapidly declining as a result of previous fire exclusion policies, mountain pine beetle (Dendroctonus ponderosae) outbreaks, and white pine blister rust (Cronartium ribicola). Blister rust is potentially the most destructive agent, killing seedlings, cone‐bearing branches, and, eventually, mature trees. We examined densities of whitebark pine regeneration and the incidence and severity of blister‐rust infection of seedlings and saplings in the 25‐year‐old Sundance Burn in the Selkirk Range of northern Idaho, an area heavily infected by blister rust. We found that the mean regeneration density of whitebark pine was significantly lower than that of two other comparably aged burns in western Montana. The low density was attributed to the severe damage to the seed source on the burn perimeter, resulting from previous infestation of mountain pine beetle and blister rust. Overall, 29% of the whitebark pine regeneration in the Sundance Burn was infected by blister rust. Age and height of seedlings were important predictors of incidence of infection, and height was the most important predictor of severity of infection. Thus, as seedlings grow larger, they present a bigger target to airborne blister‐rust spores. Because of the lack of seed production in the adjacent forest and expected mortality, regeneration of whitebark pine in the Sundance Burn will be slow. In areas of northern Idaho and northwestern Montana affected by blister rust and pine beetle, prescribed fires for managing whitebark pine ecosystems should be restricted to small areas or should require plantings of rust‐resistant seedlings.
Planting State‐Listed Endangered and Threatened Plants
Authors: Reinartz James A.
Published: March 2003

The distribution and planting of state‐listed endangered and threatened plants is outlawed in most states of the United States, yet listed species are commonly used in landscaping and restorations. There is a need to re‐examine policy regarding planting and propagation of endangered and threatened plants outside of planned recovery efforts. Potential advantages associated with increased outplanting of rare species include (1) improved public education and relations; (2) demographic security derived from creation of new populations; (3) provision of new, appropriate gene‐flow opportunities; (4) applied research opportunities; and (5) ability to regulate a currently uncontrolled activity. Potential disadvantages are (1) confusion of natural and planted populations; (2) bureaucratic problems with protection of planted populations; (3) potential far inappropriate gene flow between natural and planted populations causing outbreeding depression and loss of genetic purity of natural populations; and (4) extension of the natural geographic and ecological range of the species. Policies, regulations, and nursery practices exist that would maximize the potential advantages and minimize the risks associated with the distribution of endangered and threatened plants. Policy considerations discussed include selection of appropriate species, production of appropriate and high‐quality genetic stock, and regulation of outplanting programs. I weigh the risks and benefits of a program that would allow the general public access to some state‐listed plants for natural landscaping. I conclude that a less restrictive but enforceable set of policies and regulations may be preferable to the status quo.
A Regional Landscape Analysis and Prediction of Favorable Gray Wolf Habitat in the Northern Great Lakes Region
Authors: Mladenoff David J. , Sickley Theodore A. , Haight Robert G. , Wydeven Adrian P.
Published: March 2003

Over the past 15 years the endangered eastern timber wolf (Canis lupus lycaon) has been slowly recolonizing northern Wisconsin and, more recently, upper Michigan, largely by dispersing from Minnesota (where it is listed as threatened). We have used geographic information systems (GISs) and spatial radiocollar data on recolonizing wolves in northern Wisconsin to assess the importance of factors in defining favorable wolf habitat. We built a multiple logistic regression model applied to the northern Great Lakes states to estimate the amount and spatial distribution of favorable wolf habitat at the regional landscape scale. Our results suggest that areas with high probability of favorable habitat are more extensive than previously estimated in the northern Great Lake States. Several variables were significant in comparing new pack areas in Wisconsin to nonpack areas, including land ownership class, land cover type, road density, human population, and spatial landscape indices such as fractal dimension (land cover patch boundary complexity), land cover type contagion, landscape diversity, and landscape dominance. Road density and fractal dimension were the most important predictor variables in the logistic regression models. The results indicate that public forest land and private industrial forest land are both important in managing for a broad‐ranging animal such as the wolf. Our data portray favorable habitat that is highly fragmented along development corridors in northern Wisconsin, which may be responsible for the slow growth of the wolf population. Upper Michigan, which is just beginning to be colonized by wolves, has very large, contiguous areas of likely habitat approaching the importance of those in northeastern Minnesota. If continuing development or wolf control restrict dispersing wolves from moving from Minnesota to Wisconsin, and Wisconsin habitat becomes more marginal through further fragmentation, Michigan has the potential to maintain a significant wolf population independent of Minnesota and serve as a source population for Wisconsin. However, a simple island/corridor model of wolf habitat in Wisconsin does not seem to apply. Wolves apparently move throughout the landscape, across many unfavorable areas, but establishment success is restricted to higher quality habitat. Source‐sink dynamics may be operating here, and they suggest that reduction of the Minnesota population in the near term may affect recovery in Wisconsin and Michigan. Our analysis is an example of use of long‐term monitoring data and large‐scale cross‐boundary regional analysis that must be done to solve complex spatial questions in resource management and conservation.
Conservation Implications of Introduced Game Birds in High‐Elevation Hawaiian Shrubland
Authors: Cole F. Russell , Loope Lloyd L. , Medeiros Arthur C. , Raikes Jane A. , Wood Cynthia S.
Published: March 2003

