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Habitat associations and distribution Modeling of tHe endangered frog Pseudophilautus zorro in sri lanka
Abstract
Basic ecological information is of critical importance for the development of conservation strategies for endangered amphibian species. The Gannoruwa Shrub Frog (Pseudophilautus zorro) is an endangered endemic and a geographically restricted frog found in mid elevations of the central highlands of Sri Lanka whose ecology is little known. We assessed: (1) aspects of microhabitat associations; (2) the realized niche to identify potential areas of occupancy using Ecological Niche Modeling (ENM); and (3) estimated the Extent of Occurrence (EOO) and Area of Occupancy (AOO) of P. zorro with new locality data and predicted data. The results indicate that there is a significant positive relationship between leaf litter thickness and number of individuals of P. zorro in quadrats and a significant relationship between percentage of canopy cover and number of individuals of P. zorro in quadrats. Pseudophilautus zorro is more abundant in broad-leaf forests than pine forests. ENM predicted highly suitable areas (suitability > 80%) in the Kandy, Matale, and Kegalle districts in Sri Lanka. The EOO and AOO of P. zorro with new occurrence data was 558 km 2 and 9 km 2 , and with predicted data, 2,374 km 2 and 612 km 2 respectively, indicating an increase in EOO and AOO. The data on microhabitat preferences and predicted habitats will be invaluable to formulate in-situ and ex-situ conservation strategies for this species.
... Species in tropical montane regions may be especially vulnerable to climate change because they are expected to move upwards, since altitudinal migration changes environmental conditions much more frequently than latitudinal migration in the tropics (Freeman and Freeman, 2014), and there will be progressively less area to move into at the tops of mountains (Rahbek et al., 2019). Yet few studies have been conducted on Sri Lankan biodiversity using SDM (Bandara et al., 2022;Rupasinghe et al., 2021;Karunarathna et al., 2021;Ukuwela et al., 2020), and only a few of them have included future predictions (Amarasinghe et al., 2021;De Mel et al., 2023;Wijerathne et al., 2024). ...
Rapid climate change and ongoing habitat destruction pose a serious threat to global biodiversity. Understanding how species shift their geographical distributions in response to climate change is important for planning conservation actions for the biodiversity of isolated islands like Sri Lanka. Here, we used Maximum Entropy (MaxEnt) modeling to predict current and future (by 2100) distributions of 233 vertebrate endemics to Sri Lanka under three general circulation models of the atmosphere (GCMs) and three shared socioeconomic pathways (SSPs). We used six bioclimatic layers, together with land use, human population, elevation, and the distance to water, as environmental factors for SDMs. Resultant maps were used to calculate the area of habitat (AOH) of each species. Using general linear mixed models, we identified a significant influence of GCM, SSP, and current elevation on the change in AOH. The southwestern wet zone and the montane areas of Sri Lanka were found to be the most suitable regions for the species currently and in the future. However, all climate change scenarios indicated endemic species extinctions, which may be proportionally fewer for mammals and birds, but are expected to occur for all SSPs in amphibians and reptiles, ranging from 1.4%-22.5% of these taxa in SSP5. Also, species declines were specific and severe at higher elevations. Our study highlights the risk to montane endemic vertebrates, yet given the vulnerability of the wet zone to urbanization, even lowland endemic species face an uncertain future.
... and the built-in GRASS plug-in was used to calculate Pearson's correlation coefficients for all pairs of variables Qiao 2016, QGIS.org 2023). For highly correlated pairs (|r| > 0.8), we selected bioclimatic layers based on knowledge of the species and those shown to be relevant in modeling of related species (Table 1; Najibzadeh et al. 2017;Kidov and Litvinchuk 2021;Rai et al. 2021;Rupasinghe et al. 2021;Jiang et al. 2022). ...
Environmental niche models are useful tools for generating hypotheses for the distribution of species and informing conservation planning, especially at the edge of species’ ranges and for those with limited data. Here we report on the recent documentation of four species of amphibian (Hylarana latouchii, Odorrana tianmuii, Polypedates braueri, and Zhangixalus dennysi) and one reptile (Protobothrops mucrosquamatus) with few or no previous geolocated records from Jiangsu, China. We combined our opportunistic field sampling data from Jiangsu, which is at the edge of each of these species’ ranges, with publicly available occurrence records and climatic data to generate environmental niche models for these five species using Maxent. All models showed good model performance with AUC values ranging from 0.899 to 0.983. Additional potentially suitable areas within southern Jiangsu were predicted for the four amphibian species, although the significant anthropogenic habitat modifications in the province may limit their contemporary distributions. For all five species, the climatic variable that contributed most to the model was the precipitation of the driest month (Bio 14), indicating they are limited by moisture availability. Our study adds new information about the climatic preferences of these five species and highlights the value of complementing environmental niche modeling with field surveys for robust inferences and conservation planning, particularly at the edge of species’ ranges.
... and the built-in GRASS plug-in was used to calculate Pearson's correlation coefficients for all pairs of variables Qiao 2016, QGIS.org 2023). For highly correlated pairs (|r| > 0.8), we selected bioclimatic layers based on knowledge of the species and those shown to be relevant in modeling of related species (Table 1; Najibzadeh et al. 2017;Kidov and Litvinchuk 2021;Rai et al. 2021;Rupasinghe et al. 2021;Jiang et al. 2022). ...
... There is vast knowledge gap about the basic ecology of the species, which is critical for proposing conservation strategies. Rupasinghe et al. (2021) assessed the niche of the species to identify potential areas of occupancy and, after that, calculated the area of occupancy and the extent of occurrence. Kandy, Kegalle, and Matale districts in the Sabaragamuwa and Central zones had highly suitable regions. ...
