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1.
Pond-breeding amphibians require aquatic and terrestrial habitats to complete their lifecycles, and preservation of both habitats is necessary for maintaining local populations. Current wetland regulations focus primarily on aquatic habitats, and criteria to define critical upland habitats and regulations to protect them are often ambiguous or lacking. We examined the association between the presence of seven pond-breeding amphibian species and the landscape composition surrounding 54 wetlands located within the Till Plains and the Glaciated Plateau ecoregions of Ohio, USA. We quantified landscape composition within 200 m of the wetland (“core terrestrial zone”) and the area extending from 200 m to 1 km from the wetland (“broader landscape context zone”). We constructed binary logistic regression models for each species, and evaluated them using Akaike Information Criterion. Presence of spotted salamanders (Ambystoma maculatum), Jefferson's salamander complex (A. jeffersonianum) and smallmouth salamanders (A. texanum) was positively associated with the amount of forest within the core zone. Presence of wood frogs (Rana sylvatica) was positively associated with the amount of forest within the core zone and the amount of forest within the broader landscape context zone. Presence of tiger salamanders (A. tigrinum tigrinum) was negatively associated with the cumulative length of paved roads within 1 km of the site, and presence of red-spotted newts (Notophthalmus v. viridescens) was negatively associated with the average linear distance to the five nearest wetlands. Overall salamander diversity was positively associated with the amount of forest within the core zone, and negatively associated with the presence of predatory fish and cumulative length of paved roads within 1 km of the site. Our results confirm the strong association between the structure of surrounding upland areas and amphibian diversity at breeding ponds, and stress the importance of preserving core terrestrial habitat around wetlands for maintaining amphibian diversity. 相似文献
2.
Karen E. Leyse 《Biological conservation》2004,118(1):57-65
The introduction of exotic fishes to naturally fishless waters is often associated with declines in species native to those waters. Mosquitofish, Gambusia affinis, have been introduced to waters worldwide for mosquito control. Taxa negatively affected by mosquitofish potentially include fairy shrimp (Crustacea: Anostraca) that often show high rates of endemism, and which are characteristic of naturally fishless wetlands on every continent. We tested the effects of mosquitofish on a fairy shrimp, Linderiella occidentalis, in experimental ponds that included a community of native aquatic invertebrates. We supplemented field experiments with lab trials to test whether mosquitofish preferred L. occidentalis to other prey. Survival of the fairy shrimp was significantly reduced in ponds with mosquitofish. Only 16.9% of fairy shrimp survived in ponds with mosquitofish, while 64.0% survived in control ponds. Fish presence also reduced abundance and biomass of other invertebrates. Results from feeding trials demonstrated that mosquitofish frequently prefer L. occidentalis to alternative prey. Our results suggest that introduction of mosquitofish into naturally fishless wetlands may lead to loss of diversity of their highly specialized aquatic fauna. 相似文献
3.
As rural landscapes experience increasing levels of residential development, the persistence of species that rely on them will depend on informed planning and management decisions. An understanding of habitat requirements is essential for setting priorities and developing landscape-level plans for the survival of these species. In many temperate rural landscapes, artificially created ponds may be the only wetlands available for aquatic reproduction by amphibians. The introduction of non-native fish into these ponds reduces survival and prohibits successful reproduction of many native pond-breeding amphibians. We surveyed 105 randomly selected wetlands in a primarily privately-owned, rural landscape in north Idaho, USA, for pond-breeding amphibian larvae in 2004 and 2005. We used an information theoretic multimodel inference and an algorithmic (random forests) approach to model habitat for each species based on local and landscape characteristics. We also used a mail survey to quantify how landowners value fish in their wetlands and their plans for future wetland development and fish stocking. Sixty-seven percent of pond owners reported that fishing in their pond was at least slightly important to them and 36% of owners indicated that they were at least 50% likely to add fish to their ponds in the next 5-10 years. Landscape change predictions for this area indicate that forests will become more open due to thinning; habitat models indicated that this is likely to be detrimental to long-toed salamanders and beneficial to Pacific treefrogs. Habitat models also indicate that Columbia spotted frog breeding sites consist of wetlands on flat ground with high solar insolation and that this species is sensitive to nearby development, indicating that as this landscape becomes further developed, this species may require habitat protection for persistence. 相似文献
4.
