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Papers & Reports Range-Wide Population Projections for The Northern Red-Bellied Cooter (Pseudemys rubriventris)
Authors: Jill Fleming; Jennifer F Moore; Hardin J Waddle; Julien A Martin; Evan HC Grant
Date: 2022-09-26 | Outlet: Journal of Herpetology 56:362-369
Northern Red-Bellied Cooters (Pseudemys rubriventris) have a disjunct distribution with a relictual population in southeastern Massachusetts and a larger range across the mid-Atlantic United States. The relictual population is currently listed with protections under the U.S. Endangered Species Act but the status of the population in the remainder of the species' range has not been assessed, and there is concern that it may be at risk of extinction without protection. The U.S. Fish and Wildlife Service requires scientific information of the species' status to inform conservation decisions. There is little empirical information available from P. rubriventris[I/] populations and, furthermore, the majority of what exists comes from the disjunct northern subpopulation. To fill data gaps in the species' life history and reduce geographic bias, we supplement available data from P. rubriventris[I/] with demographic rate estimates from other Pseudemys species to parameterize an age-structured population projection model. Our estimate of mean population growth rate was https://0.987 (0.92–1.04), indicating that P. rubriventris[I/] populations may be in decline. However, there was considerable uncertainty in our results, with 35% of projections resulting in stable or increasing populations. Additional uncertainty about parameter values, geographic variation, and current threats limit the assessment. We discuss the merits and limitations of our population projection modeling (PPM) approach where other analytical methods are precluded by lack of available data.
Papers & Reports Evaluating the effect of expert elicitation techniques on population status assessment in the face of large uncertainty
Authors: Jennifer F Moore; Julien A Martin; Hardin J Waddle; Evan HC Grant; Jill Fleming; Eve Bohnett; Thomas SB Akre; Donald J Brown; M T Jones; Jessica R Meck; Kevin Oxenrider; Anthony Tur; Lisabeth L Willey; Fred Johnson
Date: 2022-03-15 | Outlet: Journal of Environmental Management
We estimated population growth rate of wood turtles using a stage-structured projection matrix. The model was parameterized based on expert elicitation. The aggregation method used affected model estimates. There was evidence of a (possibly rapid) population decline.
Papers & Reports Projecting the remaining habitat for the western spadefoot (Spea hammondii) in heavily urbanized southern California
Authors: Jonathan P Rose; Brian J Halstead; Robert H Packard; Robert N Fisher
Date: 2022-01 | Outlet: Global Ecology and Conservation 33:e01944
Extensive urbanization in coastal southern California has reduced natural habitat in this biodiversity hotspot. To better conserve ecological communities, state and federal agencies, along with local jurisdictions and private stakeholders, developed regional conservation plans for southern California. Although many protected areas exist within this region, the patchwork nature of these protected areas might not provide good coverage for species that require multiple habitat components, such as amphibians with complex life histories. Because of declines in the past century, the status of the western spadefoot (Spea hammondii) in southern California is of concern to state and federal wildlife agencies. Species distribution models (SDMs) can aid in determining
the conservation status of imperiled species by projecting where suitable habitat remains and how much is protected from further development. We built SDMs that integrated site occupancy data from systematic pitfall trapping surveys and presence-only data from biodiversity databases and citizen science platforms to project the current distribution of western spadefoots in southern California. Western spadefoot occurrence was positively related to the cover of grassland or shrub/scrub and the % sand in the soil within a 1000 m buffer, and was negatively related to slope, elevation, and distance to ephemeral streams or vernal pools. Most of the remaining unprotected habitat for western spadefoots is in the southern half of its historical range in western San Diego and Riverside counties. A few large tracts of spadefoot habitat exist on U.S. Department of Defense lands and smaller tracts remain on ecological reserves owned by state and local government agencies. Only small patches of habitat remain in the northern half of this clade’s historical range in Ventura, Orange, Los Angeles, and San Bernardino counties. Existing regional conservation plans provide ostensible spatial coverage of the majority of extant habitat for western spadefoots in southern California, but most of the habitat within the jurisdiction of these plans lacks formal protection, exposing this species to further declines as urbanization continues in the 21st century.
