Eco-Morphological Grouping of Non-Dipterocarp Tree Species in a Tropical Rain Forest Based on Seed and Fruit Attributes

Abstract

Eight ecological and morphological attributes of 39 non-dipterocarp tree species were examined in the Pasoh Forest Reserve (Pasoh FR), Peninsular Malaysia. The attributes included three related to seed germination (seed longevity in the soil, responsiveness of germination to gaps and germination type), three morphological attributes of seed or fruit (fruit morphology type, seed coat character, and seed weight), and two attributes related to niche preference (successional status and life-form of adult plant). These attributes were treated as categorical data, and the dissimilarity matrix between species was subjected to clustering analysis using the UPGMA algorithm. Three cluster were recognized. The first cluster consists of 17 primary species that have short-lived seeds. These species also have large seeds, no special seed coat, and hypogeal germination that is not responsive to gaps. The second group consists of 12 gap-secondary species; most have extra long-lived seeds with epigeal germination in response to gaps, a capsule and an oily seed coat.The third cluster consists of 10 primary species, but differs from the first group in seed longevity; they have intermediate to long seed longevity (mean life ≧ 3 months and < 10 years). This group is also characterized by epigeal germination and a woody seed coat, which are common in gap-secondary species, and large seeds like those of primary species with short-lived seed. Our research suggests the existence of a third functional group, primary species with long-lived seed, which is distinct from primary and gap-secondary species in the classical meaning. The attributes that characterize this group seem to be adaptations to mammalian seed herbivores or dispersers.