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Consumers employ a variety of foraging strategies, and oftentimes the foraging strategy employed is related to resource availability. As consumers acquire resources, they may interact with their resource base in mutualistic or antagonistic ways—falling along a mutualism‐antagonism continuum—with implications for ecological processes such as seed dispersal. However, patterns of resource use vary temporally, and textbook herbivores may switch foraging tactics to become more frugivorous in periods of greater fleshy fruit availability. In this study, we investigated how fleshy fruit consumption of a generalist herbivore—the gopher tortoise (Gopherus polyphemus)—shifts intra‐annually following seasonal precipitation and subsequently examined how this shift toward increased frugivory influences the suite of plant syndromes dispersed. We noted a clear intra‐annual shift toward a more frugivorous diet which coincided with seasonal precipitation and subsequently observed a marked shift in the plant syndromes dispersed with increasing frugivory. We found that as this generalist herbivore became more frugivorous, it dispersed a greater variety of plant syndromes at low levels of frugivory. However, when the gopher tortoise exhibited high levels of frugivory, the seed load was dominated by those exhibiting the endozoochory syndrome. This study illustrates a functional shift in a seed‐dispersing herbivore toward that of a classical frugivore, suggesting that temporal variation in foraging strategy and the temporal scale in which foraging habits and seed dispersal interactions are quantified have implications for the suite of plant syndromes species disperse. Furthermore, trade‐offs may exist that provide plants with the endozoochory syndrome with a competitive advantage over seeds with contrasting traits, such as the foliage is the fruit syndrome which is expected to experience greater dispersal by classical herbivores. [ABSTRACT FROM AUTHOR]

Globally, vector‐borne diseases are increasing in distribution and frequency, affecting humans, domestic animals, and wildlife. Science‐based management and prevention of these diseases requires a sound understanding of the distribution and environmental requirements of the vectors and hosts involved in disease transmission. Integrated Species Distribution Models (ISDM) account for diverse data types through hierarchical modeling and represent a significant advancement in species distribution modeling. We assessed the distribution of the soft tick subspecies Ornithodoros turicata americanus. This tick species is a potential vector of African swine fever virus (ASFV), a pathogen responsible for an ongoing global epizootic that threatens agroindustry worldwide. Given the novelty of this method, we compared the results to a conventional Maxent SDM and validated the results through data partitioning. Our input for the model consisted of systematically collected detection data from 591 sampled field sites and 12 historical species records, as well as four variables describing climatic and soil characteristics. We found that a combination of climatic variables describing seasonality and temperature extremes, along with the amount of sand in the soil, determined the predicted intensity of occurrence of this tick species. When projected in geographic space, this distribution model predicted 62% of Florida as suitable habitat for this tick species. The ISDM presented a higher TSS and AUC than the Maxent conventional model, while sensitivity was similar between both models. Our case example shows the utility of ISDMs in disease ecology studies and highlights the broad range of geographic suitability for this important disease vector. These results provide important foundational information to inform future risk assessment work for tick‐borne relapsing fever surveillance and potential ASF introduction and maintenance in the United States. [ABSTRACT FROM AUTHOR]

Human‐mediated animal movement can expose wildlife populations to novel environments. Phenotypic plasticity can buffer against the challenges presented by novel environments, while adaptation to local ecosystems may limit resilience in novel ecosystems. Outbreeding depression during the mixing of disparate gene pools can also reduce reproductive success after long‐distance movement. Here, we use a ‘common‐garden’ population of gopher tortoises (Gopherus polyphemus), translocated from numerous sites across the state of Florida, USA, to a mitigation site in the north‐west (panhandle) region to assess whether geographic origin, outbreeding effects, and behavioral plasticity influence reproductive success in this threatened keystone species. We found that females from north‐east Florida produced clutches with lower hatching success than females from other regions. We detected regional differentiation in nest site selection behavior in the common environment of the translocation site, though these differences did not mediate the regional effect on hatching success. We also found evidence for outbreeding depression: hatching success declined with increasing parental geographic and genetic distances, dropping from 93% to 67% across the range of observed parental genetic distances. Together, these results suggest that newly admixed populations may suffer reproductive costs due to historical population differentiation, and that undetected outbreeding depression could significantly hamper conservation efforts for this species and others undergoing a variety of human‐mediated movements. [ABSTRACT FROM AUTHOR]

