Spatial pattern and seed dispersal of Lithospermum caroliniense on Lake Huron sand dunes

Abstract

Studies on spatial pattern and seed dispersal of Lithospermum caroliniense (Walt.) MacMill. on Lake Huron sand dunes revealed that the ratio of pin to thrum plants was approximately 1: 1 on the south slope of the first dune ridge and slack. However, thrum plants had a higher proportion than pin plants on the crest of the dune ridge. The density of plants was highest on the south slope as compared with the other topographical zones. The spatial pattern of plants was nonrandom and plants were clustered in each of the three topographical zones. Most dispersed seeds of L. caroliniense remained within 1 m of the parent plant. The seed dispersal was not radially symmetrical around the parent plant. The steepness of the dune slope affected the dispersal distance of some propagules. Some seeds were retained on the parent, but few of these seeds were normal. About 40 to 64% of the recovered seeds contained holes in the seed coat. Eight months after marking, about one-third of the original marked seeds were still intact.