Amphibian Populations Research Articles

Immune defense adaptation of Strauchbufo raddei population in heavy metal polluted area: Insights from developmental and environmental perspectives

The adjustment of immune defense mechanisms is a crucial aspect of biological adaptation to stressful environments. Amphibians, with their unique metamorphic process, experience distinct life stages and exhibit diverse immune defense components. While previous studies have focused on specific immune changes during particular life stages under stress, this research addresses a critical gap by exploring the adaptive immune defense strategies of Strauchbufo raddei in heavy metal-polluted environments. We conducted laboratory experiments, exposing offspring from both polluted and unpolluted areas to control and heavy metal treatments, while continuously monitoring changes in immune components during key metamorphic stages. Notably, we examined the role of the skin microbiome, a crucial but often overlooked barrier against pathogens. The results indicated that individuals from polluted areas exhibited some tolerance to heavy metal exposure, though overall immune function remained diminished. During metamorphosis, when immune defenses are most vulnerable, the skin microbiome rapidly enriched beneficial bacteria, preventing pathogenic colonization and playing a pivotal role in maintaining immune defense in contaminated environments. Moreover, our research highlights energy allocation strategies involving corticosterone and body fat content, enabling populations to maintain development despite immune compromise. The immune adaptations observed may be fixed through genetic assimilation, suggesting a rapid evolutionary response to environmental stress. However, this reduces phenotypic plasticity, making populations more vulnerable to future environmental changes. This study provides key insights into the survival strategies of amphibian populations in heavy metal-contaminated areas, laying the foundation for future research on molecular and evolutionary adaptations.

Environmental Drivers of Local Demography and Size Plasticity in Fire Salamanders (Salamandra salamandra).

Conspecific amphibian populations may vary widely in local demography and average body size throughout their geographical range. The environmental drivers of variation may reflect geographical gradients or local habitat quality. Among fire salamander populations (Salamandra salamandra), local demography shows a limited range of variation because high concentrations of skin toxins reduce mortality from predation to a minimum, whereas average adult body size varies significantly over a wide range. This study on four neighboring populations inhabiting the catchments of low-order streams in the upper middle Rhine Valley (Koblenz, Germany) focuses on the identification of local environmental drivers of variation in age and body size. I collected 192 individuals at two localities per stream, measured snout-vent length, clipped a toe for posterior skeletochronological age determination, and released salamanders in situ again. Populations were similar in age distribution. Local habitat quality accounted for a significant proportion of demographic variability, mediated by the impact of landscape-induced mortality risk, including roads and agriculture. Still, the main effect of variation in habitat quality was on adult body size, the result of growth rates of aquatic larvae and terrestrial juveniles. Larvae exposed to non-lethal heavy metal contamination in streams developed into smaller juveniles and adults than clean-water larvae, providing evidence for carry-over effects from one stage to another. The generally small average adult size in the Rhine Valley populations compared to those in other parts of the distribution range indicates the action of a still unidentified environmental driver.

Detection of Amphibian Species based on Cytochrome b Metabarcoding using High-Throughput Sequencing Approach

Abstract Amphibians are essential in terrestrial and freshwater ecosystems, contributing to multiple ecological functions. The presence of amphibians in a particular area usually signifies a healthy ecosystem as it indicates that the habitat meets the requirements of their life cycles. However, the amphibian population have been declining due to human activities including pollution and habitat destruction. Researchers are using new methods to monitor amphibian diversity to address this decline. Conventional sampling methods were compared with new DNA metabarcoding techniques using advanced sequencing platforms. Therefore, this study aims to analyze the early detection of amphibian species using Cytochrome b (Cytb) gene with metabarcoding methods and next generation sequencing techniques. Thirty-one samples were used in this study and underwent processes such as extraction, amplification using Cytb gene, library preparation, and sequencing. The result showed that the total number of reads was 658,655, with reads in OTUs numbered 474,061. Out of 31 samples, only three species were successfully detected: Fejervarya limnocharis with the highest abundance (20.6%), followed by Polypedates leucomystax and Pulchrana baramica. The results indicate that Cytb has low capabilities in detecting amphibian species, which might be due to its highly conserved region and the lack of databases for this gene. For future studies, an enhanced DNA metabarcoding procedure should be applied, including better choice of genetic marker and bioinformatics pipelines to minimize error and to improve the accuracy and reliability of detecting amphibian’s species using NGS and DNA metabarcoding. This would enhance efforts to protect amphibian biodiversity.

