How many arthropod species live in Great Smoky Mountains National Park? A comprehensive estimate of biodiversity in America’s most-visited national park

The All Taxa Biodiversity Inventory in Great Smoky Mountains National Park is an unprecedented effort to catalog all life present there. Since 1998, 11,826 species have been added to the park’s list and 21,501 total species are presently known. A current goal of the ATBI is to prioritize ongoing collection efforts to document the unknown biodiversity of the Smokies. We present preliminary results of a study estimating the total species richness of GSMNP and elucidating the taxa that are most understudied among them. We focus on the arthropods, which comprise 54% of the park’s biodiversity, are foundational to terrestrial food webs, and are experiencing worrying declines worldwide. We analyzed ~214,127 occurrence records from GSMNP with species-level identifications (6,701 species), extrapolating total richness using species accumulation curves for every taxonomic order. We also systematically surveyed taxonomists familiar with GSMNP biodiversity to estimate the undiscovered diversity within each taxon. Among the arthropods, 15 orders were thoroughly sampled (>90%), including Thysanoptera (thrips), Spirobolida (millipedes), and Mantodea (mantids) among others. In contrast, Sarcoptiformes, Mesostigmata (mites) and Lithobiomorpha (centipedes) were the most under-sampled, with only 34-45% of all estimated species currently discovered. Estimates of total diversity provided by taxonomists generally accorded with species richness estimates, suggesting that temporal data such as that collected by the park may be leveraged to prioritize biodiversity surveys. We will discuss challenges encountered during this undertaking, which may inform future studies of this kind, and how these data will be used to guide ongoing sampling efforts.