The Wallacean Shortfall and the role of historical distribution records in the conservation assessment of an elusive Neotropical snake in a threatened landscape

Documenting species distribution is essential to extinction risk asessments and subsequent conservation actions. Historical records are thus essential to understand how species are distributed and how their range has changed over time. However, using historical records might contribute to overestimating the species current range and misrepresent their conservation status. Here, we illustrate the pitfalls of this approach using a widespread but elusive Neotropical snake species, Philodryas livida (Dipsadidae Bonaparte, 1838). We mapped occurrences of this species over time and calculated its Extent of Occurrence and Area of Habitat. Our results show that due to the intense, widespread anthropic land-use transformation since the discovery of P. livida in 1920, most historical localities are now likely unsuitable for its occurrence and both its current Extent of Occurrence and Area of Habitat become remarkably smaller (5.7% and 19.1% remaining, respectively) if only localities from the last 30 years are considered. Apart from the natural elusiveness of the species, intense habitat loss and fragmentation may also explain the low number of recent records of P. livida, all concentrated within or near protected areas, indicating a putative decline in range relevant to its conservation status. We thus highlight how failing to consider the date of records and the associated land-use change over time might underestimate species range reduction and thus threat status. We strongly encourage the inclusion of the date of each occurrence record in conservation assessments, as suggested by the IUCN's mapping standards, such that historical records are carefully considered, especially in highly dynamic and threatened biomes such as the Cerrado savannas in Brazil.