WIND DISPERSAL OF FRUITS WITH VARIABLE SEED NUMBER IN A TROPICAL TREE (LONCHOCARPUS PENTAPHYLLUS: LEGUMINOSAE)

Abstract

The tropical tree, Lonchocarpus pentaphyllus (Poir.) DC. (Leguminosae‐Papilionoideae), matures indehiscent wind‐dispersed fruits containing 0–4 seeds. Most fruits are one‐seeded (82%) while less than 2% are three‐seeded. An increase in seed number per fruit correlates with increases in four characteristics expected to affect dispersal distance under field conditions: fruit weight, fruit area, square root of wing‐loading, and rate of descent in still air. The dry weight of a seed decreases with an increase in seed number per fruit. Under field conditions nearly 40% of the mature fruits fall within the radius of the tree crown. Fruits with more intact seeds are dispersed shorter distances; fruits with no developed seeds travel the farthest. Among one‐seeded fruits dispersed beyond the crown radius, dispersal distance is inversely proportional to the square root of wing‐loading. The weight of seed in these one‐seeded fruits, however, is independent of dispersal distance. Fruits with more seeds have a higher proportion of underdeveloped seeds. However, a greater proportion of two‐ and three‐seeded fruits have at least one intact mature seed than do one‐seeded fruits. This comparative study illustrates that changes in fruit morphology and weight associated with different numbers of seeds per fruit affect dispersal properties as well. A decrease in seed number per fruit increases both seed weight and dispersal distance, but it decreases the probability that a given dispersal event results in movement of an intact seed.