Loss of native habitat has been identified as one of the crucial drivers of the growing biodiversity crisis, acting toward the deleterious effects on individual fitness, functional diversity, changes in species richness and community structure. The objective of the study was to review the species distribution modeling works done in the Indian subcontinent throughout the last decade (2012–2021) to highlight the urgent issues of biodiversity conservation and sustainable management. Species distribution model (SDM), ecological niche model (ENM), and habitat suitability model (HSM) are, in general, used to predict the niche of a species. The Scopus search engine result was used for conducting the literature search of peer-reviewed articles. Topics examined included estimation of species' potential distribution area, spread of introduced species, deadly diseases or pests, habitat loss or future range shift of species due to anthropogenic alterations and climate change. The analysis showed that the majority of the works were focused on predicting native species distribution patterns (n = 119, 82%) rather than the invasion of alien species in the native ecosystem (n = 26, 18%) indicating the further scope of research in these areas. The scientific articles highlighted that the modeling results could be utilized efficiently to design conservation areas if not biased toward charismatic species. A coordinating institute at the inter-ministerial level can help to undertake policy-related planning for sustainable management and execution of decisions.
... Study site: Gannoruwa Forest Reserve is located (7º 17' N, 80º 36' E) in the Kandy District of the Central Province. The annual temperature in the area is 24.1ºC with the lowest temperatures recorded in January and highest in April and receives a mean annual rainfall of 2,131 mm, derived from both the North-East and South-West monsoons (Basnayake, 1998;Rupasinghe et al 2021). ...
Ecological responses of nocturnal predatory birds to forest cover and other geospatial predictors vary both geographically and taxonomically. Considerable knowledge gaps exist regarding the habitat associations of the Sri Lanka Frogmouth, a nocturnal bird restricted to Sri Lanka and the Indian Western Ghats. Via a 20-year island-wide survey, we searched for frogmouths in Sri Lanka to determine their habitat associations at both local and landscape scales and developed a habitat suitability model (HSM) to predict both current and future distribution. We confirmed frogmouth presence in 18% of the surveyed sites across all major bioclimatic zones (wet, intermediate, dry, and arid) from lower elevations (11-767m), comprising a broad geographic range. Frogmouth presence was mostly limited to forests (90%) with a few sites in agricultural mosaics. Land protection, altitude and both local and landscape-scale forest cover, as well as forest-cover loss at both spatial scales, were strong predictors of frogmouth presence. According to our HSM, the southwestern lowlands and parts of the intermediate zone contained the most suitable areas for frogmouths despite their smaller extent. Although the dry and intermediate zones contained extensive habitats for frogmouth, these regions were relatively less suitable. The habitat associations and geographic range of this species in Sri Lanka differ from that seen in India through negative associations with altitude and absence from montane zones, absence from degraded or severely disturbed habitats and independence from proximity to waterways. The Sri Lanka Frogmouth is sensitive to anthropogenic disturbances, including historical forest losses. We recommend landscape-scale conservation planning that incorporates both primary and mature persistent secondary forests to ensure the protection of this unique iconic species.
The amphibian fauna of Sri Lanka comprises 120 species, including 107 (~90.0%) endemic species. They belong to five families: Bufonidae, Dicroglossidae, Ichthyophiidae, Microhylidae, and Rhacophoridae. Based on distribution, we recognized five zoogeographic zones for them, Central Hills, Dry Zone, Knuckles Range, Lowland Wet Zone, and Rakwana Hills. Fifty three species were reported from the Central Hills (48 endemics [90.6%] and 42 [79.2%] threatened species). 47 species were recorded from the Lowland Wet Zone, including 36 (76.6%) endemics and 28 (59.6%) threatened species. The Knuckles Range had 25 species, of which, 19 (76.0%) were endemics and 15 (60.0%) are threatened species. 19 species were reported from Dry Zone including seven endemics (36.8%) and four threatened species (21.1%). Out of 29 species, which inhabited in the Rakwana Hills, 26 were endemics (~89.7%) including 24 (82.8%) threatened species. Species diversity along the elevational gradient was also observed with the highest species richness in the mid-elevational localities. Family Ichthyophiidae can be considered as the least studied family. Recent rediscoveries and studies have helped to reduce the number of extinct species from 21 to 18. It is speculated that some of the other extinct species have to be rediscovered or probably were misidentified as other species. About 90% of Sri Lankan amphibians occur in the regions with the highest human populations where there are established agricultural lands. Loss of habitats, competition due to anthropogenic species and invasive species, pollution (cause for malformations, parasites, and other diseases), and climate change appear to be major threats.
In this study, we used a comprehensive set of statistical metrics to investigate the historical trends in averages and extremes of rainfall and temperature in Sri Lanka. The data consist of 55 years (1961–2015) of daily rainfall, maximum temperature ( Tmax ), and minimum temperature ( Tmin ) records from 20 stations scattered throughout Sri Lanka. The linear trends were analyzed using the nonparametric Mann–Kendall test and Sen–Theil regression. The prewhitening method was first used to remove autocorrelation from the time series, and the modified seasonal Mann–Kendall test was then applied for the seasonal data. The results show that, during May, 15% of the stations showed a significant decrease in wet days, which may be due to the delayed southwest monsoon (SWM) to Sri Lanka. A remarkable increase in the annual average temperature of Tmin and Tmax was observed as 70% and 55% of the stations, respectively. For the entire period, 80% of the stations demonstrated statistically significant increases of Tmin during June and July. The daily temperature range (DTR) exhibited a widespread increase at the stations located within the southwestern coast region of Sri Lanka. Although changes in global climate, teleconnections, and local deforestation in recent decades at least partially influence the trends observed in Sri Lanka, a formal trend attribution study should be conducted.