ABSTRACT Globally, vector‐borne diseases are increasing in distribution and frequency, affecting humans, domestic animals, and wildlife. Science‐based management and prevention of these diseases requires a sound understanding of the distribution and environmental requirements of the vectors and hosts involved in disease transmission. Integrated Species Distribution Models (ISDM) account for diverse data types through hierarchical modeling and represent a significant advancement in species distribution modeling. We assessed the distribution of the soft tick subspecies Ornithodoros turicata americanus. This tick species is a potential vector of African swine fever virus (ASFV), a pathogen responsible for an ongoing global epizootic that threatens agroindustry worldwide. Given the novelty of this method, we compared the results to a conventional Maxent SDM and validated the results through data partitioning. Our input for the model consisted of systematically collected detection data from 591 sampled field sites and 12 historical species records, as well as four variables describing climatic and soil characteristics. We found that a combination of climatic variables describing seasonality and temperature extremes, along with the amount of sand in the soil, determined the predicted intensity of occurrence of this tick species. When projected in geographic space, this distribution model predicted 62% of Florida as suitable habitat for this tick species. The ISDM presented a higher TSS and AUC than the Maxent conventional model, while sensitivity was similar between both models. Our case example shows the utility of ISDMs in disease ecology studies and highlights the broad range of geographic suitability for this important disease vector. These results provide important foundational information to inform future risk assessment work for tick‐borne relapsing fever surveillance and potential ASF introduction and maintenance in the United States.

ABSTRACT Consumers employ a variety of foraging strategies, and oftentimes the foraging strategy employed is related to resource availability. As consumers acquire resources, they may interact with their resource base in mutualistic or antagonistic ways—falling along a mutualism‐antagonism continuum—with implications for ecological processes such as seed dispersal. However, patterns of resource use vary temporally, and textbook herbivores may switch foraging tactics to become more frugivorous in periods of greater fleshy fruit availability. In this study, we investigated how fleshy fruit consumption of a generalist herbivore—the gopher tortoise (Gopherus polyphemus)—shifts intra‐annually following seasonal precipitation and subsequently examined how this shift toward increased frugivory influences the suite of plant syndromes dispersed. We noted a clear intra‐annual shift toward a more frugivorous diet which coincided with seasonal precipitation and subsequently observed a marked shift in the plant syndromes dispersed with increasing frugivory. We found that as this generalist herbivore became more frugivorous, it dispersed a greater variety of plant syndromes at low levels of frugivory. However, when the gopher tortoise exhibited high levels of frugivory, the seed load was dominated by those exhibiting the endozoochory syndrome. This study illustrates a functional shift in a seed‐dispersing herbivore toward that of a classical frugivore, suggesting that temporal variation in foraging strategy and the temporal scale in which foraging habits and seed dispersal interactions are quantified have implications for the suite of plant syndromes species disperse. Furthermore, trade‐offs may exist that provide plants with the endozoochory syndrome with a competitive advantage over seeds with contrasting traits, such as the foliage is the fruit syndrome which is expected to experience greater dispersal by classical herbivores.

Line‐transect distance sampling (LTDS) surveys are commonly used to estimate abundance of animals or objects. In terrestrial LTDS surveys of gopher tortoise (Gopherus polyphemus) burrows, the presence of ground‐level vegetation substantially decreases detection of burrows of all sizes, but no field or analytical methods exist to control for spatially heterogeneous vegetation obstruction as a source of variation in detection. We propose the addition of a simple measurement of ground‐level vegetation that serves as a covariate for the detection function. We present a Bayesian hierarchical model in which covariates burrow width and nearby vegetation height help to account for detection bias and improve precision of estimated density. We investigate the performance of this covariate by simulation and by using real LTDS data collected before and after application of prescribed fire. We collected data in 2018 at the Jones Center at Ichauway in Newton, Georgia, USA. Across all simulations, our model including both covariates produced the most accurate density point estimates of any of the models tested. For our case study, our Bayesian model with vegetation covariates tended to produce similar estimates of density before and after burns. Our study indicates that any level of spatial variation in vegetation obstruction decreases detection of burrows and may lead to underestimation in population size (≤68%) and proportion of individuals with small burrow sizes (≤32%) when not considered during analysis. Our work is extensible to other terrestrial sampling efforts where systematic measurement of a spatially distributed obstructing feature is feasible during the LTDS survey. [ABSTRACT FROM AUTHOR]

