ZAHN, LAURA M. Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ 85721. - Population dynamics of the gyndioecious Bouteloua chondrosioides (Spruce-top grama).
Bouteloua chondrosioides (Poaceae) is a prennial,
gynodioecious, Chloridoid grass with both diploid (2N=20) and
polyploid (2n=40; 80) populations that vary in levels of male
sterility. B. chondrosioides was initially considered to be
hermaphroditic; however Reeder and Reeder in 1966 described a male
sterile form that makes aborted anthers (MA form) not visible to the
naked eye. This form has been observed in all populations surveyed to
date. A second, independently segregating form of male sterility has
also been recently identified. This form makes stamens of reduced
size that contain no pollen grains (MS form). Both forms have been
found in all Texas and Arizona populations observed. No correlation
between ploidy levels and levels of male sterility has been observed.
In this talk I will outline evidence from work performed to date
supporting the hypothesis that the transmission of male sterility in
the gyndioecious Bouteloua chondrosioides appears to be
primarily determined by cytoplasmic male sterility.
Key words: Bouteloua, gynodioecy