The Ring‐necked Pheasant (Phasianus colchicus) and the Chukar (Alectoris chukar) are the dominant avifauna in high‐elevation shrubland (2070–3000 m) of Haleakala National Park, Maui, Hawaii. We studied the food habits, ecological niche, and effects of these alien game birds on the native biota in this Hawaiian ecosystem. Analyses of crop contents indicated that pheasant and Chukar consumed predominantly fruits of native, woody dicots (39% and 47% respectively) and leaves (29% and 24% respectively) and flower parts (12% and 17% respectively) of alien, herbaceous dicots. Both species generally selected food items according to their relative availability, although other factors influenced choice of certain items. Invertebrates were a minor component of the game‐bird diet, suggesting that their impact on native invertebrate populations is minimal. Pheasant and Chukar occupy, at least partially, an ecological niche once held by now‐extinct or rare birds, and they appear not to be significant competitors with the endangered Nene. The role of these alien birds in facilitating seed dispersal and germination of native plant species is beneficial in restoring degraded ecosystems.
Ecological Redundancy and Long‐Term Dynamics of Vertebrate Predators in Semiarid Chile
Authors: Jaksic Fabian M. , Feinsinger Peter , Jimenez Jaime E.
Published: March 2003

In the semidesert of Aucó, Chile, four strigiform, six falconiform, and two fox species joined the suite of endothermic vertebrate predators at various times from 1987 to 1994. Different falconiforms entered and exited the suite at times roughly correlated with long‐term fluctuations in the density of small mammals, but strigiforms and foxes remained resident throughout the 7 years. Using detailed data on diets (trophic guild structure) and on resident status of the 12 predator species, we assessed whether the combination of these two criteria, if obtained in a shorter study, would have been adequate to make reasonable decisions about which species should be conserved were it possible to conserve only a subset of the 12. In particular, we evaluated whether ecological redundancy, as gauged by high diet similarity, would provide a reasonable basis for concentrating on the conservation of some species more than others. Guild structure of the predator suite at Aucó remained consistent through the first 3 years of the study, but then shifted markedly, such that conservation strategies based on apparent ecological redundancy (in diet) early on would have been misguided in the long term. Although transient species sometimes were redundant with residents, in other years the same transients played unique trophic roles, so the apparently rational strategy of concentrating conservation efforts on less‐mobile, resident species would have left gaps in ecosystem function. Likewise, a short‐term, intensive inventory of Aucó’s predators would have underestimated in some years and overestimated in others the richness of species, depending on prey resources there. We conclude that no short‐term data would have provided adequate bases for focusing conservation efforts on some species or particular habitat patches. Although realistically no such decision‐making process can be delayed until a 7‐year (or longer) data set has been accumulated, we suggest that short‐term studies of species assemblages be used cautiously when making conservation decisions.
Analysis of a Fisheries Model for Harvest of Hawksbill Sea Turtles (Eretmochelys imbricata)
Authors: Heppell Selina S. , Crowder Larry B.
Published: March 2003

The hawksbill sea turtle (Eretmochelys imbricata) is valued for its mottled shell, called bekko in Japan. Populations of hawksbills have declined worldwide, and currently there is a ban on all international trade of hawksbill shell and products (Convention on International Trade of Endangered Species of Wild Fauna and Flora). In 1992 the Bekko Association of Japan introduced a fisheries model for hawksbill sea turtles in Cuba. The model estimated a sustainable yield of 5500 turtles from Cuban feeding grounds. We examined the model to determine whether this level of harvest was reasonable. Little biological information is available for hawksbills, so the model contained a number of simplifying assumptions, and several of its parameters were unsupported by data. The population was assumed to be at equilibrium, with a constant number of recruits (1‐year‐old turtles) and constant annual survival and growth rates. We analyzed the model to see how population size and sustainable yield results were affected by changes in various model parameters, and we found that the model was most sensitive to annual survival probability, which was assumed to be a constant 90% per year for all turtles greater than 1 year old. When we entered growth curves generated by mark‐recapture data from other hawksbill populations, the model predicted a wide range of population sizes and sustainable yields. We determined that the assumptions of the current model make it unreliable for predicting sustainable yield of hawksbills, and that much research is needed to produce a more accurate model for management of this endangered species.
Developing a Sampling Strategy for Baptisia arachnifera Based on Allozyme Diversity
Authors: Ceska Jennifer F. , Affolter James M. , Hamrick J. L.
Published: March 2003

