The New World populations rapidly spread along the coast of each continent. This is a large-scale chromosomal mutation, in which entire sets of chromosomes are duplicated. Polyploidy can result from a number of different events, including errors during meiosis leading to diploid gametes. In plants, errors in mitosis can also result in polyploidy. If the mitotic nondisjunction occurs early in development, then a polyploid cell line can differentiate into germ line cells, which undergo meiosis and result in diploid gametes.
Polyploidy can be a mechanism of speciation.
Tetraploid individuals, for example, can only successfully mate with other tetraploid individuals. Genetic isolation enhances speciation processes. Triploids are often less viable, tend to be sterile, and have various other reproductive problems. For ex, grey treefrogs. Polyploidy is common in plants but rare in animals.