Life in Deserts: The Genetic Basis of Mammalian Desert Adaptation

Abstract

Deserts are among the harshest environments on Earth. The multiple ages of different deserts and their global distribution provide a unique opportunity to study repeated adaptation at different timescales. Here, we summarize recent genomic research on the genetic mechanisms underlying desert adaptations in mammals. Several studies on different desert mammals show large overlap in functional classes of genes and pathways, consistent with the complexity and variety of phenotypes associated with desert adaptation to water and food scarcity and extreme temperatures. However, studies of desert adaptation are also challenged by a lack of accurate genotype-phenotype-environment maps. We encourage development of systems that facilitate functional analyses, but also acknowledge the need for more studies on a wider variety of desert mammals. Deserts: Natural Laboratories for Studies of AdaptationDeserts (see Glossary) are the driest environments on the planet and cover at least 33% of the land surface on Earth [1]. Although mainly characterized by aridity and water scarcity, deserts also experience daily and annual extreme thermal amplitudes, and intense UV radiation [1]. Deserts have long been seen as natural laboratories for investigating how biological design is challenged by different aspects of the environment, and how organisms have adapted to these challenges [1,2]. They also offer unique opportunities to study convergent evolution at distinct points in time and space, given their well-documented geological age and diverse geographical origins [1,2].

Desert lizard diversity worldwide: Effects of environment, time, and evolutionary rate

“…We first identified Earth's largest arid systems, focusing on those delineated by Olson et al (2001) in the Biome 'Deserts and Xeric Shrublands' (Biome 13). Within this biome, we considered the major regions to be those with a substantial component of arid and hyperarid conditions, that is, with an aridity index (AI) < .2 (Parsons & Abrahams, 1994;Rocha et al, 2021). This delimitation set includes eight main arid systems (Figure 1): Atacama, Australian desert, Central Asian desert, Gobi, Kalahari, North American desert, Persian desert, and Saharo-Arabian desert.…”

“…The simplest hypothesis to explain geographic differences in species diversity relates to the total evolutionary time over which species F I G U R E 1 Desert systems considered in this study. We focused on regions with aridity indices (AI) < .2, which describe systems that are formally 'arid' or 'hyper-arid' but which exclude 'semi-arid' (Parsons & Abrahams, 1994;Rocha et al, 2021). Map in an equal-area Behrmann projection have accumulated in different regions.…”

High-Quality Reference Genome for an Arid-Adapted Mammal, the Banner-Tailed Kangaroo Rat (Dipodomys spectabilis)

“…The imperiled state of many Dipodomys populations, combined with the vast array of occupied habitat types that include arid environments, make species of this genus valuable subjects for studying the impacts of habitat degradation and fragmentation on population genomic patterns and for characterizing the genomic bases of adaptation to extreme environments. Specifically, the latter application may provide a key link between historical studies of Dipodomys kidney morphology ( Schmidt-Nielsen and Schmidt-Nielsen 1952 ; Vimtrup and Schmidt-Nielsen 1952 ) and more recent investigations of gene and protein expression related to osmoregulation in arid conditions (reviewed in Rocha et al 2021 ).…”

Convergent patterns of gene expression and protein evolution associated with adaptation to desert environments in rodents

“…The genetic basis of desert adaptation has been studied independently in a handful of species and individual genes and pathways which may underlie this adaptive phenotype have been identified (Rocha et al 2021). Here, we leverage three phylogenetically independent lineages of rodents that have all converged on a common phenotype, ultra-high urine concentration associated with desert living, to identify shared molecular changes associated with habitat type.…”