Fallacies underlying the assumption of calcium limitation on the evolution of land snails in Bermuda

Abstract

The supposed lack of calcium during glacial periods of red soil development has been cited as the principal factor influencing evolution in land snail shells on Bermuda during the Quaternary. We argue that at no time was there an appreciable deficiency of calcium carbonate on Bermuda because the red soils themselves are largely made up of carbonate and because calcium in plant tissues would have been recycled during all stages of the Quaternary by frequent forest fires. Supposed instances of very localized changes in shell thickness arose through misinterpretation of chronology. Paedomorphic populations of the subgenus Poecilozonites occur only in carbonates of the last interglacial (Marine Isotope Stage 5) and the Holocene, never in glacial red soils as maintained repeatedly by Gould.