Camouflage in arid environments: the case of Sahara-Sahel desert rodents

Ossi Nokelainen,Lekshmi B. Sreelatha,Janne K. Valkonen,Nicholas E. Scott-Samuel,João C. Campos,José Carlos Brito,Zbyszek Boratyński

doi:10.25225/jvb.20007

Ossi Nokelainen, Lekshmi B. Sreelatha + Show 5 more

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https://doi.org/10.25225/jvb.20007

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Abstract

Deserts and semi-deserts, such as the Sahara-Sahel region in North Africa, are exposed environments with restricted vegetation coverage. Due to limited physical surface structures, these open areas provide a promising ecosystem to understand selection for crypsis. Here, we review knowledge on camouflage adaptation in the Sahara-Sahel rodent community, which represents one of the best documented cases of phenotype-environment convergence comprising a marked taxonomic diversity. Through their evolutionary history, several rodent species from the Sahara-Sahel have repeatedly evolved an accurate background matching against visually-guided predators. Top-down selection by predators is therefore assumed to drive the evolution of a generalist, or compromise, camouflage strategy in these rodents. Spanning a large biogeographic extent and surviving repeated climatic shifts, the community faces extreme and heterogeneous selective pressures, allowing formulation of testable ecological hypotheses. Consequently, Sahara-Sahel rodents poses an exceptional system to investigate which adaptations facilitate species persistence in a mosaic of habitats undergoing climatic change. Studies of these widely distributed communities permits general conclusions about the processes driving adaptation and can give insights into how diversity evolves.

Highlights

Deserts and semi-deserts are characteristically open environments with limited vegetation coverage
We focus on North African desert rodents and summarize the current understanding of visual camouflage adaptation in the SaharaSahel rodent community
We outline how desert rodents are a valuable study system to tackle the following open questions, all of which are applicable to desert habitat: 1) How do animals cope with habitat heterogeneity over different spatial scales? 2) How does seasonality determine the evolution of camouflage? 3) How does rodent behaviour dictate the efficacy of anti-predator strategies? 4) How does behavioural and cognitive processing of predators facilitate camouflage efficacy? these questions may apply to other environments and/or study systems, we focus on desert rodents of Sahara-Sahel as a working example

Summary

Introduction

Deserts and semi-deserts are characteristically open environments with limited vegetation coverage. Current methodologies allow detailed insight into wild rodents: 1) phenotypic variation in fur colouration, 2) visual structure of their habitats, 3) individual variation in shyness/boldness and exploratory behaviours, 4) mobility and home range sizes, and 5) targeting inheritance and expression mechanisms of the above traits, allowing a reconstruction of their evolutionary history and testing their adaptive significance. These can be applied to natural populations on individuals in their native habitats. Reconstructed species relatedness is imperative for comparative analyses of coevolution between species’ quantitative traits (Weber & Agrawal 2012, Boratyński 2020), such as mobility, camouflage and habitat use

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