Frog Breeding Research Articles

Daily fluctuating temperatures decrease growth and reproduction rate of a lethal amphibian fungal pathogen in culture

BackgroundEmerging infectious diseases (EIDs) are contributing to species die-offs worldwide. We can better understand EIDs by using ecological approaches to study pathogen biology. For example, pathogens are exposed to variable temperatures across daily, seasonal, and annual scales. Exposure to temperature fluctuations may reduce pathogen growth and reproduction, which could affect pathogen virulence, transmission, and environmental persistence with implications for disease. We examined the effect of a variable thermal environment on reproductive life history traits of the fungal pathogen Batrachochytrium dendrobatidis (Bd). Bd causes chytridiomycosis, an emerging infectious disease of amphibians. As a pathogen of ectothermic hosts, Bd can be exposed to large temperature fluctuations in nature. To determine the effect of fluctuating temperatures on Bd growth and reproduction, we collected temperature data from breeding pools of the Yosemite toad (Anaxyrus canorus), a federally threatened species that is susceptible to chytridiomycosis. We cultured Bd under a daily fluctuating temperature regime that simulated Yosemite toad breeding pool temperatures and measured Bd growth, reproduction, fecundity, and viability.ResultsWe observed decreased Bd growth and reproduction in a diurnally fluctuating thermal environment as compared to cultures grown at constant temperatures within the optimal Bd thermal range. We also found that Bd exhibits temperature-induced trade-offs under constant low and constant high temperature conditions.ConclusionsOur results provide novel insights on variable responses of Bd to dynamic thermal conditions and highlight the importance of incorporating realistic temperature fluctuations into investigations of pathogen ecology and EIDs.

The combined effects of temperature and aromatase inhibitor on metamorphosis, growth, locomotion, and sex ratio of tiger frog (Hoplobatrachus rugulosus) tadpoles.

BackgroundThe tiger frog (Hoplobatrachus rugulosus) is widely raised by many farms in southern region of China as an economically edible frog. The growth, development, and sexual differentiation of amphibians are influenced by temperature and steroid hormone level. However, the problem of hormone residues is caused by the addition of exogenous hormones in frog breeding, it is worth considering whether non-sterol aromatase inhibitors can be used instead of hormones.MethodsIn our study, H. rugulosus tadpoles were subjected to two water temperatures (29 °C and 34 °C) and three letrozole concentrations in the feed (0, 0.1 and 1 mg/g) to examine the effects of temperature, aromatase inhibitor and their interaction on metamorphosis, locomotion, and sex ratios. A G-test and contingency table were used to analyze the metamorphosis rate of tadpoles and the survival rate of froglets after feeding for 90 days. A G-test was also used to analyze sex ratios in different treatment groups.ResultsMetamorphosis time and body size (snout–vent length, body mass and condition factor) were significantly different between the two temperature treatments. Metamorphosis time was longer and body size was increased at 29 °C compared to those at 34 °C. Letrozole concentration and the temperature × letrozole interaction did not affect these variables. The jumping distance of froglets following metamorphosis was positively associated with the condition factor; when controlling for condition factor, jumping distance was not affected by temperature, letrozole concentration and their interaction. Temperature and letrozole concentration also did not affect metamorphosis and survival rate. Sex ratio of the control group (0 mg/g letrozole) was 1:1 at 29 °C, but there were more males at 34 °C. The sex ratios of H. rugulosus treated with letrozole at 29 °C and 34 °C were significantly biased toward males, and male ratio increased as letrozole concentration increased. Furthermore, more males were produced at 34 °C than at 29 °C at each letrozole concentration.

Possible implications of weather variation on reproductive phenology of European common toad in southeastern Europe

We tracked yearly variation in breeding phenology in relation to weather parameters in a common European toad population from the southeastern part of its range. Phenological data were collected from 2001 to 2003 and from 2011 to 2017 and compared to open-access daily weather data from a nearby weather station. Data analysis revealed no significant effect of weather on initiation of breeding and a negative relationship between mean daily humidity and mean cloud cover on the duration of breeding season (P = 0.03). Further analysis showed a decreasing trend in breeding season humidity in the past 70 years. Our results predict a tendency toward longer toad breeding seasons in years with drier winter/spring. A projected decrease in humidity in this region could prolong toad breeding season, potentially exposing adults to higher predation. Therefore, the scenario of further decline in our study population should be considered and conservation measures planned accordingly.

