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

General conclusion
in fruit-frugivore interactions in Sainte Luce is crucial to understand forest dynamics here
and to provide a solid database on which to formulate conservation plans.
In the closing section of this study, the hazardous situation of the Malagasy littoral forest
at the moment is described and suggestions are made as to how my findings can be
used in the design of population habitat viability analyses (PHVA), which will further lead
to the development of conservation management plans. The littoral forest is expected to
lose numerous endemic plant and animal species in the near future because of
continuing deforestation and resultant habitat changes. Of great concern is the disruption
of plant-animal interactions. Alterations in the recruitment dynamics of plant species in
forest fragments might have unknown consequences for their long-term survival. As
forests become more fragmented, the remaining patches become increasingly isolated
and less accessible for arboreal lemur species, which were found to be important seed
dispersers for numerous plant species. Consequently, gene flow and seed dispersal
between patches become more critical for the long-term survival of many plant species.
Conversely, if fragments get too small or hunting increases, the long-term survival of
animal species will not be guaranteed either. As Holocene extinctions have shown, large
frugivores, such as E. f. collaris, are most vulnerable to habitat fragmentation. We now
know that this species is the only remaining seed disperser of large-seeded plant species
and its decline and extinction will inevitably lead to a decline and lack of regeneration of
large-seeded trees. Frugivorous birds and flying foxes are the most important mobile
seed dispersers bringing seeds into grasslands and early succession vegetation. Genetic
exchange and long distance dispersal between fragments is less likely to occur if
populations of mobile flying dispersers decrease or vanish. It is thus not only the threat of
habitat loss but also the hunting in the littoral forest that will disrupt animal-plant
dynamics. I believe my findings on seed dispersal can represent a crucial input for
underlying PHVA of conservation management plans. They will help to indicate priorities
of action and vulnerable animal and plant species, which need special protection efforts.
Obviously, it is of crucial importance to urgently protect the largest remaining intact forest
fragments, which act as reservoirs from where indigenous floral and faunal species can
colonize new habitats. In this respect, conservation zones are being established by QMM
at the moment. Furthermore, to accelerate the natural recovery process corridors and
plantations are being installed. In addition, environmental education in local schools
should be continued as active cooperation with local people is indispensable to the
success of sustainable use of land and natural resources and to actively protect the
remaining littoral forests.
To conclude, this study provided a survey on fruit availability and its fluctuations in the
littoral forest as well as an extensive three-dimensional dataset involving numerous plant
species with their corresponding phenological, morphological and biochemical traits. Fruit
diets of all frugivore species were obtained as well. Based on my results, I can conclude
with great certainty that, in the littoral forest of Sainte Luce, fleshy-fruited plants engage in
diffuse mutualisms with their dispersal agents. These interactions are quite generalized,
very ancient and extraordinarily frequent in certain communities (Willson and Traveset
2000). High unpredictability and asymmetry of interactions, coupled with an important
influence of abiotic factors, signal that mutual selection pressures between plants and
seed dispersers are greatly constrained (Levey and Benkman 1999). In Sainte Luce fruiteating
animals tend to consume many fruit species and likewise the fruits of many plants
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