Phenotypic Consequences of Chromosome Doubling

Abstract

Abstract It is important to uncouple the effects of chromosome doubling from those of hybridization or genome coexistence, because only then can we understand the manifold effects of polyploidy alone (autopolyploid) within individuals, populations, and species. The effects of chromosome doubling per se generally have been viewed as maladaptive. Levin (1945) argued that chromosome doubling radically alters the balance of multiple factors acting on a single character and that only through hybridization and selection may this imbalance be restored. Stebbins (1971, p. 126) suggested that chromosome doubling alone would hinder the evolutionary success of higher plants. I take a contrary position. In this chapter I contend that autopolyploid may generate novel types of plants and in tum may facilitate character evolution and speciation. In many species autopolyploid may significantly alter the cytological, biochemical, physiological, and developmental attributes of organisms. Autopolyploid thus may have unique or transgressed tolerances and traits that may allow the exploitation of habitats beyond the limits of their diploid progenitors. Chromosome doubling occurs in existing polyploidy, but it is more likely to produce a positive effect from a diploid base (Gottschalk, 1976). Thus, most comparisons that follow involve diploids.