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766 record(s) found.

Papers & Reports Effects of salinity and RU486 on waterborne aldosterone and corticosterone of larval northern leopard frog larvae
Authors: B J Tornabene; Creagh W Breuner; Blake R Hossack; E J Crespi
Date: 2022-02-01 | Outlet: General and Comparative Endocrinology
testIncreased salinity is an emerging contaminant of concern for aquatic taxa. For amphibians exposed to salinity, there is scarce information about the physiological effects and changes in osmoregulatory hormones such as corticosterone (CORT) and aldosterone (ALDO). Recent studies have quantified effects of salinity on CORT physiology of amphibians based on waterborne hormone collection methods, but much less is known about ALDO in iono- and osmoregulation of amphibians. We re-assayed waterborne hormone samples from a previous study to investigate effects of salinity (sodium chloride, NaCl) and a glucocorticoid receptor antagonist (RU486) on ALDO of northern leopard frog (Rana pipiens) larvae. We also investigated relationships between ALDO and CORT. Waterborne ALDO marginally decreased with increasing salinity and was, unexpectedly, positively correlated with baseline and stress-induced waterborne CORT. Importantly, ALDO increased when larvae were exposed to RU486, suggesting that RU486 may also suppress mineralocorticoid receptors or that negative feedback of ALDO is mediated through glucocorticoid receptors. Alternatively, CORT increases with RU486 treatment and might be a substrate for ALDO synthesis, which could account for increases in ALDO with RU486 treatment and the correlation between CORT and ALDO. ALDO was negatively correlated with percent water, such that larvae secreting more ALDO retained less water. Although sample sizes were limited and further validation and studies are warranted, our findings expand our understanding of adrenal steroid responses to salinization in amphibians and proposes new hypotheses regarding the co-regulation of ALDO and CORT.
Papers & Reports Hemidactylus parvimaculatus[/] (Sri lankan Spotted House Gecko)
Authors: Christopher M Pellecchia; Brad M Glorioso; Robert W Mendyk; Charles A Collen; V Ch Montross; William McGighan; K Macedo; B R Maldonado; I N Morenc
Date: 2019-09-01 | Outlet: Herpetological Review
Describes three new parish records for this exotic species in Louisiana
Papers & Reports DIADOPHIS PUNCTATUS (Ring-necked Snake)
Authors: R P Kidder; Brad M Glorioso; Katie D Gray
Outlet: Herpetological Review
A new parish record for the Ring-necked Snake in Louisiana
Papers & Reports [AMBYSTOMA OPACUM (Marbled Salamander). ATYPICAL NEST SITES.
Authors: Joshua M Hall; Brad M Glorioso; J Se Doody
Date: 2021-09-01 | Outlet: Herpetological Review
This note describes atypical locations where Marbled Salamanders, Ambystoma opacum[/], eggs have been laid off the substrate.
Papers & Reports Low occurrence of ranavirus in the Prairie Pothole Region of Montana and North Dakota contrasts with prior surveys
Authors: B J Tornabene; E J Crespi; Bernardo Traversari; Kenzi M Stemp; Creagh W Breuner; Caren S Goldberg; Blake R Hossack
Date: 2021-12-16 | Outlet: Diseases of Aquatic Organisms
Ranaviruses are emerging pathogens that have caused mortality events in amphibians worldwide. Despite the negative effects of ranaviruses on amphibian populations, monitoring efforts are still lacking in many areas, including in the Prairie Pothole Region (PPR) of North America. Some PPR wetlands in Montana and North Dakota (USA) have been contaminated by energy-related saline wastewaters, and increased salinity has been linked to greater severity of ranavirus infections. In 2017, we tested tissues from larvae collected at 7 wetlands that ranged in salinity from 26 to 4103 mg Cl l-1. In 2019, we used environmental DNA (eDNA) to test for ranaviruses in 30 wetlands that ranged in salinity from 26 to 11754 mg Cl l-1. A previous study (2013-2014) found that ranavirus-infected amphibians were common across North Dakota, including in some wetlands near our study area. Overall, only 1 larva tested positive for ranavirus infection, and we did not detect ranavirus in any eDNA samples. There are several potential reasons why we found so little evidence of ranaviruses, including low larval sample sizes, mismatch between sampling and disease occurrence, larger pore size of our eDNA filters, temporal variation in outbreaks, low host abundance, or low occurrence or prevalence of ranaviruses in the wetlands we sampled. We suggest future monitoring efforts be conducted to better understand the occurrence and prevalence of ranaviruses within the PPR.
