Dioecy‐induced spatial patterns of two codominant tree species,Podocarpus nagiandNeolitsea aciculata

Summary 1 Spatial patterns of two codominant dioecious tree species,Podocarpus nagiandNeolitsea aciculata, were analysed at Mt. Mikasa, Nara City, Japan.Podocarpus nagihas a higher shade tolerance but a narrower seed dispersal range thanN. aciculata.We examined the effects of dioecy on regeneration and coexistence of the two species. 2 Seeds ofP. nagiare dispersed by gravity around female trees. Young plants ofP. nagiwere clumped and showed significant attraction to large female trees and significant repulsion from large male trees. Dioecy therefore affected the spatial heterogeneity of plant density in theP. nagipopulation. 3 Seeds ofN. aciculataare widely dispersed by birds, and young plants ofN. aciculatatherefore showed no significant attraction to female trees. This wide dispersal of seeds moderated the effects of dioecy on the spatial pattern inN. aciculata. 4 LargeN. aciculatatrees were clumped and showed significant attraction to large maleP. nagitrees, suggesting that growth ofN. aciculatais facilitated where youngP. nagiplants are uncommon and competition is therefore less intense. 5 One effect of dioecy may be to produce a population structure forP. nagithat promotes its coexistence withN. aciculata.