Gastropod biodiversity at the 'Evolution Canyon' microsite, lower Nahal Oren, Mount Carmel, Israel

Twenty-six species of gastropods (terrestrial, shell-bearing snails and slugs) were recorded at the 'Evolution Canyon' microsite, lower Nahal Oren, Mount Carmel, Israel. Twenty-five species were recorded at the temperate, mesic north-facing slope (NFS) and 20 species at the xeric south-facing slope (SFS). Out of these species, six were NFS specific (Pilorcula raymondi hebraica, Euchondrus septemdentatus, Monacha crispulata, Pyramidula rupestris hierosolymitana, Truncatellina haasi, and Vitrea contracta) and one was SFS specific (Prolimax eustrictus). The interslope difference was probably partly due to missing forest species at the SFS in comparison with the NFS. Twenty-two species were Levantine endemics (84.6%) and four species were more widely distributed in the Palaearctic region (15.4%). The Levantine species are inhabitants of the mesic and mainly mountainous regions, but four species (Granopupa granum, Calaxis hierosolymarum, Cecilioides acicula, and Helix engaddensis) also penetrate the deserts. Seven species (Buliminus labrosus, H. engaddensis, Levantina spiriplana caesareana, Metafruticicola fourousi, Monacha syriaca, Sphincterochila cariosa, and Xeropicta vestalis joppensis) were significantly more abundant on the SFS than on the NFS. The local physical microclimatic sharp divergence leads to gastropod adaptive interslope biotic divergence caused by natural selection.