Diversity and spatial distribution of epiphytic flora associated with four tree species of partially disturbed ecosystem in tropical rainforest zone

Abstract

As components of forest communities, epiphytes influence litter and nutrient cycling while providing shelter, nesting materials and food for arboreal animals, thereby promoting diversity. Their preference for certain tree species (phorophytes) influences biodiversity and distribution, but this association is poorly understood in the tropics. We assessed the diversity and spatial distribution of epiphytes associated with four phorophytes (Alstonia booneii, Peltophorum pterocarpum, Mangifera indica and Terminalia catappa) in southern Nigeria, with number of trees sampled as 4, 29, 32 and 44, respectively. The epiphytes were delineated, sampled and identified. Soil samples were collected from tree pockets for textural and pH analyses. On the four phorophytes, 265 epiphytes under seven species (Platycerium elephantotis, Microgamma owariensis, Nephrolepis biserrata, Funaria hygrometrica, Axonopus compressus, Commelina benghalensis and Ficus spp.) and five families (Polypoidaceae, Funariaceae, Poaceae, Commelinaceae and Moraceae) were recorded. The three most abundant were Funaria hygrometrica (109), Platycerium elephantotis (102) and Microgamma owariensis (44), being present on all four phorophytes. Funaria hygrometrica and Platycerium elephantotis were the most abundant on M. indica (32 each) and T. catappa (44 and 39, respectively). Nephrolepis biserrata appeared only once on T. catappa; so too did Axonopus compressus and Commelina benghalensis on P. pterocarpum. Altogether, A. booneii, P. pterocarpum, M. indica and T. catappa had 11, 62, 89 and 103 epiphytes, respectively. Funaria hygrometrica traversed three tree strata, while others were restricted to two or even one stratum. Canopy layer, middle stratum and lower portion hosted four, five and three epiphytic species, respectively out of the seven recorded, pointing to the relative importance of light, spaciousness and moisture, respectively in epiphyte abundance on trees. Epiphytes distribution on phorophytes was not influenced by texture of the arboreal soils, but was inversely related to their pH. This study has provided useful information on epiphyte-phorophyte association in tropical environments and deserves repetition with more tree species in more natural forests.

Keywords: forest tree species, tree spatial strata, epiphyte distribution, species abundance, Nigeria