Much of fire behavior is driven by fine-scale patterns of fuel moisture; however, moisture predictions typically occur over large scales. The source of fine-scale variation in moisture results from a combination of fuelbed properties and overstory forest structure that influences water movement and distribution of solar radiation. Fine-scale moisture variation is of particular relevance in humid forests managed with frequent prescribed fire where fire behavior variation is tightly linked to differential fire effects. Results of a three-tiered experiment combining laboratory and field methods demonstrated that solar radiation exerted a strong influence on fuel moisture patterns in a temperate humid pine forest. Infrared radiation more rapidly dried Quercus and Pinus litter in laboratory experiments compared with controls. Litter exposed to sunlight during small-scale outdoor experiments was significantly drier than shaded litter. Quercus litter was wetter than Pinus on mornings, but dried more rapidly, becoming drier than Pinus litter by mid-day when exposed to sunlight. Field observations validated small-scale outdoor and laboratory results but also revealed the influence of fuel position: elevated litter was wetter than ground-level litter at peak burning time. Results provide insight into how overstory structure and composition may influence fine-scale heterogeneity of surface moisture dynamics and fire behavior.
The endangered Yellow Spotted Mountain Newt, Neurergus microspilotus, is a poorly known species that
has been reported from highland first order streams in western Iran and eastern Iraq. We used a presence-only
model to provide potential distribution for the species and identified the variables best explaining the occurrence of the species. Using available information on known localities of N. microspilotus, we developed a maximum entropy
(MaxEnt) model to predict potential distribution of this species in Iran and Iraq. After the model was validated,
we found that low (< 0–20) suitability scores for N. microspilotus presence corresponded to 52% of the total area considered (26,572 km2 ); whereas, high (80-100) suitability scores corresponded to only 2% of this area. Of the total suitable habitat, approximately 67% is located in Iran and 33% in Iraq. The model achieved a 1.8 regularized gain value with contribution of more than 51% provided by precipitation of coldest quarter as the main factor
influencing the model performance. With three protected areas in Iraq and one in Iran near or within the predicted distribution, only 2.29% of range for the species was within protected areas. The model indicated high suitability score for considerable area in Iraq that has not been searched for N. microspilotus. To preserve the species, we recommend surveys of Iraqi territory in search of N. microspilotus and to initiate studies to allocate more reserves with corridors that bridge the otherwise impermeable gaps between the breeding streams.
Climate change is one of the most-discussed issues in current global fora. The objective of this paper is to seek evidence for climate change in Sri Lanka by analyzing longterm (i.e. from 1869 to 2007) monthly data of air temperature and rainfall from seven selected locations (i.e. Anuradhapura, Kurunegala, Kandy, Ratnapura, Badulla, Nuwara Eliya and Colombo) representing the major climatic zones of the country. Decadal mean air temperatures of all selected locations, except Kandy, showed highly significant (p<0.001) linear increasing trends over the entire 140-year period considered. In all locations, including Kandy, almost continuous decadal warming has occurred during the last 6-10 decades. The rates of continuous warming in all locations except Ratnapura exceeded, by a substantial margin, the global mean (i.e. 0.074 °C decade⁻¹) during the period from 1906 to 2005. Analysis of frequency distributions of annual mean air temperatures showed that the above increases have occurred because of a shift in the entire distribution of temperatures over time rather than due to a few extremely warm years. Four out of the seven locations (i.e. Anuradhapura, Kandy, Badulla and Nuwara Eliya) examined showed statistically significant (p<0.05) linear declining trends of decadal mean annual rainfall (RFa) with time over the whole 140-year period. The highest rate of rainfall decline was shown in Nuwara Eliya at 52 mm decade-1. Within the respective trends over the 140-year period, a period of significant (p<0.05) decline of decadal mean RFa could be identified in all locations except Colombo. In particular, Kurunegala has shown a rainfall decline of 121 mm decade-1 from the 1970s onwards. Kandy and Nuwara Eliya have also shown rainfall declines in the range of 64-67 mm decade⁻¹ since 1940s and 1920s respectively. In all locations, mean RFa during the period from 1990 to 2007 was lower than that during the 1950-1989 period. The reductions ranged from 28 mm yr⁻¹ at Ratnapura to 202 mm yr⁻¹at Kurunegala. Analysis of shifts in rainfall distributions show that rainfall reductions in the years of extremely lower and higher rainfall have contributed relatively more to the mean rainfall reductions in successive periods than rainfall reductions in the years of average rainfall. In all locations, RFa showed decreasing trends, of varying strengths, with increasing mean annual temperature, Ta, with Nuwara Eliya showing the highest rate of rainfall decline (371 mm °C⁻¹). Analysis of monthly and annual rainfall data from 1950 to 1989 showed that the El Niño phenomenon reduced RFa during the following year in all locations, mainly because of rainfall reductions in June-July (South-West Monsoon) and January-February. From 1990 onwards, these post-El Niño RFa reductions have increased in all locations except Colombo and Ratnapura, where post-El Niño RFa has been higher than in normal years. Notably, in all locations, post-El Niño reductions of June-July rainfall have been absent since 1990, where RFa reductions have occurred because of reductions in January- February and October-December (North-East Monsoon) rainfall.
We created a new dataset of spatially interpolated monthly climate data for global land areas at a very high spatial resolution (approximately 1 km 2). We included monthly temperature (minimum, maximum and average), precipitation, solar radiation, vapour pressure and wind speed, aggregated across a target temporal range of 1970–2000, using data from between 9000 and 60 000 weather stations. Weather station data were interpolated using thin-plate splines with covariates including elevation, distance to the coast and three satellite-derived covariates: maximum and minimum land surface temperature as well as cloud cover, obtained with the MODIS satellite platform. Interpolation was done for 23 regions of varying size depending on station density. Satellite data improved prediction accuracy for temperature variables 5–15% (0.07–0.17 ∘ C), particularly for areas with a low station density, although prediction error remained high in such regions for all climate variables. Contributions of satellite covariates were mostly negligible for the other variables, although their importance varied by region. In contrast to the common approach to use a single model formulation for the entire world, we constructed the final product by selecting the best performing model for each region and variable. Global cross-validation correlations were ≥ 0.99 for temperature and humidity, 0.86 for precipitation and 0.76 for wind speed. The fact that most of our climate surface estimates were only marginally improved by use of satellite covariates highlights the importance having a dense, high-quality network of climate station data.
