Response of non-native European terrestrial gastropods to novel climates correlates with biogeographical and biological traits
Anticipating the propensity of species to persist outside the climatic conditions in which they are observed is important in assessing the uncertainty in climate-matching when applied to different locations or times. By using data from 27 European terrestrial gastropods (slugs and snails) established in new regions, we measured (1) the degree of climate match between native and non-native ranges and (2) the diversity of novel climatic conditions inhabited. We then tested for species traits as predictors of the patterns found.
We projected the occurrences of each species onto the climatic space defined by the two main axes of a principal components analysis. On the basis of the convex hull of native occurrences, we measured the proportion of non-native occurrences in novel climates and the diversity of the newly occupied climates. Generalized estimating equations were used to test for associations between climatic responses and species traits, while considering phylogenetic relatedness and introduction effort.
Approximately half of the species had a large proportion (> 25%) of non-native occurrences in novel climates. Climate mismatch was significantly higher for species with narrow native climatic niches, native ranges elongated in a north–south direction or native ranges with the southern limit at lower latitudes. Slugs occupied a higher diversity of novel climatic conditions than snails.
Climate matching showed varying levels of accuracy in predicting the non-native ranges of the studied species. Lower accuracy appeared to be mainly related to low levels of distributional equilibrium in native ranges. In addition, coarse-scale predictions for species that are able to take advantage of microclimatic variability – as appears to be the case with slugs – may be challenging. We conclude that species traits can contribute to understanding uncertainties in climate-matching exercises.