Amphibian chytrid prevalence on boreal toads in SE Alaska and NW British Columbia: tests of habitat, life stages, and temporal trends.

Tracking and understanding variation in pathogens such as Batrachochytrium dendrobatidis (Bd), the agent of amphibian chytridiomycosis which has caused population declines globally, is a priority for many land managers. However, relatively little sampling of amphibian communities has occurred at high latitudes. We used skin swabs collected during 2005-2017 from boreal toads Anaxyrus boreas (n = 248), in southeast Alaska (USA; primarily in and near Klondike Gold Rush National Historical Park [KLGO]) and northwest British Columbia (Canada) to determine how Bd prevalence varied across life stages, habitat characteristics, local species richness, and time. Across all years, Bd prevalence peaked in June and was >3 times greater for adult toads (37.5%) vs. juveniles and metamorphs (11.2%). Bd prevalence for toads in the KLGO area, where other amphibian species are rare or absent, was highest from river habitats (55.0%), followed by human-modified upland wetlands (32.3%) and natural upland wetlands (12.7%)-the same rank-order these habitats are used for toad breeding. None of the 12 Columbia spotted frogs Rana luteiventris or 2 wood frogs R. sylvatica from the study area tested Bd-positive, although all were from an area of low host density where Bd has not been detected. Prevalence of Bd on toads in the KLGO area decreased during 2005-2015. This trend from a largely single-species system may be encouraging or concerning, depending on how Bd is affecting vital rates, and emphasizes the need to understand effects of pathogens before translating disease prevalence into management actions.

Two amphibian species in the urban environment: changes in the occurrence, spawning phenology and adult condition of common and green toads

Many features of the urban environment, such as a warmer microclimate, can positively affect populations of birds and mammals inhabiting cities, while at the same time may affect amphibians negatively. Also, amphibians from the temperate zone need both water bodies for reproduction and terrestrial habitats for foraging and hibernation, so changes in only one of these habitats may affect them negatively, and strong declines in many species are being observed. This study was conducted on two species, reacting differently to urbanization pressure – the common toad Bufo bufo and green toad Bufotes viridis. In the 1992–1994 breeding seasons, the occurrence of spawning toads in urban water bodies was established, and such a survey was repeated 15 years later (2007–2009). Over a shorter period, the breeding phenology, as well as the condition of breeding individuals, was studied. We found that after 15 years, a significant loss of the breeding sites of the two toad species took place, and the rate of their extinction was similar (39–47%), but green toad breeding ponds were located closer to the city center than before (2.4 vs 4.6 km). In both periods, the common toad spawned in water bodies located farther from the center (ca 7.2–8.7 km). The breeding phenology of both species was related to the minimal decade temperatures of April, and the green toad started to breed later than the common toad by 9–23 days. The condition of toad individuals differed between species, and after a colder winter, common toads were in better condition than green toads.

Title: Recruitment is key to understanding amphibian’s different population-level responses to chytrid fungus infection

Understanding why related species have differing population-level responses to threats can be key to identifying conservation options for declining populations. However, this is difficult when multiple threats are implicated. Chytrid fungus (Batrachochytrium dendrobatidis: Bd) is implicated in at least 500 amphibian population declines globally, although few tangible options exist to mitigate pathogen impacts. Other threatening processes also invariably operate on most amphibians. Non-native fish, for example, can contribute to amphibian declines and may exacerbate Bd impacts. We disentangled the impacts of Bd and non-native fish upon two stream breeding frog species with differing conservation statuses to reveal vital rates that are crucial for species persistence. Litoria spenceri are threatened and historically occurred at elevations between 300–1100m asl in southeastern Australia. Litoria lesueurii are non-threatened and sympatric with L. spenceri at some sites. Using mark-recapture derived demographic rates known to correlate with climate and elevation, discrete-time deterministic population models were constructed for each species at high, moderate and low elevation sites, and multiple management scenarios. Our study reveals that age to maturation, clutch size and egg-year 1 survival influenced interspecific and intraspecific population-level responses of the two frogs to Bd impacts. Importantly, our results highlight that an amphibian population’s capacity to counteract Bd-mediated adult mortality is clearly constrained by other threats and environment interactions that moderate species recruitment. Furthermore, understanding limits to recruitment may help identify Bd mitigation strategies. In our study, disease mitigation may be best achieved at some sites by enhancing recruitment through non-native fish management.

