How much do we know about the Amazonian flora of Maranhão?

ABSTRACT Priority areas for conservation are largely defined based on information about biodiversity. However, the available information on species richness is heavily biased due to low sampling density, especially in hard-to-reach areas such as the Amazon region of Brazil. Here, we quantified the efforts to inventory the flora of the Amazonian region of Maranhão, evaluating the evolution of collection records, and presenting the data on the collections. Thus, we explore the hypothesis that, despite being located in a marginal area of the Amazon, the Amazonian region of Maranhão stands out for its uniqueness and richness, but it is under-sampled and under-represented in scientific studies. We retrieved 20,181 collection records from 89 out of 108 municipalities comprising this region. The vast majority of collection records (~48%) come from São Luís Island and the municipality of Buriticupu, the former an exception in terms of sampling density when compared to other regions/municipalities possibly due to the higher number of projects and well-structured collections. Angiosperms, especially legumes, represent the largest group, with collections distributed throughout the studied region. It is urgent to fill in the gaps identified here for the future establishment of conservation units and the recognition of the Brazilian biodiversity.