The role of parasites in regulating host abundance

It has been 11 years since Anderson and May demonstrated the theoretical ability of helminth parasites to regulate host population abundance. In this review we consider how their work has advanced our understanding of the role of parasites in host populations. In particular Marilyn Scott and Andy Dobson consider three questions. What is meant by regulation? Is there empirical evidence that parasites can regulate host population abundance? Is it possible to predict the sort of host parasite association where one is most likely to be able to detect parasites as a major regulatory force?     

The wild bird trade and African parrots: past,present and future challenges

African parrots are among the most traded of all birds listed on the appendices of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). Collapses in some wild populations due to trapping for the pet trade have highlighted the threats posed by overexploitation. Although over 3.3 million African parrots have been reported in trade since 1975, virtually no monitoring of exploited populations has taken place and basic ecological data do not exist for the majority of traded species. Greater scrutiny of the wild bird trade in Africa would help ensure the practice is compatible with conservation goals as well as minimise biosecurity risks, including the spread of infectious diseases and the establishment of invasive populations.     

Seroepidemiologic Survey of Potential Pathogens in Obligate and Facultative Scavenging Avian Species in California

Throughout the world, populations of scavenger birds are declining rapidly with some populations already on the brink of extinction. Much of the current research into the factors contributing to these declines has focused on exposure to drug residues, lead, and other toxins. Despite increased monitoring of these declining populations, little is known about infectious diseases affecting scavenger bird species. To assess potential infectious disease risks to both obligate and facultative scavenger bird species, we performed a serosurvey for eleven potential pathogens in three species of scavenging birds in California: the California condor (Gymnogyps californianus), turkey vulture (Cathartes aura) and golden eagle (Aquila chrysaetos). California condors were seropositive for avian adenovirus, infectious bronchitis virus, Mycoplasma gallisepticum, avian paramyxovirus-2, West Nile virus (WNV) and Toxoplasma gondii. Golden eagles were seropositive for avian adenovirus, Chlamydophila psittaci and Toxoplasma gondii, and turkey vultures were seropositive for avian adenovirus, Chlamydophila psittaci, avian paramyxovirus-1, Toxoplasma gondii and WNV. Risk factor analyses indicated that rearing site and original release location were significantly associated with a positive serologic titer to WNV among free-flying condors. This study provides preliminary baseline data on infectious disease exposure in these populations for aiding in early disease detection and provides potentially critical information for conservation of the endangered California condor as it continues to expand its range and encounter new infectious disease threats.     

Sexually transmitted diseases in animals

The sexual transmission of infectious agents is one of a suite of characteristics that enhance the ability of an infection to persist in low-density populations. Gary Smith and Andrew Dobson review the characteristics and control of sexually transmitted diseases in domestic animals and wildlife species.     

Terrestrial gastropod hosts of Parelaphostrongylus tenuis at the National Zoological Park's Conservation and Research Center, Virginia

Terrestrial gastropods at the National Zoological Park's Conservation and Research Center (CRC) near Front Royal, Virginia, were surveyed from June 1985 to May 1986, to assess their role in transmission of the meningeal worm, Parelaphostrongylus tenuis. A total of 670 gastropods representing 9 families and 18 species was collected. The slug Deroceras laeve accounted for 50.4% of the specimens collected. Parelaphostrongylus tenuis infections were found in 15 gastropods (2.2% prevalence) representing 5 species; 5 of the infected gastropods were D. laeve. New host records for this nematode are Ventridens collisella and Philomycus carolinianus. Infected gastropods were recovered from June through October 1985 and in May 1986. All 6 sampling locations yielded infected gastropods, suggesting this parasite is widely distributed at the CRC, and is therefore likely to continue to pose a serious threat to exotic ungulates maintained there for conservation and research purposes.     

