9701338 Stanton In some plant species, males and females live in different habitats. The goal of this project is to identify what ecological mechanisms are involved in creating such a pattern of spatial segregation of males and females in saltgrass, Distichlis spicata. Saltgrass is a central component of salt marshes on the west and east coasts of the United States as well as inland in salty and alkaline areas. To determine what mechanisms could operate to create a pattern of spatial segregation of males and females in this species, the researchers have identified molecular markers capable of differentiating clones and identifying the gender of individuals before they flower. With these tools, they can test for effects of differential germination requirements and differential seedling mortality by tracking seedlings grown from seeds in the field. Further use of molecular markers on plants in patches of known ages can determine whether differential adult mortality and differential vegetative growth contribute to the pattern in saltgrass. Also, the researchers will use transplant experiments to test for differential effects of environment on vegetative growth between males and females and to examine male and female reproductive success. The long term goal of this research project is to fully understand how ecological and evolutionary mechanisms operate to create spatial segregation of males and females in saltgrass. Spatial segregation of males and females is exhibited by more than eighteen plant species. In these species, males and females are found in environments that differ in water availability, salt levels, altitude, light levels, or nutrient levels. Strikingly, females are consistently found in less stressful environments (wetter, less salty) than males. It is difficult to understand why this spatial separation of males and females would not decrease mating efficiency for these plants. Thus, scientists are interested in knowing what mechanisms lead to spatial segregation of males and females and whether the pattern benefits individual plants. Only one study has directly addressed the question of spatial segregation of males and females as a benefit to plants, and no studies have been published that demonstrate which mechanisms are working to create this pattern in species with genetic determination of gender. It is particularly important to understand how such a pattern operates because many key wetland plant species are known to exhibit the pattern. Wetland ecosystems have a central environmental and ecological role, and in order to preserve and restore wetlands, researchers need information on wetland ecosystems particularly the factors that cause them to be resistant to degradation and resilient to change. Genetic components of populations can greatly influence their stability and consequently the stability of the whole ecosystem of which they are a part. Spatial segregation of males and females is one aspect of the genetics of many plant populations for which almost nothing is known.
