Diversity and endemism of Rubiaceae in Mexico: A revised taxonomic assessment

Rubiaceae is one of the most diverse angiosperm families in Mexico and ranks fourth in species richness among the country's vascular plants. Although numerous taxonomic and floristic studies have attempted to document its diversity, considerable discrepancies remain regarding the number of genera and species recognized for the Mexican flora, with published estimates ranging from 77 to 113 genera and from 510 to 707 species. These inconsistencies reflect differences in taxonomic treatments, regional sampling efforts, and the continuous discovery and revision of taxa. To provide a comprehensive and updated assessment of the family, a database was compiled from the principal taxonomic, floristic, and monographic studies of Mexican Rubiaceae and supplemented with specimen records obtained from national and international herbarium collections. Our analysis indicates that Rubiaceae in Mexico comprises 111 genera, including 17 endemic genera, 711 native species, and 13 introduced species. Of the native species, 363 are endemic to the country, highlighting Mexico as an important center of diversification for the family. Species richness is unevenly distributed across the national territory, with Oaxaca, Chiapas, and Veracruz representing the most diverse states, harboring 416, 365, and 318 species, respectively. Together, these states contain approximately half of all endemic Rubiaceae species recorded in Mexico. An evaluation of collection density and specimen distribution revealed important geographic gaps in botanical exploration, suggesting that only 43% of the national territory can be considered adequately sampled. This study provides an updated taxonomic checklist and proposes solutions to several conflicts at the generic level, contributing to a more stable classification of Mexican Rubiaceae. Furthermore, the results emphasize the need for additional taxonomic revisions, increased field collecting in poorly explored regions, and continued examination of herbarium specimens to improve our understanding of the diversity, distribution patterns, and endemism of Rubiaceae in Mexico.