Community science (CS) data can increasingly address a range of interesting questions in herpetology. However, data from unstructured CS projects like iNaturalist are collected in a very different manner than in traditional herpetological surveys, and this could lead to erroneous conclusions about herpetological communities. We compared inferences about species richness, diversity, and the representation of individual species from 71 sites in the United States that had both published herpetological surveys and adequate samples of iNaturalist observations. After adjusting for sample size, we found no significant differences in observed species richness between traditional survey data and iNaturalist data, and we found relatively high correlations between the two data sources in observed species richness across sites. However, the overlap between species lists derived from iNaturalist versus traditional surveys was only moderate, with reptile lists typically having 40–60% shared species and amphibian lists having 50–75% shared species. Furthermore, species diversity, and particularly evenness, differed consistently between the data sources, with observations more evenly spread among species in iNaturalist data as compared to traditional survey data. Likewise, correlations in species counts between the two data sets at individual sites were often low, and correlations in species diversity across sites were much lower than correlations in species richness. With respect to individual species, some species in each taxonomic group were consistently over- and under-represented in iNaturalist data compared to traditional survey data. Over-represented species included Red-backed Salamanders, Fowler's Toads, Eastern Fence Lizards, and Gopher Snakes, whereas under-represented species included White-spotted Slimy Salamanders, Gray Treefrogs, Six-lined Racerunners, Milk Snakes, and Musk Turtles. Overall, our results suggest that unstructured CS data could be useful for estimating species richness at individual sites or for comparing species richness across sites, particularly when sample sizes are high (e.g., hundreds to thousands of observations). However, these data sources should not be used to analyze community structure or diversity, at least without correcting for biases in CS data with respect to how likely different species are to be recorded.
Preserving different habitat types and their connectivity is essential for conserving species that migrate or disperse over heterogeneous habitats. These aspects are poorly understood for fully aquatic, often secretive amphibians, including imperiled Japanese Giant Salamanders (Andrias japonicus). A recent eDNA study found that A. japonicus inhabits small headwater tributaries, which have been overlooked as habitats for giant salamanders in the family Cryptobranchidae because such streams, susceptible to contraction and disconnection, appear too small for large aquatic salamanders. To evaluate the value of headwater tributaries as habitats, I explored the hypothesis that they would serve as suboptimal refugia for smaller adults, especially males, to avoid mate competition in the mainstem. Males compete, often via biting, to establish and guard nesting sites, resulting in injuries such as missing toes and limbs. Analyzing long-term monitoring data from the Ichi River, Hyogo, I tested the predictions: (1) tributary adults would have fewer injuries than the mainstem adults; (2) tributary adults would have poorer body conditions; and (3) the sexual dimorphism in body size would be more pronounced in the mainstem, with males being larger. I found that tributary males were as injury-prone as mainstem males, while tributary females had fewer injuries than mainstem females. Tributary adults were significantly smaller, but body condition and the body-size sexual dimorphism were similar between the two habitats. I also found that relatively large adults migrate between the mainstem and tributaries. These results rejected the hypothesis. Rather than suboptimal refugia, headwater tributaries serve as essential habitats where smaller adults can maintain body conditions comparable to their mainstem counterparts, and males are actively engaged in mate competition. These findings highlight the urgent need to conserve habitat connectivity throughout the river system for this species and, potentially, for other cryptobranchids that have suffered severe habitat fragmentation due to dams constructed across their distribution ranges.
Competition for resources in closely related species in coexistence is associated with divergence in behavioral traits, the mechanisms of which are still unclear. Italian (Podarcis siculus) and Dalmatian (Podarcis melisellensis) wall lizards have similar ecological traits and coexist in the Eastern Adriatic; however, P. siculus has invasive potential and is often larger in body size. To understand their mechanisms of coexistence, we investigated exploratory behavior, activity levels, neophilia, neophobia, and morphometrics associated with locomotion in lizards of both sexes and species from three syntopic wild populations (n = 240). Overall, P. siculus was more exploratory, active, and neophilic. Movement was likely not linked to morphology, as only one variable (number of moving segments) was linked with the larger body size of P. siculus. Males of both species were more neophilic and bigger than females in all measured morphological parameters. The reported behavioral differences could explain how these two very similar species share environments in sympatry and provide insight into species-specific traits that could explain P. siculus invasion success.
