Quaternary climate-driven diversification of Alpine grasshoppers in the central Apennines: insights into Mediterranean sky islands as centers of microendemism

Aim Pleistocene climatic oscillations profoundly shaped Mediterranean mountain biotas through recurrent cycles of isolation and connectivity. Yet, despite the Central Apennines being a major centre of local endemism, this region has received limited attention in genomic studies addressing biogeographic processes. Here, we examine how climatically driven distributional shifts have promoted microgeographic diversification and endemism in sky-island systems of this mountain region. Location Central Apennines, Italy. Taxon Italohippus (Orthoptera: Acrididae). Methods We used genome-wide ddRAD-seq data to infer phylogenetic relationships, divergence times, species limits, population structure, demographic history and introgression. Morphological differentiation was quantified using geometric and linear morphometrics of forewings. Past range dynamics and spatial patterns of climatic suitability were reconstructed by projecting species-specific environmental niche models from the Last Glacial Maximum to the present. Results Phylogenomic analyses reveal a Middle–Late Pleistocene diversification of Italohippus structured along a continuum of evolutionary divergence across the Central Apennines. Northern populations, corresponding to the taxon I. modestus, form a distinct allopatric lineage likely originating under geographic isolation and the evolution of partial reproductive barriers. In contrast, populations at the southern rear edge of the genus range, corresponding to I. albicornis, show weak genomic and morphological differentiation from I. monticola, consistent with incipient but incomplete speciation. Paleodistribution models and demographic reconstructions indicate marked latitudinal contrasts in glacial impacts, with higher availability and continuity of climatically suitable habitats and introgression in northern and central sectors and more persistent isolation in the south. Main Conclusions Our results support a biogeographic model of intermittently connected sky-island refugia in the Central Apennines, generating spatially heterogeneous opportunities for divergence and persistence across latitudes. By integrating different sources of data, we show how climatically driven distributional shifts have shaped the emergence and maintenance of geographically structured evolutionary lineages in Mediterranean mountain systems, highlighting key processes underlying the origin and persistence of endemic alpine biodiversity in the face of rapid climate warming