Imperiled species face numerous and diverse anthropogenic threats to their persistence, and wildlife managers charged with making conservation decisions benefit from a sound understanding of how populations, species, and ecosystems will respond to future changes in threats to biodiversity. In southeastern North America, the gopher tortoise (Gopherus polyphemus) is a keystone species in upland ecosystems; however, tortoise populations have declined strongly over the last century, and the species is a candidate for increased protection by the United States federal government under the Endangered Species Act (ESA). Here, we sought to support conservation decision making for G. polyphemus by developing a spatially-explicit predictive population model that linked four anthropogenic threats (climate warming, sea-level rise, urbanization, habitat degradation) to demographic vital rates and used the model to estimate future changes in the number of individuals, populations, and metapopulations across the species’ range. Using recent survey data, we projected 457 populations for 80 years into the future under scenarios varying in threat magnitude, management magnitude, and demographic uncertainty. Population projections predicted that the number of individuals, populations, and metapopulations would decline among all simulated scenarios in the next 80 years. Model predictions were more sensitive to variation in adult survival and immigration rates than to variation in threat magnitude. A scenario with decreased habitat management and threat effects from climate warming, sea-level rise, and urbanization predicted geographic variation in persistence probabilities for populations that might result in decreased genetic representation across the species' range. Our results can be used to support conservation listing decisions for the gopher tortoise as part of its federal Species Status Assessment and provide an analytical framework for how to link diverse threats to geographically-varying demographic rates during population viability analyses for wide-ranging imperiled species around the world.

Austwickia (Dermatophilus) chelonae is a filamentous, Gram-positive Actinobacteria in the Dermatophilaceae family. It has caused fatal granulomatous disease in diverse captive reptile species on three continents, but its presence in wild or free-ranging populations was unknown. An adult female gopher tortoise (Gopherus polyphemus) was presented euhydrated, but cachectic and infested with ticks, with two firm, encapsulated masses over the cranioventral neck and right stifle. The tortoise had moderate nonregenerative anemia and evidence of inflammation; plasma biochemistry data was within normal limits. Fine needle aspirate of the neck lesion revealed abundant necrosis and aggregates of cocci. Computed tomography delineated the masses and revealed an additional mass adjacent to the left zygomatic bone. After surgical excision, histology identified chronic granulomas with intralesional filamentous bacteria. Pan-bacterial 16S rRNA PCR and sequencing of the masses identified A. chelonae. Despite treatment with oxytetracycline and ceftazidime, the tortoise deteriorated and was euthanatized. An esophageal lesion consistent with A. chelonae was seen on postmortem examination, although it was determined that the tortoise ultimately succumbed to fungal pneumonia caused by Metarhizium robertsii, an entomopathogenic biotoxin sprayed as insect control. This case reveals A. chelonae is present in free-ranging chelonians in North America. This organism produces a toxin gene similar to diphtheria toxin, one of the most potent known biotoxins, which has not been previously identified outside the genus Corynebacterium. Novel PCR primers were designed for the toxin and rpoB genes, which were amplified and sequenced from two cases and compared with two available genomes. Selection analysis revealed that the toxin gene is under positive selection, which implies it interacts significantly with the immune system, making it a good candidate for immunodiagnostic test development. [ABSTRACT FROM AUTHOR]

In complex terrestrial environments, chemical signals can be the most important sensory modality for locating conspecifics for potential mating opportunities, especially in spatially segregated populations or habitats. Organisms must evolve chemical signals to maximize the efficacy of conveying information, particularly in creating trails or mate-choice cues. Long-distance transmission of chemical signals may be an increasingly important management concern for small and fractured populations or potentially threatened species, such as gopher tortoises in the southeastern U.S. Mental gland secretions have been shown to have pheromonal function in gopher tortoises, suggesting a potential role as trail or marking pheromones, allowing males to track females or other males to find females. In this study, male gopher tortoises were given paired presentations of a negative control (distilled water) with serial dilutions (1:4, 1:20, 1:100, and 1:500) of male mental gland secretions. Male tortoises were able to discern treatment differences up to 1:20 diluted secretions, responding with an array of social behaviors (e.g. for the 1:20 dilution trial, carapace alignment and head bobbing occurred more frequently for the mental gland secretion relative to the control; p < 0.01). Multivariate principal components analysis yielded PC1 (including, approach, carapace alignment, head bobbing, tasting air, sniffing, and doubleback) that differed by treatment (p = 0.0007) and also was higher for the 1:20 diluted presentation relative to the 1:500 diluted presentation (p = 0.04). This study provides insight into gopher tortoise ecology, mate-choice, and the utility of environmentally diluted mental gland secretions in the external environment when seeking mating opportunities. • Male gopher tortoise mental gland secretions have been shown to function as pheromones. • Male tortoises displayed concentration dependent behaviours. • Most social behaviours occurred for the 1/20 dilution, and avoidance behaviors occurred at 1/4 concentration. • Tortoises could not discriminate treatment with more diluted presentations. [ABSTRACT FROM AUTHOR]