Pleistocene Climate Changes and Lineage Diversification of Sphenarium Grasshoppers (Orthoptera: Pyrgomorphidae)

Pleistocene climatic fluctuations have significantly influenced biotic diversification globally, but their impacts on Neotropical insects remain understudied. Here, we evaluated the predictions of the Glacial and Interglacial Refugia models to investigate the effects of Pleistocene climate changes on four Sphenarium species: S. purpurascens, S. rugosum, S. variabile, and S. zapotecum. We analyzed phylogeographic patterns using a mitochondrial marker and conducted ecological niche and paleodistribution modeling to evaluate niche conservatism and historical distribution dynamics. We found high haplotype diversity (Hd > 0.87) and significant phylogeographic structure (N _ST-G _ST = 0.17-0.37) in all species except S. zapotecum, with non-monophyly and limited haplotype sharing among S. purpurascens, S. variabile, and S. zapotecum. A few populations showed consistent changes in population size over time. Niche analyses rejected niche conservatism among species (overlap scores < 0.20; p ≥ 0.05) and minimal geographic overlap of suitable climatic areas since the Late Pleistocene. Climatic stability areas (i.e., potential refugia) cover less than 20% of the currently known distributions of S. purpurascens, S. zapotecum, and S. rugosum. Our findings suggest that Pleistocene climatic changes drove population divergence in Sphenarium grasshoppers; however, the impacts varied among species, and neither of the refugial models fully explained all patterns. The observed genetic differentiation, niche divergence, and demographic trends suggest recent differentiation, local adaptation, and complex evolutionary histories shaped by geography and climate. This study highlights the intricate interplay between environmental changes and evolutionary processes in shaping Neotropical insect diversity.