Restoration of Chlamydotis undulata macqueenii (Houbara Bustard) Populations in Saudi Arabia: A Progress Report

During the last two decades Chlamydotis undulata (houbara bustard) has declined drastically throughout its range, due primarily to over-hunting and severe habitat degradation. The threatened extinction of local populations led the National Commission for Wildlife Conservation and Development of Saudi Arabia to implement ex- and in-situ conservation measures: (1) a captive breeding program initiated in 1986, which achieved production of a self-sustaining breeding flock as well as a surplus for reintroduction by 1992; (2) establishment of a 13,775-km2 protected area around the last known breeding population in Saudi Arabia; (3) studies of wild birds, to determine densities, feeding ecology, and habitat requirements; and (4) studies on different release techniques (adult releases, sub-adult releases, feather-cut sub-adult releases, and covey releases), carried out since 1991 within the 2,300-km² fenced and protected area of the Mahazat as-Sayd reserve.     

Is the wild rabbit (<Emphasis Type="Italic">Oryctolagus cuniculus</Emphasis>) a threatened species in spain? Sociological constraints in the conservation of species

The Wild rabbit (Oryctolagus cuniculus) is an endemic species of the Iberian Peninsula and is essential for the conservation of endangered predators. Rabbits are also of high importance as a hunting species. From 1988, rabbits suffered the severe effects of rabbit hemorrhagic disease, which caused large declines in most populations. Despite this fact, the National Red Data Lists continued to classify rabbits as a “Least Concern” species. We used available hunting bag data from 1973 to 2002 to model national trends of rabbit abundance and to evaluate the conservation status according to the criteria of the National Red Data List and the World Conservation Union (IUCN). Generalized Additive Models were used as the statistical framework. The rabbit population of Spain suffered a large decline of about 71% between 1973 and 1993. This decline was 49% in the period 1980–1990. Based on both Spanish and World Conservation Union criteria, rabbits should be listed as ‘Vulnerable’, which demands a Conservation Plan Program. We suggest that the lack of concordance between the best available evidence and the conservation status of the species is a consequence of sociological constraints in conservation decisions. Rabbit conservation could face strong opposition from important socio-economic lobby groups (hunters and farmers). As such, governments and researchers may prefer to exclude rabbits from any status category requiring conservation action, despite the evidence of decline. We call for the urgent development of a nation-wide conservation program for rabbits which includes both socioeconomic constraints and the available biological data on population trends.     

Insular bird populations can be saved from rats: a long-term experimental study of white-chinned petrels<Emphasis Type="Italic"> Procellaria aequinoctialis</Emphasis> on Ile de la Possession (Crozet archipelago)

The white-chinned petrel is a subantarctic seabird that requires urgent implementation of conservation measures for the species. At sea, adults suffer heavy mortality due to fisheries' practices. On land, introduced rats prey on chicks at several localities, and we test here if and how rats can be efficiently controlled. Since 1994, we have conducted an intensive rat-control program during each breeding season in a white-chinned petrel colony on Ile de la Possession (150 km²; Crozet archipelago, southern Indian Ocean), which had been monitored since 1986. On the same island, a control white-chinned petrel colony, where no poisoning occurred, was also monitored, and we assessed the seasonal variations of rat abundance. We compared three situations: high rat-poisoning, low rat-poisoning and control conditions without poisoning. Low-poisoning trials performed in our experimental colony between 1988 and 1991 did not lead to higher chick production than for the previous two control years. However, petrel-breeding success was significantly higher when intensive poisoning occurred (50%) than for the previous years (16%). The duration of our study (8 years before intensive poisoning, plus 8 years afterwards), combined with a comparison of petrel annual breeding success between our experimental and control colonies, allowed us to assess more effectively the impact of rats. Forty-one per cent of breeding failures occurring in non-poisoned areas were attributed to rats. We conclude that threatened insular bird populations can be conserved and restored in localities even where total rat eradication is not possible. However, only intensive and repeated (long-term) poisoning will control rats sufficiently.     

NORTH AMERICAN GRASSLAND BIRDS: AN UNFOLDING CONSERVATION CRISIS?