Amphibian populations have declined and disappeared in protected and apparently undisturbed areas around the world, especially in montane areas of the tropics. The amphibian chytrid fungus, Batrachochytrium dendrobatidis has been implicated in many of these declines. In Costa Rica most declines occurred in the highlands. We examined an amphibian collection made in Braulio Carrillo National Park in 1986 for the amphibian chytrid fungus B. dendrobatidis, prior to the well documented amphibian declines in Monteverde, along an altitudinal transect from 100 to 2600 m elev. Skin from the pelvic patch of 202 specimens corresponding to 30 species was examined histologically to determine whether the disease was present in the highlands of the park before amphibian populations declined. For comparison, in 2002 we collected and examined 18 specimens of seven species of Eleutherodactylus and Craugastor from two other lowland Caribbean sites. The chytrid fungus was present in almost all altitudes in 1986, including lower areas. The pathogen was also found in both species that later declined and in species that did not do so. We detected chytrid fungus on amphibians collected at almost all altitudes in 1986, including those sampled at 280 m. B. dendrobatidis was abundant in frogs collected in the 2002 survey, and seems to be endemic in most of Costa Rica. More retrospective museum surveys are needed in order to determine whether it can be found in the area before 1986. 相似文献
5.
Valerie J. McKenzie 《Biological conservation》2007,137(1):102-116
Landscape alterations by humans can change patterns of parasite transmission. Depending on the type alteration and the life histories of parasites and hosts, parasitism may increase or decrease. To investigate whether parasitism in tropical amphibians was associated with land use change, I studied three species of amphibians, Rana vaillanti, Eleutherodactylus fitzingeri, and Smilisca puma from the Province of Heredia, Costa Rica, in the Atlantic lowlands. Frogs were collected and examined for parasites during the rainy seasons of 2001-2003 from sites in forest or clear-cut cattle pastures. The abundances of five species of parasites and parasite species richness of R. vaillanti were significantly higher in pasture habitat. A single parasite species shared by E. fitzingeri and S. puma showed a trend of increased abundance in pasture habitats. Overall, the abundances of six parasite species (three trematodes, an intestinal nematode, an encysted nematode, and a filarial nematode) were higher in pastures, while two species (trematodes) were higher in forest. This study suggests that land use activities in tropical regions affects the abundance and richness of amphibian parasites. Converting forest to pasture may impact the abundance of amphibian parasites because subsequent water quality changes (e.g. eutrophication, higher pH) often enhance habitat and resources for intermediate hosts (e.g. snails, mosquitoes) involved in parasite life cycles. Aquatic amphibians (e.g. R. vaillanti) may be particularly prone to experiencing increases in parasitism in agricultural habitats due to the positive relationship between many aquatic intermediate hosts and water quality changes associated with agricultural land use. 相似文献
6.
We investigated the influence of landscape and wetland characteristics on pond-breeding amphibian assemblages in south-central New Hampshire, a relatively low populated and heavily forested region of the northeastern United States. This allowed us to better understand landscape influences in less disturbed areas, and to determine critical landscape disturbance thresholds, above which amphibians are negatively impacted. We sampled 61 wetlands for larval amphibians in 1998 and 1999 to examine the influence of forest cover and road density (at seven buffer distances between 100 and 2000 m) and wetland characteristics on larval amphibian assemblages. Assemblages were influenced primarily by forest cover and wetland hydroperiod. Species richness was most strongly influenced by the proportion of forest cover within 1000 m of the wetland. Several species were also influenced by forest cover, but were differentially influenced by buffer widths. Our study suggests that, at least in the northeast US, wetlands with <40% forest cover within a 1000 m radius may have depauperate larval amphibian assemblages, and forest cover above 60% within a 1000 m radius is likely to ensure species rich and abundant larval amphibian assemblages. Given the above, current federal and state regulations that focus amphibian protection efforts on narrow terrestrial buffers surrounding wetlands are likely to be inadequate. 相似文献
7.
