Sand-spurrey, Spergularia marina, is a common species of natural coastal wetland habitats throughout the world. Like most plant species, flowers of S. marina produce both male and female gametes through the production of pollen grains and ovules. However, in contrast to most species, S. marina exhibits ten-fold variation in pollen production, which represents allocation to male reproduction. In addition, S. marina individuals show three-fold variation in average ovule production (from 50 to 150 ovules per flower), although this range of variation is not uncommon in flowering plants. More importantly, the variation in both stamen number and ovule number has a genetic basic and is thus likely to show change over time in response to selection. This species, therefore, provides an excellent opportunity to investigate the causes and consequences of variation in the allocation of floral resources to male and female gametes, commonly known as "gender allocation". Currently, although there exists a great deal of theoretical work on this topic, there are no empirical studies that explore thoroughly the assumptions of this theory. For example, it has long been believed that selection to increase male allocation (e.g. high pollen production) should necessarily result in a reduction in female allocation (e.g., reduced ovule or deed production), promoting the evolution of specialized reproductive systems. This assumption, however, has never been adequately tested. Our study of the ecological genetics of sand-spurrey will test the assumptions of gender allocation theory by providing measurements of the genetic component to stamen and ovule production and measurements of any "costs" associated with increased allocation to male or female reproduction. Moreover, our data will allow an evaluation of the evolutionary flexibility of S. marina - and species similar to it - and its ability to alter its productive biology in response to changes in its increasingly threatened habitat.