the conservation status of imperiled species by projecting where suitable habitat remains and how much is protected from further development. We built SDMs that integrated site occupancy data from systematic pitfall trapping surveys and presence-only data from biodiversity databases and citizen science platforms to project the current distribution of western spadefoots in southern California. Western spadefoot occurrence was positively related to the cover of grassland or shrub/scrub and the % sand in the soil within a 1000 m buffer, and was negatively related to slope, elevation, and distance to ephemeral streams or vernal pools. Most of the remaining unprotected habitat for western spadefoots is in the southern half of its historical range in western San Diego and Riverside counties. A few large tracts of spadefoot habitat exist on U.S. Department of Defense lands and smaller tracts remain on ecological reserves owned by state and local government agencies. Only small patches of habitat remain in the northern half of this clade’s historical range in Ventura, Orange, Los Angeles, and San Bernardino counties. Existing regional conservation plans provide ostensible spatial coverage of the majority of extant habitat for western spadefoots in southern California, but most of the habitat within the jurisdiction of these plans lacks formal protection, exposing this species to further declines as urbanization continues in the 21st century.
Papers & Reports Late-season movement and habitat use by Oregon spotted frog (Rana pretiosa) in a large reservoir in Oregon, USA
Authors: Christopher A Pearl; Jennifer C Rowe; Brome McCreary; Michael J Adams
Date: 2022-03-04 | Outlet: Journal of Herpetology
Dam-created reservoirs are common landscape features that can provide habitat for amphibians, but their water level fluctuations and nonnative predators can differ markedly from more natural habitats. We compared fall movement and habitat use by the Oregon Spotted Frog (Rana pretiosa) in the reservoir pool with nearby river and pond habitats at Crane Prairie Reservoir in central Oregon, USA. Movement rate of frogs in the river and ponds declined as water temperature cooled. Reservoir frogs moved further than those in the river or ponds, and their movement rate increased as water temperature cooled. Most frog locations across all site types were in aquatic herbaceous vegetation. We did not find shifts in habitat between early and late fall. Increased movement and the lack of habitat shift in our reservoir frogs deeper into fall contrast with R. pretiosa in non-reservoir sites in this study and others. Consistent use of vegetation by reservoir frogs throughout the fall could indicate cover use in presence of fish predators. Our study provides additional detail on the range of habitats used by R. pretiosa in fall and suggests areas for further work to improve survival in constructed sites with abundant fish predators.
Papers & Reports Context-dependent variation in persistence of host populations in the face of disease
Authors: Bennett Hardy; Erin Muths; David N Koons
Date: 2021-12 | Outlet: Journal of Animal Ecology
In Focus: Valenzuela-Sanchez, A., Azat, C., Cunningham, A. A., Delgado, S., Bacigalupe, L. D., Beltrand, J., Serrano, J. M., Sentenac, H., Haddow, N., Toledo, V., Schmidt, B. R., & Cayuela, H. (2022). Interpopulation differences in male reproductive effort drive the population dynamics of a host exposed to an emerging fungal pathogen. Journal of Animal Ecology, XX, XXXX-XXXX. Understanding the nuances of population persistence in the face of a stressor can help predict extinction risk and guide conservation actions. However, the exact mechanisms driving population stability may not always be known. In this paper, Valenzuela-Sanchez et al. (2022) integrate long-term mark-recapture data, focal measurements of reproductive effort, a population matrix model, and inferences on life history variation to reveal differences in demographic response to disease in a susceptible frog species (Rhinoderma darwinii). Valenzuela-Sanchez et al. found that demographic compensation via compensatory recruitment explained the positive population growth rate in their high disease prevalence population whereas the low disease prevalence population did not compensate and thus had decreasing population growth. Compensatory recruitment was likely due to the high probability of males brooding, and the high number of brooded larvae in the high prevalence population compared to low prevalence and disease-free populations. Valenzuela-Sanchez et al. also document faster generation times in the high prevalence population, which may indicate a faster life history that may be contributing to the population’s ability to compensate for reduced survival. Lastly, the authors find a positive relationship between disease prevalence and the number of juveniles in a given population that suggest a possible prevalence threshold when increased reproductive effort may occur. Altogether, their study provides novel support for increased reproductive effort as the pathway for compensatory recruitment leading to increasing population growth despite strong negative effects of disease on adult survival. Their results also caution the overgeneralization of the effects of stressors (e.g., disease) on population dynamics, where context-dependent responses may differ among host populations of a given species.
