Quantifying rarity of intraspecific diversity at multiple spatial scales by combining fine-grain citizen-based data across national boundaries

Quantifying rarity at the intraspecific level is an important task for conservation biologists because rare phenotypes have a higher extinction risk than common ones. However, quantitative assessments of are lacking this level, preventing to adequately protect and endangered variants that part pool species. Our aim was take benefit high-resolution volunteer-based occurrence data assess quantitatively patterns facultative paedomorphosis, in Alpine newt (Ichthyosaura alpestris). This polyphenism composed two morphs, adult phenotype retaining gills metamorphosing. We included multiple spatial scales (i.e., resolution) combined 15,613 records from atlas databases seven countries European Alps understand how scale may affect metrics. analyses revealed rarer 292 times phenotype, occupying very small fragmented area occupancy. Yet, depended on resolution data. Rarity estimates were up 1300 lower coarser finer scale. Both presence threats fish introductions) make paedomorphs critically whereas widespread all scales. Altogether, these results show metrics can differ between organisms, suggesting fine-grain should be used rarity. They also combining datasets distribution atlases efficient estimate