Abstract
The terrestrial molluscan fauna of the Caatinga Dominion, a seasonally dry tropical region in north-eastern Brazil, remains one of the least-documented components of its biota, thereby limiting its inclusion in ecological, biogeographical and conservation assessments. Here, we present a diagnosis of Caatinga terrestrial molluscs by addressing three questions: how much diversity is currently known, how strongly available records are spatially biased, and how sensitive species visibility is to minimum-occurrence thresholds commonly applied in spatial analyses. We compiled 944 records representing 155 species, 62 genera and 25 families. Stylommatophora accounted for 141 species (91%), highlighting the great taxonomic concentration of the known fauna. Despite this apparent richness, records were sparse and unevenly distributed. Only 221 of 8,761 grid cells (2.5%) contained records, whereas 8,443 cells (97.4%) lay within the expected occupancy area but lacked any record. Mean sampling completeness per cell, measured as the ratio between observed and expected richness, was 0.003, and observed–expected overlap was low (Jaccard = 0.0255). Species retained under increasing occurrence thresholds declined from 88 at t = 3 to one at t = 38, revealing pronounced taxonomic invisibility. These patterns may directly affect conservation planning and the reliability of spatial analyses that depend on minimum occurrence thresholds.
Similar content being viewed by others
Near-daily reconstruction of tropical intertidal limpet life-history using secondary-ion mass spectrometry
Seasonal refuge patterns of phytoplankton trigger irregular bloom events in a contaminated environment
Anthropogenic accessibility and observer inequality dictate spatial biodiversity patterns in Malaysia
Acknowledgements
The authors acknowledge the National Council for Scientific and Technological Development (CNPq) and Brazilian Federal Agency for Support and Evaluation of Graduate Education (CAPES) for financial support to E.S.C., and the Federal Institute of Piauí (IFPI) for logistical support.
Author information
Authors and Affiliations
Corresponding author
Ethics declarations
Competing interests
The authors declare no competing interests.
Additional information
Publisher’s note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Supplementary Information
Below is the link to the electronic supplementary material.
Supplementary Material 1 (download PNG )
Supplementary Material 2 (download PNG )
Supplementary Material 3 (download XLSX )
Supplementary Material 4 (download DOCX )
Rights and permissions
Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/.
Reprints and permissions
About this article
Cite this article
Castro, E.S., Costa, E.Z.G., da Silva, E.L. et al. Taxonomic invisibility and knowledge shortfalls in terrestrial molluscs of the Caatinga Dominion, a seasonally dry tropical region.
Sci Rep (2026). https://doi.org/10.1038/s41598-026-58663-z
Received:
Accepted:
Published:
DOI: https://doi.org/10.1038/s41598-026-58663-z
Keywords
- Gastropoda
- Knowledge gaps
- Sampling completeness
- Species visibility
- Stylommatophora
- Terrestrial malacofauna
Source: Ecology - nature.com
