Physiological Responses to Elevated Temperature across the Geographic Range of a Terrestrial Salamander

Widespread species often possess physiological mechanisms for coping with thermal heterogeneity, and uncovering these mechanisms provides insight into species responses to climate change. The emergence of non-invasive corticosterone (CORT) assays allows us to rapidly assess physiological responses to environmental change on a large scale. We lack, however, a basic understanding of how temperature affects CORT, and whether temperature and CORT interactively affect performance. Here, we examine the effects of elevated temperature on CORT and whole-organism performance in a terrestrial salamander, Plethodon cinereus, across a latitudinal gradient. Using water-borne hormone assays, we found that raising ambient temperature from 15 to 25°C increased CORT release at a similar rate for salamanders from all sites. However, CORT release rate was higher overall in the warmest, southernmost site. Elevated temperatures also affected physiological performance, but the effects differed among sites. Ingestion rate increased in salamanders from the warmer sites but remained the same for those from cooler sites. Mass gain was reduced for most individuals, though this reduction was more dramatic in salamanders from the cooler sites. We also found a temperature-dependent relationship between CORT and food conversion efficiency (i.e., the amount of mass gained per unit food ingested). CORT was negatively related to food conversion efficiency at 25°C but was unrelated at 15°C. Thus, the energetic gains of elevated ingestion rates may be counteracted by elevated CORT release rates experienced by salamanders in warmer environments. By integrating multiple physiological metrics, we highlight the complex relationships between temperature and individual responses to warming climates

Data from: Salamander climbing behavior varies among species and is correlated with community composition

Species coexistence is often facilitated by behavioral strategies that minimize competition for limited resources. Terrestrial, lungless salamanders (genus Plethodon) coexist in predictable assemblages of body size guilds, but little is known about the behavioral mechanisms that promote such coexistence. Here, we considered the hypothesis that Plethodon salamanders use climbing behavior to reduce competitive interactions, thereby promoting coexistence through spatial partitioning. To explore this hypothesis, we quantified the frequency of climbing behavior at field sites where small-bodied (P. cinereus) and large-bodied (P. glutinosus) species are always present, but an intermediate-bodied species (P. montanus) is either absent, introduced, or native. We observed that climbing behavior varied among size guilds so that the smallest species climbed most frequently, followed by the intermediate, and then the large species. Further, we identified several correlates of climbing behavior that may be shaped by intraspecific and interspecific competition. Climbing frequency was positively correlated with intraspecific competition and negatively correlated with interspecific competition in the small species, unrelated to competition in the intermediate species, and positively correlated with interspecific competition in the large species. Our results suggest that Plethodon size guilds might differentially utilize climbing behavior to facilitate spatial partitioning in dense populations and communities. Further, we show how competition intensity can shape the behavior of cohabitating species, and ultimately provide insight into how behavioral plasticity and microhabitat partitioning can promote species coexistence

Spring migration and breeding distribution of female Ring-necked Ducks wintering in the southern Atlantic Flyway

