Spatial variation in water loss predicts terrestrial salamander distribution and population dynamics

Abstract

Many patterns observed in ecology, such as species richness, life history variation, habitat use, and distribution, have physiological underpinnings. For many ectothermic organisms, temperature relationships shape these patterns, but for terrestrial amphibians, water balance may supersede temperature as the most critical physiologically limiting factor. Many amphibian species have little resistance to water loss, which restricts them to moist microhabitats, and may significantly affect foraging, dispersal, and courtship. Using plaster models as surrogates for terrestrial plethodontid salamanders (Plethodon albagula), we measured water loss under ecologically relevant field conditions to estimate the duration of surface activity time across the landscape. Surface activity time was significantly affected by topography, solar exposure, canopy cover, maximum air temperature, and time since rain. Spatially, surface activity times were highest in ravine habitats and lowest on ridges. Surface activity time was a significant predictor of salamander abundance, as well as a predictor of successful recruitment; the probability of a juvenile salamander occupying an area with high surface activity time was two times greater than an area with limited predicted surface activity. Our results suggest that survival, recruitment, or both are demographic processes that are affected by water loss and the ability of salamanders to be surface-active. Results from our study extend our understanding of plethodontid salamander ecology, emphasize the limitations imposed by their unique physiology, and highlight the importance of water loss to spatial population dynamics. These findings are timely for understanding the effects that fluctuating temperature and moisture conditions predicted for future climates will have on plethodontid salamanders.

Microhabitat analyses support relationships between niche breadth and range size when spatial autocorrelation is strong

“…In turn, these effects can have consequences on species ranges (Peterman and Semlitsch 2014). For instance, tolerance to temperature and/or humidity can increase salamanders outdoor activity during warm and dry seasons, thus enhancing the probability of long-term dispersal between mountain massifs, and also allows species persistence in arid areas of the range (Peterman and Semlitsch 2014). Conversely, tolerance to light can increase activity during daytime or nearby the surface, improving foraging performance or facilitating dispersal among subterranean habitats (Lunghi et al 2018, Ficetola et al 2019.…”

Peer Review #2 of "The role of ambient temperature and body mass on body temperature, standard metabolic rate and evaporative water loss in southern African anurans of different habitat specialisation (v0.1)"

“…Specifically, we expect aquatic species to show higher EWL compared to terrestrial and semi-aquatic species, as conditions are buffered in aquatic environments (excluding biotic interactions), which may lead to reduced potential for evolutionary adaptation (Toledo & Jared, 1993). Because of the negative relationship between water loss and activity patters (e.g., Peterman & Semlitsch, 2014), we hypothesise that terrestrialadapted species would show reduced metabolic and water loss rates as an adaptation to terrestrial life (e.g., Wygoda, 1984). Likewise, species with intermediate life-histories (closely associated with water but not living in it), would exhibit an intermediary status.…”

North‐facing slopes and elevation shape asymmetric genetic structure in the range‐restricted salamander Plethodon shenandoah

“…Terrestrial Plethodon salamanders are associated with cool, moist microhabitats in mature, upland forests where temperature and moisture conditions allow for cutaneous respiration and successful foraging of invertebrates. Because Plethodon salamanders are lungless and rely on cutaneous respiration, individuals typically demonstrate avoidance of warmer temperatures and drier substrates (Peterman & Semlitsch, 2014;Riddell & Sears, 2015). Widespread Plethodon such as the red-backed salamander (Plethodon cinereus) have small home ranges (males ~ 50-75 m 2 , females ~ 5-10 m 2 ; Muñoz, Miller, Sutherland, & Grant, 2016), low fecundity, and limited, male-biased dispersal (Liebgold, Brodie, & Cabe, 2011).…”