Patterns of spatio-temporal variation in land snails: a multi-scale approach

Mechanisms which govern patterns of intra-specific vatiation in land snails were traced within areas of different size, using Brephulopsis cylindrica (Menke), Chondrula tridens (O. F. Müller), Xeropicta derbentina (Krynicki), X. krynickii (Krynicki), Cepaea vindobonensis (Férussac) and Helix albescens Rossmässler as examples. Morphometric shell variation, colour and banding pattern polymorphism as well as genetic polymorphism (allozymes and RAPD markers) were studied. The results and literature data were analysed in an attempt to link patterns to processes, with the following conclusions. Formation of patterns of intraspecific variation (initial processes of microevolution) takes different course at three different spatial scales. At micro-geographical scale the dominant role is played by eco-demographic characteristics of the species in the context of fluctuating environmental factors. At meso-geographical scale a special part is played by stochastic population-genetic processes. At macro-geographical scale more or less distinct clinal patterns are associated with basic macroclimatic indices, while the stochastic processes tend to lose importance. The basic factors of microevolutionary process which act at different spatial scales result from processes which progress over different lengths of time: micro-geographical variation patterns reflect processes which are in progress at the moment; meso-geographical variation is to a larger extent determined by processes which occurred in historic past; macro-geographical variation reflects processes which coincided with formation of the respective landscapes or climate zones. Key wordS: intra-specific vatiation, Brephulopsis cylindrica, Chondrula tridens, Xeropicta, Cepaea vindobonensis, Helix albescens, spatial scale, microevolution, multi-scale approach, morphometric variation, colour polymorphism, genetic polymorphism