Climatic niche conservatism and Pleistocene range dynamics in two Mediterranean Cistus species

Background and aims – Understanding how closely related species diverge is a fundamental issue in evolutionary biogeography, particularly in regions formed by repeated climatic oscillations. We examined the drivers of geographic separation between Cistus albidus and Cistus creticus across the Mediterranean Basin. We tested whether their divergence reflects climatic niche differentiation or historical geographic isolation associated with potential refugial patterns. Material and methods – We combined ensemble species distribution modelling, palaeoclimatic projections, climatic niche analyses in environmental space, and plastid trnL–trnF sequence-based haplotype analysis. Models were calibrated under current climatic conditions and projected to past periods to identify suitable areas and potential refugial patterns. Niche overlap and dynamics were assessed using Schoener’s D, Warren’s I, stability, expansion, and unfilling. Key results – The species showed moderate climatic niche overlap, high niche stability, and little evidence of strong climatic niche divergence. Palaeoclimatic models revealed geographically structured suitable areas, while genetic analyses indicated partial differentiation together with widespread sharing of the dominant haplotype. Overall, the results support a stronger role for geographic history and Pleistocene range dynamics than for climatic niche separation. Conclusion – The divergence between Cistus albidus and Cistus creticus appears to have been shaped primarily by historical geographic isolation and potential refugial patterns rather than by major shifts in climatic niches. This study highlights that Mediterranean plant divergence may proceed under climatic niche conservatism, with historical range changes playing a central role in structuring regional biodiversity.