bluuebunny/crossref_metadata_2025 huggingface dataset:
“Mobbing” in Hawaiian Monk Seals (Monachus schauinslani): The Value of Simulation Modeling in the Absence of Apparently Crucial Data
Authors: Starfield Anthony M. , Roth James D. , Ralls Katherine
Published: March 2003

Several small populations of Hawaiian monk seals (Monachus schauinslani) exhibit male‐biased adult sex ratios and “mobbing,” an aggressive behavior in which adult males injure and often kill adult females and immature seals of both sexes during mating attempts. Mobbing appears to be limiting the growth of some populations of this endangered species. The frequency of mobbing deaths appears to increase as a population’s sex ratio becomes increasingly male‐biased, although the exact relationship between these two variables (the mobbing response) is unknown. We developed a stochastic demographic model of a small Hawaiian monk seal population using several different assumptions about the mobbing response. We used the model to explore the origins of male‐biased sex ratios in monk seal populations and to determine whether it was possible, given the lack of data on the mobbing response, to evaluate the probable effects of alternative management strategies to address the mobbing problem. Small populations (100 to 200 seals) and those with slower growth rates were more likely to develop male‐biased adult sex ratios. Almost all of our modeling scenarios supported the immediate removal of males from populations where mobbing occurs. Our conclusions were relatively unaffected when the assumptions regarding the mobbing response were varied. Thus, a model was helpful even when apparently crucial data were unavailable.
Setting Conservation Priorities: The Importance of Endemism and Phylogeny in the Southern African Orchid Genus Herschelia
Authors: Linder H.P.
Published: March 2003

The southern and south‐central African terrestrial orchid genus Herschelia contains several rare and endangered species. The distribution patterns of the species were assessed and classified into the Rabinowitz rarity categories. The degree of rarity was correlated with habitat types and with the phylogenetic history. Of the 16 species recognized, two are too poorly known to be assessed further. Of the remainder, three species are shown to be “metaspecies,” which can be interpreted as being ancestral to five narrowly endemic species. A. strong correlation between the age of the habitats, the relative age of the species, and the degree of rarity was demonstrated. I review the phylogenetic criteria for prioritizing species for conservation, and I develop a new criterion, the ability of a species to speciate into “new” environments. This suggests that it might be better to conserve metaspecies, which are found in the mountains, rather than the autapomorphic daughter species, which are found in the ephemeral habitats of the lowlands.
Inbreeding and Extinction: A Threshold Effect
Authors: Frankham Richard
Published: March 2003

A fundamental assumption underlying the application of genetics within conservation biology is that inbreeding increases the risk of extinction. However, there is no information on the shape of the relationship, the available evidence has not distinguished genetic and nongenetic effects, and the issue is controversial. Methods were devised to separate genetic and nongenetic causes of extinction in inbred populations, and they were used to analyze data from Drosophila melanogaster, D. virilis and Mus musculus. Inbreeding markedly increased rates of extinction in all cases. All showed a threshold relationship between incremental extinction and inbreeding with low initial extinction, but they showed notably increased extinction beginning at intermediate levels of inbreeding. There was no difference in extinction levels at similar inbreeding coefficients in populations inbred at different rates (full sibling versus double first cousin). Endangered species may give little warning of impending extinction crises due to inbreeding.
Modeling the Effects of Habitat Fragmentation on Source and Sink Demography of Neotropical Migrant Birds
Authors: Donovan Therese M. , Lamberson Roland H. , Kimber Allison , Thompson Frank R. , Faaborg John
Published: March 2003

Many songbird populations in the midwestem United States are structured as a network of sources and sinks that are linked by dispersal. We used a modeling approach to examine explicitly how populations respond to incremental fragmentation of source habitat and how this response may vary depending upon two life‐history attributes: fidelity to natal habitat type and reproductive strength of the source. Fragmentation of source habitat led to a predictable decline in population for both attributes examined, but the manner in which populations declined varied depending upon the reproductive strength of the source and the level of fidelity. When the source was weak and produced few excess individuals, fragmentation of source habitats resulted in a predictable and parallel population decline of adults in both the source and the sink. In this situation high fidelity to natal habitats was important for maintenance of population size and structure. Low fidelity to weak sources resulted in population extinction; populations experienced a demographic cost by dispersing from high quality source habitat to low quality sink habitat. In contrast, when the source was strong and produced many excess individuals, fragmentation of the source led to population declines in both the source and the sink, but this decline was more abrupt in sink habitats. When the source was strong and produced a large excess of individuals, nonfidelity to natal habitats had little effect on metapopulation size and structure.
Positive Effects on Game Species of Top Predators by Controlling Smaller Predator Populations: An Example with Lynx, Mongooses, and Rabbits
Authors: Palomares F. , Gaona P. , Ferreras P. , Delibes M.
Published: March 2003