We studied amphibian populations in a human-dominated landscape, in Northern Italy, to evaluate the effects of patch quality and isolation on each species distribution and community structure. We used logistic and linear multiple regression to relate amphibian presence during the breeding season in 84 wetlands to wetland features and isolation. Jackknife procedure was used to evaluate predictive capability of the models. Again, we tested the response of each species to habitat features related to the richest communities. Amphibian presence depends strongly on habitat quality and isolation: the richest communities live in fish-free, sunny wetlands near to occupied wetlands. The negative effects of isolation do not seem to be biased by spatial autocorrelation of habitat features. The system shows strong nestedness: amphibian persistence depends on the contemporary effects of species adaptability and mobility. The commonest species, the pool frog (Rana synklepton esculenta) and the Italian tree frog (Hyla intermedia), are able to move through the matrix using canals and hedgerows, and can maintain metapopulations across the landscape; the rarest species (newts and toads) are more sensitive to habitat alteration, and they are strongly affected by isolation effects. If human exploitation of the landscape continues, only few species, mobile and opportunistic, will persist in this landscape. 相似文献
8.
Native amphibian populations are shrinking worldwide, and both parasitic infections and environmental stress from agriculture have been implicated. We investigated the principal hypothesis that environmental by-products of agricultural activity mediate parasitism in native frogs. Bullfrogs were collected from wetlands with variable landscape disturbance and water quality and examined for helminth parasites. We predicted that pesticide pollution and landscape development would be significant factors shaping the parasite communities and populations. Parasite diversity and species richness were lower in wetlands impacted by both pesticides and land use. Two parasite groups, direct life-cycle nematodes and echinostomes, were common in polluted habitats, potentially increasing frog pathology and mortality risk. In areas with agricultural landscape and reduced forest cover, parasite diversity and species richness were low, perhaps because of less parasite transmission from birds and mammals. This result suggests that land development limits terrestrial vertebrate access to wetlands. Our results indicate that parasite abundance and community structure in wetlands are influenced by factors operating locally within the wetland and more broadly in the surrounding landscape. We suggest that parasite communities in amphibians are effective indicators of ecosystem health and animal biodiversity, and thus useful tools for conservation biology. 相似文献
9.
Conservation needs for amphibians in managed timberlands may differ based upon the species present and the timber harvesting methods employed. Clearcuts have been documented to be detrimental to amphibians but the impacts of associated silvicultural edges and alternative harvesting treatments are not well understood. The primary objective of this study was to determine if amphibian abundances and body condition differed in thinned forests and intact forests, and in clearcuts and associated silvicultural edges. We also examined which environmental attributes were important in explaining observed differences. We sampled clearcuts, silvicultural edges, and adjacent late-seral forests at 10 sites in northwestern California from October 1999 to July 2002. Clearcuts at these sites ranged in age from 6 to 25 years. Five of these forest stands were intact and five had been commercially thinned at least 10 years prior to our study. Amphibian abundances were similar in thinned and unthinned forests, but body condition of the most common species was lower in thinned forests. Abundances of amphibians were nearly twice as high in forests and at silvicultural edges than in clearcuts. Clearcutting at these sites appears to have affected amphibian numbers up to 25 years post-harvest, however, silvicultural edges were suitable habitats for amphibians. While commercial thinning did not reduce amphibian numbers, it is an intermediate treatment followed by clearcutting. Where conservation of amphibians is a concern, even-aged silvicultural systems may not provide the most appropriate method for maintaining viable populations on managed forestlands in the northwestern US. 相似文献
10.