We analyzed the amount and distribution of genetic variation in Baptisia arachnifera Duncan to develop a sampling strategy for ex situ research. Baptisia arachnifera is an endangered plant species endemic to the coastal plain of Georgia (U.S.) where all populations are within 16 km of each other. A reduction in numbers of individuals has been observed during the last 50 years. Baptisia arachnifera was polymorphic at 24% of the 37 loci examined with an average of 1.32 alleles per locus. The genetic diversity index was relatively low ( He = 0.097) as expected for endemic species. Populations were in Hardy‐Weinberg equilibrium, suggesting that the species is outcrossing. Consistent with this conclusion is the observation that the majority (approximately 90%) of the genetic variation present in the species is found within individual populations. Indirect evidence of gene flow between populations was detected (   Nm = 2.35). The close proximity of the populations and the recent reduction in population sizes suggest that the populations surveyed may be fragments of a once more continuous gene pool. Based on the observed distribution of genetic diversity among populations (GST = 0.096), sampling two populations would capture 99% of the allozyme diversity surveyed. Allozyme data were used to determine which 2 of the 10 populations surveyed should be sampled to maximize the ex situ conservation of genetic diversity. Although the paper‐producing companies that own most of the land where Baptisia arachnifera occurs are modifying their harvesting techniques, the species could become extinct without more effective management and preservation efforts.
Invasibility and Effects of Amur Honeysuckle in Southwestern Ohio Forests
Authors: Hutchinson Todd F. , Vankat John L.
Published: March 2003

The Asian exotic Amur honeysuckle ( Lonicera maackii [Rupr.] Herder) has become the dominant shrub in many forests in southwestern Ohio and in some other locations in the eastern United States. Our research focused on the invasibility of forest communities and relationships of L. maackii to the abundance of tree seedlings and herbs. We surveyed 93 forest stands near Oxford, Ohio (USA) to determine L. maackii cover, time since invasion, tree canopy cover, tree basal area, and a shade tolerance index. Stepwise multiple regression indicated that greater than one‐half of the variation (r 2 = 0.550) in Lonicera cover was correlated to five variables (in descending order of importance): tree canopy cover, distance from Oxford, shade tolerance index, tree basal area, and time since invasion. The results suggest that high light levels and proximity to an abundant seed source increase forest invasibility. Tree seedling density, species richness of seedlings, and herb cover were all inversely related to L. maackii cover. When Lonicera becomes abundant, future structure and composition of forests could be affected and local populations of herbs threatened.
Demography and Population Viability of an Endangered Plant Species before and after Protection from Trampling
Authors: Maschinski Joyce , Frye Robert , Rutman Sue
Published: March 2003

Land managers often suggest fencing to protect rare plant species from being trampled in heavily used recreation areas, but there are few documented examples of the efficacy of this strategy. In a 7‐year demographic study we examined the reproduction, survival, and long‐term viability of the endangered sentry milk‐vetch (Astragalus cremnophylax var. cremnophylax) before and after protection from trampling. Demographic monitoring and population viability analyses indicated that the population has fluctuated during the 7 years. Before protection the population declined: 26% of individuals died, mortality surpassed natality, and age of first reproduction was significantly older than post‐protection. Fifty‐eight percent of the population was severely damaged. Population viability analyses of pre‐protection years predicted that the population would go extinct within 100 years. Since protection, the population stabilized, grew, and declined again. Seedlings reached reproductive maturity more quickly. Recruitment increased and peaked in 1993 coincident with abundant precipitation, but again declined in 1994. The total numbers of undamaged plants surpassed the numbers of damaged plants. Models of the post‐protection population predict stability. Multiple‐linear regression analysis indicated that winter and spring precipitation were significantly correlated with lambda. Both “good” and “bad” climatic conditions occurred during the pre‐ and post‐protection periods. Because of small population size and depauperate genetic diversity, climate will continue to influence population growth. Nevertheless, models indicate that where trampling and bad climatic conditions were coupled, extinction was accelerated. Recovery of sentry milk‐vetch will depend on continued protection, augmentation, and environmental factors, although risk of extinction remains very high.
Conservation Implications of Host Use for Rare Parasitic Plants
Authors: Marvier Michelle A. , Smith David L.
Published: March 2003

