Macroevolution of desiccation-related morphology in plethodontid salamanders as inferred from a novel surface area to volume ratio estimation approach

Evolutionary biologists have long been interested in the macroevolutionary consequences of various selection pressures, yet physiological responses to selection across deep time are not well understood. In this paper, we investigate how a physiologically-relevant morphological trait, surface area to volume ratio (SA:V) of lungless salamanders, has evolved across broad regional and climatic variation. SA:V directly impacts an organisms’ ability to retain water, leading to the expectation that smaller SA:Vs would be advantageous in arid, water-limited environments. To explore the macroevolutionary patterns of SA:V, we first develop an accurate method for estimating SA:V from linear measurements. Next, we investigate the macroevolutionary patterns of SA:V across 257 salamander species, revealing that higher SA:Vs phylogenetically correlate with warmer, wetter climates. We also observe higher SA:V disparity and rate of evolution in tropical species, mirrored by higher climatic disparity in ...