Resistance of great ramshorn <i>Planorbarius</i> (superspecies) <i>corneus</i> allospecies (Mollusca: Gastropoda: Pulmonata) from the Ukrainian river network to Mn²⁺ ions

Abstract This study examines the impact of Mn 2+ ions at varying concentrations on ecotoxicological and physiological traits of two genetic allospecies of the great ramshorn Planorbarius corneus from distinct geographic zones in Ukraine: the Polissia Forest (Irsha river, Malyn) and the Forest-Steppe (Psel river, Balakliia). The two allospecies show significant differences in their toxicological indices (LC 0 , LC 50 , LC 100 ) and in the duration of intoxication processes, as well as in mean lethal time and lethality under different concentrations of manganese chloride (p ≤ 0.05). The “western” allospecies from the cooler Polissia zone exhibited better survival and higher adaptation to manganese exposure compared to the “eastern” allospecies, which is more vulnerable in the warmer and drier Forest-Steppe region. The survival differences correlate with bioclimatic modeling, which shows significant ecological differentiation between the two allospecies’ niches. This geographic separation of ranges is also evidenced by the spatial divide of the Dnipro River, which separates the “western” and “eastern” allospecies. The study highlights the need for ecological monitoring to protect these mollusks from the escalating impacts of global warming, which are threatening their populations and habitats. The findings suggest that the adaptation of the “western” allospecies to cooler conditions provides a critical insight into survival strategies under environmental stress.