A massive decline of biodiversity is caused by land-use changes. Efforts must therefore be made to better understand the factors that govern organismal distribution, especially for countries where traditional management is about to be intensified such as in Romania. We here document the spatial distribution of amphibians from a Romanian rural landscape where land-use is still largely traditional. We related the occurrence of nine amphibian species and species richness to measures of composition and configuration of the landscape surrounding 54 ponds at three spatial scales: circular areas of 400, 600 and 800 m radii. Busy roads most severely impacted single species and amphibian richness whereas landscape composition measures, such as cover of urban areas, agricultural areas, pastures, forests and wetlands were of little importance. We suggest that the relative unimportance of landscape compositional measures on amphibians is a consequence of the traditional management of these landscapes that keep the environmental conditions favorable for most species. 相似文献
11.
T.G. Gunnarsson J.A. Gill G.F. Appleton A. Gardarsson W.J. Sutherland 《Biological conservation》2006,128(2):265-275
Iceland is responsible for many internationally important populations of breeding bird species, yet very little is currently known about how these species use the habitats available to them. Lowland areas of Iceland, in particular, have undergone significant landscape changes over the last century, such as widespread drainage of wetlands and conversion to agriculture, changes in grazing pressure and recently, extensive afforestation. The impact of these changes on breeding bird species will depend on the relative importance of different habitats for each species, and the threats facing those habitats. Here we report the results of a large-scale survey of the factors influencing patterns of habitat selection of eight populations of Charadriiform bird species throughout lowland Iceland; oystercatcher Haematopus ostralegus, golden plover Pluvialis apricaria, dunlin Calidris alpina, snipe Gallinago gallinago, whimbrel Numenius phaeopus, black-tailed godwit Limosa limosa, redshank Tringa totanus and arctic skua Stercorarius parasiticus. Ordination analyses and multiple logistic regression models are constructed to explore the components of habitats that influence the distribution of these species. Five of the eight species analysed showed significant preferences for lowland wetland habitats and four significantly selected areas containing wet features such as pools and high water tables. These results allow us to identify future conflicts in land use that are likely to result from government-supported large-scale afforestation of lowland areas and hydro-electric developments. 相似文献
12.
We used models integrating road maps, traffic volume, and snake movements to examine the potential for roads to contribute to mortality in two species of water snakes that differ in their vagility, use of terrestrial habitats, and conservation status. Road networks and traffic volumes typical of three regions in Indiana, USA, may account for mortality of 14-21% of the population per year in the more vagile, terrestrial, and imperiled copperbelly water snake (Nerodia erythrogaster neglecta) but only 3-5% mortality in the more sedentary, aquatic, and common northern water snake (Nerodia sipedon). The majority (>91%) of road crossings and associated mortality are predicted to occur during overland migrations to other wetlands, suggesting roads bisecting travel routes between wetlands may function as mortality sinks. Our models highlight the proportionately greater risk of mortality for the more vagile and imperiled species, N. e. neglecta, and suggest current wetland conservation strategies that focus on the wetland alone are unlikely to adequately protect wetland biodiversity from certain types of anthropogenic habitat modification. What is needed is a landscape approach to wetland conservation that considers not only the quality of wetlands and nearby terrestrial habitats, but also ensures that terrestrial corridors between wetlands remain permeable and offer safe passage for wildlife. 相似文献
13.
Many recent amphibian declines have been associated with chytridiomycosis, a cutaneous disease caused by the chytrid fungus Batrachochytrium dendrobatidis, but increasing evidence suggests that this pathogen may coexist with some species without causing declines. In the Venezuelan Andes, the disappearance of three anuran species during the late eighties was attributed to B. dendrobatidis. Recently, this pathogen was found to be prevalent in this region on the introduced American bullfrog, Lithobates catesbeianus. As a first step toward assessing the risk of amphibian communities to B. dendrobatidis in this region, we conducted a broad survey across multiple habitat types and an altitudinal gradient spanning over 2000 m. We diagnosed 649 frogs from 17 species using real time and conventional PCR assays, and recorded relevant abiotic characteristics of host habitats. Infection was detected in 10 native species of pond, stream and terrestrial habitats from 80-2600 m, representing nine new host records. L. catesbeianus was the most important reservoir with 79.9% of individuals infected and an average of 2299 zoospores. Among native frogs, Dendropsophus meridensis, an endangered species sympatric with L. catesbeianus, showed the highest infection prevalence and mean zoospore load (26.7%; 2749 zoospores). We did not detect clinical signs of disease in infected hosts; however, species such as D. meridensis may be at risk if environmental stress exacerbates vulnerability or pathogen loads. While surveillance is an effective strategy to identify highly exposed species and habitats, we need to understand species-specific responses to B. dendrobatidis to stratify risk in amphibian communities. 相似文献
14.
