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36 records · Page 2

Abiotic and biotic factors jointly influence the contact and environmental transmission of a generalist pathogen

The joint influence of abiotic and biotic factors is important for understanding the transmission of generalist pathogens. Abiotic factors such as temperature can directly influence pathogen persistence in the environment and will also affect biotic factors, such as host community composition and abundance. At intermediate spatial scales, the effects of temperature, community composition, and host abundance are expected to contribute to generalist pathogen transmission. We use a simple transmission model to explain and predict how host community composition, host abundance, and environmental pathogen persistence times can independently and jointly influence transmission. Our transmission model clarifies how abiotic and biotic factors can synergistically support the transmission of a pathogen. The empirical data show that high community competence, high abundance, and low temperatures correlate with high levels of transmission of ranavirus in larval amphibian communities. Discrete wetlands inhabited by larval amphibians in the presence of ranavirus provide a compelling case study comprising distinct host communities at a spatial scale anticipated to demonstrate abiotic and biotic influence on transmission. We use these host communities to observe phenomena demonstrated in our theoretical model. These findings emphasize the importance of considering both abiotic and biotic factors, and concomitant direct and indirect mechanisms, in the study of pathogen transmission and should extend to other generalist pathogens with the capacity for environmental transmission.

59 BASIC BIOLOGICAL SCIENCES↗

Divergence in heritable life history traits suggests potential for local adaptation and trade‐offs associated with a coal ash disposal site

Abstract Globally, human activities have resulted in rapid environmental changes that present unique challenges for wildlife. However, investigations of local adaptation in response to simultaneous exposure to multiple anthropogenic selection pressures are rare and often generate conflicting results. We used an in situ reciprocal transplant design within a quantitative genetic framework to examine how adaptive evolution and phenotypic plasticity contribute to the persistence of an amphibian population inhabiting an environment characterized by high levels of multiple toxic trace elements. We found evidence of phenotypic divergence that is largely consistent with local adaptation to an environment contaminated with multiple chemical stressors, tied to potential trade‐offs in the absence of contaminants. Specifically, the population derived from the contaminated environment had a reduced risk of mortality and greater larval growth and in the contaminated environment, relative to offspring from the naïve population. Further, while survival in the uncontaminated environment was not compromised in offspring from the contaminant‐exposed population, they did show delayed development and reduced growth rates over larval development, relative to the naïve population. We found no evidence of reduced additive genetic variation in the contaminant‐exposed population, suggesting long‐term selection in a novel environment has not reduced the evolutionary potential of that population. We also saw little evidence that past selection in the ASH environment had reduced trait plasticity in the resident population. Maternal effects were prominent in early development, but we did not detect any trends suggesting these effects were associated with the maternal transfer of toxic trace elements. Our results demonstrate the potential for adaptation to multiple contaminants in a wild amphibian population, which may have facilitated long‐term persistence in a heavily impacted environment.

59 BASIC BIOLOGICAL SCIENCES↗

Spatial Replication Is Important for Developing Landscape Genetic Inferences for a Wetland Salamander

Habitat fragmentation is a pressing threat to wildlife populations, and maintenance of gene flow between populations is an essential goal of conservation. Resistance surfaces have emerged as an important tool for modelling connectivity and developing management strategies to mitigate effects of habitat fragmentation. However, recent studies have noted inconsistencies in the factors most strongly associated with connectivity across different landscapes. Thus, replication of genetic-based resistance surface optimisation across landscapes may be necessary for making robust conclusions about the influence of environmental variables. Accordingly, replication represents a substantive challenge and opportunity in the field of landscape genetics. In this study, we conducted replicated landscape genetic analyses across five landscapes in Tennessee and Kentucky for a threatened wetland amphibian, the four-toed salamander (Hemidactylium scutatum). We tested multiple hypotheses of how different landscape features that could directly affect small, desiccation-intolerant amphibians (e.g., canopy cover) influenced gene flow and assessed the appropriate scale at which to model different features. We found some concordance in the landscape features that influenced gene flow (e.g., a common importance of forest cover and topography), but also some differences—potentially owing to the difference in variability of predictors across landscapes. We also found discordance in the scale of effect of different features across landscapes. In conclusion, our work emphasises that flat areas of moist forest not bisected by roads may be important for H. scutatum conservation, and our replicated design allows us to identify relationships that would have been missed if only using one study site.

