Phenotypic identity of iNaturalist records for grass snakes (n = 2944). A Entire study range, B Rhine transect, C Alpine transect, D Italian transect. Note the records of putative Natrix natrix and hybrids inside the distribution range of N. helvetica.

 
 
  Part of: Fritz U, Grismer LL, Asztalos M (2023) Hybrid zones of Natrix helvetica and N. natrix: Phenotype data from iNaturalist and genetics reveal concordant clines and the value of species-diagnostic morphological traits. Vertebrate Zoology 73: 383-395. https://doi.org/10.3897/vz.73.e103319