| Method |
Researchers used data from plant families starting with the letters A, F, L, R,
and X in (Federov AA. 1974. Chromosome Numbers
of Flowering Plants. Koenigstein, Germany:
Otto Koeltz Sci.), focusing only on genera whose chromosome numbers
were summarized in table format. To be conservative, they excluded species that
were polymorphic for chromosome number. There were at least 987 chromosomal
shifts in 8884 speciation events, implying that the rate of change of chromosome
number is ~11% per speciation event. Multiplying this by the polyploid index,
they estimate that ~2%–4% of speciation events in angiosperms involve polyploidization. For polyploid index, see equation 2 in p. 406 in article. |