Top predators have often been persecuted because of their supposed negative effects on species of economic concern on which they feed. In some cases, however, they may actually benefit their prey through intraguild predation on other smaller predators that share the prey. In each of two representative situations, in one of which lynx were present and in the other absent, we (1) estimated gross number of rabbits taken by lynx and Egyptian mongooses (smaller predators that are themselves preyed upon by lynx; (2) simulated size‐structured rabbit populations of different densities, taking into account the reproductive value of the individuals taken by predators; and (3) estimated actual rabbit densities. Numbers of rabbits taken by predators during a year were found to be between 4.8 and 9.5 times greater when lynx were not present. After a year, rabbit population growth for an initial rabbit density of 15/ha was between 12% and 22% lower when lynx were not present. For lower initial rabbit densities, the positive effect of lynx presence on rabbits was greater. Actual rabbit densities in the areas used by lynx were 2–4 times higher than in areas not used by lynx, even though these areas were similar or identical in habitat composition. These results support the suggestion that removal of top predators may sometimes have a negative effect on prey populations of human economic concern.
Sea Turtles in North Carolina Waters
Authors: Epperly Sheryan P. , Braun Joanne , Veishlow Allison
Published: March 2003

Until the turn of the century the inshore waters of North Carolina harbored populations of sea turtles large enough to support a commercial fishery. Based on a 4‐ to‐5‐year record of sighting reports by the public, interviews of recreational fishermen, and records kept by commercial fishermen the waters continue to provide important developmental habitats for loggerhead, green, and Kemp's ridley sea turtles. Leathertback and hawksbill sea turtles infrequently entered the inshore waters. Reports from the public and commercial fishermen indicated that sea turtles were present offshore North Carolina all year and were present in inshore waters April through December. Sea turtles were encountered most frequently in the Atlantic Ocean, but seasonal encounters in some inshore waters, such as Core and Pamlico Sounds, often were greater. In early May large numbers of leatherbacks were sighted in the ocean and moved northward along the beach. Reported sightings of leatherbacks declined markedly by late June. Based on incidental captures by commercial fishermen loggerhead turtles were the most numerous species in Pamlico and Core Sounds (80%), followed by green (15%) and Kemp's ridley sea turtles (5%). Most captured turtles were immature, and all were released alive. The abundance of immature sea turtles in North Carolina inshore waters serves to emphasize that southeast U.S. estuaries are important habitats for these threatened and endangered species. This recognition supported the decision of the U.S. National Marine Fisheries Service to extend the requirement for turtle excluder devices in shrimp trawls to inshore areas during the entire year, full implementation of these requirements was achieved by December 1994.
Potential Interference Between a Threatened Endemic Thistle and an Invasive Nonnative Plant
Authors: Huenneke Laura Foster , Thomson James K.
Published: March 2003

Although the establishment of nonnative plants is recognized as a threat to native ecosystems, there are few documented examples of an invasive species directly influencing a rare native plant. The Eurasian biennial Dipsacus sylvestris (teasel) is invading the central New Mexico habitat of Cirsium vinaceum, an endemic thistle that is federally listed as threatened. We documented changes in teasel distribution and abundance between 1989 and 1993 that suggest the potential for direct interactions with the native thistle. We then compared habitat characteristics, germination behavior, and performance in greenhouse and field competition trials to evaluate the potential outcome of interference between these two species. There were no significant differences in measured habitat characteristics between sites supporting C. vinaceum and those with D. sylvestris. Dipsacus was better able to germinate in low light than the thistle, suggesting that D. sylvestris might invade C. vinaceum populations but that thistle recruitment would be unlikely in dense stands of the nonnative plants. In the greenhouse growth of C. vinaceum rosettes was significantly reduced by the presence of Dipsacus, but the invader was unaffected by the thistle; results of a short‐term field experiment were equivocal but suggestive of interference between the two. We suggest criteria for managers to use in determining whether invading species pose problems for specific rare native taxa, and we discuss the constraints on experimental work where protected taxa are involved.
Effect of Harvest on Leaf Development of the Asian Palm Livistona rotundifolia
Authors: O'Brien Timothy G. , Kinnaird Margaret F.
Published: March 2003

Although palms are the most commonly harvested tree family in the world, they are susceptible to overexploitation, and many harvest schemes are not sustainable. We assessed the impact of leaf harvesting of the Asian palm, Livistona rotundifolia, in North Sulawesi, Indonesia, to determine the effect of harvest intensity on subsequent growth and to determine if current harvest practices are ecologically sustainable. We conducted experimental harvests of two intensities and compared results with a control. Leaf emergence, expansion, opening, and maturation were monitored for 1 year. Leaves in heavy and light harvest treatments grew and opened significantly faster than control leaves. Final leaf size was a function of harvest intensity: control leaves were larger (4.06 m) than light‐harvest leaves (3.62 m) and heavy‐harvest leaves (2.62 m). Census results for palms in harvested and unharvested areas indicated that palm density was twice as high and reproductive‐sized palms were 10 times more common in the unharvested area. We judged current harvest practices to be nonsustainable. Recommendations for sustainable harvesting include reduction of harvest intensity and waste and preservation of reproductive‐sized palms.
Population Viability Analysis of American Ginseng and Wild Leek Harvested in Stochastic Environments
Authors: Nantel Patrick , Gagnon Daniel , Nault Andrée
Published: March 2003