59 BASIC BIOLOGICAL SCIENCES↗

Development and Validation of a Scoring System for Abnormalities in the Gopher Frog (Rana capito)

Headstarting efforts are thought to be critical in supplementing populations of the at-risk Gopher Frog (Rana capito); however, recent efforts have occasionally resulted in juveniles with developmental abnormalities. In response, we developed a scoring system to collect quantitative data on the presence and severity of these developmental abnormalities. Our objective was to describe and validate the abnormality scoring system so that it can be used by all Gopher Frog headstarting facilities. The scoring system covers five primary conditions encompassing commonly observed abnormalities. Two groups of participants with different levels of prior experience working with Gopher Frogs assigned scores to a set of images presented to them for each condition. We used intra-class correlation coefficients (ICC) to test the scoring system for inter- and intra-rater agreement as well as agreement with the benchmark standard (established by the authors). We found high ICC values for inter-rater agreement, intra-rater agreement, and agreement to the benchmark standard indicating either excellent or good reliability for all five conditions and for all raters when grouped together. These findings support the reliability and validity of the proposed developmental abnormality scoring system. Gopher Frog headstarting facilities can implement this scoring system to assist in tracking the frequency and severity of abnormalities observed in future headstarting efforts. We hope that by creating a reliable scoring system for Gopher Frogs, it can provide an overall framework and serve as a valuable resource to evaluate abnormalities across any amphibian species.

abnormality↗

Advancing wildlife connectivity in land use planning: a case study with four-toed salamanders

Stable habitat connections that wildlife can safely traverse are essential to biodiversity conservation and healthy ecosystems. We developed high-resolution landscape connectivity models to predict resistance to movement by a threatened wetland-obligate amphibian, the four-toed salamander ( Hemidactylium scutatum ), and identified priority management areas on the 13,000-ha Department of Energy Oak Ridge Reservation (ORR) from 2019 to 2022. We developed a resistance surface based on aerial light detection and ranging data (LiDAR), >30 years of field-based mapping of forest, hydrologic, and geologic features, and contemporary population surveys, alongside derived predictors at <1-m resolution. We then modeled predicted movement corridors using a circuit theory-based modeling approach. We worked closely with land management and natural resources personnel to integrate ecological modeling with broader land use priorities, monetary costs, and feasibility. We identified important terrestrial and aquatic areas on ORR and simulated management scenarios to promote stable connections for four-toed salamanders. This approach allowed us to narrow down a list of 438 potential habitat manipulation sites to 10 sites where open-bottomed culverts and buffers could be implemented. This smaller-scale restoration approach produced a similar increase in landscape connectivity while costing <20% of a larger-scale approach based on barrier removal. We successfully identified feasible, cost-effective management strategies that integrated knowledge from a variety of sources. In conclusion, we offer a strategy that permitted integration of wildlife management goals into infrastructure upgrades wherein wildlife was not an initial consideration.

60 APPLIED LIFE SCIENCES↗

Invasive wild pig ( Sus scrofa ) diets on barrier islands in the southeastern United States

BACKGROUND: Biological invasions are a leading cause of reductions in global biodiversity. Islands are particularly sensitive to invasions, which often result in cascading impacts throughout island communities. Wild pigs (Sus scrofa) are globally invasive and pose threats to numerous taxa and ecosystems, particularly for islands where they have contributed to declines of many endemic species. However, the impacts of wild pig diet on the flora and fauna remain understudied in many island systems. RESULTS: We used DNA metabarcoding of wild pig fecal samples to quantify the seasonal diet composition of wild pigs on three barrier islands in the southeastern United States. Wild pigs exhibited a diverse diet dominated by plants, but also including marine and terrestrial animals. The diet composition of plants varied seasonally and between islands. Consumption of invertebrates also changed seasonally, with a shift to coastal invertebrates, particularly crabs, in spring and summer. Vertebrates were found in <10% of samples, but spanned broad taxa including amphibians, fish, mammals, and reptiles. Species consumed by wild pigs indicate that wild pigs use a variety of habitats within barrier islands for foraging, including maritime forests, saltmarshes, and beaches. CONCLUSIONS: An observed shift to beach foraging during sea turtle nesting season suggests wild pigs have potential to hinder nesting success on islands without established management programs. These findings provide insight into the diverse diets of wild pigs on barrier islands and highlight the need for removal of wild pigs from sensitive island ecosystems because of their potential impacts to native plant and animal communities. © 2024 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