Daily rainfall totals are analyzed for the main agro-climatic zones of Sri Lanka for the period 1976–2006. The emphasis is on daily rainfall rather than on longer-period totals, in particular the number of daily falls exceeding given threshold totals. For one station (Mapalana), where a complete daily series is available from 1950, a longer-term perspective on changes over half a century is provided. The focus here is particularly on rainfall in March and April, given the sensitivity of agricultural decisions to early southwest monsoon rainfall at the beginning of the Yala cultivation season but other seasons are also considered, in particular the northeast monsoon. Rainfall across Sri Lanka over three decades is investigated in relation to the main atmospheric drivers known to affect climate in the region: sea surface temperatures in the Pacific and Indian Oceans, of which the former are shown to be more important. The strong influence of El Niño and La Niña phases on various aspects of the daily rainfall distribution in Sri Lanka is confirmed: positive correlations with Pacific sea-surface temperatures during the north east monsoon and negative correlations at other times. It is emphasized in the discussion that Sri Lanka must be placed in its regional context and it is important to draw on regional-scale research across the Indian subcontinent and the Bay of Bengal.
The area under the receiver operating characteristic (ROC) curve, known as the AUC, is currently considered to be the standard method to assess the accuracy of predictive distribution models. It avoids the supposed subjectivity in the threshold selection process, when continuous probability derived scores are converted to a binary presence–absence variable, by summarizing overall model performance over all possible thresholds. In this manuscript we review some of the features of this measure and bring into question its reliability as a comparative measure of accuracy between model results. We do not recommend using AUC for five reasons: (1) it ignores the predicted probability values and the goodness-of-fit of the model; (2) it summarises the test performance over regions of the ROC space in which one would rarely operate; (3) it weights omission and commission errors equally; (4) it does not give information about the spatial distribution of model errors; and, most importantly, (5) the total extent to which models are carried out highly influences the rate of well-predicted absences and the AUC scores.
Species richness was positively correlated with leaf-litter depth, and negatively correlated with elevation. Herpetofaunal density also tended to increase with litter depth and decline with elevation. A strong positive correlation existed between species richness and herpetofauna density. Evenness was highly variable and independent of both leaf-litter depth and elevation. Local herpetofaunas typically consist of a few very common species along with a large number of comparatively rare species. -from Authors
Pseudophilautus hypomelas (Günther, 1876), was previously known from the type collection of 14 specimens deposited in the Natural History Museum, London. There has been no record of this species since the original description by Günther in 1876, and subsequently this species was considered extinct. In recent explorations however, the species has been rediscovered from the Peak Wilderness, Central Hills of Sri Lanka, with a rediscription of the species from fresh collections.
Comparisons among three forest stands at La Selva were made of biomass, abundance, richness, relative abundance, evenness and species overlap of herpetofauna collected in leaf litter plots. The forest stands were primary forest and two different cacao plantations abandoned for five and 25 yr. Abundance and biomass of herpetofauna were greater in more recently disturbed sites, but evenness, richness, and diversity were greater in less recently disturbed sites. The more recently disturbed sites also had deeper leaf litter, which may influence prey availability, and higher percent canopy open, which may lead to extremes in temperature and moisture availability, compared to undisturbed primary forest. Herpetofaunal restoration is thus a relatively slow process, and presence of primary forest is important for maintenance of some rare species. -from Author
Quantitative and qualitative samples of amphibian and lizard faunas were taken from forest litter in Costa Rica and compared with similar samples collected in Borneo, the Philippines, and Panama. Animal abundance is about ten times greater in Costa Rican lowland wet forest than in Borneo. Radically different routes and rates of energy flow are postulated to account for the difference. In a series of upland (1010-1425 m) samples in the Philippines, the number of litter lizards and frogs increases with elevation. A single upland (1200 m) Costa Rican sample contains about three times as many animals per 100 m2 as two lowland sites. This increase with altitude correlates well with hypotheses that overall tropical forest productivity is greatest at intermediate elevations. Herpetofaunal densities are greater in wet areas compared to dry sites and flat terrain compared to slopes. These observations are linked to the greater variation and lesser total litter fall in dry sites and/or slopes. The number of species of amphibians and lizards regularly inhabiting the litter is similar in all wet lowland forests studied. Increasing elevation and decreasing rainfall correlate with faunas having fewer species. The former is seen as the result of the differential ability of lowland species to invade uplands, and the latter as a decrease in the kind and duration of frog-spawning sites. Reduced equitability with increasing elevation is principally due to the much greater proportional increase of the commonest species. In the evolution of American and Bornean-Philippine wet lowland faunas, frogs with direct development (Eleutherodactylus) have radiated in the former in the same fashion that skinks have in the latter.
Aim
Species distribution models have been widely used to tackle ecological, evolutionary and conservation problems. Most species distribution modelling techniques produce continuous suitability predictions, but many real applications (e.g. reserve design, species invasion and climate change impact assessment) and model evaluations require binary outputs, and thresholds are needed for these transformations. Although there are many threshold selection methods for presence/absence data, it is unclear whether these are suitable for presence‐only data. In this paper, we investigate mathematically and empirically which of the existing threshold selection methods can be used confidently with presence‐only data.
Location
We used real spatially explicit environmental data derived from the western part of the state of V ictoria, south‐eastern A ustralia, and simulated species distributions within this area.
Methods
Thirteen existing threshold selection methods were investigated mathematically to see whether the same threshold can be produced using either presence/absence data or presence‐only data. We further adopted a simulation approach, created many virtual species with differing prevalences in a real landscape in south‐eastern A ustralia, generated data sets with different proportions of pseudo‐absences, built eight types of models with four modelling techniques, and investigated the behaviours of four threshold selection methods in these situations.
