Habitat associations of pool-breeding amphibians in eastern Massachusetts,USA

There is a pressing need to develop a sound conservation strategy for pool-breeding amphibians, which includes gaining a better understanding of the habitat and landscape-scale characteristics associated with populations. To investigate relationships between amphibian species richness and characteristics of breeding pools and surrounding landscapes, we surveyed 85 pools in eastern Massachusetts (USA) in 1996 and 1997. A total of 11 species was detected, with most pools having 2–5 species. Pools were typically small, 77.6% were <0.2 ha, but most pools (72%) had hydroperiods that persisted at least into August in most years. Based on linear regression analyses, species richness was positively associated with three within-pool variables (pool surface area, hydroperiod, and the amount of emergent vegetation), and a landscape-level variable (presence of another breeding pool within 1 km), while one within-pool variable (tree canopy cover) exhibited a significant negative association with species richness. These within-pool habitat variables and connectivity to other breeding pools are important characteristics to consider when attempting to identify breeding sites that could provide core habitat in conservation reserves designed for the conservation of pool-breeding amphibian species richness. Conservation reserves for pool-breeding amphibian populations should include pool complexes functioning as habitat for metapopulations. Core pool habitats within such reserves should be large (0.5–1.0 ha), with seasonal hydroperiods that persist into August or that dry in some years, and with sufficient emergent vegetation to provide diverse microhabitats and refugia.     

Conservation Value of Landscape Supplementation for Howler Monkeys Living in Forest Patches

Many animal populations are forced to inhabit very small forest patches, which may threaten their long-term survival. In some cases, animals in these forest remnants are able to supplement their diet by using resources outside of their home patch, a process named 'landscape supplementation'. Although this is probably a key process for population survival in fragmented landscapes, little is known about the ability of most animal species to move through the matrix and feed from different landscape elements. In this paper we report several cases of landscape supplementation by two groups of Mexican mantled howler monkeys Alouatta palliata mexicana inhabiting two different forest patches in Los Tuxtlas, Mexico. Our observations show that howler monkeys used several landscape elements, such as isolated trees, live fences and neighboring forest patches to supplement their diet. These observations underline the importance of these landscape elements for the survival of forest-dependent animals in highly fragmented landscapes, as they can provide important food resources and, hence, can be considered as potential extensions of their home range. However, the degree of protection the landowner provides to howler monkeys and proper management of these landscape elements are key aspects in determining the use of these elements by these animals.     

Relations Between Regional–Local Habitat Loss and Metapopulation Properties of Epiphyllous Bryophytes in the Brazilian Atlantic Forest

Richness and occupancy patterns of epiphyll bryophytes in a fragmented landscape of tropical rain forests in northeastern Brazil (Murici Ecological Station) were investigated to assess the influence of regional and local disappearance of habitat on epiphyllous metapopulation indicators. Bryophytes were collected from ten forest fragments, from the fragment's border to 100 m inside the forest. The number of colonized phorophytes and the cover on leaves were scored. Decreasing trends in regional and local abundance linked to habitat loss were observed, which may be related to the sexual and asexual expression. Although fertility was not related to constancy in the fragments, frequently fertile species colonized more sites within fragments than infertile species. Landscape metrics and indicators of habitat quality explained better the variation in epiphyll richness and occupancy than distance from the forest's edge. This suggests that the abrupt habitat quality modification resulting from edge creation is secondary in the area studied, while irreversible landscape modifications still play an important role. The results add to empirical support that metapopulations are prone to negative and long-term effects in fragmented landscapes. Thus, the selection of priority areas for conservation must take into account the remaining amount of habitat as well as the connectivity between the landscape's patches.     

Habitat suitability and connectivity implications for the conservation of the Persian leopard along the Iran–Iraq border

Habitat fragmentation has major negative impacts on wildlife populations, and the connectivity could reduce these negative impacts. This study was conducted to assess habitat suitability and structural connectivity of the Persian leopard along the Iran–Iraq border (i.e., the Zagros Mountains) and compare the situation of identified core habitats and connectivity with existing conservation areas (CAs). An ensemble modeling approach resulting from five models was used to predict habitat suitability. To identify core habitats and corridors along the Iran–Iraq border, factorial least‐cost path analyses were applied. The results revealed that topographic roughness, distance to CAs, annual precipitation, vegetation/cropland density, and distance to rivers were the most influential variables for predicting the occurrence of the Persian leopard in the study area. By an estimated dispersal distance of 82 km (suggested by previous studies), three core habitats were identified (two cores in Iran and one core in Iraq). The largest cores were located in the south and the center of the study area, which had the highest connectivity priorities. The connectivity from these cores was maintained to the core within the Iraqi side. Only about one‐fifth of detected core habitats and relative corridors were protected by CAs in the study area. Detected core habitats and connectivity areas in this study could be an appropriate road map to accomplish the CAs network along the Iran–Iraq border regarding Persian leopard conservation. Establishing transboundary CAs, particularly in the core habitat located in the center of the study area, is strongly recommended to conserve existing large carnivores, including the Persian leopard.     

