Rediscovering the Selaginella flora of Puebla, Mexico: New records reveal underestimated richness

Background and Aims: Puebla ranks as the seventh most diverse Mexican state in terms of plant species. Despite this, only 24 Selaginella species had been recorded for the state as of 2022, fewer than in neighboring Oaxaca (53 spp.) and Veracruz (33 spp.). This work aims to update current knowledge of Selaginella diversity in Puebla by documenting newly recorded species, comparing the state’s taxonomic diversity with that of neighboring states, and providing an identification key for the species known from the state. Methods: We conducted extensive fieldwork, reviewed herbarium specimens, and analyzed database records from 2014 to the present. We also calculated the Selaginella Taxonomic Biodiversity Index (TBI, taxa/lnA) for Puebla and its neighboring states. Key results: We documented seven new species records, increasing the known diversity of Selaginella in Puebla to 31 species. This represents 38.75% of all Selaginella taxa reported in Mexico, of which eight are endemic to the country. To aid identification, a dichotomous key was developed. The TBI for Puebla (3.0 taxa/lnA) equaled that of Veracruz and represented approximately 65% of the value recorded for Oaxaca (4.6 taxa/lnA). The most frequently recorded species were S. lepidophylla, S. pallescens, and S. stellata. The highest species richness was found in montane cloud forests (16 spp.) and xeric scrublands (8 spp.), with most species distributed across the northeastern (16 spp.) and northwestern (15 spp.) mountain ranges. Conclusions: The genus Selaginella is well represented in Puebla. Ongoing field collections and systematic review of herbarium specimens, particularly in underexplored southern areas of the state, are essential for refining the regional checklist and understanding species distribution patterns.