Papers & Reports Testing whether adrenal steroids mediate phenotypic and physiologic effects of elevated salinity on larval tiger salamanders
Authors: Brian J Tornabene; E J Crespi; Creagh W Breuner; Blake R Hossack
Outlet: Integrative Zoology
Salinity (sodium chloride, NaCl) from anthropogenic sources is a persistent contaminant that negatively affects freshwater taxa. Amphibians can be susceptible to salinity, but some species are innately or adaptively tolerant. Physiological mechanisms mediating tolerance to salinity are still unclear, but changes in osmoregulatory hormones such as corticosterone (CORT) and aldosterone (ALDO) are prime candidates. We exposed larval barred tiger salamanders (Ambystoma mavortium) to environmentally relevant NaCl treatments (<32–4000 mg·L?1) for 24 days to test effects on growth, survival, and waterborne CORT responses. Of those sampled, we also quantified waterborne ALDO from a subset. Using a glucocorticoid antagonist (RU486), we also experimentally suppressed CORT signaling of some larvae to determine if CORT mediates effects of salinity. There were no strong differences in survival among salinity treatments, but salinity reduced dry mass, snout–vent length, and body condition while increasing water content of larvae. High survival and sublethal effects demonstrated that salamanders were physiologically challenged but could tolerate the experimental concentrations. CORT signaling did not attenuate sublethal effects of salinity. Baseline and stress-induced (after an acute stressor, shaking) CORT were not influenced by salinity. ALDO was correlated with baseline CORT, suggesting it could be difficult to decouple the roles of CORT and ALDO. Future studies comparing ALDO and CORT responses of adaptively tolerant and previously unexposed populations could be beneficial to understand the roles of these hormones in tolerance to salinity. Nevertheless, our study enhances our understanding of the roles of corticosteroid hormones in mediating effects of a prominent anthropogenic stressor.
Papers & Reports Effects of salinity and RU486 on waterborne aldosterone and corticosterone of larval northern leopard frog larvae
Authors: Brian 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 Impacts of a Non-indigenous Ecosystem Engineer, the American Beaver (Castor canadensis), in a Biodiversity Hotspot
Authors: Jonathan Q Richmond; Camm C. Swift; Thomas A. Wake; Cheryl S Brehme; Kristine L Preston; Barbara E. Kus; Edward L Ervin; S Tremor; Tritia Matsuda; Robert N Fisher
Date: 2021-11-18 | Outlet: Frontiers in Conservation Science 2:752400
Non-native species having high per capita impacts in invaded communities are those that modulate resource availability and alter disturbance regimes in ways that are biologically incompatible with the native biota. In areas where it has been introduced by humans, American beaver (Castor canadensis) is an iconic example of such species due to its capacity to alter trophic dynamics of entire ecosystems and create new invasional pathways for other non-native species. The species is problematic in several watersheds within the Southern California-Northern Baja California Coast Ecoregion, a recognized hotspot of biodiversity, due to its ability to modify habitat in ways that favor invasive predators and competitors over the region's native species and habitat. Beaver was deliberately introduced across California in the mid-1900s and generally accepted as non-native to the region up to the early 2000s; however, articles promoting the idea that beaver may be a natural resident have gained traction in recent years, due in large part to the species' charismatic nature rather than by presentation of sound evidence. Here, we discuss the problems associated with beaver disturbance and its effects on conserving the region's native fauna and flora. We refute arguments underlying the claim that beaver is native to the region, and review paleontological, zooarchaeological, and historical survey data from renowned field biologists and naturalists over the past ~160 years to show that no evidence exists that beaver arrived by any means other than deliberate human introduction. Managing this ecosystem engineer has potential to reduce the richness and abundance of other non-native species because the novel, engineered habitat now supporting these species would diminish in beaver-occupied watersheds. At the same time, hydrologic functionality would shift toward more natural, ephemeral conditions that favor the regions' native species while suppressing the dominance of the most insidious invaders.