Yetiştiriciliği yapılan ova kurbağasından (Pelophylax ridibundus, Pallas 1771) izole edilen bakteriyel etkenler

Marsh frogs (Pelophylax ridibundus) are preferred in European cuisine. In recent years, interest in farming of marsh frogs has increased, but little is known about their bacterial diseases. This research was carried out in a marsh frog farming operation in Mersin, Turkey, in order to determine the bacterial diversity. For this purpose, a total of 339 frog, 30 water, and 8 feed samples were collected. Isolation and identification of bacteria were carried out by conventional techniques and the VITEK-2 compact system. Antimicrobial susceptibility testing was performed by Kirby-Bauer disc diffusion method. A total of 239 isolates of 49 different species, including 31 Gram negative rod-shaped bacteria, 9 Gram positive rod-shaped sporeforming bacteria, and 9 Gram positive cocci-shaped non-sporeforming bacteria have been identified. These bacteria species were detected from 25 (83.3%) water, 5 (62.5%) feed samples, and 64 (84.2%) of 76 frog specimens. Antimicrobial susceptibility and MAR index values ranged between 1.4-95.8% and 0.13-0.73, respectively. In conclusion, the presence of opportunistic pathogenic bacteria in water, feed and frog specimens, which could pose risk for frogs and human health, have been detected in the marsh frog farm in Mersin. This study reveals, that further investigations are necessary for sustainable marsh frog breeding in Turkey.

Brown frog breeding phenology in south Sweden 1990 – 2017: are data subsets robust?

- Field data on breeding phenology of Ranaarvalis and R.temporaria for the period 1990- 2017 in Scania, Sweden are presented and analysed. There was no temporal trend for R.temporaria. ForR.arvalisthe results were mixed, one out of two approaches found a trend to earlier breeding. The lack of a consistent trend in breeding phenology is unsurprising considering that local mean air temperatures in February, March and April showed no significant trends over the study period. To test the robustness of the conclusion, different subsets of the data (years or ponds) were also analysed for trends. For most subsets the conclusions remained the same. Possible bias arising from the choice of which years to include in an analysis of trends is discussed.

Brown frog breeding phenology in south Sweden 1990 – 2017: are data subsets robust?

Field data on breeding phenology of Rana arvalis and R. temporaria for the period 1990 - 2017 in Scania, Sweden are presented and analysed. There was no temporal trend for R. temporaria. For R. arvalis the results were mixed, one out of two approaches found a trend to earlier breeding. The lack of a consistent trend in breeding phenology is unsurprising considering that local mean air temperatures in February, March and April showed no significant trends over the study period. To test the robustness of the conclusion, different subsets of the data (years or ponds) were also analysed for trends. For most subsets the conclusions remained the same. Possible bias arising from the choice of which years to include in an analysis of trends is discussed.

Positive correlation between dispersal and body size in Green Frogs (Rana clamitans) naturally colonizing an experimental landscape

Dispersers are often assumed to have the mean phenotype observed across the entire metapopulation, despite growing evidence of dispersal–phenotype correlations. We examined three dispersal–phenotype correlations in Green Frogs (Rana clamitans Latreille, 1801 = Lithobates clamitans (Latreille, 1801)). Two were in traits that have been previously tied to fitness (body size and body condition), while a third (relative hindlimb length) has been linked to movement performance. We constructed a spatially dispersed array of experimental ponds in close proximity to source ponds known to support Green Frog breeding populations. Over the course of two breeding seasons (four sampling periods), we measured phenotypes of all Green Frogs that had colonized the experimental ponds and a sample of individuals from the source ponds. After only 1 month, a positive correlation was detected between dispersal and body size within the population of dispersers occupying the experimental ponds. After a 2nd month, this positive dispersal – body size correlation was also present when comparing the population of dispersers to the population of nondispersers remaining at the source ponds. Even if generated solely by plasticity, a positive correlation between dispersal and body size (a trait tightly linked to fitness) has the ability to alter metapopulation capacity and thus the probability of regional species persistence.