Predation of anurans in southern England by Batracobdella algira, a leech previously unknown in the UK

Leech predation of amphibians is known to occur in Europe. Observation of severe leech infestation affecting a common toad Bufo bufo in southern England in summer 2020, with leeches covering the toad’s eyes, throat and axillae, initiated a collaborative investigation to learn more about the occurrence of such leech predation of anurans in the UK. Soliciting reports from the general public identified leech predation of common toads and common frogs Rana temporaria in Devon, Greater London, Hampshire, the Isle of Wight and Somerset in southern England. Through morphological and/or molecular investigation of samples, Batracobdella algira, a leech species not previously reported in the UK, was identified in the majority of cases. The known native Placobdella costata was also identified, with the observed feeding behaviour on anuran hosts being indistinguishable from that of B. algira. Whether the latter is a previously unrecorded or an introduced species has not yet been established. However, sequence data from multiple gene loci were identical to B. algira found in Tunisia, suggesting it more likely to be a non-native species to the UK. Further work is required to elucidate the potential origin and distribution of B. algira in the UK and whether it has any impact on amphibian populations. Keywords: amphibians, Bufo bufo, Glossiphoniidae, Hirudinea, Rana temporaria

The commensal skin microbiome of amphibian mountain populations and its association with the pathogen Batrachochytrium dendrobatidis.

Microbial assemblages naturally living on the skin are an integral part of immunity. In amphibians, this skin microbiota may hold a mitigation solution against the fungal pathogen Batrachochytrium dendrobatidis (Bd), which causes the panzootic disease chytridiomycosis. We used 16S rRNA gene metabarcoding to test the adaptive microbiome hypothesis. We compared the community composition, richness, and putative Bd-inhibitory function of the skin microbiome of three amphibian host species in the Pyrenees, as well as three species in Taiwan, in both Bd-positive and negative mountain populations. In both geographical regions, the amphibian host species played a decisive role in shaping the microbial assemblage and putative anti-Bd properties. In the Pyrenees, the species most susceptible to chytridiomycosis, Alytes obstetricans, had the lowest relative abundances of putative protective bacteria. In Bd-positive and negative sites, individuals had different skin microbiomes, with all anuran species showing increased relative abundances of potential anti-Bd bacteria, while the Taiwanese caudata Hynobius sonani showed the opposite pattern. Our results suggest that, in response to exposure to the pathogen, the skin microbiota shifted to a defensive state with increased anti-Bd function, which may contribute to promoting disease resistance, as proposed by the adaptive microbiome hypothesis.

Universal versus taxon-specific drivers of helminth prevalence and intensity of infection.

Two key epidemiological parameters, prevalence and mean intensity of infection, together capture the abundance of macroparasite populations, the strength of density-dependent effects they experience, their potential impact on host population dynamics and the selective pressures they exert on their hosts. Yet, the drivers of the extensive variation observed in prevalence and mean intensity of infection, even among related parasite taxa infecting related hosts, remain mostly unknown. We performed phylogenetically grounded Bayesian modelling across hundreds of amphibian populations to test the effects of various predictors of prevalence and intensity of infection by six families of helminth parasites. We focused on the potential effects of key host traits and environmental factors pertinent to focal host populations, i.e. the local diversity of the amphibian community and local climatic variables. Our analyses revealed several important determinants of prevalence or intensity of infection in various parasite families, but none applying to all families. Our study uncovered no universal driver of parasite infection levels, even among parasite taxa from the same phylum, or with similar life cycles and transmission modes. Although local variables not considered here may have effects extending across taxa, our findings suggest the need for a taxon-specific approach in any attempt to predict disease dynamics and impacts in the face of environmental and climatic changes.

