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

This article examines how biased and unreliable distribution records, particularly those of "false cosmopolitan species," affect the understanding of non-marine tardigrade (water bear) diversity and biogeography in Central and South America's Neotropical and Andean regions. Using two datasets—one including all records and another excluding dubious records of species erroneously considered cosmopolitan—the study finds that most tardigrade records in these regions are geographically and taxonomically biased, with unreliable records inflating species richness estimates and obscuring true biogeographic patterns. Excluding these dubious records reduces data volume by over 65%, revealing that sampling remains uneven and insufficient across biogeographic provinces, which limits accurate macroecological inference. The authors conclude that removing unreliable records is a necessary first step toward more realistic macroecological studies of tardigrades, but emphasize that increased, systematic sampling and integrative taxonomic methods, including DNA barcoding, are essential to improve knowledge of tardigrade biodiversity and distribution in under-sampled Neotropical areas.