Environmental watering triggers rapid frog breeding in temporary wetlands within a regulated river system

The Murray–Darling basin is the most extensively regulated river system in Australia and delivery of environmental water is increasingly being used in its management. Due to their sensitivity to hydrological changes, frogs are often targets of environmental watering actions, and site-specific data on their habitat and water requirements are essential for achieving optimal ecological outcomes. I investigated the spatial and temporal response of frogs to the environmental watering of temporary wetlands in the lower River Murray region to determine if watering (timing, duration and quality) triggered a breeding response and provided opportunities for juvenile recruitment. Frog and tadpole surveys were conducted each month from December 2014 to April 2015 at watered temporary wetlands and permanent wetlands along on the River Murray in South Australia. All seven frog species known from the lower Murray valley bred opportunistically after deliberate flooding of temporary wetland sites. Breeding was immediate and was observed at all watered sites. Tadpole development was largely synchronous and rapid, with the majority of frogs metamorphosing 3 to 4 months after wetlands were inundated. The abundance and diversity of tadpoles and frogs was significantly greater in watered wetlands than in permanent wetlands. Wetlands required inundation for a minimum duration of 4 months over summer and autumn to allow sufficient time for tadpoles to complete development. Environmental watering of wetlands via pumping, whilst highly localised, can target key ecological assets in dry conditions, and may provide critical breeding opportunities and refugia for maintaining frog species and their ecological roles.

Landscape context is more important than wetland buffers for farmland amphibians

In regions with high rates of wetland loss, remnant wetlands and constructed ponds can provide important breeding habitat for amphibians. However, such wetlands are often embedded in a matrix of agricultural fields, potentially putting species within these wetlands at risk. One recommendation for conservation of amphibians in agriculture-dominated landscapes is to maintain a buffer of permanent vegetation around the wetland. However, it is not clear how wide wetland buffers must be to effectively conserve amphibians in agriculture-dominated landscapes or what vegetation types are suitable buffer vegetation. Furthermore, it is not clear whether wetland buffers produce similar—or better—conservation outcomes for amphibians than actions conducted at larger spatial extents. We addressed these questions using data from anuran (frog and toad) breeding call surveys in 36 wetlands in rural eastern Ontario, Canada. First, we tested for the effects of 49 different wetland buffer measurements on anuran richness, relative anuran abundance, and the abundance/probability of occurrence of individual species. These 49 measurements represented all combinations of seven different ways to measure the wetland buffer size and seven types of buffer vegetation. Wetland buffer size was measured as the minimum width of buffer vegetation contiguous with the wetland and proportion of the area within 5, 16, 30, 50, 120, or 300 m of the wetland containing buffer vegetation that was contiguous with the wetland. Then, to compare the strength of effect of wetland buffers versus landscape context on anurans, we compared the wetland buffer measurement with the strongest positive effect on each anuran response (from the previous analysis) to the effects of three landscape-scale variables: area of woodland; area of wetlands, streams, rivers, and lakes; and road density. We did not detect positive effects of wetland buffers on anuran richness or relative anuran abundance. This is because positive effects of wetland buffers on individual species were rare, i.e. positive effects were only supported for two of the six species with enough data to model individually: American toads (Anaxyrus americanus) and green frogs (Lithobates clamitans). Furthermore, we found that the landscape context had much stronger effects on relative anuran abundance than the wetland buffer, with effect sizes ranging from 4 (road density) to 14 (woodland cover) times that of the wetland buffer. These findings suggest that guidelines for anuran conservation in agricultural landscapes should generally focus on protection of terrestrial habitat at the landscape scale rather than on maintenance of wetland buffers.

An amphibian with a contracting range is not more vulnerable to pesticides in outdoor experimental communities than common species.