Many populations of threatened American ginseng (Panax quinquefolium) and vulnerable wild leek (Allium tricoccum) have declined and gone extinct because of overharvesting in Canada. We assessed the impact of harvesting on populations of these species in stochastically varying environments and estimated their extinction thresholds and minimum viable populations. With both species we used four transition matrices taken from the literature in stochastic population projections under various harvesting regimes. For American gingseng the mean population growth rate (λ) declined with increasing harvesting rate (h) according to the number of years between harvests (tr), as −0.54 htr−0.90. When plants with more than two leaves are harvested every 5 years, a harvest rate of approximately 30% was sufficient to bring the λ below the equilibrium value of 1.0. Extinction thresholds, the minimum number of plants needed to rebuild a population, varied from 30 to 90 plants, and the minimum viable population size was estimated at 170 plants. Only a dozen populations known in Canada exceed 170 plants, so most populations could not support any harvesting without serious threats to their long‐term persistence. For wild leek, two harvesting strategies were identified from confiscated, illegal harvests from Gatineau Park (Québec): (1) “choosy” harvesters collect fewer but larger bulbs, and (2) “busy” harvesters collect numerous but smaller bulbs. These data allowed simulations of more‐realistic harvesting strategies. The rate of the decline λ along the harvest gradient was faster for wild leek than for ginseng and varied with harvesting strategies. At harvesting rates between 1 and 8% the probability that λ falls below the equilibrium value was less than 5%. The extinction threshold of wild leek was estimated at 140–480 plants and the minimum viable population at 300—1030 plants, according to the threshold chosen. Remnant wild leek populations in Québec rarely contain more than a few hundred plants, indicating the serious threat commercial harvesting represents for this species. For both species we found that the whims of a stochastically varying environment significantly reduce sustainable harvest levels.
Survey of Columnar Cacti and Carrying Capacity for Nectar‐Feeding Bats on Curaçao
Authors: Petit Sophie , Pors Leon
Published: March 2003

We estimated the population sizes of the three species of columnar cacti that grow on the island of Curaçao using ground and aerial transects, and we examined the island’s carrying capacity for two species of nectar‐feeding bats that depend on nectar from the flowers of these cacti. We calculated carrying capacity based on the daily availability of mature flowers between January and December 1993 and the field energy requirements of bats as estimated from an equation for eutherian mammals (low estimate) and one for passerine birds (high estimate) based on body mass. Additional energy requirements of pregnancy and lactation were taken into account. We estimated that 461,172 columnar cacti were present on Curaçao (38% Subpilocereus repandus, 51% Stenocereus griseus, and 11% Pilosocereus lanuginosus). May through September are the critical months when bats rely most heavily on cactus for food. July 1993 was a bottleneck with the smallest number of mature flowers per day. July and August were months of greatest energy demand because females were lactating. We estimate that the carrying capacity for Glossophaga longirostris in July, when the bat (Leptonycteris curasoae) population was 900, was near 1200, an estimate that fits the observed population size of nectar‐feeding bats on the island. We suggest that the extensive removal of native vegetation occurring on Curaçao be strictly regulated because further destruction of the cacti will result in a decrease and potential loss of the already low populations of nectar‐feeding bats.
Phylogeographic Subspecies Recognition in Leopards (Panthera pardus): Molecular Genetic Variation
Authors: Miththapala Sriyanie , Seidensticker John , O'Brien Stephen J.
Published: March 2003

The incorporation of precise definitions for taxonomic units into wildlife legislation has necessitated the reevaluation of the taxonomy of endangered and threatened species. We used the subspecies recognition criteria proposed by Avise and Ball (1990) and O’Brien and Mayr (1991) to examine the infraspecific taxonomy of the leopard, Panthera pardus, a geographically widespread species with 27 currently recognized trinomial designations. Samples from named subspecies revealed appreciable genetic diversity using three molecular methods: allozymes, mitochondrial DNA restriction sites, and feline‐specific minisatellites. Continental populations and subspecies from Africa and Asia possessed the highest amount of molecular genetic variation, whereas relatively lower amounts of diversity were present in island populations. Molecular data were analyzed using three phylogenetic methods (distance‐matrix, maximum parsimony, and maximum likelihood) to resolve genetic differentiation below the species level The combined results revealed phylogenetic distinction of six geographically isolated groups of leopards: (1) African, (2) central Asian, (3) Indian, (4) Sri Lankan, (5) Javan, and (6) east Asian. Based on the combined molecular analyses and supporting morphological data (Miththapala 1992), u,e recommend that subspecific leopard taxonomy be revised to comprise eight subspecies: (1) P. p. pardus, Africa; (2) P. p. saxicolor, central Asia; (3) P. p. fusca, Indian subcontinent; (4) P. p. kotiya, Sri Lanka; (5) P. p. melas, Java; (6) P. p. orientalis, Amur; (7) P. p. japonensis, northern China; and (8) P. p. delacouri, southern China. In most cases, designated subspecies conform to historic geological barriers that would have facilitated allopatric genetic divergence.
Translocations and the Preservation of Allelic Diversity
Authors: Stockwell Craig A. , Mulvey Margaret , Vinyard Gary L.
Published: March 2003