Papers & Reports Site- and individual-level contamination affects infection prevalence of an emerging infectious disease of amphibians
Authors: Kelly L Smalling; Brittany A Mosher; L Iwanowicz; Keith A Loftin; Adam Boehlke; C R Muletz; N Cortes-Rodriguez; R Femmer; Evan HC Grant
Date: 2022-01-09 | Outlet: Environmental Toxicology and Chemistry
Emerging infectious disease outbreaks are one of multiple stressors responsible for amphibian declines globally. In the northeastern United States, ranaviral diseases are prevalent in amphibians and other ectothermic species, but there is still uncertainty as to whether their presence is leading to population level effects. Further, there is also uncertainty surrounding the potential interactions among disease infection prevalence in free-ranging animals and habitat degradation (co-occurrence of chemical stressors). The current study was designed to provide field-based estimates of the relationship between amphibian disease and chemical stressors. We visited 40 wetlands across three protected areas, estimated the prevalence of ranavirus among populations of larval wood frogs and spotted salamanders, and assessed chemical and biological stressors in wetland habitats and larval amphibians using a suite of selected bioassays, screening tools and chemical analyses. Estimated ranavirus occupancy varied among the three protected areas and ranged from https://0.27 to https://0.55 with considerable variation within protected area. Of the stressors evaluated, ranavirus prevalence was strongly and positively related to concentrations of metalloestrogens (metals with the potential to bind to estrogen receptors) and total metals in wetland sediments and weakly and negatively related to total pesticide concentrations in larval amphibians. These results can be used by land managers to refine habitat assessments to include such environmental factors with the potential to influence disease susceptibility.
Papers & Reports Geographic variation and thermal plasticity shape salamander metabolic rates under current and future climates
Authors: David J Muñoz; David AW Miller; R Schilder; Evan HC Grant
Date: 2022-01-15 | Outlet: Ecology and Evolution
Predicted changes in global temperature are expected to increase extinction risk for ectotherms, primarily through increased metabolic rates. Higher metabolic rates generate increased maintenance energy costs which are a major component of energy budgets. Organisms often employ plastic or evolutionary (e.g. local adaptation) mechanisms to optimize metabolic rate with respect to their environment. We examined relationships between temperature and standard metabolic rate across four populations of a widespread amphibian species to determine if populations vary in metabolic response and if their metabolic rates are plastic to seasonal thermal cues. Populations from warmer climates lowered metabolic rates when acclimating to summer temperatures as compared to spring temperatures. This may act as an energy saving mechanism during the warmest time of the year. No such plasticity was evident in populations from cooler climates. Both juvenile and adult salamanders exhibited metabolic plasticity. Although some populations responded to historic climate thermal cues, no populations showed plastic metabolic rate responses to future climate temperatures, indicating there are constraints on plastic responses. We postulate that impacts of warming will likely impact the energy budgets of salamanders, potentially affecting key demographic rates, such as individual growth and investment in reproduction.
Papers & Reports Multi-scale patterns in occurrence of an ephemeral pool-breeding amphibian
Authors: Brian J Halstead; Jonathan P Rose; D R Clark; Patrick M Kleeman; Robert N Fisher
Date: 2022-03 | Outlet: Ecosphere
Species distributions are governed by processes occurring at multiple spatial scales. For species with complex life cycles, the needs of all life stages must be met within the dispersal limitations of the species. Multi-scale processes can be particularly important for these species, where small-scale patterns in specific habitat components can affect the distribution of one life stage, whereas large-scale patterns in land cover might better explain the distribution of other life stages. Using a conditional multi-scale model, we evaluated which aspects of the landscape and local environment are most strongly related to occupancy patterns of western spadefoots (Spea hammondii). In northern and central California, the proportion of grassland land cover within 2 km of a site was positively related to the occurrence of the northern clade of the western spadefoot. At the pond scale, we found that western spadefoots were more likely to breed in pools with lower pH. Our results indicate that protecting remaining grasslands for adult spadefoots and ensuring multiple pools with diverse characteristics and hydroperiods so at least some pools result in successful breeding will likely be necessary to conserve western spadefoots, especially with a changing climate. Considering the processes that affect species distributions at multiple life stages and spatial scales is an essential component of effective conservation.
