Effects of gut passage,feces, and seed handling on latency and rate of germination in seeds consumed by capuchins (Cebus capucinus)

One of the key measures of the effectiveness of primary seed dispersal by animals is the quality of seed dispersal (Schupp: Plant Ecol 107/108 [1993] 15–29). We present data on quality of seed dispersal by two groups of white‐faced capuchins (Cebus capucinus) in Costa Rica to test the hypothesis that capuchin seed handling results in effective primary dispersal for some fruit species they consume. We examined seed handling for 27 plant species, and germination rates of 18 species consumed by capuchins. For five of the most commonly swallowed seed species, we determined germination rates and average time to germination (latency) for seeds ingested and defecated by capuchins and compared these to seeds removed directly from fruit and planted. For the same five species, we compared germination rates and latency for passed seeds planted in capuchin feces to those cleaned of feces and planted in soil. For three of five species, differences in proportion of germinated seeds were significantly higher for gut passed seeds than for controls. For four of five species, germination latency was significantly faster for gut passed seeds than for controls. Feces had either no effect on seed germination rate or precluded germination. Data presented here support the hypothesis that white‐faced capuchins are effective primary dispersers. Am J Phys Anthropol 2009. © 2009 Wiley‐Liss, Inc.     

Chimpanzee (Pan troglodytes) Seed Dispersal in an Afromontane Forest: Microhabitat Influences on the Postdispersal Fate of Large Seeds1

We examined the postdispersal fate of large seeds (≥5 mm) dispersed by chimpanzees in an afromontane forest to evaluate aspects of the effectiveness of seed dispersal by chimpanzees, Pan troglodytes. We assessed the influence of six microhabitat characteristics on seed persistence and germination in seeds dispersed in chimpanzee feces and “wadges.” A total of 257 fecal samples and 56 wadges were located over a 4‐mo period by tracking a semi‐habituated chimpanzee community on day follows. Forty‐nine (19.1%) of the fecal samples contained large seeds from five different tree species. The majority of fecal samples with seeds contained seeds from the mature forest tree Olea capensis (Oleaceae) (83.7%). Forty‐two wadges (75%) contained seeds from the mature forest tree Syzygium guineense (Myrtaceae). Seeds were monitored at their deposition site for removal and germination up to 49 d following deposition. We collected data on the microhabitat surrounding each fecal and wadge sample. Multivariate analyses indicated that while fecal and wadge samples were not clustered into particular microhabitats, there was little overlap in the microhabitats in which wadges and fecal samples were deposited. Significantly more seeds persisted over 49 d in wadges (67.9%) than in feces (30.3%). Elevation was the only microhabitat variable determined to have a significant influence on seed persistence, whereas slope was determined to have a significant influence on germination.     

Dispersión Primaria de Semillas por Primates y Dispersión Secundaria por Escarabajos Coprófagos en Tikal,Guatemala1

We linked primary dispersal by spider monkeys (Ateles geoffroyi) and howler monkeys (Alouatta pigra) to post‐dispersal seed fate by studying the effects of dung type and defecation pattern on secondary seed dispersal by dung beetles. First, we described the defecation patterns for both primate species. Howler monkeys generally defecated in groups (88% of observed defecations), with each individual producing on average 31 g of dung, resulting in a large area of the forest floor (31 m²) covered by large amounts of dung (clumped spatial pattern). Spider monkeys generally (96% of observed defecations) defecated individually, each individual producing an average of 11 g of dung, resulting in a small area of the forest floor (2 m²) covered by small amounts of dung (scattered spatial pattern). Secondly, we captured dung beetles using as bait the dung of both primate species, to detect differences in the assemblages of these secondary seed dispersers attracted to the dung of both primates. More individual dung beetles, but not more species, were attracted to howler monkey dung than to spider monkey dung. Finally, we assessed experimentally (using plastic beads as seed mimics) how dung type (Ateles vs. Alouatta) and defecation pattern (scattered vs. clumped) affect secondary seed dispersal by dung beetles. We found that post‐dispersal seed fate was affected by dung type, with more seeds being buried when present in howler monkey dung, than in spider monkey dung, but was not affected by defecation pattern. It is important to consider post‐dispersal processes, such as secondary seed dispersal by dung beetles, when comparing species of primary dispersers.     