60 APPLIED LIFE SCIENCES↗

Remedial effectiveness of a pond biomanipulation: Habitat value and concentrations of polychlorinated biphenyls in fish

The fish and plant communities in a pond contaminated with polychlorinated biphenyls (PCBs) in East Tennessee, USA, were manipulated to reduce ecological and human-health risk associated with exposure to the chemical contaminants. We evaluated the success of the remedial action using a habitat valuation approach, as well as measuring PCB concentrations in fish. Risk reduction objectives included: alter the fish community to favor fish that do not resuspend, bioaccumulate, or biomagnify PCBs; stabilize contaminated sediments to improve water quality; and stabilize shoreline soils and enhance riparian habitat. Fish targeted for removal included gizzard shad, largemouth bass, and nonnative carp. Reduced PCB concentrations in fish have characterized the new bluegill-dominated community, although a weir-overtopping event led to the need for additional removals of gizzard shad and largemouth bass. Sunfish abundance is high, as was intended. Moreover, amphibian and waterbird diversities have increased in the years following biomanipulation, possibly owing to improvements in the riparian zone and increased structural (vegetation) complexity in both the aquatic and terrestrial environment. Thus, the remedial action has improved aspects of habitat value, and PCB concentrations in sunfish have dropped below the remediation level (risk-based target value) for this pond (1 µg/g in fish fillets or 2.3 µg/g in whole body fish).

63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTAN↗

Conserved chromatin and repetitive patterns reveal slow genome evolution in frogs

Frogs are an ecologically diverse and phylogenetically ancient group of anuran amphibians that include important vertebrate cell and developmental model systems, notably the genus Xenopus. Here we report a high-quality reference genome sequence for the western clawed frog, Xenopus tropicalis, along with draft chromosome-scale sequences of three distantly related emerging model frog species, Eleutherodactylus coqui, Engystomops pustulosus, and Hymenochirus boettgeri. Frog chromosomes have remained remarkably stable since the Mesozoic Era, with limited Robertsonian (i.e., arm-preserving) translocations and end-to-end fusions found among the smaller chromosomes. Conservation of synteny includes conservation of centromere locations, marked by centromeric tandem repeats associated with Cenp-a binding surrounded by pericentromeric LINE/L1 elements. This work explores the structure of chromosomes across frogs, using a dense meiotic linkage map for X. tropicalis and chromatin conformation capture (Hi-C) data for all species. Abundant satellite repeats occupy the unusually long (~20 megabase) terminal regions of each chromosome that coincide with high rates of recombination. Both embryonic and differentiated cells show reproducible associations of centromeric chromatin and of telomeres, reflecting a Rabl-like configuration. Our comparative analyses reveal 13 conserved ancestral anuran chromosomes from which contemporary frog genomes were constructed.

59 BASIC BIOLOGICAL SCIENCES↗

Hierarchical biota-level and taxonomic controls on the chemistry of fossil melanosomes revealed using synchrotron X-ray fluorescence

Fossil melanosomes, micron-sized granules rich in melanin in vivo, provide key information for investigations of the original coloration, taxonomy and internal anatomy of fossil vertebrates. Such studies rely, in part, on analysis of the inorganic chemistry of preserved melanosomes and an understanding of melanosome chemical taphonomy. The extent to which the preserved chemistry of fossil melanosomes is biased by biotic and abiotic factors is, however, unknown. Here we report the discovery of hierarchical controls on the inorganic chemistry of melanosomes from fossil vertebrates from nine biotas. The chemical data are dominated by a strong biota-level signal, indicating that the primary taphonomic control is the diagenetic history of the host sediment. This extrinsic control is superimposed by a biological, tissue-level control; tissue-specific chemical variation is most likely to survive in fossils where the inorganic chemistry of preserved melanosomes is distinct from that of the host sediment. Comparative analysis of our data for fossil and modern amphibians reveals that most fossil specimens show tissue-specific melanosome chemistries that differ from those of extant analogues, strongly suggesting alteration of original melanosome chemistry. Collectively, these findings form a predictive tool for the identification of fossil deposits with well-preserved melanosomes amenable to studies of fossil colour and anatomy.

