Characterization of animal communities involved in seed dispersal and predation of Guibourtia tessmannii (Harms) J.Léonard,a species newly listed on Appendix II of CITES

Characterization of the ecology of endangered timber species is a crucial step in any forest management strategy. In this study, we described the animal communities involved in seed dispersal and predation of a high‐value timber species Guibourtia tessmannii (Fabaceae; Detarioideae), which is newly listed on Appendix II of CITES. We compared the animal communities between two forest sites (Bambidie in Gabon and Ma'an in Cameroon). A total of 101 hr of direct observations and 355 days of camera trapping revealed that a primate (Cercopithecus nictitans nictitans) and a hornbill (Ceratogymna atrata) were important seed dispersers in Gabon. Conversely, a greater presence of a rodent (Cricetomys emini), which could act both as predator and disperser, was observed in Cameroon. This study suggests that animal communities involved in seed dispersal of G. tessmannii may vary depending on environmental conditions and anthropogenic impacts. However, further studies are needed to properly identify the factors involved in seed dispersal and predation of G. tessmannii.     

Effect of distance,aggregation, and habitat on levels of seed predation for two mammal — dispersed neotropical rain forest tree species

The effect of seed aggregation and distance from conspecific trees on seed predation was experimentally examined for two neotropical tree species, Macoubea guianensis (Apocynaceae) and Pouteria sp. (Sapotaceae) in a lowland tropical rain forest in northeastern Peru. Results of these experiments are discussed in the context of the Janzen-Connell model (Janzen 1970; Connell 1971), which predicts decreased seed survival near parent trees due to either density-or distance-responsive mortality, and Howe's model (Howe 1989) which predicts that trees with seeds dispersed in clumps (aggregated) will not suffer density-dependent predation, and will have higher survival of seeds near the parent tree than other trees. We also examined whether predation on seeds of these species was affected by seed placement in or near 30-m-wide strips regenerating after clear-cutting. Both species appeared to be mammal-dispersed but differed in how frugivores handled seeds, seed size, overall fruit crop size, and gemination time. Neither of the two species studied appeared to suffer seed predation in a manner predicted by the Janzen-Connell model, and patterns of seed predation for only one of the species was similar to predictions of Howe's model. For neither species did seed predation along the edge of, or in the center of, regenerating clear cuts differ from predation 15 m into the primary forest. For Pouteria, seed predation in and near regnerating strips was significantly greater than around forest trees, but the opposite pattern held for Macoubea. Overall, seed predation was much greater on Macoubea. The difference in seed predation for these two species was most likely a result of differences in the types of seed predators that attacked these two species.     

Physical and chemical properties of fruit and seeds eaten byPithecia andChiropotes in Surinam and Venezuela

Pithecia pithecia andChiropotes satanas are seed predators that eat fruits with hard pericarps. We measured resistance to puncturing and crushing of fruit and seeds eaten by these two pitheciins at two localities: in evergreen rain forest at Raleighvallen-Voltzberg, Surinam, and in tropical dry/transitional moist forest on islands in Guri Lake, Venezuela. Average measurements of pericarp hardness were similar at both sites for fruit eaten byChiropotes, but a higher maximum value was obtained at the rainforest site.Chiropotes andPithecia both ate fruits that had harder pericarps than did fruits eaten byAteles paniscus, but crushing resistances of seeds eaten were lower than values forAteles. Thus, both pitheciins selected fruits with hard pericarps and soft seeds, although there were notable intergeneric differences in hardness of fruit ingested. When fruit became scarce,Pithecia ate more flowers, whileChiropotes continued to eat fruits with hard seed coverings. Chemical analysis of species of seeds eaten byPithecia suggests that they avoided seeds with extremely high tannin levels, though they tolerated moderate tannin levels in combination with high levels of lipids. We propose that sclerocarpic harvesting (the preparation and ingestion of fruit with a hard pericarp) allows pitheciin monkeys to obtain nutritious seeds, with reduced tannins, that are softer than those ingested by other frugivores.Presented at XIIIth Congress, International Primatological Society, July 27, 1990.     

