Comparative Distribution Projections of Hydrophilic and Xerophytic Invasive Species in Turkey Under CMIP6 Climate Scenarios.

Climate change imposes varying pressures on the potential distribution of invasive alien plant species, depending on their specific ecological strategies and physiological tolerances. In this study, the projected potential ranges within Turkey of the hydrophilic Eichhornia crassipes (water hyacinth) and the markedly xerophytic Solanum elaeagnifolium (silverleaf nightshade) were compared under several CMIP6 climate scenarios: SSP2-4.5, SSP3-7.0 and SSP5-8.5. Species distribution models were produced using an ensemble modelling framework combining Maximum Entropy (MaxEnt), Random Forest (RF) and Boosted Regression Trees (BRT) in the R statistical computing environment, yielding excellent predictive performance for both taxa. Model outputs revealed strongly divergent, indeed opposing, spatial responses between the two species. Rather than persisting stably within its current range, E. crassipes is projected to undergo a severe contraction of its suitable habitat across all emission scenarios, as increasing drought severity and the degradation of wetland habitats progressively outweigh any potential benefit from milder winters, restricting the species to highly fragmented coastal micro-refugia. In contrast, S. elaeagnifolium displays a more complex, non-linear trajectory: an initial, pronounced expansion into the interior agricultural basins of the Aegean hinterland and Southeastern Anatolia through the mid-century, followed by a marked contraction by 2100 as extreme thermal and arid conditions exceed the species' physiological tolerance limits, particularly under the higher emission scenarios. These results demonstrate that climate change does not confer a uniform range-expansion advantage on invasive taxa. Instead, effective management requires dynamic, species-specific strategies-including early warning systems, strict quarantine measures, and spatially explicit, climate-informed risk mapping that account for both the timing and directionality of range shifts.