Climate change-driven range contraction in the aquatic Fern Marsilea minuta L. (Marsileaceae): implications for wetland plant conservation.

Due to changes in temperature and precipitation patterns, aquatic and semi-aquatic plant species are seriously threatened by climate change. This study evaluated how Marsilea minuta L., a small aquatic fern found in tropical and subtropical wetlands, would be affected by climate change across geographic regions. Maximum Entropy (MaxEnt) was used to simulate species distributions using 963 spatially filtered occurrence records and five bioclimatic variables (BIO1, BIO2, BIO6, BIO12, and BIO13), selected after a thorough multicollinearity analysis. The BCC-CSM1.1 general circulation model was used to anticipate future climate scenarios for 2050 and 2070 under Representative Concentration Pathways (RCP) 2.6 and 8.5. The model showed outstanding prediction ability (AUC = 0.91, TSS = 0.71). According to current distribution modeling, M. minuta has a limited climatic niche that is focused between 30°N and 30°S, with South Asia, Southeast Asia, and equatorial Africa providing the best habitat. The most significant predictor was found to be the annual mean temperature, which was followed by precipitation variables and the lowest temperature of the coldest month. With net habitat losses ranging from 7.3% under RCP 2.6 (2050) to 17.2% under RCP 8.5 (2070), future predictions showed progressive range contractions across all scenarios. The gains were limited to isolated areas at higher latitudes, whereas habitat losses were concentrated at range edges. According to limiting factor analysis, the minimum temperature of the coldest month limited 28.3% of areas, mostly at higher latitudes, whereas annual precipitation limited dispersion throughout 34.7% of the investigated areas. The Congo Basin and South Asia were found to be possible climate refugia that might sustain stable, favorable conditions in a variety of scenarios. According to response curve analysis, ideal conditions include low diurnal temperature ranges, frost-free winters, high wet-season precipitation surpassing 1200 mm, and an annual mean temperature of 20-25 °C. These findings emphasize M. minuta susceptibility to climate change and the necessity of proactive conservation measures, such as safeguarding recognized refugia. Improvement of wetland connectivity and incorporation of climate factors into more comprehensive wetland management initiatives. Because losses under high-emission scenarios significantly outweighed those under strict mitigation paths, the projected range reductions highlight the crucial relevance of greenhouse gas mitigation in limiting biodiversity consequences.