In areas with heavy pesticide use, it is easy to attribute population declines to environmental contamination. The Blanchard's cricket frogs (Acris blanchardi) is an amphibian experiencing declines and range contractions across its distribution in the Midwest Corn Belt (USA). Experimental studies suggest that cricket frogs are sensitive to pesticides, but there are few studies examining this species' susceptibility to contaminants in realistic environments or comparing relative impacts with other anuran species. I reared 3 summer breeding anurans in outdoor mesocosms posthatching through metamorphosis to examine the effects of 2 insecticides (imidacloprid and carbaryl) and 1 herbicide (glyphosate with polyoxyethylene tallow amine) on larval development and metamorphosis. Cricket frogs were positively affected by insecticide exposure, likely a result of changes in the food web that increased food abundance. However, metamorphosis of green frogs (Lithobates clamitans) and gray tree frogs (Hyla chrysoscelis) appeared unaffected by pesticide exposure. The results of the present study suggest that the impacts of pesticides alone are unlikely to have population-level impacts for the anurans examined. Environ Toxicol Chem 2018;37:2699-2704. © 2018 SETAC.

Widespread Elevational Occurrence of Antifungal Bacteria in Andean Amphibians Decimated by Disease: A Complex Role for Skin Symbionts in Defense Against Chytridiomycosis.

Emerging infectious disease is a growing threat to global health, and recent discoveries reveal that the microbiota dwelling on and within hosts can play an important role in health and disease. To understand the capacity of skin bacteria to protect amphibian hosts from the fungal disease chytridiomycosis caused by Batrachochytrium dendrobatidis (Bd), we isolated 192 bacterial morphotypes from the skin of 28 host species of frogs (families Bufonidae, Centrolenidae, Hemiphractidae, Hylidae, Leptodactylidae, Strabomantidae, and Telmatobiidae) collected from the eastern slopes of the Peruvian Andes (540–3,865 m a.s.l.) in the Kosñipata Valley near Manu National Park, a site where we previously documented the collapse of montane frog communities following chytridiomycosis epizootics. We obtained isolates through agar culture from skin swabs of wild frogs, and identified bacterial isolates by comparing 16S rRNA sequences against the GenBank database using BLAST. We identified 178 bacterial strains of 38 genera, including 59 bacterial species not previously reported from any amphibian host. The most common bacterial isolates were species of Pseudomonas, Paenibacillus, Chryseobacterium, Comamonas, Sphingobacterium, and Stenotrophomonas. We assayed the anti-fungal abilities of 133 bacterial isolates from 26 frog species. To test whether cutaneous bacteria might inhibit growth of the fungal pathogen, we used a local Bd strain isolated from the mouthparts of stream-dwelling tadpoles (Hypsiboas gladiator, Hylidae). We quantified Bd-inhibition in vitro with co-culture assays. We found 20 bacterial isolates that inhibited Bd growth, including three isolates not previously known for such inhibitory abilities. Anti-Bd isolates occurred on aquatic and terrestrial breeding frogs across a wide range of elevations (560–3,695 m a.s.l.). The inhibitory ability of anti-Bd isolates varied considerably. The proportion of anti-Bd isolates was lowest at mid-elevations (6%), where amphibian declines have been steepest, and among hosts that are highly susceptible to chytridiomycosis (0–14%). Among non-susceptible species, two had the highest proportion of anti-Bd isolates (40 and 45%), but one common and non-susceptible species had a low proportion (13%). In conclusion, we show that anti-Bd bacteria are widely distributed elevationally and phylogenetically across frog species that have persisted in a region where chytridiomycosis emerged, caused a devastating epizootic and continues to infect amphibians.

Evolutionary radiation of earless frogs in the Andes: molecular phylogenetics and habitat shifts in high-elevation terrestrial breeding frogs.

The loss of hearing structures and loss of advertisement calls in many terrestrial breeding frogs (Strabomantidae) living at high elevations in South America are common and intriguing phenomena. The Andean frog genus Phrynopus Peters, 1873 has undergone an evolutionary radiation in which most species lack the tympanic membrane and tympanic annulus, yet the phylogenetic relationships among species in this group remain largely unknown. Here, we present an expanded molecular phylogeny of Phrynopus that includes 24 nominal species. Our phylogeny includes Phrynopus peruanus, the type species of the genus, and 10 other species for which genetic data were previously unavailable. We found strong support for monophyly of Phrynopus, and that two nominal species—Phrynopus curator and Phrynopus nicoleae—are junior synonyms of Phrynopus tribulosus. Using X-ray computed tomography (CT) imaging, we demonstrate that the absence of external hearing structures is associated with complete loss of the auditory skeletal elements (columella) in at least one member of the genus. We mapped the tympanum condition on to a species tree to infer whether the loss of hearing structures took place once or multiple times. We also assessed whether tympanum condition, body size, and body shape are associated with the elevational distribution and habitat use. We identified a single evolutionary transition that involved the loss of both the tympanic membrane and tympanic annulus, which in turn is correlated with the absence of advertisement calls. We also identified several species pairs where one species inhabits the Andean grassland and the other montane forest. When accounting for phylogenetic relatedness among species, we detected a significant pattern of increasing body size with increasing elevation. Additionally, species at higher elevations tend to develop shorter limbs, shorter head, and shorter snout than species living at lower elevations. Our findings strongly suggest a link between ecological divergence and morphological diversity of terrestrial breeding frogs living in montane gradients.

