Size-dependent ESS sex allocation in wind-pollinated cosexual plants: fecundity vs. stature effects

To theoretically investigate the single and compound effects of relative fecundity and relative stature of plants on size-dependent sex allocation (SDS) in wind-pollinated cosexual species, we developed a game model and analysed ESS sex allocation of large and small plants having totally or partially different reproductive resources and different pollen and seed dispersal areas in a population. We found that e.g. when both sized plants have large pollen dispersal areas relative to their seed dispersal areas, which plants are male-biased is largely determined by relative fecundity (t) and relative size of seed dispersal area (k) of the large plants to the small plants: If t > k, large plants tend to be more male-biased even if relative size of pollen dispersal area of large to small plants (l) is smaller than k. If t < k, large plants tend to be more female-biased even if with very large l, e.g. infinity l. Comprehensively, neither very large relative size of pollen to seed dispersal area, nor great expansion of pollen dispersal area with plant size, such as previous models assumed, is important for the increasing maleness with plant size in our model. (C) 2003 Elsevier Science Ltd. All rights reserved.