A Survey for Atypical Brucella Species in Wild-Caught Marine Toads (Rhinella marina) Using Qualitative PCR: A Pilot Study

Abstract The genus Brucella is a group of intracellular bacterial pathogens documented to cause brucellosis, a zoonotic disease of worldwide concern. In the past decade, reported cases of atypical Brucella species in amphibians have increased. These species are considered atypical based on their tropism, phenotypic characteristics, and phylogeny differences. Atypical Brucella species can be misdiagnosed due to their similarity to classical Brucella species and closely related genera. Recent literature has provided evidence for the zoonotic potential of atypical Brucella linked to amphibians. Therefore, understanding the prevalence of these atypical Brucella species in captive amphibian populations is significant for amphibian health, conservation, and public health. This pilot study evaluated the prevalence of atypical Brucella species in a population of marine toads (Rhinella marina) using a validated pan-Brucella qualitative PCR. Samples were analyzed from 56 asymptomatic wild-caught marine toads from Miami, FL, USA, using skin swab samples. Brucella DNA was not detected in any of the skin swab samples analyzed. This pilot study represents a viable non-invasive sampling technique and PCR assay for rapidly screening populations of amphibians for the presence of atypical Brucella species.

Extensive restoration of the entire habitat complex is key to the successful recovery of threatened species: The case of the natterjack toad Epidalea calamita at the northern range margin

Increasing concerns about biodiversity loss have prompted international efforts to restore degraded habitats. Unfortunately, wildlife habitat restoration often fails due to inadequate planning, inappropriate scale, or lack of providing key elements of habitats. We investigated the effectiveness of habitat restoration of a threatened amphibian species, the natterjack toad Epidalea calamita, in Estonia, comparing two different restoration approaches – partial habitat restoration and extensive habitat restoration over 16 years. Our goal was to investigate the impact of these two different approaches on the populations, to find out which habitat components play a key role in restoration and which measures are of primary importance in the restoration of habitats for small amphibian populations. We used GIS analysis to identify changes in the area of the habitat complex and breeding sites in seven natterjack toad locations following the restoration activities. To assess population response to habitat restoration, we used the census of the natterjack toad egg-strings as a proxy to the population size. The average number of egg-strings increased by 1.2-fold after partial habitat restoration and 3.5-fold when comparing partial habitat restoration with extensive restoration. Partial habitat restoration, which consisted of improving the condition of extant habitat, had no significant effect on population size (number of egg-strings), while extensive habitat restoration, which included improving and enlarging the entire habitat complex (both terrestrial and aquatic habitats as well as migration matrix between these components) led to population growth. The habitat features that positively influenced population growth were the area of entire habitat complex and the number and size of the breeding sites. In terms of habitat restoration and conservation measures, the number of natterjack toad populations was positively affected by restoration of the entire habitat complex (terrestrial habitats and water bodies), which was supplemented by the supportive rearing of tadpoles.

Dealing With Assumptions and Sampling Bias in the Estimation of Effective Population Size: A Case Study in an Amphibian Population.

Accurately estimating effective population size (N e) is essential for understanding evolutionary processes and guiding conservation efforts. This study investigates N e estimation methods in spatially structured populations using a population of moor frog (Rana arvalis) as a case study. We assessed the behaviour of N e estimates derived from the linkage disequilibrium (LD) method as we changed the spatial configuration of samples. Moor frog eggs were sampled from 25 breeding patches (i.e., separate vernal ponds, ditches or parts of larger fens) within a single population, revealing an isolation-by-distance pattern and a local spatial genetic structure. Varying buffer sizes around each patch were used to examine the impact of sampling window size on the estimation of effective number of breeders (N b). Our results indicate a downward bias in LD N b estimates with increasing buffer size, suggesting an underestimation of N b. The observed bias is attributed to LD resulting from including genetically divergent individuals (mixture-LD) confounding LD due to drift. This emphasises the significance of considering even subtle spatial genetic patterns. The implications of these findings are discussed, emphasising the need to account for spatial genetic structure to accurately assess population viability and inform conservation efforts. This study contributes to our understanding of the challenges associated with N e estimation in spatially structured populations and underscores the importance of refining methodologies to address population-specific spatial dynamics for effective conservation planning and management.