Papers & Reports Trade-offs in initial and long-term handling efficiency of PIT-tag and photographic identification methods
Authors: Lindsey S Roberts; Bennett Hardy; Erin Muths; Abigail Feuka; Larissa L Bailey
Date: 2021-07 | Outlet: Ecological Indicators
Individual identification is required for long-term investigations that examine population-level changes in survival or abundance, and mechanisms associated with these changes in wild populations. Such identification generally requires the application of a unique mark, or the documentation of characteristics distinctive to each individual animal. To minimize impacts to often declining populations, scientific and ethical concerns encourage marking strategies that minimize handling time (i.e., stress) for captured individuals. We examined the relative efficacy of passive integrated transponder (PIT)-tagging and photo-identification to identify individual Boreal toads (Anaxyrus boreas boreas) in field and indoor settings. We evaluated whether initial handling time was influenced by identification method (PIT-tag or photo-identification) or environment (field or indoor) and assessed the applicability of each method in long-term monitoring programs. Initial handling time was higher for PIT-tagging than photo-identification and higher in the field than in an indoor environment; however, handling time for previously PIT-tagged individuals was greatly reduced such that photo-identification led to > 5.5 times more handling time than PIT-tagging over the course of a toad's lifetime. Investigators must determine the trade-off between initial and subsequent handling times to minimize the expected cumulative handling time for an individual over the course of a study. Cumulative handling time is a function of the study design and the species’ survival and detection probabilities. We developed a Shiny Application to allow investigators to determine the identification method that minimizes handling time for their own study system.
Papers & Reports Mapping climate-resistant vernal pools: hydrologic refugia for amphibian reproduction under droughts and climate change
Authors: Evan HC Grant; Jennifer M Cartwright; TL Morelli
Vernal pools of the northeastern United States provide important breeding habitat for amphibians but may be sensitive to droughts and climate change. These seasonal wetlands typically fill by early spring and dry by mid-to-late summer. Because climate change may produce earlier and stronger growing-season evapotranspiration combined with increasing droughts and shifts in precipitation timing, management concerns include the possibility that some pools will increasingly become dry earlier in the year, potentially interfering with amphibian life-cycle completion. In this context, a subset of pools that continue to provide wetland habitat later into the year under relatively dry conditions might function as ecohydrologic refugia, potentially supporting species persistence even as summer conditions become warmer and droughts more frequent. We used approximately 3,000 field observations of inundation from 450 pools to train machine-learning models that predict the likelihood of pool inundation based on pool size, day of the year, climate conditions, short-term weather patterns, and soil, geologic, and landcover attributes. Models were then used to generate predictions of pool wetness across five seasonal time points, three short-term weather scenarios, and four sets of downscaled climate projections. Model outputs are available through a user-friendly website allowing users to choose the inundation thresholds, time points, weather scenarios, and future climate projections most relevant to their management needs. Together with long-term monitoring of individual pools at the site scale, this regional-scale study can support amphibian conservation by helping to identify which pools may be most likely to function as ecohydrologic refugia from droughts and climate change.
Papers & Reports Comparative Effects of Energy-Related Saline Wastewaters and NaCl on Hatching, Survival, and Fitness-Associated Traits of Two Amphibian Species
Authors: B J Tornabene; Creagh W Breuner; Blake R Hossack
Date: 2021 | Outlet: Environmental Toxicology and Chemistry
Increased salinity (sodium chloride; NaCl) is a prevalent and persistent
contaminant that negatively affects freshwater ecosystems. Although
most studies focus on effects of salinity from roads salts (primarily
NaCl), high-salinity wastewaters from energy extraction (wastewaters)
could be more harmful because they contain NaCl and other toxic
components. Many amphibians are sensitive to salinity and their eggs
are thought to be the most sensitive life history stage. However, there
are few investigations with salinity that include eggs and larvae
sequentially in long-term exposures. We investigated the relative effects
of wastewaters from a large energy reserve, the Williston Basin (USA),
and NaCl on northern leopard (Rana pipiens) and boreal chorus
(Pseudacris maculata) frogs. We exposed eggs to salinity and tracked
responses through larval stages (for 24 days). Wastewaters and NaCl
reduced hatching and larval survival, growth, development, and activity
while also increasing deformities. Chorus frog eggs and larvae were
more sensitive to salinity than leopard frogs suggesting species-specific
responses. Contrary to previous studies, eggs of both species were less
sensitive to salinity than larvae. Our ecologically relevant exposures
suggest that accumulating effects can reduce survival relative to starting
experiments with unexposed larvae. Alternatively, egg casings of some
species may provide some protection against salinity. Notably, effects of
wastewaters on amphibians were predominantly due to NaCl rather than
other components. Therefore, findings from studies with other sources of
increased salinity (e.g., road salts) could guide management of
wastewater-contaminated ecosystems, and vice versa, to mitigate
effects of salinization.
