Fruit-frugivore interactions in a Malagasy littoral forest - Universiteit ...

Frugivore guild
Relations between fruits and disperser
assemblages in the littoral forest
of south-east Madagascar:
a community level approach
AN BOLLEN, LINDA VAN ELSACKER, JÖRG GANZHORN
JOURNAL OF TROPICAL ECOLOGY (SUBMITTED)
ABSTRACT
Interactions among fleshy fruits and frugivore assemblages are presented from a oneyear
study in the littoral forest of Sainte Luce, south-eastern Madagascar. This
community level approach allows us to evaluate the relative contribution of different
frugivores to seed dispersal and predation. For this, interactions between 136 consumed
fruit species and 13 frugivorous species were studied. Fruit and seed size are the most
important physical factors determining food selection of all consumer species. While birds
favour lipid-rich fruits, mammals seem to avoid them. The lemur species that go into
hibernation clearly prefer sugar rich fruit pulp. In general, there is substantial dietary
overlap among consumer species and animals seem to be quite flexible to eat whatever
is available. This might be related to unpredictable fruit availability, which in turn, might be
one of the reasons for the evolution of the depauperate frugivore guild here. Nevertheless
all frugivores have different impacts on seed dispersal. Eulemur fulvus collaris is
particularly important for the dispersal of large-seeded species. Birds and flying foxes
ensure genetic exchange and plant regeneration between and outside forest fragments.
In terms of conservation, heterogeneous seed transport is particularly important for this
severely degraded littoral forest.
INTRODUCTION
Interactions between fleshy-fruited plant species and the community of vertebrate
frugivores have been studied in the tropics worldwide (Leighton 1982; Gautier-Hion et al.
1985; Dowsett-Lemaire 1988; Corlett 1996; Kitamura et al. 2002; Ingle 2003), where
zoochorous plant species make up the majority of the flora (Howe and Smallwood 1982;
Fleming et al. 1987). The fleshy pulp of endozoochorous fruits attracts its consumers by a
wide array of morphological traits and offers a nutritional reward for potential seed
dispersers. In general, fruits are eaten and dispersed by a variety of animals even though
some fruit traits are more likely to attract one taxonomic group of potential dispersers
than another (Howe 1984; Gautier-Hion et al. 1985; Herrera 1987; Dowsett-Lemaire
1988; Terborgh 1990; Jordano 1992, 1995; Fisher and Chapman 1993; Erikkson and
Ehrlen 1998). In this respect diffuse and broad co-adaptations are revealed when
analysing feeding selection resulting in ‘fruit character syndromes’ (Van der Pijl 1969;
Gautier-Hion et al. 1985). However, the definition of syndromes is problematic as traits
are defined differently in each study. Therefore it is necessary to evaluate diets of
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