North American waterfowl conservation, management, and harvest regulation are delegated across administrative flyways and primarily guided by breeding population estimates. The Ring-necked Duck (Aythya collaris) is a late-nesting migratory species that winters and breeds across all of the United States Fish and Wildlife Service administrative flyways. We used satellite telemetry to characterize the spring migration and breeding distribution of 25 female Ring-necked Ducks marked in the southern Atlantic Flyway, USA in the winters of 2017-2018 and 2018-2019. Mean migratory initiation date was 17 March (range: 24 Feb - 5 April) and mean migratory completion date (i.e., arrival to a suspected breeding site) was 16 May (range: 17 April - 27 June), with migratory duration averaging 61.1 days (95% CI: 53.6 - 68.6 days). Total migratory distance averaged 3,409.6 km (95% CI: 2,956.7 - 3,862.6 km). Individuals took, on average, 3.3 stopovers (95% CI: 2.7 - 4.0 stopovers) that lasted an average of 13.5 days (95% CI: 13.3 - 13.8 days). The majority of individuals migrated northwestward and primarily traveled within the Mississippi Flyway prior to reaching Canada. Ten of 25 marked birds migrated through but did not settle in the Prairie Pothole Region (PPR) during the time when the Waterfowl Breeding Population and Habitat Survey (WBPHS) was conducted. Total indicated bird population estimates could be inflated if individuals are counted in multiple WBPHS strata. We also note that 24 of 25 marked birds bred outside of strata comprising the WBPHS eastern survey area, which suggests that more Ring-necked Ducks wintering in the Atlantic Flyway breed outside of the WBPHS eastern survey area than is currently assumed by a scaling parameter incorporated in Atlantic Flyway models used to estimate population size. Individuals from a single wintering site in the southern Atlantic Flyway dispersed widely across two states (USA), five provinces, and one territory (CAN) during the breeding season. Our results support concerns over the efficacy of the WBPHS for Ring-necked Ducks and other late-nesting waterfowl and suggest that the bounds of the scaling parameter incorporated in the Atlantic Flyway multi-stock population model may need to be widened to more accurately account for individuals breeding outside of the Flyway

Physiological measurements in the eastern red-backed salamander - corticosterone release rate and thermal performance

Data was collected in the laboratory using field-collected salamanders (Plethodon cinereus) from 4 study sites in ME, NY, MD, and VA. The file was created using Microsoft Excel. The column headings are as follows: experiment (indicates which of the physiological studies the data corresponds to); site code (indicates the state of origin); site name (specifies the collection site); site heat value (refers to the mean daily maximum temperature at the collection site as explained in the associated manuscript); salamander ID (a unique code given to each study animal); experimental temp (15 or 25°C as explained in the associated manuscript); sex (m or f); svl (snout-vent length measured to posterior edge of cloaca); tail length (measured from posterior edge of cloaca); total length (svl + tail length); mass (refers to the mass recorded at the time of corticosterone sampling); corticosterone release rate (see associated manuscript for methodology); performance initial mass (refers to the mass recorded at the start of each thermal performance trial); performance final mass (refers to the mass at the end of each performance trial); days between mass (refers to the number of days that passed between initial and final mass events); performance (% change in mass/day); ingestion (total number of flies consumed/day during performance trial)

Data from: Physiological responses to elevated temperature across the geographic range of a terrestrial salamander

Widespread species often possess physiological mechanisms for coping with thermal heterogeneity, and uncovering these mechanisms provides insight into species responses to climate change. The emergence of non-invasive corticosterone (CORT) assays allows us to rapidly assess physiological responses to environmental change on a large scale. We lack, however, a basic understanding of how temperature affects CORT, and whether temperature and CORT interactively affect performance. Here, we examine the effects of elevated temperature on CORT and whole-organism performance in a terrestrial salamander, Plethodon cinereus, across a latitudinal gradient. Using water-borne hormone assays, we found that raising ambient temperature from 15 to 25&[deg]C increased CORT release at a similar rate for salamanders from all sites. However, CORT release rate was higher overall in the warmest, southernmost site. Elevated temperatures also affected physiological performance, but the effects differed among sites. Ingestion rate increased in salamanders from the warmer sites but remained the same for those from cooler sites. Mass gain was reduced for most individuals, though this reduction was more dramatic in salamanders from the cooler sites. We also found a temperature-dependent relationship between CORT and food conversion efficiency (i.e., the amount of mass gained per unit food ingested). CORT was negatively related to food conversion efficiency at 25&[deg]C but was unrelated at 15&[deg]C. Thus, the energetic gains of elevated ingestion rates may be counteracted by elevated CORT release rates experienced by salamanders in warmer environments. By integrating multiple physiological metrics, we highlight the complex relationships between temperature and individual responses to warming climates