Phenotypic plasticity under desert environment constraints: mandible variation in the dwarf fat-tailed jerboa, Pygeretmus pumilio (Rodentia: Dipodidae)

Arid areas have a comparatively narrow range of habitat types, with restricted variation in environmental parameters, leaving narrow boundaries for phenotypic variation to correlate with ecological variables. To test this presumption, we explored variation in size and shape of the mandible in the dwarf fat-tailed jerboa Pygeretmus pumilio (Kerr, 1792) under the constraints of a rigorous desert environment. Size varied significantly and predictably with geographic position and demonstrated a strong, non-linear longitudinal pattern. Moreover, size was associated with several other climatic variables, but not with soil properties or with proxies for primary productivity. Our results suggest that, for rodents exposed to rapid and extreme changes, larger size may have multiple advantages, i.e. in maintaining euthermia during cold nights and efficient water metabolism under aridity stress; in accumulating fat reserves for hibernation; and digging deeper burrows, better protected from surface extremes. Shape varied clinally along the longitudinal transect, and the pattern was affected more by temperature than by precipitation. We conclude that the success of dwarf fat-tailed jerboa in occupying an extensive geographic range relies on their ability to meet environmental heterogeneity through cohesive and diverse responses, including physiology, behaviour, life-history traits, and morphological plasticity.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author