59 BASIC BIOLOGICAL SCIENCES↗

Outsourced hearing in an orb-weaving spider that uses its web as an auditory sensor

Hearing is a fundamental sense of many animals, including all mammals, birds, some reptiles, amphibians, fish, and arthropods. The auditory organs of these animals are extremely diverse in anatomy after hundreds of millions of years of evolution, yet all are made up of cellular tissue and are morphologically part of the bodies of animals. Here, we show that hearing in the orb-weaving spider Larinioides sclopetarius is not constrained by the organism’s body but is extended through outsourcing hearing to its extended phenotype, the proteinaceous, self-manufactured orb web. We find that the wispy, wheel-shaped orb web acts as a hyperacute acoustic antenna to capture the sound-induced air particle movements that approach the maximum physical efficiency better than the acoustic responsivity of all previously known eardrums. By sensing the motion of web threads, the spider remotely detects and localizes the source of an incoming airborne acoustic wave, such as those emitted by approaching prey or predators. By outsourcing its acoustic sensors to its web, the spider is released from body size constraints and permits the araneid spider to increase its sound-sensitive surface area enormously, up to 10,000 times greater than the spider itself. The spider also enables the flexibility to functionally adjust and regularly regenerate its external "eardrum" according to its needs. The outsourcing and supersizing of auditory function in spiders provides unique features for studying extended and regenerative sensing and designing novel acoustic flow detectors for precise fluid dynamic measurement and manipulation.

60 APPLIED LIFE SCIENCES↗

Reassessing Hybrid Vigor or Hybrid Dysfunction Using Physiological Trade-Offs in an Endangered Salamander System

Fitness of interspecific hybrids can be higher or lower than that of their parental genotypes, with major ramifications for evolution and conservation. A recent study found that hybrid tiger salamanders had higher metabolic rates than their parental forms. Specifically, the ratio of resting metabolic rate to water loss, which was used as a measure of performance, was greater in hybrids. Recent genetic research showed that over half of the experimental subjects in that study were genetically pure California tiger salamanders (Ambystoma californiense) misclassified as hybrids. We reanalyzed the data using the corrected identification of hybrids and parentals. As expected, updating the classification revealed even stronger evidence for differences between hybrids and parentals. Hybrids had higher resting metabolic rates and greater water loss than parentals. The ratio of resting metabolic rate to water loss was also higher in hybrids. However, we suggest that this ratio might not be a positive measure of salamander performance. Higher metabolic rate means higher energy expenditure, and higher water loss suggests increased risk of desiccation. Both are major challenges for terrestrial amphibians, especially salamanders, which are hypothesized to be low-energy, low-water-loss specialists. Under this hypothesis, the ratio of energy expenditure to water loss is a ratio of two costs rather than a ratio of benefit to cost. While our analyses corroborate and strengthen the previous statistical results, we suggest that high resting metabolic rate is better interpreted as hybrid dysfunction, not vigor. Here, both hypotheses are speculative, and specific research on the fitness effects of these physiological differences is needed to resolve this important ecological question.

Ambystoma californiense↗

Dynamic zinc fluxes regulate meiotic progression in Caenorhabditis elegans

Abstract Zinc influx and efflux events are essential for meiotic progression in oocytes of several mammalian and amphibian species, but it is less clear whether this evolutionary conservation of zinc signals is also important in late-stage germline development in invertebrates. Using quantitative, single cell elemental mapping methods, we find that Caenorhabditis elegans oocytes undergo significant stage-dependent fluctuations in total zinc content, rising by over sevenfold from Prophase I through the beginning of mitotic divisions in the embryo. Live imaging of the rapid cell cycle progression in C. elegans enables us to follow changes in labile zinc pools across meiosis and mitosis in single embryo. We find a dynamic increase in labile zinc prior to fertilization that then decreases from Anaphase II through pronuclear fusion and relocalizes to the eggshell. Disruption of these zinc fluxes blocks extrusion of the second polar body, leading to a range of mitotic defects. We conclude that spatial temporal zinc fluxes are necessary for meiotic progression in C. elegans and are a conserved feature of germ cell development in a broad cross section of metazoa.

