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The Guinea savanna-forest mosaic of West Africa is particularly rich in animal-dispersed plants. African savannas harbour the richest dung beetle community worldwide. The role of primates and dung beetles in natural plant regeneration and biodiversity maintenance in this ecosystem, however, is still poorly understood. The present study on olive baboons (Papio anubis Lesson 1827, Cercopithecinae) at Comoé National Park (CNP), north-eastern Ivory Coast, revealed that western olive baboon populations differ in several ways from their eastern conspecifics. Baboons are commonly regarded as predators of the seeds of their food plants. In the savanna-forest mosaic of West Africa, however, they are highly frugivorous and are important seed dispersers of a high number of woody plant species that differ in fruit type and seed size. They disperse intact seeds of at least 22% of the woody plant species of the regional plant pool. Their "seed dispersal potential", regarding seed number and seed sizes, is comparable to that of the much larger great apes. Relative to the availability in the regional pool of woody plant species, baboons preferred trees to shrubs and lianas as fruit sources and especially included larger fruit into their diet. Among several morphological fruit traits investigated, fruit type and fruit colour best described whether baboons included a species into their diet, whereas fruit type and seed size best predicted whether baboons predated upon the seeds of a food plant species. Seed size is an important plant fitness trait that can influence several steps between fruiting and the establishment of a plant´s offspring. Seed size can vary considerably within and among individuals of the same species. Primates may select for certain seed sizes within a species for a number of reasons, e.g. to decrease indigestible seed load or to increase pulp intake per fruit. Within eight out of ten plant species investigated, which differed in fruit type, seed number and seed size, olive baboons were selective in fruit choice regarding seed size. Seed size selection by olive baboons seems to be influenced, among other traits, by the amount of pulp rewarded per fruit relative to seed load, which varies with fruit and seed shape. Being a habitat generalist (with a preference for forest habitats) and able to move comparatively long distances, the olive baboon might be especially important for the biodiversity maintenance of distant forest islands. Because most woody plant species at the study site had medium-sized to large fruits and seeds, olive baboons may be crucial for seed dispersal and plant recruitment in this ecosystem. Their importance for seed dispersal of plants with small fruits should not, however, be underrated. Observation of frugivores at a typical "bird-dispersed" tree species showed that classification of seed dispersers on the basis of fruit syndromes alone can be misleading. Olive baboons disperse seeds in their faeces in a clumped manner, which generally is regarded disadvantageous for plants. Yet, seeds from all plant species being naturally present in baboon dung during seasonal peaks of dung beetle activity apparently can be scattered locally by dung beetles. Dung beetle activity at baboon faeces deposited in the two habitats was high, totalling 99 species from 26 genera. The probability and pattern of secondary seed dispersal by dung beetles depend on the structure and composition of the dung beetle community, which, in turn, seems to be strongly determined by vegetation type. I thus expected pronounced differences in secondary seed dispersal by dung beetles between seeds deposited by baboons in the savanna and in the forest. Experiments indicated that compared to seeds dispersed by baboons into the forest, seeds that end up in the savanna generally have a higher probability of (a) being removed by dung beetles, (b) being horizontally scattered by telecoprids, (c) being rapidly removed from the place of primary deposition and (d) being secondarily dispersed over larger distances. In general, savanna plants and plant habitat generalists the seeds of which baboons disperse into the savanna should profit most from secondary seed dispersal by dung beetles.
Leonia cymosa (Violaceae) is a small tree from the under story of the Amazonian rain forest. I investigated the seed dispersal ecology of L. cymosa in plots of old growth terra firme forest located within the Cuyabeno Faunistic Reserve in north-eastern Ecuador. This species offered good conditions to examine the variation of traits of individual trees and the way they are linked with fruit removal from each tree. With this study I aimed to address the question whether frugivores exert selection pressures on fruits and the fruiting regime of fleshy fruited plants. The mean height of a fruiting L. cymosa was 6.6 m (range: 2 - 12.6 m). The median tree density was 11.8 trees per hectare. Trees grew in clusters consisting of different numbers of trees of different heights. L. cymosa flowered two times a year, in late February to March and in October. The respective fruiting seasons occurred in August/September and between March and May. The fruit pulp of L. cymosa contained the sugars fructose, glucose, and sucrose, the total soluble sugar being the first important nutritional compound of the fruit pulp. The second important compound was proteins. No lipids were found in the fruit pulp. The variation of nutritional quality of the fruits was high within trees. Nonetheless, significant differences were found among trees in all nutrient constituents studied. The maximum of ripe fruits produced per season by a single tree was 427. Median productivity of the trees was 45 ripe fruits throughout the fruiting season in 1999 (n=57) and 36 ripe fruits in 2000 (n=92). The maximum standing crop of fruits in a tree was 324 fruits (counted in 2000). Black mantle tamarins, Saguinus nigricollis (Callitrichidae), and squirrel monkeys, Saimiri sciureus (Cebidae), and possibly an unknown nocturnal frugivore consumed the fruits of L. cymosa at my study site. Green-rumped acouchis (Myoprocta pratti, Dasyproctidae) consumed fallen fruits and seeds underneath the trees. Black mantle tamarins and squirrel monkeys differed widely in their effectiveness as seed dispersers. Black mantle tamarins swallowed the seeds together with the fruit pulp and defecated intact seeds far away from the mother tree. Squirrel monkeys opened the fruits to suck and gnaw on the fruit pulp, and then dropped seeds to the forest floor below the tree crowns. Each of my study plots fell into the core home range of one group each of S. nigricollis and S. sciureus. Thus, the frugivore assemblage is small and disperser availability is limited for the individual tree of L. cymosa. In a sample of 6 trees of comparable and high fruit crop size, the total of ripe fruits removed from a tree throughout the whole fruiting season by the reliable seed disperser S. nigricollis was neither significantly correlated with the content of any of the nutrients measured in the fruit pulp (fructose, glucose, sucrose, total protein; pulp does not contain lipids), nor with total metabolisable energy, seed to pulp weight ratio, or water content of the fruit pulp. Feeding preferences for single sugars determined by other laboratory studies were not confirmed by this field study. The reliable seed disperser S. nigricollis does not seem to exert selective pressure on the nutrient content of the fruits of L. cymosa. Seasonal fruit crop size was the main predictor of all aspects of fruit removal by the effective disperser of L. cymosa, Saguinus nigricollis, as well as by the non-disperser, Saimiri sciureus. Trees with larger seasonal fruit crop size had a higher probability to have fruits removed by the disperser than those with small seasonal fruit crop sizes. They also had a higher number of fruits removed by the seed disperser. However, the proportion of fruits removed by the disperser decreased with increasing seasonal fruit crop size. In contrast, probability of fruit removal, the number of fruits removed, and the proportion of fruits removed by the non-disperser increased with increasing seasonal fruit crop sizes. The observed differences between disperser and non-disperser are due to differences in feeding capacity, group size and foraging behavior. Tamarins were less likely to harvest Leonia trees that were not or less completely covered by surrounding vegetation. This probably reflects a behavior to avoid predation by forest raptors. At high con-specific fruit abundance in the neighborhood, the proportion of fruits removed by tamarins was reduced. This suggests competition of trees for the disperser. My study revealed selection of the disperser on seasonal fruit crop size of L. cymosa. My results are consistent with the “fruit crop size hypothesis”. FCSH appears to constitute a valid framework also in the monkey-dispersed L. cymosa. My findings also show that factors beyond the tree’s control influenced fruit removal from Leonia trees. Disperser-mediated selection may be constrained (yet not impeded) by neighborhood conditions.