Role of Temperature and Water in the Ecology of Lungless Salamanders

Abstract

Water economy and thermal relations of plethodontid salamanders were studied in the laboratory and in the field. Laboratory measurements included behavioral responses in temperature and relative humidity gradients, rates of dehydration and dehydration at various relative humidities and soil—moisture levels, and determination of critical thermal maxima by rapid controlled heating to a definite endpoint. Salamanders were acclimated to a combination of three temperatures and two photoperiods: 5°C, 16 hr of light alternating with 8 hr of darkness (LD 16:8); 5°C, (LD 8:16); 15°C (LD 16:8); 15°C (LD 8:16); 25°C (LD 16:8); and 25°C (LD 8:16). Three series of experiments were conducted on 20 populations representing 14 species. Critical thermal maximum increased with an increase in acclimation temperature indicating that the salamander's heat resistance was readily altered by its previous thermal history. Salamanders selected a definite range of temperatures and did not merely avoid extremes in the thermal gradient. Thermal preferenda were relatively stable for each species and were not significantly affected by either acclimation temperature or photoperiod. Rate of dehydration was dependent upon body size, drying power of the air, and ambient temperature. Interspecific differences in dehydration rates appeared to be related in part to differences in size. Species composed of small individuals lost weight faster than species made up of large individuals. As the vapor pressure deficit increased the dehydration rate increased. Dehydration was more rapid at higher temperatures. Rehydration rate increased as the percentage of weight loss due to dehydration increased and was more rapid at higher temperatures. Salamanders absorbed water from soil when soil—moisture tension was as high as 2.8 atm at 25°C. All species absorbed water from unsaturated soil at similar rates that were dependent upon soil—moisture content. Salamanders in the humidity gradient responded positively to differences in the moisture content of the air, and all but one species were more than 70% successful in selecting the highest relative humidity available in the gradient. Interspecific differences were apparent, but were not always correlated with habitat preferences. Plethodon glutinosus did not show any specific adaptation in its thermal responses or water relations that would account for its widespread distribution in the eastern United States. Plethodon ouachitae and P. caddoensis apparently have survived in the Ouachita Mountains due to favorable microhabitats and their ability to burrow deep beneath talus—covered slopes during hot and dry summers. Surface activity of P. caddoensis is limited in the summer by hot and dry conditions in its microhabitat.

Evidence that climate sets the lower elevation range limit in a high‐elevation endemic salamander

“…While elevation is a major factor in defining distributional patterns of eastern Plethodon , local habitat factors (which may be independent of elevation) also influence patterns of distribution and mediate the outcome of species’ interactions (Jaeger, 1971a; Rissler, Barber, & Wilbur, 2000). Plethodon communities, especially those restricted to high elevations, are expected to be particularly sensitive under current predictions of future climate change (Bernardo & Spotila, 2006; Walls, 2009) because of their thermal and hydric physiologic limits (Spotila, 1972). Both temperature and relative humidity control distribution patterns for salamanders in the genus Plethodon (Bernardo & Spotila, 2006; Kozak & Wiens, 2010), which rely on cutaneous moisture for respiration and whose activity is related to temporal and spatial patterns of cool and moist microhabitats (Feder, 1983).…”

Environmental and Anthropogenic Factors Influencing Salamanders in Riparian Forests: A Review

“…Critical thermal maximum and preferred temperature values are often species-specific and may account for differences in distributions [77,78]. Elevation of stream temperatures could threaten species of torrent salamanders in the Pacific Northwest by causing physiological stress, and extended periods of exposure to warm water may be lethal to some salamanders [65,78].…”

“…For instance, plethodontid salamanders are lungless and rely on cutaneous respiration; to sustain efficient gas exchange, their skin must be kept moist. Therefore, plethodontid salamanders are limited to moist environments and their activity is restricted to periods of high soil moisture [63,77,[104][105][106]. Moisture may furthermore be a factor in the magnitude and timing of annual breeding migrations [69,107].…”

Plant Climbing in the Northern Two-lined Salamander, <em>Eurycea bislineata</em>, in Algonquin Provincial Park, Ontario

“…Lungless salamanders are extremely sensitive to environ mental conditions, such as ambient air temperature and soil moisture (Spotila 1972). When exposed to dry conditions, lungless salamanders rapidly lose water and have a restricted foraging time (Feder and Londos 1984).…”

“…To avoid dry conditions, lungless salamanders seek refuge under cover, where humidity remains consistently high. Typically, lungless salamanders emerge to forage at night or under wet conditions (Spotila 1972).…”