Results
Three threshold selection methods were not affected by pseudo‐absences, including max SSS (which is based on maximizing the sum of sensitivity and specificity), the prevalence of model training data and the mean predicted value of a set of random points. Max SSS produced higher sensitivity in most cases and higher true skill statistic and kappa in many cases than the other methods. The other methods produced different thresholds from presence‐only data to those determined from presence/absence data.
Main conclusions
Max SSS is a promising method for threshold selection when only presence data are available.
AimInterest in species distribution models (SDMs) and related niche studies has increased dramatically in recent years, with several books and reviews being prepared since 2000. The earliest SDM studies are dealt with only briefly even in the books. Consequently, many researchers are unaware of when the first SDM software package (bioclim) was developed and how a broad range of applications using the package was explored within the first 8 years following its release. The purpose of this study is to clarify these early developments and initial applications, as well as to highlight bioclim's continuing relevance to current studies. LocationMainly Australia and New Zealand, but also some global applications. Methods
We outline the development of the bioclim package, early applications (1984–1991) and its current relevance. Resultsbioclim was the first SDM package to be widely used. Early applications explored many of the possible uses of SDMs in conservation biogeography, such as quantifying the environmental niche of species, identifying areas where a species might be invasive, assisting conservation planning and assessing the likely impacts of climate change on species distributions. Main conclusionsUnderstanding this pioneering work is worthwhile as bioclim was for many years one of the leading SDM packages and remains widely used. Climate interpolation methods developed for bioclim were used to create the WorldClim database, the most common source of climate data for SDM studies, and bioclim variables are used in about 76% of recent published MaxEnt analyses of terrestrial ecosystems. Also, some of the bioclim studies from the late 1980s, such as measuring niche (both realized and fundamental) and assessing possible impacts of climate change, are still highly relevant to key conservation biogeography issues.
Cited By (since 1996):1, Export Date: 14 June 2013, Source: Scopus
A survey to assess the amphibian diversity of Ambagamuwa area in the mid-hills of Sri Lanka was carried out from January-February 2003 and in August 2007. Five different habitat types including gardens, primary forests, secondary forests, paddy fields and tea plantations were systematically sampled and investigated for amphibians. The survey revealed a total of 19 amphibian species with eleven of them endemic to the island and nine of them listed in the 2007 IUCN red list of threatened species. Two new frog species of the genus Philautus were discovered in this area. The overall existence of a high number of threatened species and the possible existence of so far undiscovered species strikes the importance of an urgent conservation of this area.
Two distinct nesting behaviours are reported from 98 clutches (80 in situ and 18 ex situ) of 17 species of direct-developing Philautus from Sri Lanka. The species examined, belong to three communities spanning 400–2,200 m elevation. Sixteen species are 'ground nesters', depositing 6–155 cream or white eggs in 5–35 mm deep nests excavated by the female in the rainforest floor. This is the first record of terrestrial egg burying in soil by the direct-developing anurans, a behaviour commonly employed by tetrapod reptiles. A single species (Philautus femoralis) however, is an arboreal nester, depositing 7–22 green, adhesive eggs in a disc-like mass on the underside of leaves. Parental care is not provided by any of the species. Larval development in Philautus differs from the Neotropical direct-developing leptodactylid, Eleutherodactylus coqui: the former lack external gills and have a rudimentary cement gland, a coiled gut and a larger, spatulate, heavily vascularized tail. They also lack an egg tooth. The first two of these apparently primitive characters have so far been observed only in aquatic anuran tadpoles and not in direct-developing larvae. Furthermore, the Philautus larvae studied possess atrophied internal gills, respiration apparently being facilitated primarily via the tail.
Abstract We investigated the structure, composition and environmental correlates of leaf-litter invertebrate assemblages in Pinus radiata plantations and in neighbouring native eucalypt woodland in the Jenolan Caves Karst Conservation Reserve, south-east Australia. Invertebrate assemblages of plantations were compared with remnant eucalypt woodland located well away from the influence of plantations to determine the direct effects of plantations as a result of habitat-replacement with a non-native plantation species. We also included in our comparisons edge habitat of eucalypt woodland located immediately adjacent to plantations. This unique edge habitat is exposed to the intrusion of large volumes of pine leaf-litter from plantations, which has the potential to affect indirectly invertebrate assemblages of surrounding woodland. We found that species richness of invertebrates was significantly lower in pine plantations compared with remnant eucalypt woodland. There was a complete absence of species from 12 invertebrate orders that were found in surrounding eucalypt woodland. A rich and abundant native plant understorey that provides increased habitat heterogeneity is the most likely explanation for the richer invertebrate assemblage found in remnant eucalypt woodland. The total abundance of all invertebrate taxa in pine plantations in winter was significantly higher than in remnant eucalypt woodland, pine-litter edges and pine-free edges. Plantations were characterized by particularly high abundances of species in two orders, Acari and Collembola. High abundances of acarine and collembolan species in plantations were associated with a decompositional environment represented by comparatively higher moisture contents and higher C : N ratios of both leaf-litter and soil, higher soil conductivity and lower soil pH. We suggest that implementation of The Plantation Biodiversity Benefits Score will be a fruitful way forward to assess the environmental benefits that can be gained from pine plantations in this region of south-eastern Australia.
1. Species distribution models are increasingly used to address questions in conservation biology, ecology and evolution. The most effective species distribution models require data on both species presence and the available environmental conditions (known as background or pseudo-absence data) in the area. However, there is still no consensus on how and where to sample these pseudo-absences and how many.
2. In this study, we conducted a comprehensive comparative analysis based on simple simulated species distributions to propose guidelines on how, where and how many pseudo-absences should be generated to build reliable species distribution models. Depending on the quantity and quality of the initial presence data (unbiased vs. climatically or spatially biased), we assessed the relative effect of the method for selecting pseudo-absences (random vs. environmentally or spatially stratified) and their number on the predictive accuracy of seven common modelling techniques (regression, classification and machine-learning techniques).
