Removal of historical taxonomic bias and its impact on biogeographic analyses: a case study of Neotropical tardigrade fauna

Abstract

Large-scale databases are crucial for macroecology research, yet not entirely bias-free. Studying the biogeography of metazoan microfauna utilizing such databases is challenging, and added biases can further hinder them. Incidence data of tardigrade species from Central and South America are geographically biased, comprising mostly species erroneously considered cosmopolitan. The impact of these biases on macroecological studies is still unknown. This paper evaluates how biased distribution records affect understanding of non-marine tardigrade distribution patterns in the Neotropical region. Using two datasets (including and excluding dubious records of allegedly cosmopolitan species), we assess how well biogeographic regions are sampled, estimate tardigrade species’ richness, and analyse whether including dubious records can alter our comprehension of their macroecology. We demonstrate how biogeographic regions are still not fully sampled, and that including unreliable records influences how many species remain to be discovered. Since records of ‘false cosmopolitan species’ represent most records, their removal increases uncertainty while yielding distribution patterns more likely to be accurate. Disregarding untrustworthy distribution records of ‘false cosmopolitan species’ is the first step to better understanding tardigrade macroecology in the Neotropics, and probably worldwide. However, additional, preferably systematic sampling is required before we can infer general tardigrade biodiversity patterns in under-sampled regions.