Environmental Suitability Modeling in Conservation of Restinga Flora in the Southeast and South Brazilian: Pleroma hirsutissimum & Pleroma clavatum (Melastomataceae)

This study investigated the historical distribution and environmental factors determining the occurrence of Pleroma hirsutissimum (Cogn.) P.J.F. Guim. & Michelang. and Pleroma clavatum (Pers.) P.J.F. Guim. & Michelang. along the southeastern and southern coasts of Brazil. Revised occurrence records were integrated with information on Protected Areas (Conservation Units – CUs) and climatic, topographic, edaphic, and land-use variables to evaluate the conservation status of remnant populations and identify environmentally suitable areas for conservation and restoration of Restinga ecosystems. Both species belong to Melastomataceae and are characteristic pioneers of Restinga vegetation. P. hirsutissimum is endemic to the Cabo Frio Vegetation Diversity Center (CFVDC) in Rio de Janeiro and is classified as Critically Endangered, whereas P. clavatum has a broader distribution from Rio de Janeiro to Santa Catarina. Occurrence records were updated and validated using digital herbarium databases and taxonomic expertise, removing geographic and nomenclatural inconsistencies. Historical analyses revealed a marked increase in collections after the establishment of CUs, highlighting their importance for protecting P. hirsutissimum, although some populations remain in unprotected and disturbed areas. In contrast, P. clavatum showed larger populations, mainly in São Paulo and Paraná, but only 34% of its records occur within protected areas, indicating important conservation gaps. Environmental analyses identified Isothermality, Minimum Temperature of the Coldest Month, Precipitation of the Wettest Month, Mean Wind Speed, Actual Evapotranspiration, Solar Radiation, Soil pH, and Soil Sand Content as the main factors influencing species distribution. MaxEnt models constrained by native vegetation cover showed high predictive performance, indicating a highly restricted environmental niche for P. hirsutissimum and broad suitability for P. clavatum. These findings support the use of P. clavatum in Restinga restoration and coastal stabilization, while reinforcing the value of P. hirsutissimum as a bioindicator of environmental quality and the Cabo Frio coastal upwelling system.