In some tropical regions, following the abandonment of agriculture and pastures, secondary forests can recover plant species richness and forest structure (e.g. canopy cover, biomass); however, the importance of these secondary forests for fauna is not clear. Secondary forests can benefit fauna by providing suitable habitats, connecting forests fragments, and increasing gene flow. Previous studies of forest regeneration have showed different levels of amphibian recovery. In Puerto Rico, 1–5 years old secondary forests achieved similar amphibian species richness and composition in comparison with old-growth forests, while in Brazil secondary forests from 14 to 19 years of recovery only recovered 60% of the species of old-growth forests. We evaluated amphibian recovery in secondary forests in northeastern Costa Rica, by assessing amphibian recovery in 12 secondary forests that vary in age of recovery and in three old-growth forests using visual and acoustic surveys. Our sites varied in terms of their landscape (e.g. amount of surrounding forest) and forest characteristics (e.g. forest age, aboveground biomass, basal area, number of tree species, number of stems, leaf-litter depth), but there was no relationship between these characteristics and amphibian species richness or species composition. We found that amphibians are recovering rapidly in secondary forests in Costa Rica, and even young forests (10–16 years) had similar species richness and composition in comparison with old-growth forests. These forests are providing suitable microhabitats conditions for amphibians. In addition, this study highlights the importance of landscape characteristics. The abundance of amphibian species sources (e.g. forest patches) and connections between forests appear to be helping the species colonize these sites. Worldwide, the area of secondary forests is increasing, and our results show that these habitats are suitable for a diversity of amphibian species, suggesting that these forests can help reduce amphibian population and species decline. 相似文献
15.
16.
Amphibians are globally threatened by anthropogenic habitat loss, the wildlife trade and emerging diseases. Previous authors have hypothesized that the spread of the amphibian disease chytridiomycosis (Batrachochytrium dendrobatidis) and amphibian ranaviruses are associated with the international trade in live amphibians. The North American bullfrog (Rana catesbeiana) is thought to be a carrier of these pathogens, is globally traded as a live commodity, and is sold live in US markets. We obtained importation data for all live amphibians, and parts thereof, into three major US ports of entry (Los Angeles, San Francisco and New York) from 2000 to 2005. Importation of live amphibians into these ports totaled almost 28 million individuals over this 6-year period. We collected samples from freshly-imported market frogs and found infection with both pathogens in all three cities and all seasons, with an overall infection prevalence of 62% (306/493) and 8.5% (50/588) for B. dendrobatidis and ranaviruses, respectively, by PCR. This study definitively identifies these two important pathogens in recently imported live market frogs and suggests that the amphibian trade can contribute to introductions of these pathogens into new regions. It provides support for the recent listing of B. dendrobatidis and ranaviral diseases by the OIE, and provides evidence for measures to be taken to eradicate these pathogens from the trade. 相似文献
17.