Translocation is a tool commonly used for the conservation of threatened and endangered fish species. Despite extensive use, the biological implications of translocation remain poorly understood. Of particular interest is the effect of translocation on genetic variability. Maintenance of genetic variability in these “refuge” populations is assumed to be important for both short‐ and long‐term success. We examined allozyme variability at 16 loci for western mosquitofish (Gambusia affinis) populations with known histories of introduction. Refuge populations had significantly lower levels of heterozygosity. Refuge populations also had considerably lower levels of allelic diversity than parental populations. All losses were of relatively rare alleles (frequency less than 0.1 in parental population). These losses were probably due to an undocumented bottleneck early in the introduction history. These results were surprising because the initial transplant involved 900 fish and because mosquitofish have numerous reproductive traits that should minimize the effects of bottlenecks on genetic diversity. A literature review revealed that genetic variability is often reduced in refuge populations and that such reductions typically involve the loss of alleles. We suggest that translocated populations be examined periodically for losses of genetic variability.
Fishery Recovery in a Coral‐reef Marine Park and Its Effect on the Adjacent Fishery
Authors: McClanahan T.R. , Kaunda‐Arara B.
Published: March 2003

Numbers offish and their wet weights were estimated in Kenyan coral‐reef lagoons on seven reefs over 6 years. Two sites were protected from fishing for over 20 years, whereas the other five sites were heavily fished in recent years. A heavily fished site was converted into a marine park (Mombasa Marine National Park, approximately 10 km2 no fishing allowed), and the number of fishers allowed was slowly decreased between August 1991 and August 1992. The area adjacent to the park was converted into a marine reserve (only fishing traps, lines, and gill nets allowed) that provided fishing grounds for fishers excluded from the park. Data from a fish‐landing site adjacent to the newly created marine park were collected for 3 years and analyzed to determine the effect of the park’s creation on fish catches. Results suggest that fishing in the reserve reduced fish wet weight by about a factor of 10 and reduced fish numbers and species richness by a factor of two. Both field studies and landing data suggest harvesting at a bionomic equilibrium. For example, approximately 65% of the landing site’s fishing grounds were protected with the creation of the park, and 65% of the fishers quit the studied landing, leaving nearly the same density of fishers in the remaining area (∼ 12 fishers/km2). Further, fishers using pull seines were excluded from the reserve, and their numbers were replaced by fishers using other gear (mostly basket traps). Although the overall catch per unit effort increased by about 110% after the park’s creation, the total fish landed decreased by 35% and the catch per unit effort decreased toward the end of the study period despite increasing fish abundance in the park. Although establishment of small parks elsewhere have increased the total catch, the large park we studied did not; one reason may have been the lower ratio of edge to park area of the large park. Alternatively, the park’s edge may have provided a good fishing area, so fishing effort may have been highest along the park’s edge. Consequently, a barrier may have been created that restricted fish dispersal to most of the reserve. Therefore, the area that had an increased catch was small (< 1 to 2 km from the edge) and could not compensate for the lost fishing area. Most fish species within the park showed recovery after fisher exclusion. Total fish wet weights 3 years after the fishers’ exclusion were 25% below the older marine parks. Poor recovery of the herbivoroas parrot and surgeonfish can account for much of this shortfall. Competition for resources with sea urchins appear to be slowing recovery of these two groups. A study site 2.5 km from the park’s southern boundary, in the reserve section of the protected area, showed no changes in fish abundance over the study period, despite changing gear regulations.
Effects of Clearcutting on Habitat Use and Reproductive Success of the Ovenbird in Forested Landscapes
Authors: King David I. , Griffin Curtice R. , Degraff Richard M.
Published: March 2003

We studied Ovenbirds (Seiurus aurocapillus) in northern New Hampshire during 1992 and 1993 to determine whether edge‐related changes in habitat use and reproductive success reported in fragmented landscapes exist in predominantly forested landscapes. Six study plots were placed adjacent to four recent clearcuts (2.1–5 ha) and extended 400 m into the forest interior. Nests, territories, and territorial males obtaining mates were equally distributed in edge (0–200 m) and interior (201–400 m) areas. Nest survival was higher in the forest interior in 1992 and for 1992 and 1993 combined. The proportion of pairs fledging ≥ 1 young, fledgling weight, and fledgling wing‐chord did not differ between edge and interior in either year. Number of young fledged per pair was slightly lower in edge areas, but these differences were not significant. We conclude that clearcutting in extensively forested landscapes can affect Ovenbird reproductive success. Nevertheless, the effect on Ovenbird populations is moderated by the abundance of mature forest cover in the region and by the tendency of Ovenbirds to renest after initial nest failure.
Developing a Criterion for Delisting the Southern Sea Otter under the U.S. Endangered Species Act
Authors: Ralls Katherine , Demaster Douglas P. , Estes James A.
Published: March 2003

