Can remnant frugivore species effectively disperse tree seeds in secondary tropical rain forests?
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Date
2009
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Biodiversity and Conservation
Abstract
Seed dispersal by frugivores in tropical rain forests is important for maintaining
viable tree populations. Over the years, vertebrate assemblages in tropical forests have
been altered by anthropogenic disturbances, leading to concerns about the ability of
remnant vertebrates to substitute for the lost or declining vertebrate populations. We
compared vertebrate composition and frugivore visitation rates as an indirect measure of
rate of seed dispersal in three tropical rain forests in Uganda, namely Mabira, Budongo and
Kibale Forests. Mabira is highly disturbed, Kibale is little and Budongo is intermediate.
The aim was to determine whether vertebrate assemblages in differentially disturbed
forests had comparable abilities to disperse seeds and whether tree species were equally
vulnerable to loss of seed dispersers. Assemblages of forest generalist species were similar
in all forests, but specialists were less abundant in the heavily disturbed forest. Remnant
frugivores in the heavily disturbed forest were mainly small-bodied species that spat seeds
beneath fruiting trees compared to large-bodied species observed in the less disturbed
forests that ingested and carried away the seeds. We postulate that the quantity of seeds
dispersed in heavily disturbed forests is much reduced due to low visitation rates of
frugivores and the absence of large frugivores that consume large quantities of fruit. The
quality of seed dispersal is affected as well by the distance over which seeds are moved.
Assessment of vulnerability of trees shows no evidence for disperser substitution for trees
producing large fruits. Fruit trees with low nutritional contents and digestibility were least
visited in frugivore-impoverished forests. The loss of large specialist frugivores is likely to
affect recruitment of many trees, especially of species that cannot establish beneath adult
conspecifics.
Description
Keywords
Large vertebrates, Disturbance, Hunting, Fruit size, Visitation rate
Citation
Babweteera, F., & Brown, N. (2009). Can remnant frugivore species effectively disperse tree seeds in secondary tropical rain forests?. Biodiversity and Conservation, 18(6), 1611-1627. DOI 10.1007/s10531-008-9546-6