Print ISSN: 0031-0247
Online ISSN: 2274-0333
Hypoplasia: CT-scan or naked eye?
Eocene otoliths (Clinchfield Formation), Georgia
New elephant cranium from early Pliocene Ileret, Kenya
Early adaptive radiation of Theridomorpha
Evolution et extinction des reptiles marins au Mésozoïque
Rates of evolution in divergent species lineages as a test of character displacement in the fossil record : tooth size in Paleocene Plesiadapis (Mammalia, Proprimates)character displacement; character divergence; fractal time series; Plesiadapis; Rates of evolution
Two species lineages of North American late Paleocene Plesiadapis exhibit a pattern of size divergence from a common ancestral lineage. Time series of fossils in each of these lineages are analyzed to test the idea that size divergence represents competitive character displacement. The critical factor in a test of character divergence is showing that divergent lineages evolved directionally rather than randomly (multifactorially). Analysis of evolutionary rates and their temporal scaling in Plesiadapis shows that both divergent species lineages have the scaling slope expected for lineages evolving randomly rather than directionally, and size divergence in Plesíadapis does not represent character displacement. Rates of evolution commonly observed on a per-generation time scale are high enough to produce character displacement within a few generations. Thus character displacement is not likely to be visible on scales of time that can be studied in the fossil record.
Published in Vol. 25, Fasc. 2-4 (1996)