Papers & Reports Evaluation of regulatory action and surveillance as preventive risk-mitigation to an emerging global amphibian pathogen Batrachochytrium salamandrivorans (Bsal)
Authors: D A Grear; Brittany A Mosher; Katherine LD Richgels; Evan HC Grant
Date: 2021-07-02 | Outlet: Conservation Biology
The emerging amphibian pathogen Batrachochytrium salamandrivorans (Bsal) is a severe threat to global urodelan (salamanders, newts, and related taxa) biodiversity. Bsal has not been detected, to date, in North America, but the risk is high because North America is one of the global hotspots for urodelan biodiversity. The North American and United States response to the discovery of Bsal in Europe was to take a risk-based approach to preventive management actions, including interim regulations on importation of captive salamanders and a large-scale surveillance effort. Risk-based approaches to decision-making can extend to adaptive management cycles by periodically incorporating new information that reduces uncertainty in an estimate of risk or to assess the effect of mitigation actions which reduce risk directly. Our objectives were to evaluate the effects of regulatory action on the introduction of Bsal to the U.S., quantify how a large-scale surveillance effort impacted consequence risk, and to combine other new information on species susceptibility to re-evaluate Bsal risk to the U.S. Import regulations effectively reduced import volume of targeted species, but new research on species susceptibility suggests the list of regulated species was incomplete regarding Bsal reservoir species. Not detecting Bsal in an intensive surveillance effort improved confidence that Bsal was not present, however, the overall risk-reduction impact was limited because of the expansive area of interest (conterminous United States) and limited time frame of sampling. Overall, the preventive actions in response to the Bsal threat did reduce Bsal risk in the U.S. and we present an updated risk assessment to provide information for adaptive decision-making.
Papers & Reports Amphibian population responses to mitigation: relative importance of wetland age and design
Authors: Emily B Oja; L K Swartz; Erin Muths; Blake R Hossack
Date: 2021 | Outlet: Ecological Indicators
Wetland creation is a common practice to mitigate for the loss of natural wetlands. However, there is still uncertainty about how effectively created wetlands replace habitat provided by natural wetlands. This uncertainty is due in part because post-construction monitoring of biological communities, and vertebrates especially, is rare and typically short-term (< 5 years). We estimated occupancy of 4 amphibian species in 8 created mitigation wetlands, 7 impacted wetlands, and 7 reference wetlands in the Greater Yellowstone Ecosystem in Wyoming, USA. Mitigation wetlands were created to replace wetland habitat that was lost during road construction and ranged in age from 1 to 10 years when sampled. Impacted wetlands were natural wetlands partially filled by road construction and were adjacent to a highway. We sampled for amphibian larvae during 6 summers from 2013 to 2020 and used multi-species occupancy models that estimated detection and occupancy of each of 4 amphibian species to determine how amphibian responses changed over time, especially in mitigation wetlands. Occupancy did not differ between impacted and reference wetlands for any of the 4 amphibian species. Western Toads (Anaxyrus boreas) were most common (although briefly) in created wetlands, and occupancy of Columbia Spotted Frogs (Rana luteiventris), Western Tiger Salamanders (Ambystoma mavortium), and Boreal Chorus Frogs (Pseudacris maculata) was lower in created wetlands than in impacted or reference wetlands. Wetland area was positively associated with occupancy for all 4 species and wetland vegetation cover was positively associated with Boreal Chorus Frog and Columbia Spotted Frog occupancy; these results emphasize the importance of design characteristics when planning mitigation wetlands. The link between wetland age and occupancy was complex and included threshold and quadratic relationships for three of the four species, but only Boreal Chorus Frog occupancy was still increasing slowly at the end of our study. Our results indicate created wetlands did not attain the suitability of impacted and natural wetlands for local amphibians, even several years after construction. The complicated relationships between wetland age and species-specific occupancy illustrate the importance of long-term monitoring in describing population responses to the construction of wetlands as mitigation for wetland loss.
