Mating systems of diploid and allotetraploid populations of Tragopogon (Asteraceae). II. Artificial populations

Polyploidization has long been recognized as an important force in the dive rsification of plants. Theoretical models predict that polyploids may be ex pected to exhibit higher rates of self-fertilization than do closely relate d diploid species. Wild populations of the neopolyploid Tragopogon mirus (4 n) exhibited slightly higher rates of outcrossing than did populations of o ne of its progenitors, T. dubius (2n). In the current study, outcrossing ra tes in populations of T. dubius and T. mirus were estimated using artificia l arrays constructed to maximize the chances of detecting outcrossing event s. The artificial diploid population is more highly outcrossing (t=0.727; f amily-level estimates range from 0.00 to 1.32) than the tetraploid populati on (t=0.591; family-level estimates range from 0.00 to 1.14), although the difference between them is not statistically significant. The results of th is study, combined with those of the previous work on wild populations, sug gest that mating systems in these species vary more among populations than between ploidal levels. This could be because of the relatively recent orig ins of the tetraploid species; there may have been insufficient time since the formations of the tetraploids for shifts in mating systems to occur.