title: Animal evolution. Cope's rule in the evolution of marine animals.
abstract: Cope's rule proposes that animal lineages evolve toward larger body size over time. To test this hypothesis across all marine animals, we compiled a data set of body sizes for 17,208 genera of marine animals spanning the past 542 million years. Mean biovolume across genera has increased by a factor of 150 since the Cambrian, whereas minimum biovolume has decreased by less than a factor of 10, and maximum biovolume has increased by more than a factor of 100,000. Neutral drift from a small initial value cannot explain this pattern. Instead, most of the size increase reflects differential diversification across classes, indicating that the pattern does not reflect a simple scaling-up of widespread and persistent selection for larger size within populations.
authors.affiliation: Department of Geological and Environmental Sciences, Stanford University, 450 Serra Mall, Stanford, CA 94305, USA. naheim@stanford.edu.
authors.forename: Noel A
authors.initials: NA
authors.lastname: Heim
authors.affiliation: Department of Geological and Environmental Sciences, Stanford University, 450 Serra Mall, Stanford, CA 94305, USA.
authors.forename: Matthew L
authors.initials: ML
authors.lastname: Knope
authors.affiliation: Department of Geological and Environmental Sciences, Stanford University, 450 Serra Mall, Stanford, CA 94305, USA.
authors.forename: Ellen K
authors.initials: EK
authors.lastname: Schaal
authors.affiliation: Department of Mathematics and Statistics, Swarthmore College, Swarthmore, PA 19081, USA.
authors.forename: Steve C
authors.initials: SC
authors.lastname: Wang
authors.affiliation: Department of Geological and Environmental Sciences, Stanford University, 450 Serra Mall, Stanford, CA 94305, USA.
authors.forename: Jonathan L
authors.initials: JL
authors.lastname: Payne
mesh_terms: D000818:Animals; D059001:Aquatic Organisms; D005075:Biological Evolution; D049628:Body Size