Papers & Reports Corticosterone Mediates a Growth-Survival Tradeoff for an Amphibian Exposed to Increased Salinity
Authors: B J Tornabene; Blake R Hossack; E J Crespi; Creagh W Breuner
Date: 2021-08-09 | Outlet: Journal of Experimental Zoology Part A
Life-history tradeoffs are common across taxa, but growth-survival tradeoffs—which usually enhance survival at a cost to growth—are less frequently investigated. Increased salinity (NaCl) is a prevalent anthropogenic disturbance that may cause a growth-survival tradeoff for amphibians. Although physiological mechanisms mediating tradeoffs are seldom investigated, hormones are prime candidates. Corticosterone (CORT) is a steroid hormone that independently influences survival and growth and may provide mechanistic insight into growth-survival tradeoffs. We used 24-d trials to test effects of salinity (0 – 4000 mg/L Cl-) on growth, development, survival, CORT responses, and tradeoffs among traits of larval Northern Leopard Frogs (Rana pipiens). We also tested experimentally suppressed CORT signaling to determine whether CORT signaling mediates effects of salinity and life history tradeoffs . Increased salinity reduced survival, growth, and development. Suppressing CORT signaling in conjunction with salinity reduced survival further, but also attenuated negative effects of salinity on growth and development. CORT of control larvae increased or was stable with growth and development, but decreased with growth and development for those exposed to salinity. Therefore, salinity dysregulated CORT physiology. Across all treatments, larvae that survived had higher CORT than larvae that died. By manipulating CORT signaling, we provide strong evidence that CORT physiology mediates the outcome of a growth-survival tradeoff. To our knowledge, this is the first study to concomitantly measure tradeoffs between growth and survival and experimentally link these changes to CORT physiology. Identifying mechanistic links between stressors and fitness-related outcomes is critical to enhance our understanding of tradeoffs.
Papers & Reports Assessing the ecological functionality and integrity of natural ponds, excavated ponds and stormwater basins for conserving amphibian diversity
Authors: K L Smalling; Sara E Breitmeyer; John F Bunnell; Kim J Laidig; Patrick M Burritt; Marilyn C Sobel; Jonathan A Cohl; Michelle L Hladik; Kristin M Romanok; Paul M Bradley
Date: 2012-08-20 | Outlet: Global Ecology and Conservation 30, e01765
Wetlands provide ecological functionality by maintaining and promoting regional biodiversity supporting quality habitat for aquatic organisms. Globally, habitat loss, fragmentation and degradation due to increases in agricultural activities and urban development have reduced or altered geographically isolated wetlands, thus reducing biodiversity. The objective of this study was to assess the relative ecological function and integrity of natural ponds, excavated ponds and stormwater basins for amphibian diversity in the New Jersey Pinelands, USA by comparing hydrologic conditions, water quality, pesticide concentrations (water, sediment and tissue) and plant and anuran assemblages. Twenty-four wetlands were selected based on surrounding land-use and sampled for a variety of abiotic and biotic variables. Abiotic and biotic wetland variables were similar between natural and excavated ponds, with notable differences between the ponds and stormwater basins. Natural and excavated ponds displayed characteristic Pinelands water quality (low pH, high organic carbon, and low pesticide concentrations), exhibited high ecological integrity and supported native anuran species. Stormwater basins and degraded ponds surrounded by altered land-use exhibited degraded water quality (high pH, high pesticide concentrations) and were dominated by non-native and introduced plant and anuran species. Results from this study can broadly inform resource conservation strategies for amphibians and other communities with a diverse range of habitat requirements, particularly in areas where conservation and development are competing priorities. To conserve biodiversity in changing landscapes, wetlands with similar functionality and land-use characteristics need to be identified and managed to preserve water quality for species of conservation concern.
