Macroecological invisibility in apple snails (Gastropoda: Ampullariidae): uneven occurrence and molecular coverage across public repositories

Abstract

Apple snails (Ampullariidae) are freshwater gastropods of ecological and economic importance, but their digital representation remains uneven across taxa, regions and data types. Using a 171-species taxonomic reference, we integrated global occurrence and molecular data to assess repository coverage, spatial usability, threshold-based visibility and sampling completeness. The public occurrences comprised 13 349 spatially unique records representing 119 species. Observation-based records accounted for 70.4% of this total and were concentrated in regions where invasive lineages are well documented. Restricting spatial analyses to native-range scientific collections retained only 3614 records for 113 species. Although 154 species were detected in the Global Biodiversity Information Facility (GBIF) species-level records, only 119 had directly spatially usable records; 35 species were GBIF-present, but spatially non-usable, and 17 were not detected in GBIF. Genetic coverage exhibited similar limitations. Public molecular repositories yielded 8730 records across BOLD and GenBank before cross-repository de-duplication, representing 58 species and leaving 113 species without public molecular data. Macroecological visibility declined sharply as minimum occurrence thresholds increased. Sampling completeness remained uneven, with a median of zero in most region-by-resolution combinations, despite apparent improvements at coarser spatial grains. These combined shortfalls systematically leave the principal tropical centres of native diversity analytically under-represented.