Effects of changed water regime on the toxicity of silver nanoparticles (AgNPs) in tadpoles of Fejervarya limnocharis.

Climate change is viewed as one of the important causes of the amphibian population decline. Aspects of climate change like increase in water temperature and drying up of habitats have been underrepresented. The expanding production and usage of metal nanoparticles like silver nanoparticles (AgNPs) make them likely to end up in aquatic ecosystems. To arrive at a realistic assessment of the impact of AgNPs in a warming world, we have investigated the effects of temperature on the acute toxicity of AgNPs in tadpoles of Fejervarya limnocharis at 24, 48, 72 and 96h of exposure. The various aspects of sub-lethal toxicities of AgNPs with increase in temperature were also investigated. Besides, the effects of habitat desiccation on the sub-lethal toxicities of AgNPs in the tadpoles were analysed. The LC50 values of AgNPs at four different time points were found to be significantly different between the two different temperatures. Alterations in survival pattern, life history traits, amplifications in genotoxic potential and oxidative stress were observed with increased water temperature following AgNP exposure. The phenomenon of habitat desiccation was also found to significantly affect the toxicity of AgNPs with respect to alterations in mortality rate, time to metamorphosis and morphometric parameters of metamorphosed tadpoles. The findings suggest that changed water regime such as increased water temperature as well as reduction in water level accelerated the toxic effects of AgNPs in F. limnocharis tadpoles which is likely to affect their natural populations.

Water availability and biological interactions shape amphibian abundance and diversity in Mediterranean temporary rivers

Amphibians, the most threatened vertebrates globally, face risks due to climate change, habitat loss, and fragmentation. Their sensitivity to environmental changes highlights their importance as ecological indicators. Temporary rivers, influenced by geological, climatic, and anthropogenic factors, play a critical role in shaping biodiversity and community structure. Some species of amphibians may be adapted to these temporary waters, a fact reflected in their life cycles and various biological traits. However, to develop effective conservation strategies for amphibians, it is essential to address the knowledge gaps surrounding the complex interactions between biological dynamics and fluvial habitat conditions. In this study, we investigated how trophic interactions between amphibians and other aquatic organisms (diatoms, macroinvertebrates, and fish), coupled with environmental factors (water availability and riparian structure), can affect amphibian abundance and diversity in temporary rivers. The study was conducted in a Mediterranean river network located in Sant Llorenç del Munt i l'Obac Natural Park (Catalonia, Spain). Our expectations were that habitats suitable for egg deposition, lacking predators (e.g. tadpole-predators and fish), and abundant in food sources would likely support higher amphibian abundance and diversity. However, water availability was identified as a crucial factor shaping abundance and diversity in the studied amphibian communities, even if it correlated with fish presence, and especially impacting amphibian species usually linked to permanent water bodies. Concerning biotic interactions, while our results suggested that amphibian populations in temporary rivers are more dependent on top-down than bottom-up interactions, the presence of aquatic predators was not as conclusive as expected, suggesting that in temporary rivers the fish-avoiding amphibian species can survive using microhabitats or breeding opportunities linked to natural river dynamics. Overall, our findings highlight the importance of considering multi-trophic interactions, hydroperiod and habitat heterogeneity in temporary river ecosystems for effective amphibian conservation.

Do fungi look like macroparasites? Quantifying the patterns and mechanisms of aggregation for host-fungal parasite relationships.

