Conservation and Ecology of Reptiles and Amphibians III

Contributed Paper
ROOM: Room 140 – Aztec
SESSION NUMBER: 103
 

1:10PM Impacts of Stream Disturbances on an Appalachian Stream Salamander Assemblage
William Sutton; Michael Osborne; Jeff Bailey; Thomas Pauley
Globally, amphibians are threatened by a variety of stressors, including landscape destruction and landuse change, emerging pathogens, aquatic pollution, and global climate change. Salamanders in the family Plethodontidae represent the only amphibian family where species lack lungs and rely completely on cutaneous respiration. These adaptations increase the vulnerability of these organisms to ecological disturbance, which makes them keen indicators of ecological condition. We evaluated the impacts of stream disturbance on a stream salamander assemblage at 45 streams in West Virginia over a two-year period. We used a combination of transect and quadrat surveys to survey and capture salamanders. We used both multivariate approaches and N-mixture models to evaluate impacts of stream disturbances. We captured 463 adult salamanders and 1,535 larval salamanders representing 9 species throughout the study period. We found that salamanders in the genus Desmognathus had lowest abundance in degraded streams and reached greatest abundance in highest quality streams. The most commonly captured species, which included larval Northern and Southern Two-lined Salamanders (Eurycea bislineata and E. cirrigera), tended to reach greatest abundance at sites with intermediate disturbance levels. A variety of detection-level covariates impacted abundance estimates and included ecoregion of study site, date of survey, and survey technique. Collectively, agricultural and mountaintop-removal mining operations appear to be the greatest threat to salamanders in streams throughout the study region. Our study defines the greatest threats to stream salamanders throughout the state and also provides an additional evaluation of using salamanders as indicators of aquatic biological condition.
1:30PM Connectivity Vs Isolation: A Case Study of Gene Flow in an Imperiled Salamander
Eric Hoffman; Steve A. Johnson; Sarah May; Anna Farmer; Stacey Lance
The Striped Newt (Notophthalmus perstriatus) is endemic to the xeric uplands of southern Georgia and northern Florida. The species has declined throughout its range due to habitat loss and degradation, as well as recent unexplained declines in the western part of its range. Georgia and western clade populations are limited to a few scattered populations, which are separated by large areas of unsuitable habitat. In contrast, Florida’s peninsular populations are more robust and distributed across a number of public properties, which are somewhat interconnected by Florida’s conservation land system. We used 10 polymorphic microsatellite markers to evaluate how contemporary patterns of gene flow and genetic diversity influence population dynamics and effective population size within and among 18 populations found throughout the species range. We sought to determine the degree of gene flow between ponds, properties, and states and to compare the genetic diversity between different populations in order to examine the genetic health and connectivity of populations. Our data indicated that little gene flow occurs between populations. Indeed, STRUCTURE indicated that all 18 populations represented unique genetic units (i.e. k=18), that global FST=0.13, and that there was a strong pattern of isolation-by-distance. Our results provide unique insight into the mechanisms influencing patterns of gene flow among populations of N. perstriatus, which will allow us to better manage this declining, imperiled species.
1:50PM Seasonal Growth Rates and Responses to Increasing Temperature Across Five Red-Backed Salamander Populations
David J. Muñoz; David AW Miller; Chris Sutherland; Evan H. Campbell Grant; Tanya Matlaga
While scientists are increasingly confident in how climate will change over the next century, there is little consensus how most wildlife species will be impacted and how populations might respond. Here we present findings in how individual growth rates of a common woodland amphibian, the red-backed salamander (Plethodon cinereus), is impacted by inter-annual weather conditions. We use four to eight years of mark-recapture data on two Pennsylvania populations, one New York population, one Massachusetts population, and one Maryland population to estimate seasonal growth rates and the impact of temperature on growth rates. We found that salamanders grow similarly on an annual basis, but their peak season of growth varies drastically among populations. Our findings show that some populations may see reduced individual growth rates of 60-75% whereas others show no correlation with temperature. Our study suggests two important findings: 1) species responses are not static, i.e. populations respond differently to warm conditions 2) reduced individual growth rates suggest it will either take longer for salamanders to reach reproductive maturity or salamanders will have to reach reproductive maturity at smaller sizes. Understanding differences in population responses to climate change is the first step in developing effective management techniques. Our findings also suggest that for a common woodland amphibian in the eastern United States, climate will likely threaten population persistence.
