DIVERSITY OF FRUIT TREES AND FRUGIVORES IN A NIGERIAN MONTANE FOREST AND ADJACENT FRAGMENTED FORESTS

Abstract

The study was conducted to examine and compare the species composition, diversity, and richness of both fruit trees and frugivores between a protected natural forest – Main Forest (MF), and unprotected forest fragments (A, B, and C) within a Nigerian montane forest ecosystem. Five 20m x 20m quadrats were randomly distributed in each of the sites for the enumeration of fruit trees while the identification and enumeration of frugivores was carried out using the Random Walk/Watch method. Alpha diversity was measured using both Simpson and Shannon-Wiener indices while similarity or otherwise dissimilarity in species composition between each pair of the sites was measured using Sorenson’s index. Pearson’s correlation coefficient (r) was used to examine the correlation between the diversity of fruit trees and frugivores. The highest number of fruit tree species was encountered in MF (46), followed by Fragment A (24) while 21 species were encountered in each of fragments B and C. The highest number of frugivorous species was encountered in MF (39), followed by each of Fragments A and B (26) while 25 species were encountered in C. Birds accounted for over 70 per cent of the frugivorous species observed within the five taxonomic groups in all the sites. Both the fruit trees and frugivore species composition varied more between the main forest and each of the fragments than between each pair of the fragments. However, the level of dissimilarity in species composition between the main forest and the fragments was more with the fruit trees than the frugivores. A total of 36, 34, and 33 fruit tree species found in MF were not found in fragments C, B, and A respectively while 26 frugivorous species were common to MF & A and MF & B, while MF & C have 24 species in common. The diversity of fruit trees and that of frugivores were highly correlated. Both the number and diversity of fruit trees and frugivores were higher in the protected main forest than in each of the forest fragments.