Terrestrialization in gastropods: lineages, ecological constraints and comparisons with other animals

Abstract

Abstract Evolutionary transitions from water to land are infrequent. The physical contrasts between these media are amplified by biological differences in the patterns of selection. A new compilation, based on published phylogenetic and fossil evidence, identifies 30 separate instances of terrestrial colonization by gastropods, at least 12 from the sea and 14 from freshwater. Pre-Cenozoic transitions, mainly from freshwater and all tropical, resulted in high terrestrial diversity. Most Cenozoic colonizations were local, especially on oceanic islands, and yielded few terrestrial species. An increasingly predator-rich terrestrial environment after the Cretaceous made colonization on land unlikely except in cryptic habitats and on islands. Colonization from the sea became possible only in the Cenozoic, when marine lineages became specialized for life on the upper seashore. The results are compared with terrestrial colonizations by other groups of plants and animals.