Spatial Pattern of Sex Expression in Silver Maple (Acer saccharinum L.): Morisita's Index and Spatial Autocorrelation

Abstract

The spatial patterns of sex for 490 silver maple trees in 1 natural area in Michigan [USA] were examined using Morisita''s index and spatial autocorrelation techniques. Morisita''s index showed that trees of similar size as well as trees of each sex were significantly clumped. Size and sex were spatially autocorrelated. Because trees of different sexes differ in size, both the spatial patterns of size within each sex and of sex within different size classes were analyzed. Trees of similar sizes were clumped, and size was autocorrelated within each sex, but sexes were distributed randomly within each size class. These data suggest patches of silver maple consisting of similar-sized trees with sexes scattered randomly within, in proportions unique to that size class. This spatial pattern results in females pollinated by males and bisexuals pollinated by themselves or each other, thus, influencing mate selection and recombination among individuals within the population.