A new species of Amazonian snouted treefrog (Hylidae: Scinax) with description of a novel species-habitat association for an aquatic breeding frog.

The genus Scinax is one of the most specious genera of treefrogs of the family Hylidae. Despite the high number of potential new species of Scinax revealed in recent studies, the rate of species descriptions for Amazonia has been low in the last decade. A potential cause of this low rate may be the existence of morphologically cryptic species. Describing new species may not only impact the taxonomy and systematics of a group of organisms but also benefit other fields of biology. Ecological studies conducted in megadiverse regions, such as Amazonia, often meet challenging questions concerning insufficient knowledge of organismal alpha taxonomy. Due to that, detecting species-habitat associations is dependent on our ability to properly identify species. In this study, we first provide a description of a new species (including its tadpoles) of the genus Scinax distributed along heterogeneous landscapes in southern Amazonia; and secondly assess the influence of environmental heterogeneity on the new species’ abundance and distribution. Scinax ruberoculatus sp. nov. differs from all nominal congeners by its small size (SVL 22.6–25.9 mm in males and 25.4–27.5 mm in females), by having a dark brown spot on the head and scapular region shaped mainly like the moth Copiopteryx semiramis (or a human molar in lateral view, or a triangle), bicolored reddish and grey iris, snout truncate in dorsal view, bilobate vocal sac in males, by its advertisement call consisting of a single pulsed note with duration of 0.134–0.331 s, 10–23 pulses per note, and dominant frequency 1,809–1,895 Hz. Both occurrence and abundance of the new species are significantly influenced by silt content in the soil. This finding brings the first evidence that edaphic factors influence species-habitat association in Amazonian aquatic breeding frogs.

Influence of damming on anuran species richness in riparian areas: A test of the serial discontinuity concept.

Almost all large rivers worldwide are fragmented by dams, and their impacts have been modeled using the serial discontinuity concept (SDC), a series of predictions regarding responses of key biotic and abiotic variables. We evaluated the effects of damming on anuran communities along a 245‐km river corridor by conducting repeated, time‐constrained anuran calling surveys at 42 locations along the Broad and Pacolet Rivers in South Carolina, USA. Using a hierarchical Bayesian analysis, we test the biodiversity prediction of the SDC (modified for floodplain rivers) by evaluating anuran occupancy and species diversity relative to dams and degree of urbanized land use. The mean response of the anuran community indicated that occupancy and species richness were maximized when sites were farther downstream from dams. Sites at the farthest distances downstream of dams (47.5 km) had an estimated ~3 more species than those just below dams. Similarly, species‐specific occupancy estimates showed a trend of higher occupancy downstream from dams. Therefore, using empirical estimation within the context of a 245‐km river riparian landscape, our study supports SDC predictions for a meandering river. We demonstrate that with increasing distance downstream from dams, riparian anuran communities have higher species richness. Reduced species richness immediately downstream of dams is likely driven by alterations in flow regime that reduce or eliminate flows which sustain riparian wetlands that serve as anuran breeding habitat. Therefore, to maintain anuran biodiversity, we suggest that flow regulation should be managed to ensure water releases inundate riparian wetlands during amphibian breeding seasons and aseasonal releases, which can displace adults, larvae, and eggs, are avoided. These outcomes could be achieved by emulating pre‐dam seasonal discharge data, mirroring discharge of an undammed tributary within the focal watershed, or by basing real‐time flow releases on current environmental conditions.

