Institute of Evolution and Ecology (EvE)

The Theba Survey

Theba pisana is a helicoid land snail whose range extends over large parts of Europe, North Africa and Western Asia. It has also been introduced to other continents. Theba pisana is a highly polymorphic species, with almost every individual having its own shell pattern. With the aim of recording the environmental dependence of pigmentation intensity across the distribution range, a call was made in 2018, coordinated by our research group together with the University of Le Havre, for scientific colleagues to collect individuals from their natural habitats and send them to Tübingen. A total of more than 19 000 individuals from more than 150 sites were measured planimetrically and densitometrically and their pigmentation intensity was computed with bioclimatic and Normalized Difference Vegetation Index (NDVI) data.

The following questions are the focus of interest:

  • Is the pigmentation of these snails stronger associated with climatic or vegetation ecological parameters? Does thermal selection or selection by predation dominate on a continental scale?
     
  • Is it possible to draw up a map of pigmentation intensity over the entire distribution range?
     
  • Based on predicted climate change in Europe, how will the range of this species and the distribution of pigmentation patterns change? Will extinction processes occur? Is the selection pressure due to environmental warming having different effects in the different climates of Europe?

Participating people:

Coordination: Heinz-R. Köhler & Thomas Knigge
Team Tübingen: Janne K.Y. Burmester, Lilith Sawallich, Rita Triebskorn & Henri A. Thomassen
Contributors: Zeev Arad, Thierry Backeljau, Yvan Capowiez, Luis J. Chueca, Melina Coelho da Silva, Mark S. Davies, Leonardo Favilli, Josep Florit Gomila, Joseph Heller, Stefanie Krais, Alexandre Lobo da Cunha, Giuseppe Manganelli, Silvia Mazzuca, Tiphaine Monsinjon, Catarina Moreira, Gregorio Moreno-Rueda, Amalia Piro, Tamara Prieto, Josep Quintana Cardona, Emilio Rolan-Alvarez, Ben Rowson, M. Jill Saffrey, Menno Schilthuizen, Hannah Schmieg, Alexandra E. Staikou & Guillermo Tomás Faci