Papers & Reports Increased growth rates of stream salamanders following forest harvesting
Authors: J C Guzy; Brian J Halstead; Kelly M Halloran; Jessica A Homyak; J D Willson
Date: 2021-10-24 | Outlet: Ecology and Evolution
Timber harvesting can influence headwater streams by altering stream productiv-ity, with cascading effects on the food web and predators within, including stream salamanders. Although studies have examined shifts in salamander occupancy or abundance following timber harvest, few examine sublethal effects such as changes in growth and demography. To examine the effect of upland harvesting on growth of the stream- associated Ouachita dusky salamander (Desmognathus brimleyorum), we used capture– mark– recapture over three years at three headwater streams embed-ded in intensely managed pine forests in west- central Arkansas. The pine stands sur-rounding two of the streams were harvested, with retention of a 14- and 21- m- wide forested stream buffer on each side of the stream, whereas the third stream was an unharvested control. At the two treatment sites, measurements of newly metamorphosed salamanders were on average 4.0 and 5.7 mm larger post- harvest compared with pre-harvest. We next assessed the influence of timber harvest on growth of post- metamorphic salamanders with a hierarchical von Bertalanffy growth model that included an effect of harvest on growth rate. Using measurements from 839 individual D. brimleyorum recaptured between 1 and 6 times (total captures, n = 1229), we found growth rates to be 40% higher post-harvest. Our study is among the first to examine responses of individual stream salamanders to timber harvesting, and we discuss mechanisms that may be responsible for observed shifts in growth. Our results suggest timber harvest that includes retention of a riparian buffer (i.e., stream-side management zone) may have short-term positive effects on juvenile stream salamander growth, potentially offsetting negative sublethal effects associated with harvest.
Papers & Reports Responses of migratory amphibians to barrier fencing inform the spacing of road underpasses: a case study with California tiger salamanders (Ambystoma californiense) in Stanford, CA, USA
Authors: Cheryl S Brehme; J Tracey; Brittany Ewing; Michael Hobbs; A E Launer; Tritia Matsuda; Esther M. Cole Adelsheim; Robert N Fisher
Date: 2021-11 | Outlet: Global Ecology and Conservation 31:e01857
Migratory amphibians are at high risk of negative impacts when roads intersect their upland and breeding habitats. Road mortality can reduce population abundance, survivorship, breeding, recruitment, and probability of long-term persistence. Increasingly, environmental planners recommend installation of under-road tunnels with barrier fencing to reduce mortality and direct amphibians towards the passages. Often, the permeability of these barrier and passage systems to amphibian population movements are unknown. We studied the movements of California tiger salamanders (CTS: Ambystoma californiense) in relation to solid and mesh barrier fencing attached to a 3-tunnel system between upland and breeding habitats in Stanford, California. We deployed active-trigger cameras along the fencing, used pattern recognition software to identify individuals by their unique spot patterns, and calculated individual salamander movement distances, speed, direction changes, and “success” at reaching the tunnel system. We found that migrating adult CTS moved an average of 40 m along barrier fencing before turning back into the habitat or “giving-up”. This short distance, in comparison to long migratory movements, may be explained by the orientation mechanisms salamanders use to reach their breeding sites. The probability CTS found a passage decreased rapidly with increasing distance from the tunnel system, particularly if individuals turned the “wrong” way after encountering the fence. Salamanders changed directions more often and spent more time along mesh fencing. Our results suggest that a maximum of 12.5 m between passages along CTS migration routes should allow approximately 90% of adult salamanders to encounter road crossings. Additionally, use of solid fencing or a visual barrier on mesh fencing may help to lead salamanders to passages most efficiently. These considerations can assist those seeking to design effective road mitigation for CTS and other migratory amphibians.
