Polyploidy in Plant Taxa: Summary

Abstract

The preceding seven papers deal with the distribution and evolutionary significance of Polyploidy in each of the major plant taxa. Polyploidy, the multiplication of entire chromosomal complements, is the most widespread and distinctive cytogenetic process affecting higher plant evolution. Approximately 36% of the species of flowering plants have gametic chromosome numbers which are multiples of the basic diploid number found within their respective genera, but between 70 and 80 percent may, in fact, have Polyploidy in their evolutionary history. The percent of intrageneric Polyploidy in ferns is even higher and the occurrence of intergeneric Polyploidy is equivalent to that in angiosperms. Studies to date have been largely confined to the aforementioned groups, especially the dicotyledonous angiosperms. However, the preceding papers suggest that Polyploidy may be an important aspect of evolution among at least certain groups of the thallophytes. The only group in which Polyploidy is con-spicuously rare is the gyminosperms.