Exploring Myrtaceae diversity in the Caatinga: understanding the knowledge gaps for conservation

Context Myrtaceae stands out as one of the significant woody plant families in the Caatinga. Although its wide morphological variability and well-known ability to influence the provision of ecological services in other ecosystems are recognized, little is known about the richness of the family in the Caatinga. Aim We aimed to compile a comprehensive catalog of Myrtaceae species present in the Caatinga and pinpoint areas with the highest species diversity and those that are poorly sampled as a foundation to investigate the conservation status of the group. Methods We collected specimens in situ and analyzed available herbarium collections. The geographical data were used to produce maps of collection effort, species richness (SR), and richness estimation (RE) by Jackknife 1. Key results We recorded 125 species across nine genera, of which 51 occur within conservation units (CU) or indigenous areas (IA). Of the 18 taxa endemic to the Caatinga vegetation, only six are protected by CU or IA. The collection effort shared some similarities with SR; however, most of the Caatinga is still poorly sampled. The RE marked two main hotspots of diversity, encompassing CUs in the territories of the states Pernambuco, Ceará, and Bahia, with a species richness estimated by RE up to 68% higher than SR. Conclusions Our research has underscored the significance of ongoing collection efforts, taxonomic investigations, and conservation initiatives aimed at preserving the diversity of Myrtaceae in the Caatinga. Implications The collection efforts and taxonomic investigations contribute to understanding the conservation status and the real diversity of Myrtaceae species.