Persistence of the effect of frugivore identity on post‐dispersal seed fate: consequences for the assessment of functional redundancy

Large frugivores play an important role as seed dispersers and their extinction may affect plant regeneration. The consequences of such extinctions depend on the likelihood of other species being functionally redundant and on how post‐dispersal events are affected. We assess the functional redundancy of two seed dispersers of the Atlantic Forest, the muriqui (Brachyteles arachnoides) and the tapir (Tapirus terrestris) through the comparison of their seed dispersal quality, taking into account post‐dispersal events. We compare tapirs and muriquis for: (1) the dung beetle community associated with their feces; (2) the seed burial probability and burial depth by dung beetles; and (3) the seed mortality due to predators or other causes according to burial depth. We determine how seed burial affects seed dispersal effectiveness (SDE) and compare the dispersal quality of four plant species dispersed by these frugivores. Muriqui feces attract 16‐fold more dung beetles per gram of fecal matter and seeds experience 10.5‐fold more burial than seeds in tapir feces. In both feces types, seed mortality due to predation decreases with burial depth but seed mortality due to other causes increases. Total seed mortality differ within plant species according to the primary disperser. Therefore, the effect of seed burial on SDE varies according to the plant species, burial depth, and primary disperser. As tapirs and muriquis differently affect the seed fate, they are not functionally redundant. Since the effect of the primary disperser persists into the post‐dispersal events, we should consider the cascading effects of these processes when assessing functional redundancy.     

Effects of Seed Dispersal by Three Ateline Monkey Species on Seed Germination at Tinigua National Park, Colombia

We examined the effect of seed ingestion by three ateline primates: woolly monkeys, Lagothrix lagothricha; spider monkeys, Ateles belzebuth; and, red howler, Alouatta seniculus on germination rates and latency periods of seeds of several plant species in Tinigua National Park, Colombia. We collected dispersed seeds from feces and control seeds from the parental trees and washed them for germination trials. For the majority of plants, dispersed seeds germinated as well or better than control seeds did. Although spider monkeys depend more heavily on fruits than the other monkey species do, they were not more efficient than howlers or woolly monkeys at improving germination rates. A considerable proportion of the seeds dispersed by howlers and woolly monkeys showed reduced latency periods to germination, but spider monkeys showed less effect on reducing germination time. This result may be related to longer gut retention times, but such a trend has not been observed in other primate species. We conclude that, like many other primates, ateline monkeys are effective seed dispersers in terms of their effects on the seeds they swallow because they rarely decrease their germination rates. We discuss problems that make interspecific comparisons difficult, such as inappropriate control seeds and differences associated with germination substrates, and we stress the importance of studying other components of seed dispersal effectiveness.     

Neglected seed dispersers: endozoochory by Javan lutungs (Trachypithecus auratus) in Indonesia

Leaf monkeys are known to be leaf eaters, and thus, their potential role as seed dispersers has been neglected. However, they do also feed on fruits. To examine the role of leaf monkeys as endozoochorous seed dispersers, we studied the Javan lutung (Trachypithecus auratus) in Indonesia. We compared multiple aspects of seed dispersal processes (amount and diversity of seeds ingested, dispersal distance, and germination rate) of lutungs with that of the sympatric long‐tailed macaque (Macaca fascicularis). Over the study period, 54 percent of the lutung feces contained intact seeds, which was equivalent to the macaque feces contained seeds (62%). Seeds of at least six plant species were detected in the lutung feces, which was less than those found in the macaque feces (>19 plant species). The main species of seeds defecated by both lutungs and macaques was Ficus spp. (seed size: 0.7 mm). Seed shadow, estimated from travel distance (range: 1–299 m) and gut passage rate (24–96 h), had a unimodal‐distribution with a peak at 51–100 m, and was shorter than that reported in published accounts of macaques and other similar and smaller sized frugivores. Finally, germination rates of Ficus spp. seeds ingested by both lutungs and macaques were lower than that of the control seeds. These results imply that the dispersal effectiveness of lutungs would be lower than that of the sympatric primate frugivores. However, at a population level, lutungs could play a significant role as seed dispersers for the small‐seeded species, and therefore, more research into their frugivorous habits is warranted.     

