Morphological redescription and ecological niche modelling of Gustavia santanderiensis (Lecythidaceae), with a key for the genus in the Magdalena Valley, Colombia

Background and aims – Gustavia santanderiensis is a tree species from the Magdalena Valley described around a century ago. Despite the species’ morphological plasticity, restricted range, and ecology, the species has been greatly understudied. This study aims to establish a clear taxonomic framework for the species based on its morphology and to determine its distribution and predicted range, ecological niche, and conservation status. Material and methods – A careful revision of herbarium specimens was performed along with field work in the type locality. We used the occurrence records to build an Ecological Niche Model (ENM) using the maximum entropy algorithm through the kuenm package. The accessibility area was constructed by overlapping the records with the ecoregions that encompass the Magdalena Valley. The model was generated using a unique set of bioclimatic variables, with their contributions and permutation importance estimated. Key results – The flower colour in Gustavia santanderiensis , previously described by Knuth and Mori as white petals, varies considerably. Surprisingly, none of the specimens cited by Mori and Prance (1979) in their monograph corresponds to G. santanderiensis . Its geographic range is more restricted than previously known, excluding its occurrence in Brazil, and it is now endemic to Colombia. According to the ENM, the species occurs between 100 and 680 m in areas where the annual mean temperature and annual precipitation range do not vary significantly. The annual mean temperature, isothermality, and temperature seasonality were the variables with the highest contributions and permutation importance in the model. Conclusion – Gustavia santanderiensis is an endangered, endemic species of the Magdalena Valley, characterised by remarkable flower colour variation that warrants further investigation. In addition to redescribing this species, we provide the first taxonomic key for Gustavia in the Magdalena Valley, which will serve as a diagnostic tool for the species in one of Colombia’s most diverse yet fragmented regions.