The more things change: Trait variance provides evidence of pervasive mosaic evolution
(Phys.org)—Despite evidence that phenotypic change does not always occur uniformly across all species members and lineages, single size or shape traits are often used to represent species-level change in its entirety. Recently, however, scientists in the Department of Geology at the Field Museum of Natural History in Chicago and at the Museum für Naturkunde in Berlin asked a deceptively simple question – Are (or when are) single traits adequate representations of species-level change? – and answered it by asking another: How often do single traits show conflicting patterns in the same sequence? To answer the second, they examined trait variation frequency in fossils, finding that within most lineages, evolutionary mode (the pattern of evolution, as opposed to its rate) does indeed vary across traits – and the probability of these patterns conflicting within a given lineage patterns increases in proportion to the number of traits analyzed. Moreover, the evolution of...