Papers & Reports Evaluating Corticosterone as a Biomarker for Amphibians Exposed to Increased Salinity and Ambient Corticosterone
Authors: B J Tornabene; Blake R Hossack; E J Crespi; Creagh W Breuner
Date: 2021-07 | Outlet: Conservation Physiolology 9(1): coab049
Salinization is harmful to amphibians and waterborne corticosterone could be a useful biomarker. Salinity was only associated with waterborne corticosterone for one of three amphibian species. Ambient corticosterone likely confounded associations and possibly influenced amphibian physiology. We provide suggestions to improve reliability of waterborne corticosterone as a biomarker of salt stress.
Papers & Reports Metal accumulation varies with life history, size, and development of larval amphibians
Authors: K L Smalling; Emily B Oja; Danielle M Cleveland; J M Davenport; Collin A Eagles-Smith; Evan HC Grant; Patrick M Kleeman; Brian J Halstead; Kenzi M Stemp; B J Tornabene; Z J Bunnell; Blake R Hossack
Date: 2021-06-26 | Outlet: Environmental Pollution 287: e117638
Amphibian larvae are commonly used as indicators of aquatic ecosystem health because they are susceptible to contaminants. However, there is limited information on how species characteristics and trophic position influence contaminant loads in larval amphibians. Importantly, there remains a need to understand whether grazers (anurans) and predators (salamanders) provide comparable information on contaminant accumulation or if they are each indicative of unique environmental processes and risks. To better understand the role of trophic position in contaminant accumulation, we analyzed composite tissues for 10 metals from larvae of multiple co-occurring anuran and salamander species from 20 wetlands across the United States. We examined how metal concentrations varied with body size (anurans and salamanders) and developmental stage (anurans) and how the digestive tract (gut) influenced observed metal concentrations. Across all wetlands, metal concentrations were greater in anurans than salamanders for all metals tested except mercury, selenium (Se), and zinc (Zn). Concentrations of individual metals in anurans decreased with increasing weight and developmental stage. In salamanders, which are predatory, metal concentrations were less correlated with weight, indicating diet played a role in contaminant accumulation. Based on batches of similarly sized whole-body larvae compared to larvae with their digestive tracts removed our results indicated that tissue type strongly affected perceived concentrations, especially for anurans (gut represented 50–90% of all metals except Se and Zn). This suggest the reliability of results based on whole body sampling could be biased by metal, larval size, and development. Overall, our data suggest that metal concentrations differs among orders (anuran and salamanders) which suggests that metal accumulation is unique to feeding behavior and potentially trophic position. To truly characterize exposure risk in wetlands, species of different life histories, sizes and developmental stages should be included in biomonitoring efforts.
Papers & Reports Resilience of native amphibian communities following catastrophic drought: evidence from a decade of regional-scale monitoring
Authors: W Moss; T McDevitt-Galles; Erin Muths; Steven Bobzien; J Purificato; P TJ Johnson
1. The increasing frequency and severity of drought has the potential to exacerbate existing global amphibian declines. However, interactions between drought and coincident stressors, coupled with high interannual variability in amphibian abundances, can mask the extent and underlying mechanisms of drought-induced declines. The application of dynamic occupancy modeling to longitudinal monitoring data estimates the effect of specific variables on population change, providing key insights into potential management strategies for drought resilience.
2. We synthesized a decade (2009 – 2019) of amphibian survey data from multiple monitoring programs across the California Bay Area and used occupancy modeling to estimate the influence of drought, invasive species, and land use on species’ persistence and colonization probabilities. The geographic and temporal scale of our dataset, consisting of 2574 surveys of seven species in 473 ponds, allowed us to quantify regional trends for an entire community of pond-breeding amphibians.
3. An extreme drought from 2012 – 2015 resulted in losses of breeding sites, with 51% of ponds drying in 2014 compared to <10% in non-drought years. Pond drying reduced persistence rates, and nearly every species exhibited reduced occupancy during the drought, with some species (American bullfrogs and California newts) declining by > 25%. Drought reduced occupancy via additional mechanisms beyond habitat loss; for example, lower spring precipitation (an important cue for breeding) was associated with reduced colonization.
4. During drought, native species’ persistence was higher in permanent relative to temporary ponds, even though these sites were also more likely to contain invasive fish and bullfrogs, which generally reduced native amphibian occupancy. Many of these permanent ponds dried during the worst year of drought, leading to extirpations of invasive species that appeared long-lasting. In contrast, native species rebounded quickly with returning rains and showed evidence of full recovery.
