Differences in skull morphology among rodent species are associated with climate

What is it about?

Desert ecologists are interested in understanding how organisms adapt to aridity. In this study, we tested whether changes in skull and dental morphology in rodents is associated with climate, and aridity in particular. Whats novel about this work is our ability to account for evolutionary relationships among the compared species through the use of recently published phylogenies (evolutionary trees) of various rodent groups. In addition to this, by using various phylogenetic methods, we detected frequent transitions between mesic and desert habitats, with a directional bias toward the mesic-to-desert transition.

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Why is it important?

Many of the pioneering studies that investigate desert adaptation were conducted before the availability of detailed phylogenies, accurate bioclimatic data, and species distribution data, all of which provide context in interspecific comparisons. After correcting for the strong phylogenetic signal, we still find a significant and strong correlation between habitat aridity and specializations associated with auditory sensitivity (auditory bulla inflation) and respiratory water retention (nasal passage elongation) but not in characters associated with dietary specialization (lower incisor shape). No other significant associations were found between habitat or aridity and any other cranial, jaw, or dental traits. Bullar hypertrophy is among the strongest patterns of convergent cranial desert adaptation in rodents and indicates that adaptation plays a similar role in shaping the evolution of this structure in different desert rodent groups.

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