Geographic patterns of behavior and thermal physiology in a widespread lungless salamander, Plethodon cinereus.
I'm broadly interested in thermal adaptations and the ways in which physiological traits affect population viability in the face of emergent threats.
The eastern red-backed salamander (Plethodon cinereus) is the most widely distributed woodland lungless salamander. It occupies more than half of the geographic distribution of the entire genus and lives farther north than any other Plethodon species. This raises two major unanswered questions: How does P. cinereus thrive in such a wide range of temperatures, and does it possess adaptations that will buffer the consequences of climate warming?
I collected salamanders from 13 populations, spanning 10.1° latitude, 12.6° longitude, and 1468.7 m in elevation. Overall, these sites experience a range of 10.99°C in mean annual temperature (BioClim variable BIO1).
Do salamanders maintain body temperatures that maximize performance? For this project, I tested the relationship between thermal optimum for energy assimilation and thermal preference in low-stress (wet) and high-stress (dry) conditions in the lab. To determine whether salamanders exhibit behavioral thermoregulation in natural conditions, I measured the relationship between body temperatures and environmental temperatures in field-active salamanders from populations across an elevation gradient (550 – 1,250 m above sea level).
Manuscript in prep - A. Novarro
How do hormonal responses to temperature vary among populations, and what are the ecological consequences? In this study, we compared the response of a stress hormone (Corticosterone or CORT) to a thermal challenge among four eastern study sites (ME, NY, MD, and VA). We also explored the relationship between CORT release rate and food conversion efficiency (i.e., the efficiency with which salamanders convert food into energy reserves), and whether this relationship is temperature-dependent. To measure CORT release rates, we used a noninvasive waterborne assay method.
Manuscript in prep - A. Novarro, C. Gabor, C. Goff, T. Mezebish, L. Thompson, and K. Grayson
Do thermal sensitivity and thermal limits vary among populations? If so, is variation driven by environmental conditions and/or phylogenetic history? To explore these questions, we compared critical thermal limits (i.e., the highest and lowest temperatures a salamander can tolerate before losing critical motor functions) and energy assimilation (i.e., the amount of ingested energy remaining after egestion) among populations. To determine the drivers of variation in these traits, we ran models to determine the relative importance of environmental temperatures and phylogenetic clade.
Project in progress.
How does population variation in thermal physiology affect our projections of species' responses to climate change? Few attempts have been made to predict Plethodontid responses to climate change, and often ignore the potential buffering capacity of population-level variation in physiological traits. Our goal is to use bioenergetic models to identify populations or clades of greatest concern.
Project in progress; Photo credit: NOAA, 2015