Recent surveys of recovery plans indicate that criteria, such as population sizes, for delisting species from the U.S. Endangered Species Act (ESA) are often unrealistically low by scientific standards. We describe the delisting criterion for the threatened southern sea otter (Enhydra lutris nereis) developed by the Southern Sea Otter Recovery Team. A major oil spill is the most serious threat to this sea otter population. After extensive modeling of oil spills, the recovery team concluded that it was not scientifically defensible to develop a delisting criterion in terms of a single probability of extinction over a specified time period. Instead, the team decided to define a size at which it would consider the population endangered and to consider the population threatened as long as a major oil spill might reduce it to that size. The effective population size (Ne) for endangered status was set at 500, estimated to be about 1850 otters. Using a spill the size of the Exxon Valdez spill (250,000 bbl), the oil spill model was iterated to generate a frequency distribution of the number of sea otters contacted by oil, from which the team estimated that less than 800 otters would be killed by 90% of the simulated spills. Thus, the delisting criterion was set at 1850 + 800 = 2650 individuals. There have been several proposals to improve the Endangered Species Act by providing quantitative guidance, in the form of specific probabilities of extinction within some time frame or specific criteria like those used by the World Conservation Union as to the levels of extinction risk represented by the terms “threatened” and “endangered.” Experiences of the Sea Otter Recovery Team indicate that guidelines should not be overly rigid and should allow flexibility for dealing with specific situations. The most important consideration is to appoint a recovery team that is both technically well qualified and unconstrained by pressures from management agencies.
Trophy Hunting and Wildlife Conservation in Zambia
Authors: Lewis Dale M. , Alpert Peter
Published: March 2003

For wildlife conservation to succeed in developing countries, people who live in or near protected areas must receive benefits that offset the costs of their reduced access to natural resources. International trophy hunting is currently generating significant economic benefits for residents of game management areas in Zambia. This has been made possible through a revolving fund and an administrative program that direct revenues from trophy hunting to local wildlife management and community development projects. Benefits might be enhanced by better biological information for management, greater local participation in the allocation and operation of hunting concessions, and the promotion of ecological and ethical standards for trophy hunting. An international system of certification for trophy hunting operations could foster these improvements.
The Effectiveness of Removing Predators to Protect Bird Populations
Authors: Côté Isabelle M. , Sutherland William J.
Published: March 2003

The control of predators for nature conservation purposes is becoming an increasingly important issue. The growing populations of predator species in some areas and the introduction of predators in other areas have led to concerns about their impact on vulnerable bird species and to the implementation of predator control in some cases. This is set against a background of increasingly fragmented semi‐natural habitats and declining populations for many species. To assess the efficiency of predator removal as a conservation measure, the results of 20 published studies of predator removal programs were meta‐analyzed. Removing predators had a large, positive effect on hatching success of the target bird species, with removal areas showing higher hatching success, on average, than 75% of the control areas. Similarly, predator removal increased significantly post‐breeding population sizes (i.e. autumn densities) of the target bird species. The effect of predator removal on breeding population sizes was not significant, however, with studies differing widely in their reported effects. We conclude that predator removal often fulfills the goal of game management, which is to enhance harvestable post‐breeding populations, but that it is much less consistent in achieving the usual aim of conservation managers, which is to maintain and, where appropriate, increase bird breeding population sizes. This may be due to inherent characteristics of avian population regulation, but also to ineffective predator removal and inadequate subsequent monitoring of the prey populations.
Genetic Diversity in the Endangered Lily Harperocallis flava and a Close Relative, Tofieldia racemosa
Authors: Godt Mary Jo W. , Walker Joan , Hamrick J. L.
Published: March 2003

We examined genetic diversity in 464 individuals of the monotypic lily Harperocallis flava in its two habitats (seepage bogs and a roadside right‐of‐way) and five populations of a co‐occurring related lily, Tofieldia racemosa. The endangered H. flava, endemic to the Apalachicola lowlands of the Florida panhandle, was monomorphic for the 22 loci scored. In contrast, T. racemosa had a high proportion of polymorphic loci ( Ps = 68.2%; Pp = 47.7%) with moderate genetic diversity (   Hes = 0.134; Hep = 0.114). Estimated gene flow was moderately high ( Nm = 2.07) for T. racemosa, with most (93%) of the total genetic diversity found within populations. Despite the low level of genetic divergence, some isolation by distance was detected among T. racemosa populations. Harperocallis flava and other species without discernable genetic variation pose special problems for conservation biologists because genetic criteria are not available for the development of ex situ and in situ conservation and management strategies.
Reserve Selection in a Species‐Rich and Fragmented Landscape on the Agulhas Plain, South Africa
Authors: Lombard A. T. , Cowling R. M. , Pressey R. L. , Mustart P. J.
Published: March 2003