5. Synthesis and applications: Despite experiencing one of most severe droughts in a millennium, native species displayed high resilience. Due to longer recovery times by non-native relative to native species, drought presents a valuable management opportunity to remove invaders from key refugia, and we highlight the value of maintaining hydroperiod diversity to promote the persistence of multiple species.
Papers & Reports Staggered-entry analysis of breeding and occupancy dynamics of Arizona Toads from historically occupied habitats of New Mexico, USA
Authors: M J Forzley; Mason J Ryan; I M Latella; J T Giermakowski; Erin Muths; Brent H Sigafus; Blake R Hossack
Outlet: Copeia
For species with variable phenology, it is often challenging to produce reliable estimates of population dynamics or changes in occupancy. The Arizona Toad (Anaxyrus microscaphus) is a southwestern USA endemic that has been petitioned for legal protection, but status assessments are limited by a lack of information on population trends. Also, timing and consistency of Arizona Toad breeding varies greatly, making it difficult to predict optimal survey times or effort required for detection. To help fill these information gaps, we conducted breeding season call surveys during 2013–2016 and 2019 at 86 historically occupied sites and 59 control sites across the species’ range in New Mexico. We estimated variation in mean dates of arrival and departure from breeding sites, changes in occupancy, and site-level extinction since 1959 with recently developed multi-season staggered-entry models, which relax the within-season closure assumption common to most occupancy models. Optimal timing of surveys in our study areas was approximately March 5 - March 30. Averaged across years, estimated probability of occupancy was 0.58 (SE = 0.09) for historical sites and 0.19 (SE = 0.08) for control sites. Occupancy increased from 2013 through 2019. Notably, even though observer error was trivial, annual detection probabilities varied from 0.23 to 0.75 and declined during the study; this means naïve occupancy values would have been misleading, indicating apparent declines in toad occupancy. Occupancy was lowest during the first year of the study, possibly due to changes in stream flows and conditions in many waterbodies following extended drought and recent wildfires. Although within-season closure was violated by variable calling phenology, simple multi-season models provided nearly identical estimates as staggered-entry models. Surprisingly, extinction probability was unrelated to the number of years since the first or last record at historically occupied sites. Collectively, our results suggest a lack of large, recent declines in occupancy by Arizona Toads in New Mexico, but we still lack population information from most of the species’ range.
Papers & Reports Thermal conditions predict intraspecific variation in senescence rate in frogs and toads
Authors: Hugo Cayuela; Rebecca M McCaffery; Thierry Frétey; Benedikt R Schmidt; Kurt Grossenbacher; Omar Lenzi; Blake R Hossack; Brad A Lambert; Johan Elmberg; J Merilä; J Gippet; David S Pilliod; Erin Muths
Date: 2021-11 | Outlet: PNAS
Variation in temperature is known to influence mortality patterns in ectotherms. Even though a few experimental studies on model organisms have reported a positive relationship between temperature and actuarial senescence (i.e., the increase in mortality risk with age), how variation in climate influences senescence rate across the range of a species is still poorly understood in free-ranging animals. We filled this knowledge gap by investigating the relationships linking senescence rate, adult lifespan, and climatic conditions using long-term, capture-recapture data from multiple amphibian populations. We considered two pairs of related anuran species from the Ranidae (Rana luteiventris, Rana temporaria) and Bufonidae (Anaxyrus boreas, Bufo bufo) families, which diverged more than 100 mya and are broadly distributed in North America and Europe. Senescence rates were positively associated with mean annual temperature in all species. In addition, lifespan was negatively correlated with mean annual temperature in all species except A. boreas. In both R. luteiventris and A. boreas, mean annual precipitation and human environmental footprint both had negligible effects on senescence rates or lifespans. Overall, our findings demonstrate the critical influence of thermal conditions on mortality patterns across anuran species from temperate regions. In the current context of further global temperature increase predicted by IPCC scenarios, a widespread acceleration of aging in amphibians is expected to occur in the decades to come, which might threaten even more seriously the viability of populations and exacerbate global decline.