S.E. Foster 《Biological conservation》2006,127(2):158-166
Within species habitat use may depend on age, season or sex of an individual. The distribution of males and females may vary both temporally and spatially due to differences in the costs of reproduction and the distribution of critical resources. Conservation of a species requires knowledge of the habitat use of both sexes in order to predict the population size and protect all habitats that a species requires. Adult dragonfly populations often have highly male-biased sex ratios at the breeding habitat. This bias has been attributed to females using alternative habitats to avoid male harassment, or to high female mortality. We monitored adult Hine’s emerald dragonfly (Somatochlora hineana Williamson) populations, in breeding and non-breeding habitats in Door County, Wisconsin and found significant differences in habitat use between males and females. Males primarily used wetland habitats, while females primarily used dry meadows and marginal breeding habitats, only coming into wetlands to lay-eggs or find mates. We assessed food resources in the different habitats and found that high quality insect prey (primarily adult Diptera) were more available in the wetland habitat, indicating that these areas were likely a more productive foraging area for adult dragonflies. The fact that females appear to avoid the wetland habitat is consistent with the hypothesis that male harassment alters female distribution patterns. Consideration of the patterns of habitat use by S. hineana indicates the need to develop a broader understanding of the importance of non-wetland areas in the conservation of wetland species. 相似文献
18.
Pierre-André Crochet Olivier Chaline Claude Pierre Guillaume 《Biological conservation》2004,119(3):297-304
We investigated long term changes in an amphibian community in the Languedoc area of Southern France by comparing results of a survey of 56 ponds made in the early 1970s with results of a survey of the same localities in 2001. Based on the frequency of new occurrences and disappearances of species in the sample ponds, there is no sign of a general decline of amphibians in this area. Most species showed non-significant variation in frequency of occurrence or had increased. “Green frogs” (Rana perezi/ridibunda/kl. grafi) showed clear signs of decline, but this is a local phenomenon rather than a decline at the regional scale. Pelodytes punctatus probably declined also, possibly due to its sensitivity to fish introduction. The species richness in the ponds has also remained stable except in ponds where fish have been introduced. The only adverse impact of human activities that we could detect was thus the introduction of fish, which had a significantly adverse effect on amphibian species richness. 相似文献
19.
Monitoring programs have the potential to identify population declines and differentiate among the possible cause(s) of these declines. Recent criticisms regarding the design of monitoring programs have highlighted a failure to clearly state objectives and to address detectability and spatial sampling issues. Here, we incorporate these criticisms to design an efficient monitoring program whose goals are to determine environmental factors which influence the current distribution and measure change in distributions over time for a suite of amphibians. In designing the study we (1) specified a priori factors that may relate to occupancy, extinction, and colonization probabilities and (2) used the data collected (incorporating detectability) to address our scientific questions and adjust our sampling protocols. Our results highlight the role of wetland hydroperiod and other local covariates in the probability of amphibian occupancy. There was a change in overall occupancy probabilities for most species over the first three years of monitoring. Most colonization and extinction estimates were constant over time (years) and space (among wetlands), with one notable exception: local extinction probabilities for Rana clamitans were lower for wetlands with longer hydroperiods. We used information from the target system to generate scenarios of population change and gauge the ability of the current sampling to meet monitoring goals. Our results highlight the limitations of the current sampling design, emphasizing the need for long-term efforts, with periodic re-evaluation of the program in a framework that can inform management decisions. 相似文献
20.
In the Midwestern United States, agricultural landscapes with scattered patches of fragmented forest are common. To investigate the relationship between amphibian distributions and wetland, woodlot, and landscape characteristics, we studied the pond-breeding amphibians within a 15,450-ha plot in rural north-central Ohio. We surveyed 25 woodlots and one area of continuous riparian forest for amphibians, and each surveyed woodland contained at least one temporary wetland. We used Akaike's Information Criterion (AIC) to evaluate the effectiveness of 13 a priori models in predicting total amphibian species richness, anuran richness, caudate richness, and the presence of individual species in woodlots. We identified 13 species of amphibians within the study plot, and every woodlot contained at least one amphibian species. The most important variable in predicting total amphibian and anuran species richness was hydroperiod. For caudates, woodlot edge-to-area ratio, hydroperiod, pH, and ammonia were important characteristics in predicting species richness. Woodlots within agricultural landscapes are important refuges for amphibians. 相似文献