Fashion or function? Relaxed selection and stasis are key features of the evolution of stripes, bands and collars in Sceloporus lizards (Squamata: Phrynosomatidae).

This article investigates the evolutionary history and selective pressures shaping three types of black dorsal markings—longitudinal stripes, transverse bands, and collars—on Sceloporus lizards. Using phylogenetic comparative analyses across 59 species, the study finds that longitudinal stripes evolved primarily in small-bodied, terrestrial, egg-laying species and are associated with antipredator functions, especially when sexual selection is weak. Transverse bands evolved more slowly and are linked mainly to arboreal species, likely enhancing camouflage. Collars appear strongly connected to sexual size dimorphism and parity mode, with live-bearing (viviparous) lineages retaining collars over long evolutionary periods, possibly due to hormonal constraints. Overall, the findings highlight that these dorsal patterns have evolved largely independently under different selective regimes involving predator evasion, sexual signaling, and physiological constraints.