Impacts of taxonomic change on the Amazonian palm flora

Although taxonomy is an evolving discipline, taxonomic change is rarely accounted for in macroecological studies. By tracking the history of species descriptions and synonymizations of more than 800 names of Amazonian palms, we reveal shifts in species counts across space and time, the factors associated with taxonomic lumping, and the time needed to detect synonyms. The 175 Amazonian palm species known to date are the result of a gradual accumulation of new descriptions and a few distinct revisions events that led to the recognition of approximately 800 heterotypic synonyms. Most of these synonyms were detected after the mid-1990s and caused an 80% decrease in species counts within just three decades. The time to detect synonyms ranged from 3 to 227 years. Species with a large population, widespread distribution, and those described early were more frequently lumped. This suggests undetected synonyms inflate species richness unevenly across taxa and regions. Our study highlights how much taxonomic revisions can affect our understanding of biodiversity. Without them, we risk building our ecological analyses and conservation assessments on shaky ground.