The Agulhas Plain on the southern tip of South Africa falls within the world’s “hottest” hot‐spot of plant diversity and endemism. Fynbos communities and renoster shrubland form the dominant vegetation types on the plain, but these have been severely fragmented by agriculture, alien plant invasions, and coastal resort development. Most of the vegetation communities are under‐represented within existing protected areas, and most of the land is privately owned. We recommend that a contractual national park, involving both private and public land owners, be established on the plain, and we have developed a reserve‐selection algorithm that provides a flexible tool for selecting representative areas for protection. The algorithm is a stepwise heuristic, with rules for including mandatory areas, forcing adjacency, and excluding undesirable areas. The selection units of the algorithm are 3 × 3 km cells, and the goal of the algorithm is to simultaneously select different target areas ( percentages of total areas) of 11 vegetation types, as well as one population of each of the 99 endemic species, in the smallest area possible. Eight variations of the algorithm were run to provide flexibility in the results. Between 55 and 61 cells (out of a total of 193) were selected, 45 of which were common to all variations. Invoking the adjacency rule, or avoiding alien cells, costs less than 5% extra area. Six of the vegetation types are close to their targets, and the remaining 5 are over‐represented by between 46–166%. Percentage over‐representation is negatively and significantly correlated with percentage target. Between 72–78% of endemic species are represented more than once in the final sets of cells, and the gamma diversity of the Agulhas Plain is incidentally accommodated for. We suggest that the 45 cells common to all algorithm variations form the core of the contractual national park. Final reserve boundaries will differ from those of the selection units, so, as management boundaries are progressively defined, the algorithm can be rerun to account for the changes in the reserved areas of target features. We thus provide a dynamic and flexible tool for reevaluating priorities during the development of a park.
Managing Stand Structure as Part of Ecologically Sustainable Forest Management in Australian Mountain Ash Forests
Authors: Lindenmayer David B. , Franklin Jerry F.
Published: March 2003

Ecologically sustainable management of temperate forests is a complex task that involves balancing potentially conflicting land uses such as wood production and nature conservation. We argue that a variety of strategies implemented at different spatial scales is required for biodiversity conservation in temperate forests where wood production is permitted. This is a form of “risk‐spreading;” if one option is ineffective for a given species, it may still be conserved as a result of the implementation of other approaches. At the largest scale, there is a clear need for reserves to protect representative samples of forest ecosystems. Within landscapes broadly designated for timber harvesting, intermediate‐scale strategies such as the implementation of networks of streamside reserves and wildlife corridors are important for biodiversity conservation. At smaller spatial scales within harvested areas, critical habitat components for forest‐dependent organisms like large old trees and logs must be provided. We focus on the importance of these fine‐scale attributes for the conservation of biodiversity within logged forests using the mountain ash (  Eucalyptus regnans) forests of the Central Highlands of Victoria as a case study. Forest managers must develop silvicultural practices that maintain and perpetuate critical stand attributes essential for the conservation of forest‐dependent organisms. To this end, a shift is required from the extensive use of clearfelling to the adoption of new silvicultural techniques that maintain more structurally complex multi‐aged stands. The maintenance of key structural features should be used as a template to guide harvesting methods to ensure that production forests contribute to biodiversity conservation, not only in mountain ash forests, but also temperate wood production elsewhere around the world.
The Use by Rain Forest Mammals of Natural Forest Fragments in an Equatorial African Savanna
Authors: Tutin C. E. G. , White L. J. T. , Mackanga‐Missandzou A.
Published: March 2003

Two contrasting vegetation types occur in the Lopé Reserve in central Gabon: tropical rain forest dominates but areas of savanna containing natural forest fragments also exist. How forest mammals use the forest fragments has broad implications for conservation and management of tropical ecosystems because the natural landscape at Lopé mimics the fragmentation of forests produced increasingly by human action. The Lopé savannas result from climate induced vegetation changes over the past 20,000 years and are currently maintained by active management because, without regular burning, they are colonized by forest. Forty‐five species of large mammal (body weight ≥2 kg ) have been recorded at Lopé and, although none are savanna specialists, some use the savanna habitat. Sweep censuses were conducted monthly over 2 years in 13 forest fragments. The census sites were small (0.4–11 ha), completely or largely surrounded by savanna, and up to 450 m from continuous rain forest. Population density and biomass were calculated for the 26 species of mammals encountered (nocturnal species were rarely seen) and compared to data previously collected in adjacent continuous forests. Total biomass (6010 kg km−2) was highest in the forest fragments. Compared to adjacent, continuous forest, elephants (  Loxodonta africana) were less common whereas buffalo (Syncerus caffer) and red river hog ( Potamochoerus porcus) were much more numerous. Of eight species of diurnal primates, four were more common, two occurred at similar densities, and two were much less common in the fragmented habitat. Most mammalian species moved between continuous forest and the fragments but two species of guenon and six species of duiker appeared to reside permanently in some fragments. The diversity and high biomass of large mammals found within the forest outliers at Lopé is surprising and suggests that fragmentation per se will not be catastrophic for most of these species.
Succession and Disturbance in Sandhills Vegetation: Constructing Models for Managing Biological Diversity
Authors: Lesica Peter , Cooper Stephen V.
Published: March 2003