Regeneration filters in post-agricultural fields of Puerto Rico and Ecuador

To better understand how rainforest regenerates after agriculture I sampled the seed rain and seed bank, and set out seeds and seedlings, on microsites defined by distance to the forest in fields both in Puerto Rico and Ecuador. I found that (1) total seeds, species richness and life-form richness were twice as great in the Ecuador seed rain compared to Puerto Rico but Puerto Rico seeds were more evenly distributed among species and (2) total seedlings from the seed bank were similar between Puerto Rico and Ecuador, (3) the majority of seeds were lost to predation among all species and study sites, (4) seed disease was absent in P. aduncum and Miconia prasina, and no seeds germinated for Gonzalagunia spicata and P. riparia, (5) in Ecuador pathogenic disease claimed more seeds than germinated for all species, and Solanum ovalifolium was the only species that had seeds germinate but did not lose seeds to disease, (6) also in Ecuador, insect predation was significantly lower in the forest border for P. aduncum, and seed disease was significantly greater at the 10 m micro site for S. ovalifolium, (7) distance has a significant effect on seedling height and basal diameter, (8) losses of leaf area due to herbivory and pathogens were always low and (9) biomass and leaf specific mass were significantly reduced in the border and forest microsites. I conclude that Ecuador fields had more seeds, species, and life-forms than Puerto Rico fields, predation was the most severe post-dispersal seed filter in all fields, seeds that survived predation on Puerto Rico were lost either to disease or germination but to both mechanisms in Ecuador, all three seed mechanisms in Ecuador fields showed distance effects of seedling growth but not survivorship.     

Effects of microhabitat on palm seed predation in two forest fragments in southeast Brazil

The establishment of plants depends crucially on where seeds are deposited in the environment. Some authors suggest that in forest understory seed predation is lower than in gaps, and higher than at the forest edge. However, most studies have been carried out in large forest patches and very little is known about the effects of microhabitat conditions on seed predation in forest fragments. We evaluated the effects of three microhabitats (gaps, forest edge, and understory) on seed predation of two palm species (Euterpe edulis and Syagrus romanzoffiana) in two semi-deciduous forest fragments (230 and 2100 ha) in southeast Brazil. Our objective was to test two hypotheses: (1) Low rodent abundance in small fragments as a result of meso-predator action levels leads to lower seed predation in small fragments. (2) Most mammal species in small fragments are generalists with respect to diet and habitat, so that seed predation is similar in different microhabitats (gaps, forest edge and understory) in the small fragment, but not in the larger one. The study community of small fragments is usually composed of generalist species (in diet and habitat aspects), so we expected the same rate of seed predation among microhabitats (gaps, forest edge and understory) in the tested smaller fragment. The experiment was carried out in the dry season (for E. edulis) and in the wet season (for S. romanzoffiana) in 1999. We conclude that post-dispersal seed predation in forest fragments can be directly connected with mammal communities, reflecting their historical and ecological aspects.     

Diet and dental topography in pitheciine seed predators

Pitheciines (Pithecia, Chiropotes, and Cacajao) are a specialized clade of Neotropical seed predators that exhibit postcanine teeth with low and rounded cusps and highly crenulated occlusal surface enamel. Data on feeding ecology show that Pithecia consumes proportionally more leaves than other pitheciine species, and comparative studies demonstrate its greater molar relief and relative shearing potential. However, data on pitheciine food mechanics show that Pithecia masticates seeds with greater crushing resistance than those preferred by Chiropotes. This variation predicts an opposing morphology characterized by low and more rounded occlusal surfaces in Pithecia. We build on previous research using new methods for molar surface shape quantification by examining pitheciine second molar shearing crest length, occlusal relief, surface complexity, and surface curvature relative to nonseed specializing platyrrhines and within the context of the observed interspecific variation in pitheciine feeding ecology. Consistent with the previous analyses, our findings demonstrate that pitheciine molars exhibit low shearing, relief, and curvature compared with nonseed predators, independent of phylogeny. Pitheciines also exhibit highly “complex” occlusal topography that promotes the efficient breakdown of tough seed tissues. Overall, Pithecia, Chiropotes, and Cacajao share a similar topographic pattern, suggesting adaptation to foods with similar structural and/or mechanical properties. However, Cacajao differs in surface complexity, which reflects some variation in its feeding ecology. Contrary to the predictions, Pithecia and Chiropotes do not differ in any of the topographic variables examined. The range of demands imposed on the postcanine teeth of Pithecia might therefore select for an average topography, one that converges on that of Chiropotes. Am J Phys Anthropol, 2013. © 2012 Wiley Periodicals, Inc.     