59 BASIC BIOLOGICAL SCIENCES↗

AmeriFlux FLUXNET-1F CA-TPD Ontario - Turkey Point Mature Deciduous

This is the AmeriFlux Management Project (AMP) created FLUXNET-1F version of the carbon flux data for the site CA-TPD Ontario - Turkey Point Mature Deciduous. This is the FLUXNET version of the carbon flux data for the site CA-TPD Ontario - Turkey Point Mature Deciduous produced by applying the standard ONEFlux (1F) software. Site Description - The forest is approximately 90 years old. Naturally regenerated on sandy terrain and abandoned agricultural land. Predominantly hardwood species with a few scattered conifers. Site has been managed (thinned) in the past. It has a high biodiversity with 573 tree and plant species, 102 bird species, 23 mamal species and 22 reptile and amphibian species (SWALSREP Report, 1999). The dominant tree species is white oak (Quercus alba), with other scattered broadleaf Carolinian species including sugar and red maple (Acer saccharum, A. rubrum), American beech (Fagus grandifolia), black and red oak (Q. velutina, Q. rubra) and white ash (Fraxinus americana) . There are also scattered conifers, mostly white and red pine (Pinus strobes, P. resinosa), comprising about 5% of the trees. Average tree height is 25.7 m with a stand density of 504 ± 18 trees per hectare. Average tree diameter at breast height is 22.3 cm and basal area is 0.06 m2 or approximately 29 square meters per hectare.

Arain, M. Altaf↗

Herpetological Survey for the Lawrence Livermore National Laboratory Site 300

Pursuant to Subcontract Number B644180 between ECORP Consulting, Inc. (ECORP) and Lawrence Livermore National Security, LLC. (LLNS) at Lawrence Livermore National Laboratory (LLNL), ECORP conducted focused herpetological surveys at LLNL’s Experimental Test Site (Site 300) during the spring of 2021. The results of these surveys will provide supporting information for a Site-wide Environmental Impact Statement (SWEIS). The herpetological surveys targeted three special-status reptile species including Blainville’s (coast) Horned Lizard (Phrynosoma blainvillii), Northern California Legless Lizard (Anniella pulchra), and San Joaquin Coachwhip (Masticophis flagellum ruddocki) on the approximately 6,800-acre Site 300 in Alameda and San Joaquin counties. Special-status amphibian species were not targets of this survey effort.

54 ENVIRONMENTAL SCIENCES↗

Eurycea lucifuga (Cave Salamander). Diet.

Eurycea lucifuga is a common and widespread facultative inhabitant of caves and springs in the southeastern and central United States (Powell et al. 2016. Peterson Field Guide to Reptiles and Amphibians of Eastern and Central North America. Houghton Mifflin Harcourt, Boston, Massachusetts. 512 pp.). This species is known to feed on a variety of invertebrates, such as snails, crustaceans, beetles, and flies (Peck 1974. Nat. Speleol. Soc. Bull. 36:7–10). Although several millipede species also can serve as prey for E. lucifuga, some are presumably avoided due to the presence of defensive secretions (e.g., Abacionidae, Paradoxosomatidae). Captive feeding trials and field study show that E. lucifuga do not actively prey upon cave-obligate Tetracion millipedes, which produce defensive secretions comprised primarily of the compound p-cresol (Peck and Richardson 1976. Annales de Speleologie 31:175–182). On the other hand, Pseudotremia millipedes, which do not possess chemical defenses, are a significant component of the diet of cave-dwelling E. lucifuga (Peck and Richardson 1976, op. cit.)