Abstract:The Centennial Sandhills of southwest Montana support a mosaic of shrub‐dominated vegetation in various stages of succession. The persistence of rare plants and plant communities depends on the presence of both early and late seral vegetation. Disturbances by fire, grazing, and burrowing are important processes opposing plant succession and influencing vegetation dynamics. We sampled vegetation in wind erosion (blowout), deposition, and stabilized sites on upper and lower slopes. Canonical correspondence analysis was employed to describe vegetation changes that occur during succession as soil organic matter and plant canopy cover increase and bare soil decreases. We used information on the effects of fire, ungulate grazing, and pocket gopher ( Thomomys talpoides) burrowing, and our empirically derived successional sequence, to develop a model of sandhills vegetation dynamics operating at local and regional scales. The model suggests that fire followed by intense ungulate grazing may be the only way to restore early seral vegetation to areas of low topographic relief. In areas of high topographic relief, restoring presettlement fire frequency should be adequate to maintain pocket gopher habitat and thus a high proportion of early seral vegetation. These hypotheses should be tested through a process of adaptive management aimed at sustaining a mosaic of early and late seral vegetation capable of supporting the full spectrum of native species.
Nesting Success of a Neotropical Migrant in a Multiple‐Use, Forested Landscape
Authors: Morse Solon F. , Robinson Scott K.
Published: March 2003

Abstract:We studied the nesting success of an individually marked population of Kentucky Warblers (Oporornis formosus), a species that nests in disturbed and undisturbed forests, in a heterogeneous, managed forest site in the Shawnee National Forest in southern Illinois from 1992 to 1995. We examined the effects of forest stand type (clearcuts of various ages, tree plantations, and older forest) and distance from habitat edges on rates of nest predation and brood parasitism by Brown‐headed Cowbirds (  Molothrus ater). Brood parasitism levels gradually decreased from 60% to 3% ( nests) over a distance of 2 km from an agricultural edge proximal to a known cowbird foraging site (a pig feedlot), but they did not vary with distance from any other kinds of edges or with forest stand type. Rates of nest predation ( nests) did not vary with distance from any edges, but they were significantly lower in older forest than within even‐aged clearcuts, a tree plantation, and in successional vegetation adjacent to a residential facility. These results suggest that, even in fragmented landscapes with high overall levels of parasitism and nest predation, management practices within and immediately adjacent to forest tracts can affect the nesting success of some species, but not necessarily as a simple function of distance from edge. For the Kentucky Warbler, our results suggest that a management strategy that avoids even‐age silviculture and leaves core stands of older forest far from cowbird feeding areas can increase nesting success to levels similar to those measured in more forested landscapes.
Effects of a Commercial Baitworm Harvest on Semipalmated Sandpipers and Their Prey in the Bay of Fundy Hemispheric Shorebird Reserve
Authors: Shepherd Philippa C. F. , Boates J. Sherman
Published: March 2003

Abstract:The conservation of key stopover sites for migratory wading birds is important because there are so few and because in some cases they support entire populations. In Minas Basin in the Bay of Fundy, over 500,000 Semipalmated Sandpipers (Calidris pusilla) on southward migration feed on the abundant amphipodCorophium volutator. When a baitworm harvesting industry began there in 1985 (focused on bloodworms [Glycera dibranchiata]), concerns were raised about the potential effects of this activity on the foraging behavior of Semipalmated Sandpipers and on the density and age structure of their principal prey,C. volutator. Core sampling for invertebrates and paired focal sandpiper observations were undertaken in disturbed (dug) and undisturbed sediment. Semipalmated Sandpiper foraging efficiency decreased by 68.5% in dug sediment, corresponding to observed reductions in prey density. The decreased foraging efficiency may also have been related to reductions in prey availability due to the obstruction of visual and tactile prey cues caused by turning and loosening of the surface sediment. The overall density (adult and juvenile) ofC. volutatordecreased by 38.8% in dug sediment in the first year of baitworm harvesting, due to direct mortality and lower juvenile recruitment. JuvenileC. volutatorwere particularly susceptible to disturbance (55% decrease in dug sediment); because they overwinter to become the next year’s potential breeders, this decrease can be expected to compound with each subsequent year of harvesting. All the significant, negative effects of baitworm harvesting on Semipalmated Sandpiper foraging behavior and on the density and age structure of their principal prey,C. volutator, were realized after only one season of digging. Semipalmated Sandpipers foraging in harvested areas may take longer to deposit the fat required for migration, thereby delaying their arrival on the wintering grounds or forcing them to depart without sufficient fat loads.
Reproductive Synchrony in Brucellosis‐Exposed Bison in the Southern Greater Yellowstone Ecosystem and in Noninfected Populations
Authors: Berger Joel , Cain Steven L.
Published: March 2003

