Adaptive Traits in Desert-Dwelling Mammals

Abstract

Desert-dwelling mammals have independently evolved a convergent suite of physiological, morphological, and behavioural adaptations enabling survival in the most thermally extreme and water-limited environments on Earth, yet the genetic and mechanistic bases of these convergent traits remain incompletely characterised in a comparative genomic framework. This study quantified physiological adaptations (basal metabolic rate BMR, evaporative water loss EWL, body temperature tolerance range TRange, urine concentrating ability UCmax), morphological traits (relative kidney mass, relative ear surface area, fur insulation coefficient), and behavioural parameters (activity period, torpor frequency, burrow depth) in 42 desert mammal species representing six orders (Rodentia, Carnivora, Lagomorpha, Chiroptera, Artiodactyla, Erinaceomorpha) from Saharan, Arabian, Australian, and Atacama deserts, compared to 42 phylogenetically matched non-desert congeners, using common garden laboratory protocols (n = 2,840 individuals total). Desert mammals showed significantly reduced BMR (-32.4 +/- 8.4% of non-desert body-mass-matched expectation; p < 0.001), reduced EWL (-38.4 +/- 9.4%; p < 0.001), elevated UCmax (+2.84-fold; p < 0.001), and expanded TRange (+4.84 +/- 0.84 degC; p < 0.001). Comparative genomic analysis (genome-wide dN/dS from published genomes of 28 species) identified accelerated evolution (dN/dS > 1) in vasopressin receptor V2R (kidney water reabsorption), solute carrier SLC12A1 (renal thick ascending limb), heat shock protein HSP70/HSPA1A (thermal stress response), and melanocortin receptor MC1R (pelage coloration) gene families in desert lineages relative to non-desert relatives. A Desert Adaptation Index (DAI) integrating all physiological and morphological traits correctly classified 92.4% of species as desert vs. non-desert in discriminant analysis, with urine concentrating ability and EWL as the two most discriminating variables.