Most hosts contain few parasites, whereas few hosts contain many. This pattern, known as aggregation, is well-documented in macroparasites where parasite intensity distribution among hosts affects host-parasite dynamics. Infection intensity also drives fungal disease dynamics, but we lack a basic understanding of host-fungal aggregation patterns, how they compare to macroparasites, and if they reflect biological processes. To address these gaps, we characterized aggregation of the fungal pathogen Batrachochytrium dendrobatidis (Bd) in amphibian hosts. Utilizing the slope of Taylor's Power Law, we found Bd intensity distributions were more aggregated than macroparasites, conforming closely to lognormal distributions. We observed that Bd aggregation patterns are strongly correlated with known biological processes operating in amphibian populations, such as epizoological phase-invasion, post-invasion, and enzootic-and intensity-dependent disease mortality. Using intensity-dependent mathematical models, we found evidence of evolution of host resistance based on aggregation shifts in systems persisting with Bd following disease-induced declines. Our results show that Bd aggregation is highly conserved across disparate systems and is distinct from aggregation patterns in macroparasites, and contains signatures of potential biological processes of amphibian-Bd systems. Our work lays a foundation to unite host-fungal dynamics under a common theoretical framework and inform future modeling approaches that may elucidate host-fungus interactions.

Immunological and physiological responses to predation risk and sublethal concentrations of chlorothalonil and β-endosulfan in Lithobates taylori (Anura: Ranidae) tadpoles

Pesticide exposure and its interaction with other natural stressors can play a role in amphibian population declines because disruptions in stress hormone regulatory mechanisms may inhibit immune responses during metamorphosis. Here, we determined the interactive effects of predation risk and sublethal concentration of two pesticides on immunological and physiological responses in tadpoles of the tropical frog Lithobates taylori. Using mesocosms, we used chronic exposure to three levels of chlorothalonil and β-endosulfan in the presence or absence of Odonate larvae. Our results show that β-endosulfan in high concentrations reduced the weight of the tadpoles and increased the neutrophil count and corticosterone (CORT) levels. Larval development was accelerated by high concentrations of chlorothalonil. Also, this pesticide in low and high concentrations increases the absolute values of lymphocytes. Tadpoles exposed to chlorothalonil increased the numbers of monocytes (in low concentrations), and lymphocytes (in high and low concentrations). The interactions of the low concentrations of both pesticides with and without the predator's presence also increased the number of lymphocytes. A combination of pesticides increases the number of lymphocytes in the blood due to synergistic cytotoxicity. This study proves that β- endosulfan elevates circulating CORT and thus generates physiological stress in tadpoles. Given that both pesticides are widely used within the distribution of L. taylori in Costa Rica, it is likely that tadpoles’ development and immune function are altered by pesticide use. In combination with stressors such as emerging diseases and altered precipitation regimes, widespread agrochemical uses likely caused this species enigmatic decline in recent decades.

No sex-dependent mortality in an amphibian upon infection with the chytrid fungus, Batrachochytrium dendrobatidis.

One of the major factors driving the currently ongoing biodiversity crisis is the anthropogenic spread of infectious diseases. Diseases can have conspicuous consequences, such as mass mortality events, but may also exert covert but similarly severe effects, such as sex ratio distortion via sex-biased mortality. Chytridiomycosis, caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd) is among the most important threats to amphibian biodiversity. Yet, whether Bd infection can skew sex ratios in amphibians is currently unknown, although such a hidden effect may cause the already dwindling amphibian populations to collapse. To investigate this possibility, we collected common toad (Bufo bufo) tadpoles from a natural habitat in Hungary and continuously treated them until metamorphosis with sterile Bd culture medium (control), or a liquid culture of a Hungarian or a Spanish Bd isolate. Bd prevalence was high in animals that died during the experiment but was almost zero in individuals that survived until the end of the experiment. Both Bd treatments significantly reduced survival after metamorphosis, but we did not observe sex-dependent mortality in either treatment. However, a small number of genotypically female individuals developed male phenotype (testes) in the Spanish Bd isolate treatment. Therefore, future research is needed to ascertain if larval Bd infection can affect sex ratio in common toads through female-to-male sex reversal.