2:10PM Searching for a Giant Salamander: Distribution of the Common Mudpuppy in Southeast Ohio Using Environmental DNA
Merri K. Collins; Shawn R. Kuchta
The Common Mudpuppy (Necturus maculosus) is a fully aquatic salamander native to the Midwest. This species is in decline or of conservation concern in many parts of its range. However, there is a lack of research and data on current distribution and the status of populations. Records of mudpuppy presence in Southern Ohio are outdated, collected before 1952, or between 1952 and 1989. As a secretive and nocturnal species, mudpuppies are difficult to locate using traditional field methods. We used environmental DNA (eDNA), a non-invasive biological monitoring tool, alongside traditional field surveys to determine presence or absence of the mudpuppy at ten sites in Southeast Ohio. Eight of these were historic sites where a specimen was recorded between 1952-1989. While we found mudpuppies at only one site using field surveys, we found them in 6 out of 10 stream sites, and 4 out of 8 historic sites, using eDNA. Thus, we established presence in two new sites. We also collected 6 months of water quality data for each site. Using a logistic regression model, maximum water temperature, steam cover, and riparian zone scores derived from a Qualitative Habitat Evaluation Index (QHEI) were found to be correlated with mudpuppy presence. This information provides insight into the current distribution and management for a species of conservation concern in southeastern Ohio.
2:30PM The Use of Species Distribution Models and Environmental DNA to Evaluate the Distribution of the Eastern Hellbender in Tennessee, U.S.A.
Jeronimo Silva; William Sutton; Stephen Spear; Michael Freake
The Eastern Hellbender (Cryptobranchus alleganiensis alleganiensis) is a long-lived, fully-aquatic salamander that inhabits cool, well-oxygenated streams and rivers in the eastern United States. Although once abundant, C. a. alleganiensis populations have experienced major declines across the historical range due to habitat degradation, siltation, aquatic contaminants, and infectious diseases. Tennessee provides some of the best remaining habitat for C. a. alleganiensis throughout the known geographic range. However, standardized state-wide distribution assessments have been limited to known populations, and status of other C. a. alleganiensis populations remains unknown. We used current and historical occurrence data, in combination with landscape and environmental covariates, to create a species-specific predictive habitat model using a species distribution modeling (SDMs) approach. We then used the resulting model to identify remaining functional populations of C. a. alleganiensis and areas of special concern using environmental DNA sampling techniques. We discovered over 15 new C. a. alleganiensis populations across Tennessee that were previously unknown. The overarching goal of this project is to encourage efficient use of time and resources to effectively manage and conserve the few remaining secure, yet declining, hellbender populations throughout the state of Tennessee.