Linking frugivore activity to early recruitment of a bird dispersed tree,Eugenia umbelliflora (Myrtaceae) in the Atlantic rainforest

Seed dispersal by animals is a complex process involving several distinct stages: fruit removal by frugivores, seed delivery in different microhabitats, seed germination, seedling establishment, and adult recruitment. Nevertheless, studies conducted until now have provided scarce information concerning the sequence of stages in a plant's life cycle in its entirety. The main objective of this study was to evaluate the immediate consequences of frugivore activity for Eugenia umbelliflora (Myrtaceae) early recruitment by measuring the relative importance of each fruit‐eating bird species on the establishment of new seedlings in scrub and low restinga vegetation in the Atlantic rainforest, Brazil. We conducted focal tree observations on E. umbelliflora trees recording birds' feeding behaviour and post‐feeding movements. We also recorded the fate of dispersed seeds in scrub and low restinga vegetation. We recorded 17 bird species interacting with fruits in 55 h of observation. Only 30% of the handled fruits were successfully removed. From 108 post flight movements of exit from the fruiting trees, 30.6% were to scrub and 69.4% to low restinga forest. Proportion of seed germination was higher in low restinga than in the scrub vegetation. Incorporating the probabilities of seeds' removal, deposition, and germination in both sites, we found that the relative importance of each frugivorous bird as seed dispersers varies largely among species. Turdus amaurochalinus and Turdus rufiventris were the best dispersers, together representing almost 12% probability of seed germination following removal. Our results show the importance of assessing the overall consequence of seed dispersal within the framework of disperser effectiveness, providing a more comprehensive and realistic evaluation of the relative importance of different seed dispersers on plant population dynamics.     

Interactions between Ants and Non‐myrmecochorous Fruits in Miconia (Melastomataceae) in a Neotropical Savanna

The aim of this study was to evaluate the role of ants as secondary seed dispersers of six primarily bird‐dispersed Miconia species in the cerrados of southeastern Brazil. Vertebrate exclosure and seed germination experiments were performed for M. albicans, M. alborufescens, M. corallina, M. ferruginata, M. ibaguensis, and M. irwinii. Excluding vertebrates did not significantly alter fruit removal rate for any of the Miconia species relative to open controls. Fruits on stalks and fallen fruits were removed and transported to nests mainly by species of Atta, Acromyrmex, and Ectatomma (dispersal distance ranging from 0.1 to 45.2 m), while Camponotus ants tended to be observed removing the fruit pulp (seed cleaning) where the fruits were found. Seed manipulation by Atta decreased germination of M. irwinii, but not M. ferruginata. Germination did not occur in intact fruits, and thus seed cleaning was an important service provided by the ants. Ant nest soils did not inhibit germination of any of the Miconia species, suggesting they are a good substrate for long‐lived Miconia seeds. We conclude that ant activity could have important effects on the fate of Miconia seeds adapted for bird dispersal.     

The role of nocturnal omnivorous lemurs as seed dispersers in Malagasy rain forests

Fruit-eating animals play important roles as seed dispersal agents in terrestrial systems. Yet, the extent to which seed dispersal by nocturnal omnivores may facilitate germination and the recruitment of plant communities has rarely been investigated. Characterizing their roles in seed dispersal is necessary to provide a more complete picture of how seed dispersal processes affect ecosystem functioning. We investigated the roles and impacts of two species of nocturnal omnivorous lemur species, Microcebus jollyae and M. rufus, on seed dispersal in Madagascar's rain forests, through analysis of fecal samples and germination experiments. Data show that these lemur species, which are among the world's smallest primates, dispersed 22 plant species from various forest strata and that the defecated seeds germinated faster and at higher rates than control seeds for the eight plant species we tested. Even though mouse lemurs dispersed both native and non-native plant species, non-native plant species represented a relatively small proportion (17%). These results demonstrate that overlooked nocturnal omnivores can act as important seed dispersers, which may have critical implications for forest regeneration and the maintenance of plant diversity in fragmented/degraded forests. Finally, we provide critical insights into the previously unobserved behavior and diet of endangered nocturnal lemurs for their effective conservation.     