Abstract: The widespread and ongoing declines of North American bird populations that have affinities for grassland and grass-shrub habitats (hereafter referred to as grassland birds) are on track to become a prominent wildlife conservation crisis of the 21st century. There is no single cause responsible for the declines of grassland birds. Rather, a cumulative set of factors such as afforestation in the eastern United States, fragmentation and replacement of prairie vegetation with a modern agricultural landscape, and large-scale deterioration of western U.S. rangelands are the major causes for these declines. The North American Bird Conservation Initiative (NABCI) is a set of comprehensive and coordinated strategic actions modeled on the Joint Venture initiatives that were used to successfully implement the North American Waterfowl Management Plan. The NABCI is emerging as a potential broad-scale solution for conserving populations of grassland birds. Coordinating grassland bird conservation efforts with initiatives to stabilize and increase upland game birds that have strong affinities for grassland habitats—such as quail and prairie grouse—presents additional opportunities to leverage funding and resources that will positively impact virtually all species of North American grassland birds.     

Effects of emerging infectious diseases on host population genetics: a review

Emerging infectious diseases threaten the survival of many species and populations by causing large declines and altering life history traits and population demographics. Therefore, it is imperative to understand how diseases impact wildlife populations so that effective management strategies can be planned. Many studies have focused on understanding the ecology of host/pathogen interactions, but it is equally important to understand the effects on host population genetic structure. In this review, we examined the literature on how infectious diseases influence host population genetic makeup, with a particular focus on whether or not they alter gene flow patterns, reduce genetic variability, and drive selection. Although the results were mixed, there was evidence for all of these outcomes. Diseases often fragmented populations into small, genetically distinct units with limited gene flow among them. In some cases, these isolated populations showed the genetic hallmarks of bottlenecks and inbreeding, but in other populations, there was sufficient gene flow or enough survivors to prevent genetic drift and inbreeding. Direct evidence of diseases acting as selective pressures in wild populations is somewhat limited, but there are several clear examples of it occurring. Also, several studies found that gene flow can impact the evolution of small populations either beneficially, by providing them with variation, or detrimentally, by swamping them with alleles that are not locally adaptive. Thus, differences in gene flow levels may explain why some species adapt while others do not. There are also intermediate cases, whereby some species may adapt to disease, but not at a rate that is meaningful for conservation purposes.     

Is research effort allocated efficiently for conservation? Felidae as a global case study

Some species face greater anthropogenic threats than others, and have increased need for scarce conservation resources. Yet how resources are allocated for conservation remains little known. I examined the distribution of research effort, an index of resource allocation, across Felidae (the cat family), a diverse, widely-distributed, and threatened taxon. I performed complete searches of the published literature for all cat species from 1986 to 2007, collecting a total of 2,462 papers, of which 926 represented in situ studies. Threat status, as ranked by a World Conservation Union report in 1996, was significantly correlated with geographical range size, with narrowly distributed species tending to be more at risk. Unlike in many other taxa, threat status was not correlated with body size. The number of total and in situ publications (“research effort”) per species was significantly and positively related to body size, but not to threat status or geographical range size. Research effort, rather than being distributed according to actual threat status, is highly skewed towards large species. However, the ratio of the number of studies on the 10 smallest cat species to the number on the 10 largest species has increased significantly since 1986. Yet many species remain severely understudied; I identify 14 cat species that are threatened and have <10 in situ publications each. These species critically require a greater share of the conservation research effort.     

The influence of host plant,nitrogen fertilization and fungicide application on the abundance and seasonal dynamics of vesicular-arbuscular mycorrhizal fungi in arable soils of northern Germany

The present investigation examines whether the crop plant, increased nitrogen (N) fertilization and fungicide application influence the pattern of vesicular-arbuscular mycorrhizal fungi (VAM) populations. For this purpose, two arable field locations in Lower Saxony (Hotteln and Langreder) were chosen and the formation of mycorrhiza, spore density, number of infectious propagules (MPN) and frequency of spore types within VAM populations were investigated. The influence of crop plants was examined over two cultivation periods (1986/1987 and 1987/1988) in Hotteln, comparing winter wheat, winter barley and sugar beet. The effects of increased N fertilization and fungicide application were investigated on winter wheat in Langreder in the cultivation period 1988 only. Both the frequency of mycorrhizal infection and the spore dynamics in soil differed with the crops grown. Spore density and MPN increased until harvesting when host plants (winter wheat, winter barley) were cultivated, whereas both diminished with a non-host plant (sugar beet). Different spore types increased or decreased, according to the plant species grown, but the predominating types of the location remained constant. Increased N fertilization caused marginal inhibition of mycorrhizal infection and sporulation on winter wheat, whereas both leaf and base application of fungicides resulted in minor increases in mycorrhizal colonization of roots and sporulation in soil. Both increased N fertilization and fungicide application distinctly decreased the sporulation of one type in May, but the characteristic compositions of the VAM populations remained unchanged.     

