The Role of Flying Foxes as Seed Dispersers on the Vegetation Dynamics in a West African Forest-Savannah Mosaic in Côte d’Ivoire

The all-embracing aim of this study was to investigate the influence of flying foxes on the vegetation dynamics of plants within the highly dynamic forest-savannah mosaic of the Guinea zone in West Africa. Assuming a positive influence of flying foxes as high quality seed dispersers, I asked the following questions, summarised in three main chapters:(1) How indicative are plant traits of fruit use by flying foxes and what adaptations between plants and frugivores have evolved?(2) Are plant distribution patterns associated with seed dispersal patterns and how well does this reflect current models of disperser-plant interaction, in particular regarding advantages animal-dispersed plants may have in terms of escaping density-dependent effects near parent plants and/or colonising new habitats?(3) What seed rain patterns, in particular spatial contagion, result from the shuttling foraging behaviour of flying foxes?In the first chapter, I showed that plant traits were not necessarily predictive of fruit use by flying foxes. It appears that flying foxes do not specialise on a specific set of plant species as their diet is highly flexible and broad when compared to different groups of vertebrate dispersers where broad overlap in fruit use prevail. In general, morphological and biochemical characterisations of fruits of woody plant species showed flying foxes to disperse fruits that were mostly large with high sugar and low nitrogen contents. Further, fruit and seed size did not limit flying foxes to particular diets.In the second and third chapters, I considered the consequences of frugivory by flying foxes in a common tree species, Cola cordifolia (Cav.) R. Br. (Sterculiaceae) that is restricted to forest islands. Here, short range seed dispersal probably plays an important role in population maintenance within forest islands. In chapter 2, spatial point pattern analysis of distribution patterns of adult and juvenile Cola plants and its pattern of seed rain generated by flying foxes indicated strong spatial association between patterns. This implies that colonisation advantages and advantages of seeds and seedlings escaping density-dependent effects were apparent. Furthermore, it represents strong evidence that flying foxes significantly impact distribution patterns of plants.In the third and last chapter, inverse modelling based on maximum likelihood estimates of seed rain data supported the results of spatial pattern associations shown in the second chapter. Seed dispersal kernels showed modal seed dispersal at intermediate distances but very little dispersal near and far from parent tree crowns. Further, handling of large seeds by flying foxes enhanced germination success even though seeds do not pass the alimentary canal. Finally, seed predation and seedling survival appeared to adversely impact recruitment of Cola within forest islands. In conclusion, flying foxes affect vegetation dynamics by delivering efficient seed dispersal within forest islands, ensuring population maintenance of Cola in a highly dynamic setting governed by seasonality, high species invasion and probable high local species extinction.