Ecological factors affecting the distribution of the gastropods Aegopinella nitidula (Draparnaud, 1805) and Nesovitrea hammonis (Ström, 1765) in northwest Spain

Aegopinella nitidula and Nesovitrea hammonis are land snails whose broad-scale distributions are similar but which often occur in different habitats. We investigated possible relationships between environmental factors – biotope type (woodland, river-bank or meadow) and 20 edaphic factors – and the distributions of these two speces in northwest Spain. Frequency of occurrence of Aegopinella nitidula was significantly higher than expected in sites with low to intermediate soil Mg content, low soil pH and intermediate soil Al content. Frequency of occurrence of Nesovitrea hammonis was significantly higher than expected in meadow sites and in sites with high soil moisture content, high soil porosity, a low soil C:N ratio of 0–10, and high soil N content.