3. When using regression techniques, the method used to select pseudo-absences had the greatest impact on the model’s predictive accuracy. Randomly selected pseudo-absences yielded the most reliable distribution models. Models fitted with a large number of pseudo-absences but equally weighted to the presences (i.e. the weighted sum of presence equals the weighted sum of pseudo-absence) produced the most accurate predicted distributions. For classification and machine-learning techniques, the number of pseudo-absences had the greatest impact on model accuracy, and averaging several runs with fewer pseudo-absences than for regression techniques yielded the most predictive models.
4. Overall, we recommend the use of a large number (e.g. 10 000) of pseudo-absences with equal weighting for presences and absences when using regression techniques (e.g. generalised linear model and generalised additive model); averaging several runs (e.g. 10) with fewer pseudo-absences (e.g. 100) with equal weighting for presences and absences with multiple adaptive regression splines and discriminant analyses; and using the same number of pseudo-absences as available presences (averaging several runs if few pseudo-absences) for classification techniques such as boosted regression trees, classification trees and random forest. In addition, we recommend the random selection of pseudo-absences when using regression techniques and the random selection of geographically and environmentally stratified pseudo-absences when using classification and machine-learning techniques.
Distribution data on threatened and endangered species are often sparse and clustered making it difficult to model their suitable habitat distribution using commonly used modeling approaches. We used a novel method called maximum entropy distribution modeling or Maxent for predicting potential suitable habitat for Canacomyrica monticola, a threatened and endangered tree species in New Caledonia, using small number of occurrence records (11). The Maxent model had 91% success rate (that is, a low omission rate) and was statistically significant. The approach presented here appears to be quite promising in predicting suitable habitat for threatened and endangered species with small sample records and can be an effective tool for biodiversity conservation planning, monitoring and management.
We present software that facilitates quantitative comparisons of environmental niche models (ENMs). Our software quantifies similarity of ENMs generated using the program Maxent and uses randomization tests to compare observed similarity to that expected under different null hypotheses. ENMTools is available online free of charge from <http://purl.oclc.org/enmtools>.
Recent reports have suggested that a global decline in amphibian populations has taken place during the past few decades. Urban development is thought to affect the richness and abundances of species and, therefore, could be an important cause of decline. We estimated the richness and abundances of anurans in wetlands at a residential development and in similar wetlands at a nearby undeveloped park. The residential development originally was pine flatwoods habitat, as is the undeveloped park curiently. We also compared the anuran species' composition of the park in 1992 with the composition in 1974.
Both richness and abundances of anurans in the residential development were different than those in the undeveloped park. Employing the same amount of sampling effort at both sites, we trapped or observed 11 species at the developement and 15 species at the park, and trapped 569 individuals at the development and 1224 individuals at the park. The anuran species richness at the undeveloped park in 1992 was nearly the same as in 1974; a single rare species apparently was not present in 1992. Of the 15 species present in both surveys, 14 showed higher abundances in 1992 than in 1974.
We suggest that the current differences between the residential development and the park have resulted from degradation of both the uplands used by many species during the dry season and the temporary wetlands used by many species for reproduction. Four species especially sensitive to such degradation, Bufo quercicus, Scaphiopus h. holbrookii, Hyla femoralis, and H. gratiosa, were the species missing from the residential development.
Not all species of anurans typical of pine flatwoods appeared to be affected adversely by development. Three species of ranids, Rana utricularia, R. grylio, and R. catesbeiana, were found in higher abundances at the residential development than at the park. These ranid species breed in a wide variety of aquatic systems, including the permanent bodies of water that are now abundant in the development, and probably use the uplands less than other anurans.
If amphibian decline is international in scope, then the decline could be attributable either to global changes caused by humans, or to local, but widespread, environmental degradation, or to a combination of factors. While much recent popular focus has been on potential global causes of decline, we believe that this emphasis may have caused attention to be taken away from local causes that, as our study demonstrated, may be at least as important. We suggest that in many places, local environmental degradation is insidiously chipping away at amphibian diversity, and that more emphasis should be placed on these local causes than is now the case.
Habitat loss is known to be the main cause of the current global decline in biodiversity, and roads are thought to affect
the persistence of many species by restricting movement between habitat patches. However, measuring the effects of roads and
habitat loss separately means that the configuration of habitat relative to roads is not considered. We present a new measure
of the combined effects of roads and habitat amount: accessible habitat. We define accessible habitat as the amount of habitat
that can be reached from a focal habitat patch without crossing a road, and make available a GIS tool to calculate accessible
habitat. We hypothesize that accessible habitat will be the best predictor of the effects of habitat loss and roads for any
species for which roads are a major barrier to movement. We conducted a case study of the utility of the accessible habitat
concept using a data set of anuran species richness from 27 ponds near a motorway. We defined habitat as forest in this example.
We found that accessible habitat was not only a better predictor of species richness than total habitat in the landscape or
distance to the motorway, but also that by failing to consider accessible habitat we would have incorrectly concluded that
there was no effect of habitat amount on species richness.
Dramatic population declines have affected frogs worldwide ([1][1]), and, although new species continue to be described ([2][2]), the discovery of large new species radiations is rare. Here, we report the discovery of an endemic radiation of >100 species of Old World tree frogs (Rhacophorinae) from
The first global assessment of amphibians provides new context for the well-publicized phenomenon of amphibian declines. Amphibians
are more threatened and are declining more rapidly than either birds or mammals. Although many declines are due to habitat
loss and overutilization, other, unidentified processes threaten 48% of rapidly declining species and are driving species
most quickly to extinction. Declines are nonrandom in terms of species' ecological preferences, geographic ranges, and taxonomic
associations and are most prevalent among Neotropical montane, stream-associated species. The lack of conservation remedies
for these poorly understood declines means that hundreds of amphibian species now face extinction.
Recent extinction rates are 100 to 1000 times their pre-human levels in well-known, but taxonomically diverse groups from widely different environments. If all species currently deemed "threatened" become extinct in the next century, then future extinction rates will be 10 times recent rates. Some threatened species will survive the century, but many species not now threatened will succumb. Regions rich in species found only within them (endemics) dominate the global patterns of extinction. Although new technology provides details of habitat losses, estimates of future extinctions are hampered by our limited knowledge of which areas are rich in endemics.