Abstract:Shooting of bison ( Bison bison) in the Greater Yellowstone Ecosystem is a highly polarized, emotional issue because native ungulates exposed to brucellosis ( Brucella abortus) may infect cattle when they disperse or migrate beyond protected reserves. Both bison and elk ( Cervus elaphus) carry brucellosis, a disease that causes abortion in livestock and is often transmitted through contact with expelled fetuses or birth membranes and fluids. IfBrucella‐infected bison experience a prolonged period of birth, cattle in areas of sympatry will have increased susceptibility to disease. We tested the hypothesis that reproductive synchrony differs betweenBrucella‐free andBrucella‐infected bison by contrasting patterns between theBrucella‐exposed bison population (in Jackson Hole, Wyoming) within the southern Greater Yellowstone Ecosystem with three nonexposed populations (National Bison Range in Montana, and Wind Cave and Badlands National Parks in South Dakota) that inhabit prairies. Populations averaged 42 births per site per year. Fifty percent of all the births occurred within 1 month, and 95% within 61 days at three sites. It took 89 days for 95% of the births to occur at the noninfected Badlands site. Multiple comparison of regression slopes of the relationship between birth synchrony and the cumulative proportion of total births revealed interpopulation differences (  p< 0.01), but the brucellosis‐exposed population did not exhibit a parturition period different from that of the nondiseased populations. These among‐population similarities suggest that reproductive synchrony is not protracted inBrucella‐infected bison. AlthoughBrucellatransmission from bison to cattle occurs experimentally, captive densities during testing exceeded the mean for the Greater Yellowstone Ecosystem by about 1500 times, and that in 10 noninfected populations by more than 100 times. Although mean density can be misleading as a surrogate for the potential transmission of disease from bison to cattle, bison densities have not approached those reported for disease transmission. Among the ecological factors that may affect the spread of brucellosis from bison to cattle in the southern Yellowstone region, two stand out: (1) access to high‐quality food, perhaps because animals in superior physiological condition tend to exhibit tighter reproductive synchrony and (2) incidence of disease in elk. The timing of parturition in bison is neither a simple process nor is it likely to be based on responses to a single variable. A potentially fertile area for future investigation will concern relationships among food, reproductive synchrony, and spatial‐temporal components of bison, elk, and cattle distribution.
Rapid Extinction of Mountain Sheep Populations Revisited
Authors: Wehausen John D.
Published: March 2003

Abstract:Predicting extinction probabilities for populations of various sizes has been a primary focus of conservation biology.Berger (1990)presented an empirically based extinction model for mountain sheep (Ovis canadensis) populations in five southwestern states that predicted disappearance within 50 years of all populations estimated to number 50 sheep or fewer, but essentially no loss in that time period of populations estimated at over 100. The majority of the 122 populations he used in his analysis were from California, but his analysis did not use many of the historical size estimates for these populations. I testedBerger’s (1990)model using the complete data set from California and found—contrary to his results—that, for all size classes of population estimates, at least 61% of the populations persisted for 50 years. Also, two predictions from Berger’s model were not consistent with the data from California: (1) 10 populations have increased from estimates of 50 or fewer animals to over 100, whereas the Berger model predicted that these populations would only decline to extinction; and (2) of 27 extant populations with long enough records, 85% were estimated at least 50 years ago to be 50 individuals or fewer and should therefore be extinct by now. Berger’s model has now failed tests in three states and therefore does not support the strong population size effect on extinction probability that it first appeared to provide, and it may serve conservation poorly through misdirected effort if it is used as the basis for setting policies or taking actions.
Comparisons of Genetic Diversity in the EndangeredAdenophora lobophyllaand Its Widespread Congener,A. potaninii
Authors: Ge Song , Wang Ke‐Qing , Hong De‐Yuan , Zhang Wen‐Hui , Zu Yuan‐Gang
Published: March 2003

Abstract:Starch‐gel electrophoresis was used to examine the levels and distribution of genetic diversity in twoAdenophoraspecies: the narrow endangeredAdenophora lobophyllaand its widespread congener,A. potaninii. Based on allozyme variation at 18 putative loci, we measured high levels of genetic variability both in the endangered and the widespread species, with 83.3% of the loci being polymorphic. The mean expected heterozygosity within populations (  Hep  ) and within species (  Hes  ) were 0.234 and 0.244 forA. potaniniiand were as high as 0.210 and 0.211 forA. lobophylla. There was higher differentiation among populations inA. potaninii(  FST= 0.155) than inA. lobophylla(  FST= 0.071). The high levels of genetic diversity in the present allozyme survey are consistent with the morphological variation observed in these species and may be attributed to high outcrossing rates in theAdenophoraspecies. In addition,A. lobophyllawas identified as a distinct species on the basis of Nei’s genetic distances and thus should be given a high priority for protection. It is noteworthy that the endangeredA. lobophyllamaintains much higher genetic diversity than most endemic or narrowly distributed plant species in spite of its restricted distribution. We hypothesize thatA. lobophyllahas become endangered for ecological and stochastic reasons, including habitat destruction or environmental changes, mud slides, and human disturbance such as grazing and mowing. Consequently, habitat protection is of particular importance for conserving this endangered species.