Factors affecting reproductive success in a rare grass, Calamagrostis porteri subsp. insperata

Calamagrostis porteri A. Gray subsp. insperata (Swallen) C. W. Greene is a rare grass that is currently treated as a 'species of concern' by the U.S. Fish and Wildlife Service. Production of viable seed had never been observed, and little was known about the factors affecting this reproductive failure. In this study we examined the effects of maternal genotype, pollen source, and light intensity on caryopsis (the single-seeded fruit produced in grasses) production. Maternal genotype and pollen source (self vs. outcross) significantly affected the number of caryopses initiated, while light intensity had no significant effect. However, nearly all of the caryopses initialed aborted late in development. In the 2000+ florets we examined, only one fully filled, viable caryopsis was found. The conditions under which this caryopsis was produced suggest future courses of management.