Interannual patterns of avian diseases in wild New Zealand avifauna near conservation areas

The past few years have seen a noticeable increase in the emergence of infectious diseases in wildlife, especially vector-borne diseases, presenting a challenge for the conservation of endangered species. One such vector-borne disease, avian malaria (Plasmodium spp.) is on the rise in New Zealand avifauna, threatening bird populations that are among the most extinction-prone in the world. Furthermore, recent reports have outlined an increase in deaths of native iconic bird species specifically due to this disease. In order to help manage breakouts of this pathogen at a local scale, we need a better understanding of potential drivers of the emergence of avian malaria in wild New Zealand avifauna. Here, we set to test the role of climatic drivers in synchronizing contacts between avian hosts and vectors, assess the temporal stability of transmission dynamics between years, and determine the role of introduced species in causing spill-over of this pathogen towards native species. Our study focused on three sites that were sampled regularly during two consecutive years in the austral summer, each site being adjacent to a breeding colony of Yellow-eyed penguins (Megadyptes antipodes). Our results reveal an overall temporal stability of avian malaria incidence patterns, with a decrease in infection throughout the austral summer for both sampled years. Moreover, we highlight a phylogenetic signal among sampled bird species, with introduced species being more heavily infected by avian malaria than their native counterparts. In contrast, we found no effect of the two climatic drivers investigated, temperature and rainfall, on mosquito abundance. Our results suggest a strong effect of alien species acting as reservoirs for diseases spilling-over towards immunologically naïve species, and provide conservation managers with a critical timeframe to control avian malaria breakouts.     

Understanding population change in migratory songbirds: long-term and experimental studies of Neotropical migrants in breeding and wintering areas

Effective conservation and management of migratory bird species requires an understanding of when and how their populations are limited and regulated. Since 1969, my colleagues and I have been studying migratory songbird populations in their breeding quarters at the Hubbard Brook Experimental Forest in north-central New Hampshire, USA, and since 1986, in their winter quarters in the Greater Antilles (Jamaica). Long-term data on the abundance and demography of these populations, coupled with experimental tests of mechanisms, indicate that processes operating in the breeding area (e.g. density-dependent fecundity, food limitation) are sufficient to limit and regulate the local abundance of these species. At the same time, limiting factors operating in the non-breeding season (e.g. climate-induced food limitation in winter quarters and especially mortality during migration) also have important impacts on migrant populations. Furthermore, recent studies have shown that limiting processes during the winter period can carry over into the breeding season and affect reproductive output. These findings clearly demonstrate that to understand changes in abundance of long-distance migrant species requires knowledge of events operating throughout the annual cycle, which presents a challenge to researchers, managers and others concerned with the welfare of these species.     

Health transition: examples from the western Pacific.

