An updated plant checklist of the Brazilian Caatinga seasonally dry forests and woodlands reveals high species richness and endemism

Abstract

Plant checklists constitute the fundamental knowledge on which further hypotheses of ecology, evolution, and biodiversity conservation are built. Here, we compiled a comprehensive and taxonomically verified checklist of the flowering plant species occurring in the Caatinga. We circumscribe Caatinga to include only the dry deciduous vegetation in Northeast Brazil, corresponding to the largest continuous nucleus of the seasonally dry tropical forest and woodland biome (SDTFW) in South America. We recorded 3347 species, 962 genera, and 153 families, of which 526 species and 29 genera are endemic, and the large contribution of its non-woody component to overall diversity. These numbers reveal a remarkably high floristic diversity in the Caatinga, representing almost two fold higher species/area ratio (4.0 × 10−3 species/km2) as compared to the Amazon rainforests (2.5 × 10−3 species/km2). Most Caatinga-inhabiting species are shared with other non-SDTFW tropical biomes, probably reflecting transition zones with surrounding savannas and rain forests. This newly assembled taxonomic checklist is expected to serve not only as an updated look at the identity and counting of the Caatinga plant diversity, but will also provide aids for better understanding the origin, evolution, and ecological function of this species-rich, but highly threatened South American vegetation.