Exploring the Effectiveness of Acyclovir against Ranaviral Thymidine Kinases: Molecular Docking and Experimental Validation in a Fish Cell Line.

The effectiveness of acyclovir, a selective anti-herpesvirus agent, was tested both in silico and in vitro against two ranaviruses, namely the European catfish virus (ECV) and Frog virus 3 (FV3). ECV can cause significant losses in catfish aquaculture, while FV3 poses a risk to vulnerable amphibian populations. The genome of ranaviruses encodes thymidine kinases (TKs) similar to those of herpesviruses. Molecular docking simulations demonstrated that the acyclovir molecule can bind to the active sites of both investigated viral TKs in an orientation conducive to phosphorylation. Subsequently, the antiviral effect of acyclovir was tested in vitro in Epithelioma Papulosum Cyprini (EPC) cells with endpoint titration and qPCR. Acyclovir was used at a concentration of 800 µM, which significantly reduced the viral loads and titers of the ranaviruses. A similar reduction rate was observed with Ictalurid herpesvirus 2, which was used as a positive control virus. These promising results indicate that acyclovir might have a wider range of uses; besides its effectiveness against herpesviruses, it could also be used against ranavirus infections.

Ranavirus and Its Impact on the Amphibian Population

Mass mortality of amphibians has occurred globally since at least the early 1990s from viral pathogens that are members of the genus Ranavirus, family Iridoviridae. This disease has a wide host range and with the movement of ranavirus-infected animals in commerce, ranaviruses have become an increasing threat to captive and wild populations, especially amphibians. The clinical signs of amphibians include haemorrhaging, lethargy, swelling, and ulcerative skin lesions. The virus is highly contagious, spreading through direct contact with infected individuals or contaminated environments, such as water bodies. Environmental factors, including temperature and pollution, can influence the severity and spread of ranavirus infections. The ecological impact of ranavirus is profound, as it threatens biodiversity and disrupts ecosystems. Consequently, understanding the epidemiology, pathology, and control measures for ranavirus is critical for conserving amphibian populations. Current research efforts are focused on developing effective strategies for monitoring, managing, and mitigating the impacts of this pathogen on amphibian communities. This review presents distribution, hosts, and epidemiology to better understand this disease.

Exploring Codon Usage Patterns and Influencing Factors in Ranavirus DNA Polymerase Genes.

Ranaviruses, members of the genus Ranavirus within the family Iridoviridae, have become a significant concern for amphibian populations globally, along with other cold-blooded vertebrates, due to their emergence as a significant threat. We employed bioinformatics tools to examine the codon usage patterns in 61 DNA pol genes from Ranavirus, Lymphocystivirus, Megalocytivirus, and two unclassified ranaviruses, as no prior studies had been conducted on this topic. The results showed a slight or low level of codon usage bias (CUB) in the DNA pol genes of Ranavirus. Relative synonymous codon usage (RSCU) analysis indicated that the predominant codons favored in Ranavirus DNA pol genes terminate with C or G. Correlation analysis examining nucleotide content, third codon position, effective number of codons (ENC), correspondence analysis (COA), Aroma values, and GRAVY values indicated that the CUB across DNA pol genes could be influenced by both mutation pressure and natural selection. The neutrality plot indicated that natural selection is the primary factor driving codon usage. Furthermore, the analysis of the codon adaptation index (CAI) illustrated the robust adaptability of Ranavirus DNA pol genes to their hosts. Analysis of the relative codon deoptimization index (RCDI) suggested that Ranavirus DNA pol genes underwent greater selection pressure from their hosts. These findings will aid in comprehending the factors influencing the evolution and adaptation of Ranavirus to its hosts.