Habitat fragmentation: A long and tangled tale

In this essay: I provide a brief history of habitat fragmentation research; I describe why its “non‐questions” (‘Is habitat fragmentation a big problem for wildlife species?” and, “Are the effects of habitat fragmentation generally negative or positive?”) are important to conservation; I outline my role in tackling these questions; I discuss reasons why the culture of habitat fragmentation research is largely incapable of accepting the answers; and I speculate on the future of habitat fragmentation research.     

Forest Fragment and Breeding Habitat Characteristics Explain Frog Diversity and Abundance in Singapore

Habitat loss and fragmentation can have severe negative and irreversible effects on biodiversity. We investigated the effects of forest fragmentation on frog diversity in Singapore because of its high rates of deforestation and the demonstration that frogs are some of the most sensitive species to habitat degradation. We surveyed frog species in 12 forest fragments varying from 11 to 935 ha. We compared differences in species richness, abundance, and Shannon's index in relation to forest fragment size, connectivity (distance between fragments), and breeding habitat heterogeneity. A total of 20 species from 12 genera and five families were encountered in 12 fragments. Larger fragments and those closer to larger fragments had higher species richness. Abundance, however, was not correlated with forest area or connectivity, but we found fewer individual frogs in the larger fragments. We also found that breeding habitat heterogeneity best explained frog species diversity and abundance in forest fragments. Fragments with a high diversity of breeding habitats had more species. We found no evidence to suggest that abundance and diversity are strongly correlated, particularly in disturbed areas, but that breeding habitat heterogeneity is an under-appreciated factor that should be considered when prioritizing areas for anuran conservation. Enriching breeding habitat heterogeneity, creating corridors between fragments, and reforesting degraded areas are some of the most beneficial strategies for preserving urban frog biodiversity.     

Habitat management as a generalized tool to boost European rabbit Oryctolagus cuniculus populations in the Iberian Peninsula: a cost‐effectiveness analysis

相似文献   

Habitat fragmentation and population size of the black and gold howler monkey (Alouatta caraya) in a semideciduous forest in Northern Argentina

A population of black and gold howler monkeys (Alouatta caraya) living near the southern limit of its distribution in a semideciduous forest located in northern Argentina was studied in 2003 to evaluate the possible effects of habitat fragmentation - owing to logging - on its density and social organization within it. Aerial photographs taken in 1982, 1992, and 2001 were used to compare maps of vegetation. These maps were used to evaluate changes in the area covered by forest fragments. From March to June 2003, 10-day monthly surveys of howlers were made in each fragment. A total of 232 individual howlers were counted, belonging to 34 groups plus a solitary adult female. Groups ranged from 2 to 19 individuals (mean = 6.82, SD = 4.23), and 21% of the groups contained more than one adult male. Adults accounted for 55% of the individuals, immatures for 45%, and infants represented 13% of the total. Data obtained were compared with information available for the same population for 1982 and 1995. Results revealed no significant changes in the area of fragments, the crude and ecological density of howlers, and group composition. Group sizes and group composition of howlers suggest that the population remained stable over the past 22 years. The density, number of groups, and individuals appears not to be affected by fragmentation and logging, but crude density was low compared with other less-disturbed habitats. The status of the population remains uncertain owing to isolation, and because there are no protected areas to ensure its stability for the future.     

Alterations in mitochondrial morphology as a key driver of immunity and host defence

Mitochondria are dynamic organelles whose architecture changes depending on the cell’s energy requirements and other signalling events. These structural changes are collectively known as mitochondrial dynamics. Mitochondrial dynamics are crucial for cellular functions such as differentiation, energy production and cell death. Importantly, it has become clear in recent years that mitochondrial dynamics are a critical control point for immune cell function. Mitochondrial remodelling allows quiescent immune cells to rapidly change their metabolism and become activated, producing mediators, such as cytokines, chemokines and even metabolites to execute an effective immune response. The importance of mitochondrial dynamics in immunity is evident, as numerous pathogens have evolved mechanisms to manipulate host cell mitochondrial remodelling in order to promote their own survival. In this review, we comprehensively address the roles of mitochondrial dynamics in immune cell function, along with modulation of host cell mitochondrial morphology during viral and bacterial infections to facilitate either pathogen survival or host immunity. We also speculate on what the future may hold in terms of therapies targeting mitochondrial morphology for bacterial and viral control.     