The Industrial Revolution ushered in a rapid transition from agriculture to industrialization. Some biological effects of this transition included increasing life expectancy, reduced infant mortality, and some decline in fertility. Reduced infant mortality first brought about an increase in life expectancy, but as humans were able to control infectious diseases, child and adult mortality also decreased. Now, accidents and chronic diseases are responsible for most mortality in many age groups. This shift from infectious diseases to accidents and chronic diseases is called the health transition. Japan and US are Pacific Basin countries which have relatively high life expectancy and low infant mortality (1988, 75.54 years vs. 71.38 years, and 4.4 vs. 9.9, respectively). These figures suggest that these countries rather advanced in the health transition. Japan may have better life expectancy than the US because of the effect of environmental factors, ethnic diversity, and health care differentials by social class on cardiovascular disease and cancer mortality. China and Thailand hold intermediate positions (67.98 years (1985-1990) vs. 63.82 years (1985-1986), and 32.4 vs. 39, respectively). Some research indicates that urban conditions and factory work increase the cardiovascular disease risk among the Chinese. Recent research suggests that access to immunization and modern medical care for acute disease are the only critical variables of the health transition rather than other variables. Papua New Guinea is not progressing very well (53.18 years and 58). Papua New Guinea has not yet been able to control infectious diseases, especially malaria. This comparison illustrates that populations progress through the health transition at different rates.     

How can a character be developmentally constrained despite variation in developmental pathways?

A fundamental riddle of evolutionary developmental biology is the conservation of adult morphological patterns (Hall, 1992). Conservative patterns are either called body plans if they concern overall body design, or homologues if they concern parts of the body (Riedl, 1978; Roth, 1982; Sattler, 1984; Van Valen, 1982; Wagner, 1989a, 1989b). An adult pattern is considered conservative if it remains unchanged in spite of changes in function, as indicated by the original definition of homology by Owen, as a similarity of organs regardless of form and function (Owen, 1848). Conservation of anatomical features despite different adaptive pressures is naturally explained by developmental constraints (Wagner, 1986). However, this approach to explain the biological basis of homology is plagued by the fact that developmental pathways are often more variable than the characters that they produce (see Tab. 1) (Hall, 1992; Roth, 1988, 1991; Spemann, 1915; Wagner, 1989b). This is also true for any other application of the concept of developmental constraints. The widely held opinion that early stages of development are conservative because any early perturbation is likely to interfere with later development, is far from absolute, since a vast amount of data in comparative developmental biology speaks to developmental variation (see e.g. the examples in Tab. 1). The question then is, how can developmental constraints on adult variation be reconciled with the fact of developmental variation?     

The World Crane Action Plan: implications for conservation of cranes and wetlands in Africa

Beilfuss, R.D., Meine, C.D., & Archibald, F.W. 2000. The World Crane Action Plan: implications for conservation of cranes and wetlands in Africa. Ostrich 71 (1 & 2): 227.

The IUCN Species Survival Commission recently published The Cranes: Status Survey and Conservation Action Plan. Prepared over the past three years by the IUCN Crane Specialist Group, the document reviews the status of the world's cranes (Family: Gruidae) and their habitats, summarises recent crane conservation actions, and specifies priority measures for the future. Eleven of the 15 crane species are now proposed for inclusion on the IUCN Red List of Threatened Animals, and several subspecies and populations are critically endangered. Africa supports six species of cranes in 39 countries. The Black Crowned Crane Balearica pavonina, national bird of Nigeria, is resident in western and central Africa. The Grey Crowned Crane B. regulorum, national bird of Uganda, spans eastern and southern Africa. The Wattled Crane Bugeranus carunculahrs, largest and. rarest of Africa's cranes, ranges from Ethiopia to South Africa. The Blue Crane Anthropoides paradiseus, national bird of South Africa, is endemic to South Africa and Namibia. The Demoiselle Crane A. Virgo and Eurasian Crane Grus grus are winter visitors. Cranes have been the focus of intensive captive propagation and reintroduction programs as well as extensive habitat protection efforts. They are also excellent umbrella species for ecosystem-level conservation efforts. Wetlands that provide a home for cranes include the floodplains of the great river systems of Africa, such as Kafue Flats and Zambezi Delta of the Zambezi River system, the Okavango River Delta, the Sudd of the Upper Nile River, the Bangweulu Basin and swamps of the Zaire River system, the Senegal River Delta, and the Inner Niger River Delta, and the wetlands of Lake Chad. Small, isolated wetlands provide vital breeding habitat. This presentation will provide an overview of the action plan for those interested in cranes in particular, as well as those working in ecosystems and regions where cranes occur.     

