Spatial segregation by gender of the subdioecious shrub Thymelaea hirsuta in the Egyptian desert

The spatial distribution of sexual morphs of the subdioecious shrub Thymelaea hirsuta was analyzed in nine habitats in the Egyptian desert. The sexual morphs tended to segregate in the environment. Males were more common on slope sites, while female-biased sex ratios were observed in depressions. Nearest-neighbor analyses show that males tend to be nearest neighbors of other males and females are positively associated with other females. This segregation was found only in habitats that were markedly heterogeneous for soil chemistry. In more homogeneous soils, no segregation of the sexes was observed. The spatial segregation of the sexes of a subdioecious plant indicates that the phenomenon can occur before a species evolves strict dioecy and may even play a role in the process.