Evidence for insectivory inChiropotes satanas

Chiropotes spp. are normally considered to be entirely herbivorous, specializing in seed predation. However, we report on a single stomach ofChiropotes satanas chiropotes that contained at least 133 insects of at least ten families suggesting the possibility of facultative omnivory.     

Consistent pattern of habitat and species selection by post-dispersal seed predators in a Mediterranean mosaic landscape

There is still little information on effects of habitat degradation on post-dispersal seed predation at the landscape scale. The aim of this study was to determine the influence of habitat degradation and seed species on the variability of post-dispersal seed-predation rate. Experimental seed removal was investigated in six Mediterranean woody plant species, four trees (Pinus sylvestris, Quercus ilex, Acer opalus ssp. granatense, and Sorbus aria) and two shrubs (Berberis vulgaris and Crataegus monogyna), in an extensively used mosaic landscape on the Sierra Nevada massif (SE Spain). Seed depots were distributed over 2 years in five differently degraded landscape units, each one with three plots: shrubland; native forest; and dense, cleared and fenced reforestation stands. Predation was the highest in native forest, shrubland, and fenced reforestation, and the lowest in dense and cleared reforestation stands, being partially due to a positive correlation between shrub cover and post-dispersal seed predation. However, the main factors driving post-dispersal seed predation were intrinsic to seeds, as species preference explained most of the variance in our model for predation. The plant-species ranking was Quercus > Pinus > Sorbus > Berberis > Acer > Crataegus, the dominant tree species being the most depredated. These findings are novel because they suggest for the first time that species-selection patterns by post-dispersal seed predators tended to remain constant through both study years in all habitats comprising a mosaic landscape, whether native forest, reforestation stands or successional shrubland.     

Frugivory and Seed Fate in Bursera inversa (Burseraceae) at Tinigua Park,Colombia: Implications for Primate Conservation1

The large ateline primates are efficient seed dispersers in Neotropical forests and hunting is driving their populations to extinction, but we do not know whether other frugivores could substitute primates in their ecological role as seed dispersers. In this study we test this possibility using a potential keystone species (Bursera inversa) at Tinigua Park, Colombia. This plant species allows us to compare seed removal rates between emergent, isolated trees, without primate visitors and trees with connected crowns. We used traps to estimate fruit production and seed removal rates in six different trees, and fruiting trees were observed during 2 yr to quantify the number of seeds manipulated by different animal species. We carried out seed predation experiments to test if seed removal by predators was affected by distance or density effects. We found that the most productive trees attracted more visiting species and seed removal rates differed among trees, the lowest corresponding to trees without primate access. Seed removal rates from the ground by predators were not higher below parental trees than away from them, but the distribution of saplings in the forest suggests that seed dispersal is advantageous. Although it is likely that the effect of primate extinctions will vary depending on tree species traits, conserving the populations of primate seed dispersers is critical to maintain the ecological processes in this forest.     

Differential seed and seedling predation by crabs: impacts on tropical coastal forest composition