Papers & Reports Maximizing species distribution model performance when pairing historical occurrences with environmental variable sets of varying persistency
Authors: Jason T Bracken; Amelie Y Davis; Katherine M O'Donnell; William J Barichivich; Susan C Walls; Tereza Jezkova
Date: 2022-03-09 | Outlet: Ecosphere
Occurrence data used to build species distribution models often include historical records from locations in which the species no longer exists. When these records are paired with contemporary environmental values that no longer represent the conditions the species experienced, the model creates false associations that hurt predictive performance. The extent of mismatching increases with the number of historical occurrences and with inclusion of environmental variables that are prone to change over time. Indeed, the mismatch between occurrence data and contemporaneous environmental variables is a common dilemma when modeling rare or cryptic species, especially those of conservation concern that were once more abundant. Herein, we assess (1) the impact of historical occurrences on model performance across three sets of environmental variables of increasing persistency, and (2) the performance of models built using selected-historical occurrences from locations that showed evidence of limited environmental change over time. Concepts are tested on federally listed flatwoods salamanders, reflecting real-world conservation management efforts. We predicted, that compared to other occurrence sets, that (1) historical occurrences would perform best with environmental variables that were more persistent, (2) recent occurrences would perform best when the environmental variables were more impersistent, and that (3) our selected-historical occurrences would perform best with a combination of persistent and impersistent variables. Our results showed the expected inversion of model performance of recent and historical occurrences across environmental variables of increasing persistency when evaluated by correct predictions. However, the inversion was not seen in AUC performance, in which historical occurrences outperformed recent occurrence models across all variable sets. Selected-historical occurrences did not notably improve performance over all-historical occurrences in any metric or variable set. In order to maximize utility and performance, modelers should acknowledge potential tradeoffs from inclusion of historical occurrences and consider number and age of recent and historical occurrences available, the persistency of environmental variables considered, and how their conservation goals are reflected in model design and evaluation, particularly with respect to sensitivity vs. specificity. Our study lends support for inclusion of historical occurrences, with the potential exception of mostly impersistent variables when sensitivity is the highest priority.
Keywords: extinction debt, flatwoods salamander, historical occurrence data, maximum entropy, model performance, museum records, sensitivity and specificity
Keywords: extinction debt, flatwoods salamander, historical occurrence data, maximum entropy, model performance, museum records, sensitivity and specificity
Papers & Reports Low occurrence of ranavirus in the Prairie Pothole Region of Montana and North Dakota contrasts with prior surveys
Authors: Brian 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 The role of monitoring and research in the Greater Yellowstone Ecosystem in framing our understanding of the response of amphibians to disease
Authors: Erin Muths; Blake R Hossack
Date: 2022-02 | Outlet: Ecological Indicators
Pathogens such as ranaviruses and the novel amphibian chytrid fungus (Bd) are threats to amphibian biodiversity worldwide, including in landscapes that are protected from many anthropogenic stressors. We summarized data from studies in the Greater Yellowstone Ecosystem (GYE), one of the largest and most complete temperate-zone ecosystems on Earth, to assess the current state of knowledge about ranaviruses (2001–2020) and Bd (2000–2020) and provide insight into future threats and conservation strategies. Our comprehension of amphibian disease in the GYE is based on >20 years of monitoring, surveys, population studies, and opportunistic observations of mortality events. Diseases caused by these pathogens affect local species differently, depending on temperature, community structure, and location in the GYE. Bd has not been linked to die-offs but evidence for ongoing negative effects on survival contributes to foundational data on the effects of this pathogen in North America. There is less information on how ranaviruses affect amphibian vital rates, partly because ranaviruses are more difficult to study than Bd, but local mortality events attributed to, or consistent with, disease from ranaviruses are widespread in the GYE. The significance of disease in the long-term persistence of amphibians in the GYE is linked to anticipated changes in climate, especially drought. Other stressors, such as expected increases in visitor use and its associated impacts, are likely to exacerbate the effects of disease. Long-term information from this large, intact landscape helps to frame our understanding of the response of amphibians to disease and provides data that can contribute to management decisions, mitigation strategies, and forecasting efforts.