Both the study and management of parasites have historically focused on the control, and even elimination, of parasite populations. In contrast, rare parasitic plants represent an uncommon challenge for conservation biologists and managers who often wish to bolster populations of these parasites. Although parasitic plants may suffer any of the maladies known to affect small populations of plants, parasitic plants may also be limited by the additional suite of factors of host availability, host quality, host resistance to parasitism, and parasite preference. We describe studies that have examined parasite growth and reproductive performance with a variety of host species to argue that consideration of the host needs of parasitic plants is necessary for successful conservation of rare species using this mode of resource acquisition. Although it is clear that parasite performance varies greatly with the availability of different host species, little is known about the host requirements of most parasitic plants, and the relative importance of particular host species may not immediately be obvious. Further, because published host lists generally do not distinguish minor hosts from those that sustain parasite populations, such lists may be misleading for conservation efforts. We argue that successful conservation and restoration of parasitic plants may necessitate the management of thoughtfully selected host populations.
Global Conservation Priorities
Authors: Ginsberg Joshua
Published: March 2003

The following is an overview of the June 1998 Issues in International Conservation, which was inadvertently omitted from that issue. The editorial staff regrets this oversight.
The Role of Behavior in Recent Avian Extinctions and Endangerments
Authors: Reed J. Michael
Published: March 2003

Abstract:Understanding patterns of differential extinction and predicting the relative risks of extinction among extant species are among the most important problems in conservation biology. Although recent studies reveal that behavior can be a critical component in many species’ extinctions or endangerments, current approaches to the problem of predicting extinction patterns largely ignore behavior. I reviewed how behavior can affect population persistence and then used recent avian extinctions and endangerments to illustrate behaviors relevant to extinction risk. Behaviors that affect population persistence can be grouped as aggregation, interspecific responses, dispersal, habitat selection, intraspecific behavior, and maladaptive behavior. Behavior that can affect extinction risk is not limited to birds; for example, in many taxonomic groups (vertebrate and invertebrate) there is evidence of socially facilitated reproduction in colonial species, Allee effects on reproductive success and survival, behavioral regulation of population size, and conspecific attraction to breeding sites. Incorporating specific behaviors into models predicting extinction probabilities and patterns should improve their predictions.
Modeling Population Dynamics of a Songbird Exposed to Parasitism and Predation and Evaluating Management Options
Authors: Woodworth Bethany L.
Published: March 2003

Nest predation and parasitism are the primary causes of reproductive failure in northern temperate passerine songbirds. I demonstrate the use of a two‐step modeling approach to determine the implications of parasitism and nest predation for the population dynamics of songbird populations and to quantitatively evaluate alternative options for their management. I used a model to predict seasonal fecundity from parameters of nest success, productivity, and breeding season length ( Pease & Grzybowski 1995) and a stage‐based matrix model to examine population dynamics. I used this approach to model the population dynamics of the Puerto Rican Vireo (  Vireo latimeri), a single‐island endemic species that is exposed to high rates of parasitism by a nonnative brood parasite and to nest predation by introduced mammalian predators. The analysis showed that the introduction of the Shiny Cowbird (  Molothrus bonariensis), rather than the mammalian nest predators, caused this population to become a “sink” and is probably the cause of recent population declines. Moreover, the analysis explicitly shows that knowledge of the relationships among parasitism, predation, and population growth rate can aid in designing an effective conservation strategy. This modeling approach can be used to determine the reproductive health of a population over a range of parasitism and predation values, to test alternative hypotheses for the cause of an observed population decline, and to make a priori predictions about the outcomes of specific management actions.
Large Mammalian Herbivores and the Conservation of Arid Acacia Stands in the Middle East
Authors: Rohner Christoph , Ward David
Published: March 2003

Abstract: High mortality and poor recruitment in Acacia tree populations in many parts of the Middle East may result in loss of biodiversity. Human activities in recent decades have caused drastic changes in the water regime and the abundance of wild and domestic ungulates, which may negatively affect these trees. We studied the effects of large mammalian herbivores on the establishment of young Acacia raddiana and A. tortilis in the Arava Valley between the Red Sea and the Dead Sea, Israel. Seed accumulation under trees was high when large herbivores were excluded, and direct observations confirmed that ungulates were the main seed dispersers of these Acacia species. Insect seed predators (bruchid beetles) damaged more than 95% of seeds not consumed by ungulates. Seed germination was facilitated by gut passage through ungulates. Seedling survival was determined largely by water availability and was independent of herbivore density. Under present conditions, several years of high rainfall are necessary for successful establishment of young trees. Under severe browsing pressure by ungulates, growth in juvenile trees was delayed and smaller sizes were overrepresented. There was no evidence, however, of effects on the long‐term demography of Acacia trees, perhaps because ungulates increased seedling densities by enhancing the viability and germination of seeds. We conclude that large mammalian herbivores are essential components of arid Acacia savannas and that wild and domestic ungulates must be included in future conservation plans.