Linking water quality with amphibian breeding and development: a case study comparing natural ponds and Sustainable Drainage Systems (SuDS) in East Kilbride, Scotland

Amphibians have declined due to habitat loss and alteration. Sustainable Drainage Systems (SuDS) provide potential habitat for amphibians in urban landscapes. However, the contaminants they accumulate may cause increased pollutant exposure, and limited research has addressed whether differences in water quality between SuDS and natural ponds might restrict their use by amphibians. This study aimed to explore the effects of water quality on amphibian breeding and development in SuDS and natural ponds in East Kilbride, Scotland. A generalised linear modelling approach was employed to determine sources of variation in common frog (Rana temporaria) breeding and development in relation to pond size, pH, electrical conductivity (EC), chlorophyll and heavy metal concentrations. Key findings included that EC indicative of salt pollution was higher in SuDS than natural ponds, amphibians bred in both site types, but frog spawn clump densities were lower in SuDS, and tadpole development rates were higher in SuDS sites but decreased when aluminium concentrations exceeded concentrations those of surface water standards. However, pond desiccation was a significant element in the 2018 study year. It was concluded that natural ponds and SuDS varied in water quality but were important in supporting amphibian populations. However, water quality might influence amphibian development more than breeding attempts; implications and management recommendations are highlighted based on these observations.

Identifying Species Conservation Strategies to Reduce Disease‐Associated Declines

AbstractEmerging infectious diseases (EIDs) are a salient threat to many animal taxa, causing local and global extinctions, altering communities and ecosystem function. The EID chytridiomycosis is a prominent driver of amphibian declines, which is caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd). To guide conservation policy, we developed a predictive decision‐analytic model that combines empirical knowledge of host‐pathogen metapopulation dynamics with expert judgment regarding effects of management actions, to select from potential conservation strategies. We apply our approach to a boreal toad (Anaxyrus boreas boreas) and Bd system, identifying optimal strategies that balance tradeoffs in maximizing toad population persistence and landscape‐level distribution, while considering costs. The most robust strategy is expected to reduce the decline of toad breeding sites from 53% to 21% over 50 years. Our findings are incorporated into management policy to guide conservation planning. Our online modeling application provides a template for managers of other systems challenged by EIDs.

The impacts of overwintered green frog larvae on wood frog embryo mortality under a wetter climate

Abstract For many species, the distribution and quantity of habitat is likely to be altered under climate change scenarios. Globally, temperatures are expected to increase, but changes in precipitation will be variable with some locations expected to receive more and other locations to receive less. The amount and timing of precipitation has a strong influence on wetland hydroperiod, which is a critical factor in determining wetland use by species of pond‐breeding amphibians. Past research has focused on the direct effects of reductions in precipitation and shorter hydroperiods, such as larvae desiccation, but little attention has been given to the indirect consequences of increased precipitation and longer hydroperiods, such as changes in predation pressure. We used wood frogs (Lithobates sylvaticus), a species that typically breeds in ephemeral (temporary) wetlands, to test the hypothesis that increased precipitation and permanent wetlands would indirectly increase mortality in wood frog embryos through increases in the density of embryo predators, second‐year green frog larvae (Lithobates clamitans), limnephilid and phryganeid caddisfly larvae and red‐spotted newts (Notophthalmus viridescens). We conducted translocation experiments in 2014 and 2015. We monitored wood frog embryo hatch success and mortality from predation using open (predator access) and closed (predators excluded) cages in 16 wetlands in each year. We observed no difference in embryo hatch success between ephemeral and permanent wetlands, with water temperature, not pH, affecting hatch rates. Wood frog embryos in permanent wetlands with overwintered second‐year green frog larvae had higher mortality from predation (0.80, 95% confidence intervals 0.65–0.91) than permanent wetlands (0.42, CI 0.26–0.60) and ephemeral wetlands (0.37, CI 0.31–0.45) that lacked predatory green frog larvae. Embryo mortality from predation increased with increasing green frog larvae density. Regression models showed that ponds with larvae densities >2.5 larvae m−2 resulted in 90% embryo mortality. Caddisfly larvae and red‐spotted newt density had no effect, and pond water temperature had a weak negative effect on embryo mortality from predation. Under a wetter and warmer climate, springtime occupancy of predatory green frog larvae is likely to increase, resulting in a reduction in the amount of suitable wood frog breeding habitat. Our research suggests that indirect effects of climate change mediated through biotic interactions may play a critical role in the distribution of ephemeral wetland species.