Recently, the importance of seed predation by crabs on mangrove species distributions and densities has been established by several studies. In a tropical coastal terrestrial forest in Costa Rica, we investigated the relative importance of predation by land crabs, Gecarcinus quadratus, and hermit crabs, Coenobita compressus, on measured forest composition through a series of seed removal and seedling establishment experiments. We also used natural light-gaps and adjacent non-gap sites to test how canopy cover affects crab predation (seed removal) and seedling establishment. We found fewer tree species (S=18) and lower densities (seedlings, saplings, and adults) in the coastal zone within 100 m of coastline, than in the inland zone (S=59). Land crab densities were higher in the coastal zone (3.03±1.44 crabs m^–2) than in the inland zone (0.76±0.78 crabs m^–2), and hermit crabs were not present in the inland zone. Seed removal and seedling mortality also were higher in the coastal zone than in the inland zone, and in the open controls than in the crab exclosures. Mortality of seeds and seedlings was two to six times higher in the controls than exclosures for four of the five experiments. Crabs preferred seeds and younger seedlings over older seedlings but showed no species preferences in the seed (Anacardium excelsum, Enterolobium cyclocarpum, and Terminalia oblonga) and seedling (Pachira quinata and E. cyclocarpum) stages. We conclude that the observed differences in tree densities were caused by differential crab predation pressure along the coastal gradient, while the differences in species composition were due to predator escape (satiation) by seed quantity. Canopy cover did not affect seed removal rates, but did affect seedling survival with higher mortality in the non-gap versus gap environments. In summary, crab predation of seeds and seedlings, and secondarily canopy cover, are important factors affecting tree establishment in terrestrial coastal forests.     

Seeds and seedlings of two neotropical montane understory shrubs respond differently to anthropogenic edges and treefall gaps

Edges resulting from forest clear-cutting and treefall gaps can affect plant populations and consequently the distribution of species across landscapes. These two types of disturbance might interact to exacerbate or ameliorate “edge effects”, a rarely tested possibility. We focused on the effects of distance from forest edge (0–10, 30–40, 60–70, and 190–200 m) and habitat within forest fragments (treefall gaps and intact forest) on the early stages of development of Palicourea gibbosa and Faramea affinis, two common shrubs of montane forests in southwest Colombia. Seed germination and seedling growth did not change with distance from forest edge. Within forest fragments, however, seed germination and seedling growth were higher in treefall gaps than in intact forest understory for both species. In contrast, seed predation was influenced by distance from forest edge and in P gibbosa it depended on habitat. Seed predation was highest in the forest interior (190–200 m from forest edge) and in P. gibbosa this was true only in treefall gap habitats. These results suggest that animal mediated processes such as post-dispersal seed predation are more likely than physiological processes to be affected by anthropogenic edges. Our results provide some evidence that treefall gaps may interact with “edge effects”, however, they are inconclusive as to whether they exacerbate or ameliorate them. Received: 31 August 1998 / Accepted: 18 February 1999     

Absence of Howlers (<Emphasis Type="Italic">Alouatta palliata</Emphasis>) Influences Tree Seedling Densities in Tropical Rain Forest Fragments in Southern Mexico

The disappearance of frugivorous primates in fragmented forests can potentially lower the rates of seed dispersal and recruitment of endozoochorous tree species, thus altering plant community structure. We quantified seedling density for 7 tree species that are common in the feces of mantled howlers (Alouatta palliata) in 6 rain forest fragments in northern Chiapas, Mexico. Howlers were present in 3 of the fragments and absent in the other 3. We compared seedling density in primate sleeping sites in inhabited fragments with control sites, which were structurally similar to sleeping sites but where we did not find monkey feces, in both inhabited and uninhabited fragments. For each tree species, we determined the relationship between seedling density and the local density of seeds and adult trees. In fragments where howlers were present, seedling density for 4 of the focal tree species (Brosimum alicastrum, Dialium guianense, Manilkara zapota, and Nectandra ambigens) was greater in sleeping sites than in control sites found in the same fragments. Moreover, seedling density of Dialium guianense was greater in the control sites of fragments inhabited by howlers than in fragments where this primate is absent. Seedling density of these 4 species correlates positively with seed density on the forest floor; however, we observed no correlations between seedling density and the density of adult trees. Our results suggest that the diversity of the seedling community of tree species dispersed by howlers may decline in fragments where this seed disperser is absent. These findings, together with the fact that only 5% of the study region is currently covered by forest and 81% of the forest remnants are uninhabited by mantled howlers, suggest that the potential long-term recovery of associated populations of tropical tree species dispersed by this primate species is highly uncertain. Conservation and restoration efforts should be aimed at restoring or replacing the ecological role played by this important seed disperser in the region.     

