Seed dispersal, germination and seedling recruitment of antiaris toxicarla leschenault (moraceae): the role of primates in Bia biosphere reserve
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Date
2001-12-14
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Abstract
Antiaris toxicaria is one of Ghana’s most valuable lesser-used timber species being promoted to ensure a more balanced usage of the timber species in the forest. This study was conducted to quantify the proportion of Antiaris seeds dispersed by primates relative to other potential seed dispersers, and to examine if seed dispersal by primates conferred any advantages on Antiaris seed survival.
Trap nets covering 8.14 ± 0.7% crown area under selected trees (N=6) were used to estimate flower and fruit-fall numbers. To assess advantages of predation and dispersal by primates on Antiaris seed survival. 1800 seeds were exposed to different treatments: (a) rinsed and dried seed from ripened fruits that have fallen beneath the parent trees (“control”) (b) seed with fruit pulp attached, and (c) seeds that were spat out or dropped by monkeys after eaten the fruits (“rejecta”), at seed stations located at 10, 15, 30, 40, and 60m from fruiting parent trees. Seedling regeneration rates was assessed by laying three lOOm transects with 30 degree sector radiating from focal trees (N=7). Frugivore visitation and feeding behavior during 1200 hours of diurnal and nocturnal observation of focal trees were recorded. Temporal germination rates were further investigated by using 10 seeds per treatments in 10 replicates on filter paper and soil.
A. toxicaria trees with a mean DBH (± SE) of I 3m ± 0.26 produced 27,843 ± 11,808 flowers and 21,159 ± 9912 fruits. A potential flower predator was not observed. Seventeen mammals and 9 birds’ species ate the fruits. Monkeys (Cercopithecus campbelli and Cercopithecus Petaurista) are the main seed dispersers for Antiaris and are able to carry seeds away from Parent tree without affecting the germination capacity of the seed. Birds (such as hornbills, tauraco, plantain-eater, and fruit bat) may also be essential for Antiaris seed survival.
Germination rates did not differ (LSD, P> 0.05) between control seeds (70 & 73%) and rejecta seeds (51 & 59%) on filter paper and soil respectively. However, both control and rejccta seeds had higher germination rates than seeds with fruits attached (5 & 15%). Seed predation analysis using one-way and two-way ANOVA indicated that there were no significant differences (P>0.05) between distances and treatments All seeds of various treatments suffered heavy predation within 32 days. There was a weak correlation between DBFI and mean seedling number (R0. 1443). Seedling numbers increased from the parent tree until a peak occurs around l0m (under tree canopy) after which declining seedling numbers occurred. Linear regressions had low ability to predict seedling numbers as a function of distance from parent plants. The recruitment pattern of Antiaris toxicaria is greatly influenced by the potential seed dispersers as identified in this study, therefore any future disappearance of the dispersers may raise concerns about the reproductive ecology of A. toxicaria.
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A thesis submitted to the School of Graduate Studies,
Kwame Nkrumah University of Science and Technology, in partial
fulfilment of the requirements for the award of Master of Science, 2001