We describe a new Pseudophilautus species, P. conniffae sp. nov. from southern Sri Lanka. It was previously confused with Pseudophilautus rus (Manamendra-Arachchi & Pethiyagoda). The new species differs from the latter by the combination of the following characters: fourth toe webbing to penultimate subarticular tubercle on inner and outer sides (vs. fourth toe webbing in between penultimate and anetpenultimate subarticular tubercles on inner and outer sides), presence of conical median lingual process (vs. absent), and black patches on the posterior flank, anterior and posterior edges of the thigh (vs. black patches on the anterior surface of the thigh). Pseudophilautus conniffae sp. nov. may be sympatric with P. limbus (Manamendra-Arachchi & Pethiyagoda), which shares certain characters with the new species. The new species is, however, distinguished from P. limbus by the following characters: having supernumerary tubercles on manus (vs. lacking), absence of frontoparietal ridges (vs. presence), fourth toe webbing to penultimate subarticular tubercle on both sides (vs. fourth toe webbing between penultimate and anetpenultimate subarticular tubercle on both sides), third toe webbing to distal subarticular tubercle on both sides (vs. distal subarticular tubercle on outer side and below penultimate subarticular tubercle on inner side), and having the dorsum light brown with dark brown patches (vs. black and yellow variegated pattern on dorsum). The new species may be restricted to the southwestern wet zone of Sri Lanka. It is compared with all known Pseudophilautus species and also provided with a field key to identify it from those species that are sympatric with it or inhabit the southwestern wet zone.
Litter decomposition in terrestrial ecosystems has a major role in the biogeochemical cycling of elements in the environment. Climatic features, like temperature, rainfall, humidity, and seasonal variations affect the rate of litter decomposition. This review attempts to understand the litter decomposition process in tropical forest ecosystems. It also reviews the influence of various factors on litter degradation and techniques used for assessing leaf litter decomposition. It is observed that very few studies were conducted on litter decomposition in forest ecosystems, such as tropical and temperate forests. Hence, comprehensive studies on litter degradation have to be undertaken in order to understand the turnover rate of nutrients and other elements in these sensitive ecosystems.
Amphibian declines may frequently be associated with multiple, correlated factors . In \western North America, exotic species and hydrological changes are often correlated and are considered 2 of the greatest threats to freshwater systems. Bullfrog (Rana catcsbeiana) introductions are frequently cited as a threat to lentic-breeding anurans native to western North America and are a suspected factor in the decline of red-legged frogs (Rana aurora) in California. Introduced fish and habitat change are cited less frequently but are equally viable hypotheses. I examined the relation among introduced species, habitat, and the distribution and abundance of red-legged frogs in western Washington. Red-legged frog occurrence in the Puget Lowlands was more closely associated with habitat structure and the presence of exotic fish than with the presence of bullfrogs. The spread of exotics is correlated with a shift toward greater permanence in wetland habitats regionally. Conservation of more ephemeral wetland habitats may have direct benefits fat some native amphibians and may also reduce the threat of exotic fish and bullfrogs, both of which were associated with permanent wetlands. Research and conservation efforts for lowland anurans in the West should emphasize the complexities of multiple contributing factors to amphibian losses.
The MaxEnt software package is one of the most popular tools for species distribution and environmental niche modeling, with over 1000 published applications since 2006. Its popularity is likely for two reasons: 1) MaxEnt typically outperforms other methods based on predictive accuracy and 2) the software is particularly easy to use. MaxEnt users must make a number of decisions about how they should select their input data and choose from a wide variety of settings in the software package to build models from these data. The underlying basis for making these decisions is unclear in many studies, and default settings are apparently chosen, even though alternative settings are often more appropriate. In this paper, we provide a detailed explanation of how MaxEnt works and a prospectus on modeling options to enable users to make informed decisions when preparing data, choosing settings and interpreting output. We explain how the choice of background samples reflects prior assumptions, how nonlinear functions of environmental variables (features) are created and selected, how to account for environmentally biased sampling, the interpretation of the various types of model output and the challenges for model evaluation. We demonstrate MaxEnt’s calculations using both simplified simulated data and occurrence data from South Africa on species of the flowering plant family Proteaceae. Throughout, we show how MaxEnt’s outputs vary in response to different settings to highlight the need for making biologically motivated modeling decisions.
Models that predict distributions of species by combining known occurrence records with digital layers of environmental variables have much potential for application in conservation. Through using this module, teachers will enable students to develop species distribution models, to apply the models across a series of analyses, and to interpret predictions accurately. In addition to its original components, this module features an updated and condensed synthesis document ("A Brief Introduction to Species Distribution Modeling for Conservation Educators and Practitioners," which provides theoretical and practical guidance for the expanding field of species distribution modeling. The synthesis is supplemented by a new exercise where learners create and optimize species distribution models using Wallace, an R-based GUI (Graphical User Interface) application for ecological modeling that currently focuses on building, evaluating, and visualizing models of species niches and distributions. Additionally, there are four new PowerPoint presentations on species distribution models (the history and theory, data and algorithms, and evaluating SDMs), as well as a presentation on how to use Wallace. The original Synthesis, "Species' Distribution Modeling for Conservation Educators and Practitioners," introduces learners to the modeling approach, outlines key concepts and terminology, and describes questions that may be addressed using the approach. A theoretical framework that is fundamental to ensuring that students understand the uses and limitations of the models is then described. Additionally, it details the main steps in building and testing a distribution model, and describes three case studies that illustrate applications of the models. This module is targeted at a level suitable for teaching graduate students and conservation professionals.