Bird Communities and Biomass Yields in Potential Bioenergy Grasslands

Demand for bioenergy is increasing, but the ecological consequences of bioenergy crop production on working lands remain unresolved. Corn is currently a dominant bioenergy crop, but perennial grasslands could produce renewable bioenergy resources and enhance biodiversity. Grassland bird populations have declined in recent decades and may particularly benefit from perennial grasslands grown for bioenergy. We asked how breeding bird community assemblages, vegetation characteristics, and biomass yields varied among three types of potential bioenergy grassland fields (grass monocultures, grass-dominated fields, and forb-dominated fields), and assessed tradeoffs between grassland biomass production and bird habitat. We also compared the bird communities in grassland fields to nearby cornfields. Cornfields had few birds compared to perennial grassland fields. Ten bird Species of Greatest Conservation Need (SGCN) were observed in perennial grassland fields. Bird species richness and total bird density increased with forb cover and were greater in forb-dominated fields than grass monocultures. SGCN density declined with increasing vertical vegetation density, indicating that tall, dense grassland fields managed for maximum biomass yield would be of lesser value to imperiled grassland bird species. The proportion of grassland habitat within 1 km of study sites was positively associated with bird species richness and the density of total birds and SGCNs, suggesting that grassland bioenergy fields may be more beneficial for grassland birds if they are established near other grassland parcels. Predicted total bird density peaked below maximum biomass yields and predicted SGCN density was negatively related to biomass yields. Our results indicate that perennial grassland fields could produce bioenergy feedstocks while providing bird habitat. Bioenergy grasslands promote agricultural multifunctionality and conservation of biodiversity in working landscapes.     

Protecting Orchids in Nature Reserves: Research and Restoration Needs

Will installment of a few fences and rangers be sufficient to secure the rich orchid floral in an economically challenged area under the current rapidly changing environments? What are the research and restoration needs? We convened the Guangxi International Orchid Conservation Symposium in May 2009 in Leye county, a remote, rural area in southwestern China that is rich in orchids, to address these questions. Symposium participants examined orchid conservation issues from various angles, as reflected in this volume. Although the biological factors in orchid conservation were emphasized, social factors (i.e. protected area - people relations) were also presented here. These reviews and analyses will inform conservation workers in China as well as around the world.     

Spatial Models of Northern Bobwhite Populations for Conservation Planning

Abstract: Since 1980, northern bobwhite (Colinus virginianus) range-wide populations declined 3.9% annually. Within the West Gulf Coastal Plain Bird Conservation Region in the south-central United States, populations of this quail species have declined 6.8% annually. These declines sparked calls for land use change and prompted implementation of various conservation practices. However, to effectively reverse these declines and restore northern bobwhite to their former population levels, habitat conservation and management efforts must target establishment and maintenance of sustainable populations. To provide guidance for conservation and restoration of habitat capable of supporting sustainable northern bobwhite populations in the West Gulf Coastal Plain, we modeled their spatial distribution using landscape characteristics derived from 1992 National Land Cover Data and bird detections, from 1990 to 1994, along 10-stop Breeding Bird Survey route segments. Four landscape metrics influenced detections of northern bobwhite: detections were greater in areas with more grassland and increased aggregation of agricultural lands, but detections were reduced in areas with increased density of land cover edge and grassland edge. Using these landscape metrics, we projected the abundance and spatial distribution of northern bobwhite populations across the entire West Gulf Coastal Plain. Predicted populations closely approximated abundance estimates from a different cadre of concurrently collected data but model predictions did not accurately reflect bobwhite detections along species-specific call-count routes in Arkansas and Louisiana. Using similar methods, we also projected northern bobwhite population distribution circa 1980 based on Land Use Land Cover data and bird survey data from 1976 to 1984. We compared our 1980 spatial projections with our spatial estimate of 1992 populations to identify areas of population change. Additionally, we used our projection of the spatial distribution and abundance of bobwhite to predict areas of population sustainability. Our projections of population change and sustainability provide guidance for targeting habitat conservation and rehabilitation efforts for restoration of northern bobwhite populations in the West Gulf Coastal Plain.