Tamarins and Dung Beetles: An Efficient Diplochorous Dispersal System in the Peruvian Amazonia

Dung beetles fulfill several key functions in ecosystems but their role as secondary seed dispersers is probably one of the most complex ones. Various factors, such as seed characteristics, dispersal pattern induced by the primary disperser, season, and habitat, can affect the seed–beetle interaction. Particularly little is known about the fate of seeds primarily dispersed in small feces. The aim of this study was to investigate the effects of these factors on the dung beetle community (species composition, number and size of individuals) and its consequences on burial occurrence and depth of seeds primarily dispersed by two tamarin species. We captured dung beetles in a Peruvian rain forest with 299 dung‐baited pitfall traps to characterize the dung beetle community. Seed burial occurrence and depth were assessed by marking in situ 551 dispersed seeds in feces placed in cages. Among these seeds, 22.5 percent were buried by dung beetles after 2 d. We observed a significant effect of the amount of dung, season, time of deposition, and habitat on the number of individuals and species of dung beetles, as well as on seed burial occurrence and depth, while the tamarin species significantly influenced only the number and the size of dung beetles. This seed dispersal loop is particularly important for forest regeneration: small to large seeds dispersed by tamarins in secondary forest can be buried by dung beetles. These seeds can thus benefit from a better protection against predation and a more suitable microenvironment for germination, potentially enhancing seedling recruitment.     

Spatio–temporal Variations in Post‐dispersal Seed Fate1

The post‐dispersal fate of Chrysophyllum lucentifolium (a canopy tree; Sapotaceae) seeds was analyzed in French Guiana over three consecutive years. Experiments using 750 thread‐marked seeds were performed to investigate seed removal, predation, and caching by terrestrial vertebrates on howler monkey (Alouatta seniculus) defecation sites, where clumps of intact C. lucentifolium seeds were observed. Year‐to‐year variations in seed fate during the peak fruiting period were considered in relation to overall fruit and seed resource availability estimated by a raked‐trail survey. The effect of two forest areas, which differed in soil and floristic composition, was examined with conspecific fruiting tree density as a covariant. Exclosure versus open treatment was used to discriminate small rodents (not larger than a spiny rat) from other vertebrates. The presence of fresh howler dung did not affect seed fate after 20 days as shown by comparisons between defecation sites and control during the first year. There was a significant effect of year on the percentage of seeds remaining after 20 days. Low seed removal in 1995 and 1996 (compared to 1997) corresponded to higher overall fruiting and higher fruiting of C. lucentifolium, or the presence of alternative resources for rodents. An effect of forest area was observed on the seed removal rate, which varied with years and protection. Comparatively, an effect of forest area on the percentage of seeds lost was observed in 1996 and an effect of treatment on the percentage of seeds eaten was seen in 1995. The mode of seed caching suggested that spiny rats were the main seed remover. Results of this study suggest that greater seedling recruitment may occur when large fruit crop and high howler dispersal co‐occur with a lower impact of rodents (i.e., when rodents are saturated by abundant and diversified fruit resources such as in 1995). Such event synchrony, however, is highly unpredictable after only three years of study.     

Seed Dispersal by Monkeys and the Fate of Dispersed Seeds in a Peruvian Rain Forest1

Primary seed dispersal by two species of monkeys and the effects of rodents and dung beetles on the fate of dispersed seeds are described for a rain forest in southeastern Perú. During the six-month study period (June–November 1992) spider monkeys (Ateles paniscus) dispersed the seeds of 71 plant species, whereas howler monkeys (Alouatta seniculus) dispersed seeds of 14 species. Spider and howler monkeys also differed greatly in their ranging behavior and defecation patterns, and as a consequence, produced different seed rain patterns. Monkey defecations were visited by 27 species of dung beetles (Scarabaeidae). Dung beetles buried 41 percent of the seeds in the dung, but the number of seeds buried varied greatly, according to seed size. Removal rates of unburied seeds by rodents varied between 63–97 percent after 30 d for 8 plant species. The presence of fecal material increased the percentage of seeds removed by seed predators, but this effect became insignificant with time. Although seed predators found some seeds buried in dung balls (mimicking burial by dung beetles), depth of burial significantly affected the fate of these seeds. Less than 35 percent of Brosimum lactescens seeds buried inside dung balls at a depth of 1 cm remained undiscovered by rodents, whereas at least 75 percent of the seeds escaped rodent detection at a depth of 3 cm and 96 percent escaped at 5 cm. Both dung beetles and rodents greatly affected the fate of seeds dispersed by monkeys. It is thus important to consider postdispersal factors affecting the fate of seeds when assessing the effectiveness of frugivores as seed dispersers.     