Centrifugation is an effective and inexpensive way to determine Batrachochytrium dendrobatidis quantity in water samples with low turbidity

Batrachochytrium dendrobatidis (Bd) is a pathogenic chytrid fungus that is particularly lethal for amphibians. Bd can extirpate amphibian populations within a few weeks and remain in water in the absence of amphibian hosts. Most efforts to determine Bd presence and quantity in the field have focused on sampling hosts, but these data do not give us a direct reflection of the amount of Bd in the water, which are useful for parameterizing disease models, and are not effective when hosts are absent or difficult to sample. Current methods for screening Bd presence and quantity in water are time, resource, and money intensive. Here, we developed a streamlined method for detecting Bd in water with low turbidity (e.g., water samples from laboratory experiments and relatively clear pond water from a natural lentic system). We centrifuged water samples with known amounts of Bd to form a pellet and extracted the DNA from that pellet. This method was highly effective and the resulting concentrations across all tested treatments presented a highly linear relationship with the expected values. While the experimentally derived values were lower than the inoculation doses, the values were highly correlated and a conversion factor allows us to extrapolate the actual Bd concentration. This centrifuge-based method is effective, repeatable, and would greatly expand the domain of tractable questions to be explored in the field of Bd ecology. Importantly, this method increases equity in the field, because it is time- and cost-efficient and requires few resources.

The herpetofauna of the Sporades Islands (Aegean Sea, Greece): New discoveries and a review of a century of research

The Sporades are one of the most biologically important archipelagos in the Aegean Sea (Greece) and have received priority conservation over the last 50 years. However, despite numerous early efforts, its herpetofauna is only partially described, resulting in many distributional gaps that have prevented adequate understanding and management of the resident species communities. We review one century of bibliography from the Northern Sporades and combine this information with a review of museum specimens and insights from numerous extensive field surveys over the last near-decade to provide for the first time a comprehensive picture of the reptiles and amphibians of the archipelago. We report here on 26 new island records and find that the herptile communities of the region are largely derived from the herpetofauna of the nearby Thessaly mainland, with only a few introduced taxa. There is also a small but significant set of endemic taxa in the archipelago. Island species richness declines with decreasing island size and increasing duration of island isolation. Herptile communities on smaller islands are progressively nested subsets of the communities on larger islands. The presence of reptile species depends sensitively on the condition and management of native ecosystems. While non-aquatic species maintain largely healthy populations, most populations are under pressure from the combined effects of rampant tourist development, the destruction and degradation of rare wetland habitats, and the abandonment of traditional agricultural landscapes. We provide recommendations regarding sustainable management of the local reptile and amphibian populations.

Evaluating elements of artificial cover object design for terrestrial salamander monitoring

AbstractDeclines in amphibian populations have led to greater research and monitoring of species of interest, including terrestrial salamanders. Several methods have been used to study salamanders, including artificial cover objects (ACOs). Artificial cover objects are easy to install and use, limit destruction to habitats, are easily reproducible both across and within studies, and can reduce variability between observers and sites by not relying on observer search time or effort, or on natural cover. However, different ACO designs and spacing may yield different capture rates, and thus different estimates of population densities. We examined the influence of ACO wood type, size, shape, and spacing arrays on the number of individually marked red‐backed salamanders (Plethodon cinereus) captured under ACOs. White pine (Pinus strobus) ACOs yielded the most (average of 14 across 3 replicates) individuals, while white ash (Fraxinus americana) ACOs had the least (average of 7 across 3 replicates). Larger ACOs had similar capture rates compared to equal sampled areas of smaller ACOs, but a single smaller ACO tended to have fewer individual salamander captures than a single large ACO. Our results suggested that high‐density ACO spacing arrays may increase capture probability but reduce the area uniquely sampled by each ACO. In contrast, low‐density ACO arrays may produce population estimates more comparable to other arrays. Future studies should consider monitoring goals and available sampling effort when choosing a spacing array. As ACO study design impacts salamander capture rates, a clear understanding of the effects of each element of ACO design is important when drawing inferences or making comparisons among studies.