Mosaic evolution, mosaic selection and angiosperm phylogeny

Abstract

STEBBINS, G. L., 1984. Mosaic evolution, mosaic selection and angiosperm phylogeny. Mosaic evolution is a general pattern of evolutionary change, and is expected on the hypothesis that rvolution is basically opportunistic rather than determinate. It is most often exemplified by constancy with respect to one set of characters over a given period of time, accompanied by more or less rapid change with respect to other characteristics of the same organisms. To the extent that the characters involved are functional and adaptive, mosaic evolution must be guided by mosaic selection. A survey of character differences between species belonging to 59 of the largest genera found in the California flora indicates that mosaic selection has played an important role in the evolution of modern species of angiosperms. Mosaic evolution has also taken place with respect to dinerent chromosomal and biochemical characteristics, as is evident from comparisons between morphological, chromosomal and biochemical differences. When the widespread Occurrence of mosaic evolution and of mosaic selection are recognized, two general principles emerge: the primitive or advanced nature of individual character states cannot be deduced solely on the basis of their correlation or association with other character states which are believed to be primitive or advanced; mosaic selection provides a strong basis for the conclusion that natural selection is the most basic process that converts changing population-environment interactions into evolutionary change.