Modelling oldfield species richness in a mountain area

Seed predation by rodents affects plant population dynamics and it mayrespond to changes in vegetation structure at forest edges. This studyinvestigates the magnitude and direction of a potential edge effect intemperatedeciduous forests, and it seeks possible explanations based on predatorabundance and vegetation structure. The study was conducted at twelve forestedges in northern Switzerland; in six sites all shrubs at the forest edge wereremoved, whereas the other sites maintained a structurally rich shrub layer. Ineach site three transects were laid out from the edge towards the forestinterior. In six plots along these transects (at 1, 3, 6, 12, 25, 50m) we studied seed removal from experimental dishes, rodentabundance in live-traps and four characteristics of the vegetation structure.For both woody seed species (Prunus avium,Viburnum lantana) predation was significantly higher nearthe forest edge in the structurally rich sites; in the other sites no suchgradient was found. Selectively accessible dishes revealed that rodents werethemain predators, whereas predation by insects or molluscs was not observed.Abundance of rodents (Apodemus flavicollis, A.sylvaticus, Clethrionomys glareolus) washighestunder dense shrubs close to the forest edge. In the structurally rich sitesthere was a clear gradient of decreasing shrub cover from the edge towards theforest interior; a weaker gradient was observed in the structurally poor sites.We conclude that high shrub cover near the forest edge is the main determinantfor edge effects in seed predation, and edges without a shrub belt show no sucheffect.     

Apparent competition: an impact of exotic shrub invasion on tree regeneration

Invasion of habitats by exotic shrubs is often associated with a decrease in the abundance of native species, particularly trees. This is typically interpreted as evidence for direct resource competition between the invader and native species. However, this may also reflect indirect impacts of the exotic shrubs through harboring high densities of seed predators––known as apparent competition. Here I present data from separate seed predation experiments conducted with two shrub species exotic to North America; Rosa multiflora, an invader of abandoned agricultural land, and Lonicera maackii, an invader of disturbed or secondary forest habitats. Both experiments showed significantly greater risks of seed predation for tree seeds located under shrub canopies when compared to open microhabitats within the same site. These results indicate the potential importance of indirect impacts of exotic species invasions on native biota in addition to the direct impacts that are typically the focus of research.     

Cocoon predation on diprionid sawflies: the effect of forest fertility

Predation by small mammals is thought to be one of the main regulators of outbreaking sawfly species. It has been suggested that predation may be lower in poor and dryish forests, and this is the reason why outbreaks often begin from this type of environment. We studied experimentally how fertility of the forest site affects cocoon predation experienced by two sawfly species, the common pine sawfly Diprion pini (Linnaeus) and the European pine sawfly Neodiprion sertifer (Geoffroy). We applied a fertilization treatment to selected pine-dominated barren forest sites in Finland, and 2–4 years later monitored predation on the sawfly cocoons in fertilized and control areas. The results did not support the idea that forest fertility was related to cocoon predation. We also could not verify that small mammal abundance was related to fertility of the forest. The most obvious pattern we observed was that the two sawfly species differed dramatically in predation experienced. N. sertifer has its cocoon phase in mid-summer and experienced only moderate predation (37%) whereas D. pini, with its cocoon phase in autumn, suffered from very heavy predation (96%). Our observations suggest that if predation is important in controlling the population dynamics of the species, its impact depends more on the sawfly species and season than on the fertility of the forest site. Received: 1 March 1998 / Accepted: 25 May 1998     

Seed colour and post-fire bird predation in a Mediterranean pine forest

In a Pinus halepensis Mill. forest, a field experiment was designed to evaluate post-fire seed predation as affected by combinations of seed colour and soil substrates: light grey and black seeds combined with light grey ash, dark grey ash and pale brown sand. A survey of bird species inhabiting the area was also carried out and polyphenolic content of seed coat was assessed in seed lots of different colour. Light grey seeds were observed to be less predated on light grey ash, suggesting eucrypsis as a protective strategy against bird predation. On the contrary, no clear pattern was observed for the predation of black seeds on different substrates. In the study area both bird species breaking the seed coat and eating the endosperm and bird species swallowing the whole seed were monitored. We have estimated that more seeds were swallowed than broken, in all colour categories. Light grey seeds, which were found to have a higher content of polyphenols, were predated more than black seeds when exposed on the same substrate. Thus, no evidence was produced that the amount of polyphenols in seed coat could protect seeds from predation.     

