Heritability at the species level: analysis of geographic ranges of cretaceous mollusks.

Geographic range has been regarded as a property of species rather than of individuals and thus as a potential factor in macroevolutionary processes. Species durations in Late Cretaceous mollusks exhibit statistically significant positive relationships with geographic range, and the attainment of a typical frequency distribution of geographic ranges in the cohort of species that originated just before the end-Cretaceous extinction indicates that species duration is the dependent variable. The strong relation between geographic ranges in pairs of closely related species indicates that the trait is, in effect, heritable at the species level. The significant heritabilities strengthen claims for processes of evolution by species-level selection, and for differential survivorship of organismic-level traits owing to extinction and origination processes operating at higher levels.