The amphibian disease chytridiomycosis, caused by the waterborne chytrid fungus, Batrachochytrium dendrobatidis (Bd), has been linked to severe declines in anuran species and populations globally. Tadpoles can carry low-intensity, nonlethal Bd infections and thus could play an important role in maintaining this pathogen within ecosystems by serving as disease reservoirs. However, Bd can be challenging to detect at low levels; therefore, comprehensive, standardized methods are needed to accurately detect and diagnose infections at the tadpole life stage. Although traditional visual techniques are still employed, quantitative polymerase chain reaction (qPCR) assays have become the most common method used to identify and quantify Bd loads by amplifying DNA, and samples are typically analyzed in triplicate. Yet, studies conducting qPCR assays often utilize different sampling techniques, replicate numbers, or diagnostic criteria. This study investigates the importance of conducting triplicate qPCR assays in the detection and diagnosis of low-intensity Bd infections in tadpoles. We evaluated the relationship between Bd loads and the number of wells that test positive and assessed redetection rates by analyzing samples in two separate runs, in which each sample was analyzed in triplicate. We found that most tadpoles harbored low pathogen loads, which were primarily detected in just one out of three replicates and were rarely detected in both runs. Conversely, tadpoles with high pathogen loads yielded three positive wells and were consistently redetected. Next, we compared prevalence outcomes based on whether at least one or at least two positive wells were required for a positive diagnosis and calculated the proportion of samples misclassified as negative when single positive wells were excluded. Our results suggest that all samples yielding one or more positive wells should be considered Bd-positive and that including at least three replicates is necessary to capture low-intensity infections. Using this approach, we identified three potential reservoir species out of the seven species investigated. Bd loads differed significantly among species as well as between early and late development stage tadpoles. We recommend that future field and experimental studies assessing Bd infection in tadpoles apply these criteria to ensure that individuals, species, and life stages with low pathogen burdens are included in disease prevalence assessments.
At high temperate latitudes, extreme winter temperatures and limited shelter availability often drive the evolution of communal denning behaviors in snakes. At low temperate latitudes, less is known regarding the causes and consequences of variable overwintering strategies. Ongoing research on snake populations across eastern North America has highlighted the prevalence of Ophidiomycosis (caused by Ophidiomyces ophiodiicola, Oo), commonly known as “snake fungal disease.” Despite this, little work has investigated how Oo disease dynamics might shape overwintering site selection strategies (e.g., solitary vs. communal) within populations. We studied Timber Rattlesnakes (Crotalus horridus) from middle Georgia to quantify how winter shelter class (rock feature, stream bank, stump hole) and site type (solitary, communal) were related to variation in Oo infection load (derived from quantitative polymerase chain reaction [Cq values] and clinical [lesion] scores). By integrating disease monitoring with longitudinal recording of overwintering duration, winter body mass loss, winter body temperature, and winter activity level, we tested hypotheses regarding the possible energetic costs and benefits of communal and solitary overwintering. The solitary advantage hypothesis predicted that solitary snakes would display reduced spring Oo infection prevalence and severity relative to communal snakes, given reduced conspecific contact and the possibility of environmental Oo reservoirs in communal site soils. The communal advantage hypothesis stated that communal snakes would exhibit greater fall infection loads than solitary snakes, and in turn select communal sites for greater basking opportunities to induce behavioral fever (through safety in numbers and/or more concealed basking opportunities in rock-based microhabitats). We then expected elevated activity and body temperatures among snakes with higher infection loads to carry sublethal costs of greater winter mass loss and shorter overwintering duration. Collectively, results provided mixed support for our hypotheses but generally aligned with the solitary advantage predictions. Communal snakes were observed to more frequently use rock features as winter shelters, while solitary individuals tended to use stump holes. Lesion scores and Oo fungal loads (Cq values) in spring, but not fall, were greater among communal snakes relative to solitary snakes. However, despite variation in fungal load, most snakes tested positive (80/90 samples [89%] with Cq < 33.00). Winter body temperature was positively associated with spring fungal load, which could be a signal of behavioral fever. Interestingly, body mass loss and overwintering duration were not associated with site class, site type, or fungal load measures, indicating that energetic costs of greater infection severity among communal snakes might be cryptic and/or reflected by unmeasured variables that extend across broader timeframes. Because communal snakes did not display higher fall infection loads, the potential driver of communal site selection remains unclear. Ultimately, consideration of additional selective drivers of overwintering behavior, such as kin selection and inclusive fitness benefits, is required to more fully understand the cost-benefit trade-offs that serve to maintain solitary and communal strategies.