The federally threatened California red-legged frog (Rana aurora draytonii) has disappeared from much of its range for unknown reasons. We mapped 237 historic locations for the species and determined their current population status. Using a geographic information system (GIS), we determined latitude, elevation, and land use attributes for all sites and analyzed the spatial pattern of declines. We then compared the observed patterns of decline to those predicted by the climate change, UV-B radiation, pesticides, and habitat alteration hypotheses for amphibian decline. Declines were not consistent with the climate change hypothesis but showed a strong positive association with elevation, percentage upwind agricultural land use, and local urbanization. These results apply to patterns of decline across the entire range of R. a. draytonii in California, as well as within geographic subregions. The elevational gradient in declines is consistent with the UV-B hypothesis, although the UV-B hypothesis also predicts a north-to-south gradient in declines, which we did not observe. The association of declines with the amount of upwind agricultural land use strongly suggests that wind-borne agrochemicals may be an important factor in declines. This association was most pronounced within the Central Valley-Sierra region, where other studies have documented both transport and deposition of pesticides to the Sierra Nevada and the presence of pesticide residues in the bodies of congeneric (Rana muscosa) and more distantly related (Hyla regilla) frog species.
The forest cover in the hill country river catchment areas of Sri Lanka has been reduced to isolated patches on hilltops and a handful of reserves above the 1524 m (5000 ft) contour. Most of the land that was under forest cover at the turn of the nineteenth century is now covered with plantation crops. The districts of Kandy, Matale, Nuwara Eliya, Badulla, Ratnapura and Kegalle are the main hill country plantation areas. Within a period of less than half a century most of the forests in the hill country were cleared for plantation crops. Shifting cultivation was responsible for deforestation in the drier parts of the hill country. At the time of the British conquest of the hill country, the population of the whole island was not more than 3/4 to 1 million and they had settled in isolated villages at elevations below 1066 m. Subsistence agriculture was the main occupation of this predominantly rural population.
A soil–plant–air continuum multilayer model was developed to simulate soil respiration. The model can be used to investigate the effects of three canopy characteristics on soil thermal and hydrological properties and soil respiration: leaf area index, the maximum rate of carboxylation, and the vertical profile of leaf area density. The model did not consider physiological effects of canopy characteristics, such as the effect of photosynthesis on root respiration. Rather, it examined how changes in temperature and moisture in the soil layers, caused by changes in the plant canopy, affect soil respiration. Model validation and numerical experiments were performed using above-canopy hydrometeorological variables, including seasonal changes related to a dry season with strong evaporative demand (high solar radiation and high temperature) and a rainy season with weaker evaporative demand. The results suggest that the model can successfully reproduce seasonal changes in soil profiles of moisture, temperature, CO2 gas concentration, and respiration, and that canopy characteristics can limit soil respiration because of thermal and hydrological effects. An increase in leaf area decreased soil respiration in two ways: by decreasing soil temperature through a reduction in net radiation to the soil surface and by decreasing soil moisture through an increase in canopy transpiration. An increase in the maximum rate of carboxylation decreased soil respiration because it decreased soil moisture by increasing canopy transpiration; there was little thermal effect on soil respiration. A canopy with a denser leaf area in the upper layers created a faster wind velocity in the lower portion and on the ground than did a canopy with the same leaf area index, but with a denser leaf area in the lower layers. The faster wind velocity significantly decreased soil moisture at the soil surface and decreased soil temperature through an increase in soil evaporation; these effects decreased soil respiration. The hydrological effects of the three parameters were most evident in the dry season, while the thermal effects were evident year-round.
Studying the patterns in which local extinctions occur is critical to understanding how extinctions affect biodiversity at local, regional and global spatial scales. To understand the importance of patterns of extinction at a regional spatial scale, we use data from extirpations associated with a widespread pathogenic agent of amphibian decline, Batrachochytrium dendrobatidis (Bd) as a model system. We apply novel null model analyses to these data to determine whether recent extirpations associated with Bd have resulted in selective extinction and homogenization of diverse tropical American amphibian biotas. We find that Bd-associated extinctions in this region were nonrandom and disproportionately, but not exclusively, affected low-occupancy and endemic species, resulting in homogenization of the remnant amphibian fauna. The pattern of extirpations also resulted in phylogenetic homogenization at the family level and ecological homogenization of reproductive mode and habitat association. Additionally, many more species were extirpated from the region than would be expected if extirpations occurred randomly. Our results indicate that amphibian declines in this region are an extinction filter, reducing regional amphibian biodiversity to highly similar relict assemblages and ultimately causing amplified biodiversity loss at regional and global scales.
One hypothesis for amphibian declines is that increased dryness attributed to global climate change exposes amphibians to greater biotic threat and, consequently, greater mortality. But, little is known about behavioral responses of terrestrial amphibians to dry conditions alone or in combination with biotic threats. We used field observations and laboratory experiments to test the response of efts (terrestrial juveniles) of the eastern red-spotted newt, Notophthalmus viridescens, to separate and combined desiccation and predation risks. When only at risk of desiccation, efts moved into shade, traveled down slope, decreased activity, and adopted water-conserving postures. Efts also significantly reduced the rate of water loss by huddling and were attracted to chemical cues from conspecific efts but not from conspecific adults. Thus, efts have a variety of behaviors that reduce the risk of dehydration associated with climate change. When faced only with a predation risk, represented by adult and eft newt tissue extracts (alarm chemicals), efts reduced their activity and avoided alarm cues from both sources. When exposed to combined desiccation and predation risks, efts were less active than when exposed to either risk separately and avoided adult tissue extracts, but not eft extracts. These results suggest that under dry conditions, conspecific tissue extracts contain both attractive (huddling) and repulsive (predator-related) chemical components that induce offsetting behavioral responses. This is the first study to demonstrate moisture-dependent responses to conspecific rinses and alarm substances, underscoring the importance of considering environmental moisture and animal hydration in studies examining responses to conspecific odors and/or alarm chemicals. These results support the hypothesis that elevated dehydration risk may compromise anti-predator behavior and exacerbate amphibian population declines.
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