2:50PM Refreshment Break
3:20PM Spatial Use and Survivorship of Translocated Wild-Caught Texas Horned Lizards
Devin R. Erxleben; Kelly J. Mitchell; Jesse M. Meik; Nathan D. Rains; James C. Martin
ABSTRACT The Texas horned lizard (Phrynosoma cornutum), a state threatened species in Texas, appears to be declining throughout much of its distribution. Declines have primarily been attributed to habitat loss, introduction of red imported fire ants (Solenopsis invicta), environmental contaminants, and other factors that merit further study. Due to an overwhelming interest in restoring the lizards, a three-year study was conducted to evaluate the feasibility of reintroducing Texas horned lizards into previously occupied areas with suitable habitat. Lizards were translocated from natural populations in western Texas to the McGillivray and Leona McKie Muse Wildlife Management Area (MWMA) in the Cross Timbers and Prairies of north-central Texas, an ecoregion that has experienced apparent local extirpations of horned lizards. Lizards were translocated following a habitat restoration project to restore a 32.5-ha portion of the MWMA to mid-grass prairie. After a ten-day acclimation period and soft release, horned lizards were radio-tracked to evaluate daily movements, spatial use, sources of mortality, reproduction, and changes in body condition. Daily movement averages (1.16-174.18 m) and total area use of individuals (0.003-6.811 ha) were similar to those recorded for natural populations, with peaks in movement occurring in May and June. Annual survivorship for individuals (1.1-47.2%) was also similar to that reported from natural populations; however, there was a notable decline in survivorship across the three active seasons. Although mortality of translocated lizards was high, body condition remained relatively stable across active seasons, and reproduction occurred each year, indicating that translocation could be a viable option for restoring horned lizard populations to previously occupied parts of their range. KEY WORDS daily movement, horned lizard, Phrynosoma cornutum, reintroduction, spatial use, survivorship, Texas, translocated.
3:40PM Climate and Recruitment in Pond-Breeding Amphibians
Robert Newman
Amphibians are notoriously sensitive to environmental conditions, and no factor is more fundamental to reproductive success of pond breeding species than availability of reliable breeding habitat. In regions where breeding sites depend on precipitation for filling and persistence, metamorph production (recruitment to the terrestrial life stage) is necessarily tied to climate patterns. However, the relationship between precipitation, reproductive activity, and metamorph production can be complex, and dependent on pattern of precipitation at a number of temporal scales and interactive effects with other factors, including temperature, biotic factors such as disease, and abiotic factors such as changes in water chemistry. Detecting a signature of climate is facilitated by observation of the mechanisms over long-term field studies. I report here on two such studies, one on a desert system driven largely by daily rainfall patterns that varied from year-to-year, and the other a northern prairie wetland system in which seasonal snowfall, precipitation, and daily temperature patterns were key determinants of recruitment. In the desert system, daily rainfall frequency was at least as important a factor as seasonal total precipitation, and was also evident at broad geographic scales as large weather systems were the source of much of the precipitation. In the prairie system, seasonal snowfall and precipitation history drove wetland fluctuations and strongly influenced breeding site availability, but within-season temperature patterns were important in determining the success of breeding attempts, either directly through egg mortality (freezing events) or in association with a disease outbreak. Climate variables played both direct roles and also had indirect effects acting through other mechanisms, challenging our ability to predict impacts of climate simply from climatological data.
4:00PM Habitat Suitability for the Eastern Massasauga Rattlesnake throughout Southern Michigan
Stephanie A. Shaffer
The eastern massasauga rattlesnake (Sistrurus catenatus catenatus) is a federally threatened species ranging throughout the Great Lakes region. Conservation concerns for the species relate to habitat degradation, fragmentation, and availability of suitable areas; as such, a goal of this research was to quantify habitat suitability for the massasauga across southern Michigan using the Bailey (2010) habitat suitability index (HSI) model. During spring and summer of 2015 and 2016 we sampled 27-20-ha sites throughout southern Michigan. Site selection was based on historically confirmed or current presence of massasaugas using element occurrence data within the past 20 years. General suitability was initially assessed using aerial imagery and cover types from the National Land Cover Database to preliminarily identify sites ranging from low, medium, to high suitability. This process was based on per-site availability of herbaceous upland, wetland, and early successional vegetation types. Subsequently, we measured vegetation at all 27 sites following methods described in the HSI model. In both years measurements were taken at 10 to 12 randomly selected locations within each site. We quantified percent live herbaceous cover (optimal suitability ranging from 60-100%), percent dead herbaceous cover (51.5-96%), stem density of trees and shrubs &gt 3 m (0-58 per ha), absolute dominance of trees and shrubs &gt 3 m (0-12.1 m2/ha), percent area of early deciduous upland (0-57%), and percent area of early deciduous wetland (23-73%) per site. To validate the model, the suitability rankings were related to metrics of fitness for the species at each site including reproductive rates, occupancy, and home range size. We present this method for quantifying habitat suitability for the eastern massasauga rattlesnake, illustrating the use of the HSI model as a tool to inform habitat management decisions based on vegetation characteristics which are relevant to the species’ ecology.