Drought,post‐dispersal seed predation,and the establishment of epiphytic bromeliads (Tillandsia spp.)

Post‐dispersal, epiphyte seed predation is poorly documented. Our study on the in situ germination of two Tillandsia species in a deciduous forest in Yucatan, Mexico showed an average post‐dispersal seed predation rate by the Yucatan deer mouse (Peromyscus yucatanicus) of 90%. Post‐dispersal predation was thus more limiting than drought.     

Land-use and edge effects unbalance seed dispersal and predation interactions under habitat fragmentation

The process of fragmentation can greatly influence plant–animal interactions. To assess the degree to which it affects the balance between two interactions of opposite sign, namely seed dispersal and post-dispersal seed predation, we selected 16 patches of chestnut forest in O Courel and El Bierzo, northwestern Spain. We assessed the effect of fragmentation over two different seed dispersal–predation systems using Helleborus foetidus and Ilex aquifolium as model species. In the first case, field experiments consisted of seed-offering trays with selective exclusion of rodents and ants in a two-way orthogonal design. In the second experiment, we placed experimental branches and trays on the floor to assess seed dispersal and predation. The interactions between several fragment traits and the relative contribution of rodents, ants and birds to seed removal were analyzed by means of generalized linear mixed models. Results show that for H. foetidus, differences in seed dispersal–predation were accounted for by patch shape, which affected mainly the dispersal phase. Major seed dispersal took place in patches with a smaller edge to core ratio and high plant cover (abandoned patches), whilst the latter also showed maximum seed predation. For I. aquifolium, fragmentation effects were significant only for seed predation, which was increased in abandoned patches. This shows that the effects of habitat fragmentation can emerge at different phases depending on specific traits of the interacting animals. It also highlights the importance of traditional land-use practices in species interactions.     

Massive Seed Predation of Pseudobombax grandiflorum (Bombacaceae) by Parakeets Brotogeris versicolurus (Psittacidae) in a Forest Fragment in Brazil1

Here we report massive seed predation of Pseudobombax grandiflorum (Bombacaceae) by Botogeris versicolurus (Psittacidae) in a forest fragment in Brazil. The intensity of seed predation was very high when compared to other studies in continuous forest, perhaps resulting from a scarcity of resources in such areas. This scarcity may limit the range of parrot's diet to a few plant species. It suggests that studies of Psittacidae seed predation may be important for conservation of some plants in fragments.     

Seed survival on experimental dishes in a central European old‐growth mixed‐species forest – effects of predator guilds,tree masting and small mammal population dynamics

Predation of tree seeds can be a major factor structuring plant communities. We present a three year study on tree seed survival on experimental dishes in an old‐growth forest in central Europe in Austria. We addressed species specific, spatial and temporal aspects of post‐dispersal seed predation. Seeds of Norway spruce Picea abies, European beech Fagus sylvatica, and silver fir Abies alba were exposed on dishes in different types of exclosures which allowed access only to specific guilds of seed predators. Removal experiments were carried out in two old‐growth forests and a managed forest (macro‐sites), including micro‐sites with and without cover of ground vegetation. We conducted the experiment in three consecutive years with a mast year of beech and spruce before the first year of the study. The seed removal experiments were combined with live trapping of small mammals being potential seed predators. Our experiments showed a distinctly different impact of different predator guilds on seed survival on the dishes with highest removal rates of seeds from dishes accessible for small mammals. We observed differing preferences of small mammals for the different tree species. Seed survival in different macro‐ and micro‐habitats were highly variable with lower seed survival in old growth forests. In contrast to our assumption, and in contrast to the satiation hypothesis which assumes higher seed survival in and directly after mast years, seed survival was lower in the year following the mast year of beech when a population peak of small mammals occurred and higher in intermast periods when subsequently small mammal population crashed. This suggests a higher importance of sporadic masting shortly after mast years in intermast periods for establishment of forest trees provided that pollination efficiency is high enough in such years. Combined with the high seed mortality observed after the mast year, this corroborates the important role of seed predation for forest dynamics. An altered synchrony or asynchrony of masting of different tree species and changed masting frequencies through climate change may thus lead to strong and non‐linear effects on forest dynamics.