Papers & Reports Diverse aging rates in ectotherms provide insights for the evolution of aging and longevity
Authors: Beth A Reinke; Hugo Cayuela; Fredric J Janzen; Jean-Francois Lemaitre; Jean-Michel Gaillard; Michelle A Lawing; John B Iverson; Ditte G Christiansen; Iñigo Martinez-Solano; Gregorio Sánchez-Montes; Jorge Gutiérrez-Rodríguez; Francis L Rose; Nicola Nelson; Susan Keall; Alain J Crivelli; Theodoros Nazirides; Annegret Grimm-Seyfarth; Klaus Henle; Emiliano Mori; Gaëtan Guiller; Rebecca Homan; Anthony Olivier; Erin Muths; Blake R Hossack; Xavier Bonnet; David S Pilliod; Marieke Lettink; Tony Whitaker; Benedikt R Schmidt; Michael G Gardner; Marc Cheylan; Francoise Poitevin; Ana Golubovi?; Ljiljana Tomovic; Dragan Arsovski; Richard A Griffiths; Jan W Arntzen; Jean-Pierre Baron; Jean-Francois Le Galliard; Thomas Tully; Luca Luiselli; Massimo Capula; Lorenzo Rugiero; Rebecca M McCaffery; Lisa A Eby; Venetia Briggs-Gonzalez; Frank J Mazzotti; David Pearson; Brad A Lambert; D M Green; Nathalie Jreidini; Claudio Angelini; Graham Pyke; Jean-Marc Thirion; Pierre Joly; Jean-Paul Lena; Tony Tucker; Col Limpus; Pauline Priol; Aurélien Besnard; Pauline Bernard; Kristin Stanford; Richard King; Justin Garwood; Jaime Bosch; Franco Souza; Jaime Bertoluci; Shirley Famelli; Kurt Grossenbacher; Omar Lenzi; Kathleen Matthews; Sylvain Boitaud; Deanna H Olson; Tim Jessop; Graeme Gillespie; Jean Clobert; Murielle Richard; Andrés Valenzuela-Sánchez; Gary M Fellers; Patrick M Kleeman; Brian J Halstead; Evan HC Grant; Phillip G Byrne; Thierry Frétey; Bernard Le Garff; Pauline Levionnois; John C Maerz; Julian Pichenot; Kurtulus Olgun; Nazan Uzum; Aziz Avci; Claude Miaud; Johan Elmberg; Gregory P Brown; Richard Shine; Nathan F Bendik; Lisa O'Donnell; Courtney L Davis; Michael J Lannoo; Rochelle M Stiles; Robert M Cox; Aaron M Reedy; Daniel A Warner; Eric Bonnaire; Kristine Grayson; Roberto Ramos-Targarona; Eyup Baskale; David J Muñoz; John Measey; Andre de Villiers; Will Selman; Anne M Bronikowski; David AW Miller
Date: 2022-06-23 | Outlet: Science
Comparative studies of mortality in the wild are necessary to understand the evolution of aging, yet ectothermic tetrapods are under-represented in this comparative landscape despite their suitability for testing evolutionary hypotheses. We provide the first comprehensive study of aging rates and longevity across tetrapod ectotherms in the wild, utilizing data from 107 populations (77 species) of reptiles and amphibians. We test hypotheses of how thermoregulatory mode, temperature, protective phenotypes, and pace of life contribute to aging. Controlling for phylogeny and body size, ectotherms displayed a higher diversity of aging rates than endotherms, and included many groups with negligible aging. Furthermore, protective phenotypes and life-history tactics further explained macroevolutionary patterns of aging. By including ectothermic tetrapods, our comparative analyses enhance our understanding of aging evolution.