4:20PM Comparison of Road Surveys and Circuit Theory to Predict Hotspot Locations for Implementing Road-Effect Mitigation
Sean P. Boyle; Jacqueline D. Litzgus; David Lesbarrères
The mitigation of road effects on wildlife, especially road mortality and habitat fragmentation, has become increasingly common in the last 20 years. However, exclusion fencing and habitat connectivity structures can be very costly and several questions remain regarding how to best determine locations that will optimize mitigation success. Based on data collected across several years and across multiple landscapes and taxa, we present a comparative analysis of two methods: road surveys and circuit theory, and review their benefits and challenges to better inform decision making. Road surveys were completed in two locations over three years for large mammals and herpetofauna to identify road crossing hotspots. Circuit theory was also applied to these systems to identify crossing hotspots using habitat resistance models. Hotspot locations generated by each method were compared using binomial tests and the number and width of hotspots were compared using Wilcoxon Rank-Sum tests. Hotspot distributions were significantly different between methods for herpetofauna, but not for mammals, and road surveys produced a significantly greater number of smaller hotspots as compared to circuit theory models, implying that road surveys provide better hotspot resolution. As circuit model complexity increased, the number and width of hotspots decreased, but became diffuse across the landscape. Road surveys are a better tool for predicting optimal crossing structure location at a local scale; however, circuit theory is less costly, and can be more useful at large scales. As both approaches can offer valuable information, we argue that the combination of these two approaches (at multiple scales if possible) provides a strong basis for managers and biologists to make informed decisions about costly mitigation measures, to optimize both conservation benefits and limited funding.
4:40PM Lethal and Sub-Lethal Effects of Predators on Pathogen Transmission and Trophic Cascades
Lexington K. Eiler; Michael Chislock; Zachary Compton; Turner DeBlieux; Samantha Gallagher; Brian Tornabene; Kelton Verble; Jason T. Hoverman
Predators and pathogens (natural enemies) are fundamental components of ecological communities that have been extensively studied. Although these groups have traditionally been examined in isolation, they have the potential to influence each other within the community via their interactions with hosts or prey. We investigated the interactive effects of predatory dragonflies (Anax juniens) and a viral pathogen, ranavirus, on larval gray tree frogs (Hyla versicolor) and northern leopard frogs (Lithobates pipiens) by examining whether caged predators reduced the activity level and contact rates of larvae (thereby reducing ranavirus transmission), whether lethal predators reduced ranavirus transmission by reducing host density and activity, and how natural enemies influence trophic cascades in our system. To accomplish this, we performed a semi-natural mesocosm experiment with a factorial combination of predator and virus treatments. In the presence of caged predators, we observed a 48% reduction in tadpole activity compared to the controls and a subsequent 20% and 54% reduction in infection prevalence in tree frogs and leopard frogs, respectively. These results demonstrate a trait-mediated effect of predators on this host-parasite interaction. We also observed a 70% reduction in tadpole activity in the presence of lethal predators compared to the controls and the survival of both species was reduced by 80% with predators. As a consequence of these behavioral and density changes, infection prevalence was 61% and 89% lower in surviving tree frogs and leopard frogs, respectively. The presence of predators (caged or lethal) and ranavirus resulted in 62-132% greater periphyton biomass, indicating natural enemies caused cascading effects in our system. Collectively, these results demonstrate that the presence of multiple natural enemies in a community can initiate trait and density-mediated effects that alter host-parasite interactions and influence the magnitude of trophic cascades.

 

Contributed Paper
Location: Albuquerque Convention Center Date: September 27, 2017 Time: 1:10 pm - 5:00 pm