| Northern wild rice, Zizania palustris, is a monoecious annual of North American wetlands. It is protogynous and self-compatible but almost entirely outcrossed, since foreign pollen outcompetes self pollen. Inbreeding depression is ;Sex allocation is labile. Maleness increases with stem height or manipulations that increase vigor and height, and reverse of the usual pattern. Although seeds are resource-limited and more costly than pollen, male reproductive success increases faster with height. Pollen disperses farther and more evenly from taller stems, fathering more progeny, which are distributed farther and more platykurtically. Successive stems within plants are shorter, with smaller leaves, and smaller, more female inflorescences. Seasonal declines in floral sex ratios parallel decreases in male success due to decreased pollen dispersal and worth of ovules, supporting the Male Height Advantage model for sex allocation in wind-pollinated plants.;Sex allocation is reported for florets and fruits, ancillary parts, and whole plants, using five currencies and three stages. I give methods to find the gender of leaves, roots, and stems. Most parts contain little protein or oil, so biomass, energy content, and construction cost give similar ratios. Ash and nitrogen are more male-biassed but less appropriate currencies, since photosynthates limit reproduction. Allocation to the sexes is generally equal at the beginning of bloom or the end of male/female overlap, but female-biassed at fruiting. Intersexual resource tradeoffs are minimal. Sex allocation is less male than in Zizania aquatica. The two species interbreed and overlap geographically but Z. aquatica sets fewer and smaller fruits.;Fruiting is limited by abortions due to resource limitation and female choice, not by pollination or predation. Most progeny die from density-dependent causes between seed dispersal and germination. Seed is poorly dispersed, and sib cooperation and competition hypotheses both receive support. Male success varies more than female success. Progeny closer to the pollen source are produced with more pollen competition and are more fit. I test hypotheses concerning the favoring of monoecy over hermaphroditism. |
