177 years of diatom studies in Brazil: knowledge, gaps, and perspectives.

The actual status of the progress and the main aspects of diatom studies in Brazil remain unknown. This paper describes a survey of published studies addressing material of Brazilian origin in non-marine aquatic environments. Our objectives are to (1) summarize and categorize diatom research topics, (2) to describe how related studies evolved and developed over time, as well as respective journals, (3) to identify the most studied regions and environments, and (4) to indicate the main institutions and works addressing diatom research and related interactions. We conducted a systematic review selecting 478 studies. Since the early studies, the approach on diatom floristic exclusively was the most frequent, even though, ecological studies have been increasing since the 2000s. However, these concentrate in the southern and southeastern. It was only in the last decades that other Brazilian regions became the setting of more extensive samplings, thus reflecting on the interactions between authors and institutions from the collection sites. However, the actual biodiversity scenario of diatoms in Brazil still seems to be underestimated, which may influence further conservation measures. Finally, we indicate some suggestions aimed at filling the sampling gaps presented/highlighted in this study.