Supplementary Material for: Ecological drivers of dorsal dentate gyrus folding and hemispheric asymmetry in wild Octodon: new insights from Sobrero et al. (2016)

We reanalyzed data from Sobrero et al. (2016) to measure dorsal dentate gyrus (dDG) folding or gyrification in Octodon degus and O. lunatus as a morphological proxy for neurogenesis and macrostructural plasticity in hippocampal or extracortical regions. Using Zilles’ (ZGI) and Vogeley’s (VGI) indices, we quantified dDG gyrification across hemispheres in populations differing in habitat complexity and social behaviour. Left dDG gyrification (ZGIL) showed a preliminary association with social group size, while right dDG gyrification (VGIR) was predicted by population differences. Octodon lunatus from shrub-dense environments exhibited greater dDG folding than O. degus from open habitats, supporting an influence of habitat conditions in shaping hippocampal morphology. Although not statistically significant, hemispheric asymmetries were suggested, a trend consistent with previously reported right-lateralized DG cell numbers in O. lunatus and habitat–sociality effects on DG cell counts in O. degus from El Salitre. Overall, our results support dDG gyrification as an informative marker of neural plasticity shaped by habitat conditions, emphasizing the importance of wild models in brain–ecology research.