Seed traits and bird species influence the dispersal parameters of wetland plants

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Seed dynamics of resprouting shrubs in grassy woodlands: Seed rain,predators and seed loss constrain recruitment potential

Abstract Measuring the fate of seeds between seed production and seedling establishment is critical in understanding mechanisms of recruitment limitation of plants. We examined seed fates to better understand the recruitment dynamics of four resprouting shrubs from two families (Fabaceae and Epacridaceae) in temperate grassy woodlands. We tested whether: (i) pre‐dispersal seed predation affected seed rain; (ii) post‐dispersal seed predation limited seed bank accumulation; (iii) the size of the seed bank was related to seed size; and (iv) viable seeds accumulated in the soil after seed rain. There was a distinct difference in seed production per plant between plant families with the legumes producing significantly more seeds per individual than the epacrids. Seed viability ranged from 43% to 81% and all viable had seed or fruit coat dormancy broken by heat or scarification. Pre‐dispersal predation by Lepidopteran larvae removed a large proportion of seed from the legume seed rain but not the epacrids. Four species of ants (Notoncus ectatomoides, Pheidole sp., Rhytidoponera tasmaniensis and Iridomyrmex purpureus) were major post‐dispersal seed removers. Overall, a greater percentage of Hardenbergia (38%) and Pultenaea (59%) seeds were removed than the fleshy fruits of Lissanthe (14%) or Melichrus (0%). Seed bank sizes were small (<15 seeds m^?2) relative to the seed rain and no significant accumulation of seed in the soil was detected. Lack of accumulation was attributed to seed predation as seed decay was considered unlikely and no seed germination was observed in our study sites. Our study suggests that seed predation is a key factor contributing to seed‐limited recruitment in grassy woodland shrubs by reducing the number of seeds stored in the soil.     

Effectiveness of Spider Monkeys (<Emphasis Type="Italic">Ateles geoffroyi vellerosus</Emphasis>) as Seed Dispersers in Continuous and Fragmented Rain Forests in Southern Mexico

Seed dispersal is considered a key process determining spatial structure and dynamics of plant populations, and has crucial implications for forest regeneration. We evaluated the effectiveness of spider monkeys (Ateles geoffroyi) as seed dispersers in continuous and fragmented habitats to test if this interaction is altered in forest fragments. We documented fruit and seed handling, defecation patterns, diversity and composition of seeds in feces, and seed germination of defecated and control seeds in the Lacandona rainforest, Mexico. For most species contributing to 80% of total fruit feeding time, monkeys swallowed and spat seeds, but swallowing was the most frequent seed handling category in continuous and fragmented forests. However, the proportion of feeding records of swallowed seeds was higher in continuous forest (0.59) than in fragments (0.46), whereas the opposite was true for proportion of dropped seeds (0.16 vs. 0.31). This pattern was reflected in the number of fecal samples containing seeds, which was greater in continuous (95.5%) than in fragmented forests (82.5%). Seeds in fecal samples included a total of 71 species from 23 plant families. The numbers of defecated seed species were similar between forest conditions, and in both cases most seeds (>86%) were undamaged. Defecated seeds showed greater germination percentages than control seeds in all of the five species evaluated. Although we identified some differences in seed handling and the percentage of feces with seeds between continuous forest and fragments, our results indicate that, in general terms, spider monkeys are effective seed dispersers in both forest conditions.     

