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How complementary are large frugivores for tree seedling recruitment? A case study in the Congo Basin

Published online by Cambridge University Press:  10 July 2019

Franck Trolliet Open the ORCID record for Franck Trolliet [Opens in a new window] ,
David Bauman Open the ORCID record for David Bauman [Opens in a new window] ,
Pierre-Michel Forget ,
Jean-Louis Doucet ,
Jean-François Gillet  and
Alain Hambuckers
Franck Trolliet*
Affiliation:
Unité de Biologie du Comportement, UR SPHERES, Université de Liège, Quai van Beneden 22, 4020, Liège, Belgium
David Bauman
Affiliation:
Laboratoire d’Ecologie Végétale et Biogéochimie, Université Libre de Bruxelles, 50 av. F. D. Roosevelt, CP 244, 1050 Brussels, Belgium Environmental Change Institute, School of Geography and the Environment, University of Oxford, Oxford OX1 3QY, UK
Pierre-Michel Forget
Affiliation:
UMR 7179 MECADEV CNRS-MNHN, Muséum National d’Histoire Naturelle, Département Adaptations du vivant, Brunoy, France
Jean-Louis Doucet
Affiliation:
TERRA Research Center, Central African Forests, Gembloux Agro-Bio Tech, Université de Liège, Belgium
Jean-François Gillet
Affiliation:
TERRA Research Center, Central African Forests, Gembloux Agro-Bio Tech, Université de Liège, Belgium Nature Forest Environment [freelance in tropical forestry], Belgium
Alain Hambuckers
Affiliation:
Unité de Biologie du Comportement, UR SPHERES, Université de Liège, Quai van Beneden 22, 4020, Liège, Belgium
*
*Author for correspondence: Franck Trolliet, Email: [email protected]
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Abstract

Large frugivores provide critical seed dispersal services for many plant species and their extirpation from forested ecosystems can cause compositional shifts in regenerating plant cohorts. Yet, we still poorly understand whether large seed-dispersers have complementary or redundant roles for forest regeneration. Here, to assess the functional complementarity of large-bodied frugivores in forest regeneration, we quantified the effects of varying abundance of hornbills, primates and the forest elephant on the density, species richness and the mean weighted seed length of animal-dispersed tree species among seedlings in five sites in a forest–savanna mosaic in D. R. Congo, while accounting for percentage forest cover and the local presence of fruiting trees. We found that the abundance of primates was positively associated with species richness of seedlings, while percentage forest cover was negatively associated (R2 = 0.19). The abundance of hornbills, the presence of elephants and percentage forest cover were positively associated with mean seed length of the regenerating cohort (R2 = 0.13). Spatially explicit analysis indicated that some additional processes have an important influence on these response indices. Primates would seem to have a preponderant role for maintaining relatively high species richness, while hornbills and elephant would seem to be predominantly responsible for the recruitment of large-seeded trees. Our results could indicate that these taxa of frugivores play complementary functional roles for forest regeneration. This suggests that the extirpation of one or more of these dispersers would likely not be functionally compensated for by the remaining taxa, hence possibly cascading into compositional shifts.

Keywords

Complementing functionsCongo BasindefaunationMoran’s eigenvector maps (MEM)regenerationseed dispersalspatial autocorrelationtropical forestvariation partitioning
Type
Research Article
Information
Journal of Tropical Ecology , Volume 35 , Issue 5 , September 2019 , pp. 223 - 236
Copyright
© Cambridge University Press 2019 

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