Ecology and population genetics of wild rice (Zizania spp.)

Wild rice, Zizania spp., is a genus of locally rare but important emergent grasses found in the near shore or shallow lake and river habitats of North America. These plants provide important ecological services such as sediment stabilization and nutrient retention, serve as food and shelter for many types of wildlife, and are a crucial component of the culture of a number of Native American tribes in the Upper Midwest. Habitat loss and fragmentation has limited the size and connectivity of the remaining stands of Zizania aquatica L, annual wild rice, making it a species of conservation interest to many public and private agencies throughout its range. The goals of our research were to examine how a set of Z. aquatica seed provenances respond to the environmental stresses of water depth and early season shading, as well as to compare microsatellite diversity between three of the seed provenances. In the first greenhouse experiment, we found that the wild rice grew optimally in saturated, but not submerged, soils. Plants grown in only periodically watered soils experienced drought stress while plants grown at the deepest treatment exhibited signs of light stress, suggesting that there may be a relatively narrow range of water depths in which Z. aquatica can grow. In the second greenhouse experiment, we found that shaded plants grew slower and accumulated less biomass early in the season than those exposed to full sun, but that the shaded plants were able to recover once given full sun during the aerial leaf stage. However, inflorescence production was delayed by the early season shading which could affect reproductive outcomes. We also found that seed provenance influenced the growth of wild rice in both experiments, and similar provenance differentiation was seen in the microsatellite study. Our research suggests that both environmental conditions and the choice of seed source may affect the outcome of wild rice conservation or restoration efforts