Seed dispersal by Galápagos tortoises

Aim Large‐bodied vertebrates often have a dramatic role in ecosystem function through herbivory, trampling, seed dispersal and nutrient cycling. The iconic Galápagos tortoises (Chelonoidis nigra) are the largest extant terrestrial ectotherms, yet their ecology is poorly known. Large body size should confer a generalist diet, benign digestive processes and long‐distance ranging ability, rendering giant tortoises adept seed dispersers. We sought to determine the extent of seed dispersal by Galápagos tortoises and their impact on seed germination for selected species, and to assess potential impacts of tortoise dispersal on the vegetation dynamics of the Galápagos. Location Galápagos, Ecuador. Methods To determine the number of seeds dispersed we identified and counted intact seeds from 120 fresh dung piles in both agricultural and national park land. To estimate the distance over which tortoises move seeds we used estimated digesta retention times from captive tortoises as a proxy for retention times of wild tortoises and tortoise movement data obtained from GPS telemetry. We conducted germination trials for five plant species to determine whether tortoise processing influenced germination success. Results In our dung sample, we found intact seeds from > 45 plant species, of which 11 were from introduced species. Tortoises defecated, on average, 464 (SE 95) seeds and 2.8 (SE 0.2) species per dung pile. Seed numbers were dominated by introduced species, particularly in agricultural land. Tortoises frequently moved seeds over long distances; during mean digesta retention times (12 days) tortoises moved an average of 394 m (SE 34) and a maximum of 4355 m over the longest recorded retention time (28 days). We did not find evidence that tortoise ingestion or the presence of dung influenced seed germination success. Main conclusions Galápagos tortoises are prodigious seed dispersers, regularly moving large quantities of seeds over long distances. This may confer important advantages to tortoise‐dispersed species, including transport of seeds away from the parent plants into sites favourable for germination. More extensive research is needed to quantify germination success, recruitment to adulthood and demography of plants under natural conditions, with and without tortoise dispersal, to determine the seed dispersal effectiveness of Galápagos tortoises.     

Seed dispersal by the Florida box turtle (<Emphasis Type="Italic">Terrapene carolina bauri</Emphasis>) in pine rockland forests of the lower Florida Keys,United States

Seed dispersal by animals is one of the most important plant-animal mutualisms, but saurochory, the dispersal of seeds by reptiles, has received little attention. We investigated the role of the Florida box turtle (Terrapene carolina bauri) as a seed dispersal agent in pine rockland forests of the lower Florida Keys and examined the effect of turtle digestion on seed germination. We obtained seeds of 11 species with fleshy fruits and 2 species with non-fleshy fruits (a grass and legume) from the feces of 145 box turtles collected on Key Deer National Wildlife Refuge from 1999 to 2000. We planted the seeds of nine species and germination percentage (percentage of seeds that germinated during the experiment) varied from 10% to 80%. Comparative germination experiments were conducted with Thrinax morrissii, Serenoa repens, and Byrsonima lucida. We compared the germination percentage and germination rate (number of days from planting to seedling emergence) of seeds from three treatments (seeds recovered from feces, control seeds with pulp, and control seeds without pulp) and continued these experiments for up to 2 years. Passage through the box turtle digestive tract greatly enhanced the germination percentage and germination rate of S. repens, but decreased the germination percentage of B. lucida and T. morrissii, and decreased germination rate for T. morrissii. Subsequent destructive seed viability tests revealed that many ungerminated T. morrissii seeds remained viable, suggesting long-term seed dormancy may occur, even after passage through the turtle digestive system. In addition, the proportion of ungerminated seeds which remained viable was greater for seeds recovered from turtle feces than from control seeds with pulp. Furthermore, removal of fleshy pulp either manually or by the turtle digestive system may allow T. morrissii to escape insect predation.     

Primary Seed Dispersal by Red Howler Monkeys and the Effect of Defecation Patterns on the Fate of Dispersed Seeds1

The effectiveness of a seed disperser depends on the quantity and quality of dispersal. The quality of dispersal depends in large part on factors that affect the post–dispersal fate of seeds, and yet this aspect of dispersal quality is rarely assessed. In the particular case of seed dispersal through endozoochory, the defecation pattern produced has the potential of affecting the fate of dispersed seeds and consequently, dispersal quality and effectiveness. In this study, I assessed the effects of dung presence and dung/seed densities on seed predation by rodents and secondary dispersal by dung beetles. In particular, I compared seed fates in clumped defecation patterns, as those produced by howler monkeys, with seed fates in scattered defecation patterns, as those produced by other frugivores. I also determined the prevalence of red howler monkeys (Alouatta seniculus) as seed dispersers at the plant community level in Central Amazonia by determining the number of species they dispersed in a 25–month period. I found that dung presence and amount affected rodent and dung beetle behavior. Seed predation rates were higher when dung was present, and when it was in higher densities. The same number of seeds was buried by dung beedes, in dumped versus scattered defecation patterns, but more seeds were buried when they were inside large dung–piles versus small piles. Seed density had no effect on rodent or dung beetle behavior. Results indicate that caution should be taken when categorizing an animal as a high or low quality seed disperser before carefully examining the factors that affect the fate of dispersed seeds. Red howler monkeys dispersed the seeds of 137 species during the study period, which is the highest yet reported number for an Alouatta species, and should thus be considered highly prevalent seed dispersers at the plant community level in Central Amazonian terra firme rain forests.     

