Scrutinizing the Wallacean shortfall: global gaps in snakeoccurrence data across space and environmen

Abstract

Occurrence records are fundamental for ecological and evolutionary research, provid-ing key information on species’ geographic ranges. However, these records are oftentaxonomically, spatially, and temporally biased, requiring caution in their use. Here,we analysed the spatial coverage of occurrence records for over 3500 snake speciesworldwide to identify geographical gaps, biases, and priority areas for surveys. We cal-culated completeness metrics to detect well-sampled cells and assessed whether thesecells adequately represent the climatic conditions across biogeographic realms. We alsoidentified priority areas for surveys based on geographic and environmental distancesfrom well-sampled cells, which may reflect different environmental conditions and spe-cies. Our results show that the number of well-sampled cells is higher in the Nearctic,Western Palearctic, and Australasia, whereas the Afrotropical, Eastern Palearctic, andIndomalayan realms remain poorly sampled. Although the Neotropical realm hasa relatively high number of well-sampled cells, they are spatially clustered, leavinglarge areas under-sampled. Overall, well-sampled cells fail to represent the majorityof climatic types present in each realm; also, rare climates are underrepresented inthe Nearctic, Neotropical, and Indomalayan realms. We highlight priority areas in allrealms, particularly in high-latitude regions of the Nearctic and Palearctic and in low-latitude regions of the Neotropical, Afrotropical, Indomalayan, and Australasia realms.While the low number of occurrence records in extremely high latitudes may reflectlow abundance and species richness, these areas can still harbour undescribed speciesand high taxonomic uncertainty. However, given the limited funding and resources,we suggest that redirecting survey efforts to neglected and species-rich regions is essen-tial for enhancing strategic planning for snake biodiversity conservation.