Bird species richness in vegetation fences and in strips of residual rain forest vegetation at Los Tuxtlas, Mexico

Fragmentation of the lowland tropical rain forest has resulted in loss of animal and plant species and isolation of remaining populations that puts them at risk. At Los Tuxtlas, Mexico, lowland rain forests are particularly diverse in the avian fauna they contain and while most of the forests have been fragmented by human activity, many of the fragments still harbor diverse assemblages of bird species. In these landscapes, linear strips of residual rain forest vegetation along streams as well as linear strips of vegetation fences (live fences) crossing the pastures might provide some connectivity to bird populations existed in forest fragments. We investigated bird species richness and relative abundance in one 6-km long section of live fences (LF) bordering a dirt road and in two 6-km long sections of residual forest vegetation along a river (MR) and one permanent stream (BS). We used point count procedures which resulted in the count of 2984 birds representing 133 species. At the LF site we detected 74% of the species, 72% at the BS site and 57% at the MR site. Only 38% of the species were common among sites. Neotropical migratory birds accounted for 34–41% of the species counted at all sites. While edge and open habitat birds accounted for 6–10% of the species and for 50% of the records at the three vegetation strips, about 90% of the species were forest birds. Distance to forest fragments and degree of disturbance of the vegetation seemed to negatively influence bird species presence at the BS and MR strips. Rarefaction analysis indicated that the LF strip was richer in species than the other two sites, but the occurrence of the three vegetation strips in the landscape seem to favor the presence of many more species. We discuss the value of these vegetation strips to birds as stepping stones in the fragmented landscape.     

Modelling the effect of habitat fragmentation on range expansion in a butterfly

There is an increasing need for conservation programmes to make quantitative predictions of biodiversity responses to changed environments. Such predictions will be particularly important to promote species recovery in fragmented landscapes, and to understand and facilitate distribution responses to climate change. Here, we model expansion rates of a test species (a rare butterfly, Hesperia comma) in five landscapes over 18 years (generations), using a metapopulation model (the incidence function model). Expansion rates increased with the area, quality and proximity of habitat patches available for colonization, with predicted expansion rates closely matching observed rates in test landscapes. Habitat fragmentation constrained expansion, but in a predictable way, suggesting that it will prove feasible both to understand variation in expansion rates and to develop conservation programmes to increase rates of range expansion in such species.     

First Report of Chytridiomycosis in a Dying Toad (Anura: Bufonidae) from Cuba: A New Conservation Challenge for the Island

Infection by the chytrid fungus Batrachochytrium dendrobatidis was detected in a male Bufo longinasus dunni, a small toad endemic to central Cuba. The individual was severely infected and in decaying condition. Sections of the skin were examined through standard histological procedures. Several stages of the fungus were confirmed and are illustrated in this contribution. Implications for amphibian conservation in Cuba are discussed.     

Do Orthoptera Need Human Land use in Central Europe? The Role of Habitat Patch Size and Linear Corridors in the Białowieża Forest, Poland

We studied Orthoptera, Dermaptera, and Blattodea of the Białowieża Forest (Poland) in order to assess (1) the minimum patch size of open habitat necessary for each species, (2) the role of linear corridors as habitat, and (3) the impact of herbivores on diversity by comparing the fauna at periods of different ungulate densities. Many species occurred in the farthest clearings from the forest edge to arable land. Two third of species occurred in clearings smaller than 10,000 m². Dry linear corridors of 10–40 m width and wet linear corridors of 100–200 m width had a species richness that corresponded to that of clearings of about 10,000 m². Four species disappeared from the Białowieża Forest when ungulate density decreased from 20 individuals/km² (3000 kg/km² biomass) at the beginning of the 20th century to 10 individuals/km² (1000 kg/km²) at the end of the 20th century. We conclude that most Orthoptera, Dermaptera, and Blattodea species could survive in Central Europe if human land use was replaced by intensive grazing and browsing by wild herbivores.     

Habitat percolation transition undermines sustainability in social-ecological agricultural systems

Steady increases in human population size and resource consumption are driving rampant agricultural expansion and intensification. Habitat loss caused by agriculture puts the integrity of ecosystems at risk and threatens the persistence of human societies that rely on ecosystem services. We develop a spatially explicit model describing the coupled dynamics of an agricultural landscape and human population size to assess the effect of different land-use management strategies, defined by agricultural clustering and intensification, on the sustainability of the social-ecological system. We show how agricultural expansion can cause natural habitats to undergo a percolation transition leading to abrupt habitat fragmentation that feedbacks on human's decision making, aggravating landscape degradation. We found that agricultural intensification to spare land from conversion is a successful strategy only in highly natural landscapes, and that clustering agricultural land is the most effective measure to preserve large connected natural fragments, prevent severe fragmentation and thus, enhance sustainability.     

