Dataset: Sampling effort drives recorded pteridophyte richness: knowledge gaps across northeastern Brazil

This dataset contains all data compiled and analyzed for the study of collection effort and knowledge gaps for ferns and lycophytes (pteridophytes) across the nine states of northeastern Brazil. Data were compiled from the Flora e Funga do Brasil (2025), the Global Biodiversity Information Facility (GBIF; accessed January 2026), and the speciesLink network. The dataset includes: (1) species richness per state comparing Prado et al. (2015) and Flora e Funga do Brasil (2025); (2) biome complexity factors (BCF) assigned to each state with justification; (3) step-by-step Knowledge Gap Index (KGI) calculations; (4) temporal distribution of herbarium records per state per decade (pre-1960 to 2020–2025); (5) data used for the logarithmic regression analysis between GBIF occurrence records and species richness; and (6) summary statistics of the 12,025 unique occurrence records by state. A total of 530 species (486 ferns, 44 lycophytes) distributed across 28 families and 93 genera were recorded for the region.