An inventory of the ferns and lycophytes of the Lower Tapajos River Basin in the Brazilian Amazon reveals collecting biases, sampling gaps, and previously undocumented diversity

Ferns and lycophytes are an excellent group for conservation and species distribution studies because they are closely related to environmental changes. In this study, we analyzed collection gaps, sampling biases, richness distribution, and the species conservation effectiveness of protected areas in the Lower Tapajos River Basin using ferns and lycophytes as a model group. We built a database based on herbarium specimens that were taxonomically verified and georeferenced. We then examined the relationship between sampling effort and documented species richness and tested for collection bias towards access routes (navigable rivers and roads). We made a comparison of species composition among the study areas and sixteen other areas in the Brazilian Amazon using non-metric multidimensional scaling (NMDS) and tested whether floristic similarity was correlated with geographic distance. We found that more than 92% of the area is unsampled and that collecting effort is highly biased towards areas along access routes, such as roads and navigable rivers. Only four out of the seven protected areas in the Lower Tapajos Basin had records of ferns and lycophytes. We present here species checklists for those areas. In total, we recorded 151 species of 60 genera and 24 families. Five species are new records for the state of Para, and nine out of the 151 species recorded occur only outside protected areas. Species composition is most similar among areas sharing similar vegetation types; geographic closeness does not necessarily reflect floristic similarity. We conclude that the fern and lycophyte flora the Brazilian Amazon is still far from complete and recommend the direction of future collection efforts to other under-sampled portions of the region. Such a sampling strategy will reduce sampling bias and providing a better knowledge base for the conservation of Amazonian fern and lycophyte diversity.