Conservation needs of amphibians in China: A review

The conservation status of all the amphibians in China is analyzed, and the country is shown to be a global priority for conservation in comparison to many other countries of the world. Three Chinese regions are particularly rich in amphibian diversity: Hengduan, Nanling, and Wuyi mountains. Salamanders are more threatened than frogs and toads. Several smaller families show a high propensity to become seriously threatened: Bombinatoridae, Cryptobranchidae, Hynobiidae and Salamandridae. Like other parts of the world, stream-breeding, high-elevation forest amphibians have a much higher likelihood of being seriously threatened. Habitat loss, pollution, and over-harvesting are the most serious threats to Chinese amphibians. Over-harvesting is a less pervasive threat than habitat loss, but it is more likely to drive a species into rapid decline. Five conservation challenges are mentioned with recommendations for the highest priority research and conservation actions.     

Temperature alters reproductive life history patterns in Batrachochytrium dendrobatidis,a lethal pathogen associated with the global loss of amphibians

Understanding how pathogens respond to changing environmental conditions is a central challenge in disease ecology. The environmentally sensitive fungal pathogen Batrachochytrium dendrobatidis (Bd), which causes the amphibian disease chytridiomycosis, has spread globally causing amphibian extirpations in a wide variety of climatic regions. To gain an in‐depth understanding of Bd's responses to temperature, we used an integrative approach, combining empirical laboratory experiments with mathematical modeling. First, we selected a single Bd isolate and serially propagated two lineages of the isolate for multiple generations in two stable thermal conditions: 4°C (cold‐adapted lineage) and 23°C (warm‐adapted lineage). We quantified the production of infectious zoospores (fecundity), the timing of zoospore release, and zoospore activity in reciprocal temperature transplant experiments in which both Bd lineages were grown in either high or low temperature conditions. We then developed population growth models for the Bd lineages under each set of temperature conditions. We found that Bd had lower population growth rates, but longer periods of zoospore activity in the low temperature treatment (4°C) compared to the high temperature treatment (23°C). This effect was more pronounced in Bd lineages that were propagated in the low temperature treatment (4°C), suggesting a shift in Bd's response to low temperature conditions. Our results provide novel insights into the mechanisms by which Bd can thrive in a wide variety of temperature conditions, potentially altering the dynamics of chytridiomycosis and thus, the propensity for Bd to cause amphibian population collapse. We also suggest that the adaptive responses of Bd to thermal conditions warrant further investigation, especially in the face of global climate change.     

Conservation needs of amphibians in China: A review

The conservation status of all the amphibians in China is analyzed,and the country is shown to be a global priority for conservation in comparison to many other countries of the world.Three Chinese regions are particularly rich in amphibian diversity:Hengduan,Nanling,and Wuyi mountains.Sala-manders are more threatened than frogs and toads.Several smaller families show a high propensity to become seriously threatened:Bombinatoridae,Cryptobranchidae,Hynobiidae and Salamandridae.Like other parts of the world,stream-breeding,high-elevation forest amphibians have a much higher likeli-hood of being seriously threatened.Habitat loss,pollution,and over-harvesting are the most serious threats to Chinese amphibians.Over-harvesting is a less pervasive threat than habitat loss,but it is more likely to drive a species into rapid decline.Five conservation challenges are mentioned with recommendations for the highest priority research and conservation actions.     

Sap-feeding Insect Communities as Indicators of Habitat Fragmentation and Nutrient Subsidies

Upland salt marsh vegetation is particularly prone to habitat fragmentation and nutrient run-off due to coastal development and nearby agriculture. By examining how communities of sap-feeding insects respond to natural variation in plant-patch size and an experimental nutrient addition we explored how species with particular life history traits (e.g. dispersal ability and over-wintering style) might be used to indicate the effects of habitat fragmentation (patch area) and nitrogen subsidies on food webs. Sap-feeders that were superior dispersers or over-wintered in concealed microhabitats persisted well in small patch sizes. In contrast, species that were both immobile and over-wintered in exposed stages were more sensitive to decreasing patch size. Furthermore, mobile sap-feeders colonized and established populations on nitrogen-subsidized patches more rapidly than less mobile taxa. Thus, patterns in community composition (mobile vs. sedentary sap-feeders) can be used as key indicators of both habitat fragmentation and allochthanous nitrogen subsidies. Both patch size and nutrient subsidy altered trophic structure with a higher predator to herbivore ratio occurring in small compared to large patches and in control compared to nitrogen-subsidized habitats where herbivore outbreaks occurred. Our data suggest that conserving large habitat patches and minimizing nitrogen input is critical for maintaining sap-feeder diversity and preserving food-web structure.