Papers & Reports Sex-related differences in aging rate are associated with sex chromosome system in amphibians
Authors: Hugo Cayuela; J Lemaître; Jean-Paul Lena; Victor Ronget; Iñigo Martinez-Solano; Erin Muths; David S Pilliod; Jean-Francois Lemaitre
Date: 2021-12 | Outlet: Evolution
Sex-related differences in mortality are widespread in the living world. Although sexual selection and environmental conditions might drive sex-specific variation in lifespan, recent findings suggest that sex chromosome systems are also involved. However, the influence of sex chromosome systems on aging rate (i.e., the rate of increase of mortality with age), a mortality metric that only partially correlates with lifespan, has not been investigated so far, due to an apparent lack of demographic data from clades including both XY (with heterogametic males) and ZW (with heterogametic females) sex-determination systems. Taking advantage of a unique collection of capture-recapture datasets in amphibians, a vertebrate group where XY and ZW systems have repeatedly switched over the past 200 million years we examine whether sex heterogamety can predict sex-differences in aging rates. We show that variation in aging rate only accounts for a moderate proportion of the variation in lifespan, similarly to what has been reported in mammals. Moreover, our results demonstrate that the system of genetic sex-determination has a critical impact on aging rate in clades that include closely related taxa with XY vs. ZW systems. In both systems the heterogametic sex experiences a higher aging rate compared to the homogametic sex. This new finding suggests that exposed recessive deleterious mutations on the X/Z chromosome (the “unguarded X/Z effect”) or repeat-rich Y/W chromosome (the “toxic Y/W effect”) could accelerate aging in the heterogametic sex.
Papers & Reports Demography of the Oregon spotted frog along a hydrologically modified river
Authors: Jennifer C Rowe; Adam Duarte; Chris A Pearl; B McCreary; P K Haggerty; J W Jones; Michael J Adams
Date: 2021-06-21 | Outlet: Ecosphere
Altered flow regimes can contribute to dissociation between life history strategies and environmental conditions, leading to reduced persistence reported for many wildlife populations inhabiting regulated rivers. The Oregon spotted frog (Rana pretiosa) is a threatened species occurring in floodplains, ponds, and wetlands in the Pacific Northwest with a core range in Oregon, USA. All life stages of R. pretiosa are reliant on aquatic habitats, and inundation patterns across the phenological timeline can have implications for population success. We conducted capture-mark-recapture (CMR) sampling of adult and subadult R. pretiosa at three sites along the Deschutes River downstream from two dams that regulate flows. We related the seasonal extent of inundated habitat at each site to monthly survival probabilities using a robust design CMR model. We also developed matrix projection models to simulate population dynamics into the future under current river flows. Monthly survival was strongly associated with the extent and variability of inundated habitat, suggesting some within-season fluctuations at higher water levels could be beneficial. Seasonal survival was lowest in the winter for all three sites, owing to limited water availability and the greater number of months within this season relative to other seasons. Population growth for the two river-connected sites was most strongly linked to adult survival, whereas population growth at the river-disconnected site was most strongly tied to survival in juvenile stages. This research identifies population effects of seasonally limited water and highlights conservation potential of enhancing survival of particularly influential life stages.
Papers & Reports Enhanced between-site biosecurity to minimize herpetofaunal disease-causing pathogen transmission
Authors: Deanna H Olson; K H Haman; M J Gray; Reid N Harris; T Thompson; M Iredale; M Christman; J Williams; Michael J Adams; Jennifer R Ballard
Date: 2021 | Outlet: Herpetological Review
We describe biotic and abiotic factors that interact with field work to contribute to gradients in human-mediated herpetofaunal pathogen transmission (i.e., translocation) risk between sites. Using biotic and abiotic criteria, we identify site conditions that correspond to high risk for pathogen import [to a site] or high risk for pathogen export [from a site] for implementation of enhanced between-site biosecurity procedures to forestall human-mediated pathogen transmission. Our field-site criteria are based on seven contexts of the pathogen (occurrence, habitat), host(s) (occurrence, habitat, species richness), and geography (distance/topography, geopolitical land use) (Table 1). We do not provide an explicit decision tree because site contexts can be complex, and single contexts may be weighted heavily in some biosecurity decisions, warranting case-by-case decisions. A more conceptual decision tree (Fig. 1) about pathogen export or import can be more flexibly applied as site context vary. Our aim is to provide a rapid process to develop a qualitative narrative to support decisions for between-site herpetological disease biosecurity.