Biased research generates large gaps on invertebrate biota knowledge in Brazilian freshwater ecosystems

Abstract

Research biases are common and constant issues in biological research, with major consequences for biodiversity conservation. Freshwaters represent one of the most threatened ecosystems worldwide, but knowledge of freshwater biota is unevenly distributed due to bias toward marine and terrestrial groups. Therefore, detecting biases and associated knowledge gaps is crucial to steer future research effort and to guide applicable conservation policies for freshwater ecosystems. In this study, we investigated the existence of biases and gaps in knowledge about the biodiversity of invertebrate fauna (zooplankton, mollusks and freshwater crabs) in the hydrographic regions of Brazil. We searched for all studies published in this country on zooplankton, mollusks and freshwater crabs, in the Web of Science database. Subsequently, the number of papers was classified by taxonomic group and hydrographic region to detect research biases. Each report within a paper between a given taxonomic group and a hydrographic region was termed as a case. We also recorded human population density for each hydrographic region. Among the taxonomic groups, zooplankton was the most studied taxon, followed by mollusks and crabs, and it was also dominant across the hydrographic regions. The hydrographic region of Paraná comprised the largest number of cases for the three invertebrate groups. We detected a disproportionately low increase of number of cases in relation to human population density in the hydrographic regions. The identification of the major gaps reported here limits our ability to draw scenarios for the conservation of hydrographic regions and their megadiverse biota in Brazil.