59 BASIC BIOLOGICAL SCIENCES↗

NECTURUS MACULOSUS (Common Mudpuppy). NESTING

Common Mudpuppies (Necturus maculosus maculosus) are the most widespread and wellstudied of the Proteidae, ranging from northern Georgia into eastern Canada and west to the Great Plains. Despite this extensive range, most of our knowledge of life history traits for mudpuppies is based on studies occurring in the northern half of its range, specifically the Great Lakes region. Little is known regarding life history traits in the southern portion of its range. In Tennessee, N. maculosus is thought to occur statewide in permanent streams, rivers, and likely in reservoirs and lakes. Literature suggests that parturition and nest-guarding in N. maculosus maculosus occurs in late winter through spring, but there are no published observations to verify this in Tennessee (Pasachnik and Niemiller 2011. In Niemiller and Reynolds [eds.], The Amphibians of Tennessee, pp. 231-233. University of Tennessee Press, Knoxville, Tennessee). Here, we report four observations of N. maculosus maculosus nests that were discovered while conducting snorkel surveys and lifting cover objects opportunistically for aquatic salamanders from 2011 to 2017, and approximate timing of laying in three river tributaries to the Tennessee River.

Nelson, Stephen K.↗

Alkaloids are associated with increased microbial diversity and metabolic function in poison frogs

Shifts in host-associated microbiomes can impact both host and microbes. It is of interest to understand how perturbations, like the introduction of exogenous chemicals, impact microbiomes. In poison frogs (family Dendrobatidae), the skin microbiome is exposed to alkaloids that the frogs sequester for defense. These alkaloids are antimicrobial; however, their effect on the frogs’ skin microbiome is unknown. To test this, we characterized microbial communities from field-collected dendrobatid frogs. Then, we conducted a laboratory experiment to monitor the effect of the alkaloid decahydroquinoline (DHQ) on the microbiome of two frog species with contrasting alkaloid loads in nature. In both datasets, we found that alkaloid-exposed microbiomes were more phylogenetically diverse, with an increase in diversity among rare taxa. Further, to better understand the isolate-specific response to alkaloids, we cultured microbial isolates from poison frog skin and found that many isolates exhibited enhanced growth or were not impacted by the addition of DHQ. To further explore the microbial response to alkaloids, we sequenced the metagenomes from high- and low-alkaloid frogs and observed a greater diversity of genes associated with nitrogen and carbon metabolism in high-alkaloid frogs. From these data, we hypothesized that some strains may metabolize the alkaloids. We used stable isotope tracing coupled to nanoSIMS (nanoscale secondary ion mass spectrometry), which supported the idea that some of these isolates are able to metabolize DHQ. Together, these data suggest that poison frog alkaloids open new niches for skin-associated microbes with specific adaptations, such as alkaloid metabolism, that enable survival in this environment.

59 BASIC BIOLOGICAL SCIENCES↗

Short-term exposure to elevated suspended sediment increases oxygen uptake of gilled larval Eastern Hellbender ( Cryptobranchus alleganiensis ) salamanders

Freshwater ecosystems are increasingly impacted by anthropogenic elevated levels of suspended sediment that may negatively affect aquatic organisms, including salamanders. Although increasing fine sediment in streams has been suggested as a reason for population declines, to date no study has empirically assessed the effect of suspended sediment on gilled larval Eastern Hellbenders (Cryptobranchus alleganiensis (Sonnini de Manoncourt and Latreille, 1801)), a critical life-history stage and a species of conservation concern. We used custom respirometers to elucidate effects of suspended sediments on larval Eastern Hellbender oxygen uptake in trials conducted in situ in Georgia (USA) streams. Mean oxygen uptake increased and was significantly higher in trials when larval salamanders were exposed to suspended sediment (mean = 5.06 mg O 2 /L for 800 mg/L of sediment treatment vs. 2.25 mg O 2 /L for 0.00 mg/L of sediment control). This may indicate elevated physiological stress in response to short-term exposure to suspended sediments. Qualitatively, individuals in both groups exhibited rocking behavior in response to low oxygen (hypoxia), albeit at different frequencies (sediment exposure = 7.6 rocks/min and control = 2.1 rocks/min). Larval salamanders may be able to temporarily compensate for low oxygen through increased rocking behavior when high suspended sediment loads are present, with future respirometry research needed.

hypoxia↗