Comparative Seed Dispersal Effectiveness of Sympatric Alouatta guariba and Brachyteles arachnoides in Southeastern Brazil1

I compared the effectiveness of sympatric brown howlers (Alouatta guariba) and muriquis (Brachyteles arachnoides) as seed dispersers in terms of quantitative and qualitative attributes. I hypothesized that differences in feeding and behavioral patterns between these large‐bodied folivorous/frugivorous primates would lead to dissimilarities in their effectiveness as endozoochoric seed dispersal agents. The study was carried out in a semideciduous forest fragment of Fazenda Barreiro Rico, southeastern Brazil. Through behavioral sampling of frugivory and defecation events as well as analyses of fecal samples, I determined that A. guariba dispersed fewer species and produced a lower proportion of dung with intact seeds than B. arachnoides. There was no difference between the number of seeds in fecal samples of A. guariba and B. arachnoides. These primates affected to a similar degree both germination percentage and latency to germination of seeds they ingested or removed the pulp from. Howlers and muriquis were also similar in carrying seeds away from the parent trees. Contrary to muriquis, howlers defecated seeds under the canopy of conspecific lianas, where seeds are expected to suffer high mortality rates, and voided seeds predominantly in a clumped pattern. B. arachnoides was a more effective seed disperser when compared to A. guariba in some attributes evaluated, but not in others. Given the interspecific variation in recruitment patterns of tropical plants and the loss of frugivorous bird species at the study site, the differences between howlers and muriquis in their abilities as seed dispersers may crucially influence the composition and maintenance of seedling diversity.     

Seed dispersal by ants in the semi-arid Caatinga of North-East Brazil

BACKGROUND AND AIMS: Myrmecochory is a conspicuous feature of several sclerophyll ecosystems around the world but it has received little attention in the semi-arid areas of South America. This study addresses the importance of seed dispersal by ants in a 2500-km(2) area of the Caatinga ecosystem (north-east Brazil) and investigates ant-derived benefits to the plant through myrmecochory. METHODS: Seed manipulation and dispersal by ants was investigated during a 3-year period in the Xingó region. Both plant and ant assemblages involved in seed dispersal were described and ant behaviour was characterized. True myrmecochorous seeds of seven Euphorbiaceae species (i.e. elaiosome-bearing seeds) were used in experiments designed to: (1) quantify the rates of seed cleaning/removal and the influence of both seed size and elaiosome presence on seed removal; (2) identify the fate of seeds dispersed by ants; and (3) document the benefits of seed dispersal by ants in terms of seed germination and seedling growth. KEY RESULTS: Seed dispersal by ants involved one-quarter of the woody flora inhabiting the Xingó region, but true myrmecochory was restricted to 12.8 % of the woody plant species. Myrmecochorous seeds manipulated by ants faced high levels of seed removal (38-84 %) and 83 % of removed seeds were discarded on ant nests. Moreover, seed removal positively correlated with the presence of elaiosome, and elaiosome removal increased germination success by at least 30 %. Finally, some Euphorbiaceae species presented both increased germination and seedling growth on ant-nest soils. CONCLUSIONS: Myrmecochory is a relevant seed dispersal mode in the Caatinga ecosystem, and is particularly frequent among Euphorbiaceae trees and shrubs. The fact that seeds reach micro-sites suitable for establishment (ant nests) supports the directed dispersal hypothesis as a possible force favouring myrmecochory in this ecosystem. Ecosystems with a high frequency of myrmecochorous plants appear not to be restricted to regions of nutrient-impoverished soil or to fire-prone regions.