Potential Effects of Ateline Extinction and Forest Fragmentation on Plant Diversity and Composition in the Western Orinoco Basin,Colombia

Cattle and agricultural farming in the western Orinoco Basin began in 1555, and since then fragmentation of continuous forest has occurred. We evaluated the effects of the disturbances and the absence of large primates on plant community composition, diversity, and regeneration patterns. Atelines (Lagothrix and Ateles) inhabited the lowlands close to the Andean mountains, but no longer live in fragmented habitats. Their absence may have negative effects on plant populations because atelines play important roles as seed dispersers in neotropical forests, especially for large-seeded plants, which are rarely swallowed by other seed dispersers. We compared 2 1-ha vegetation plots in forest fragments north of the La Macarena Mountains with 7 plots in continuous forest in Tinigua National Park. Both sites share the same climatic conditions and have similar geological origins. There is floristic affinity between forests with similar ecological characteristics; the fragmented forests are also less diverse than the continuous forests. As predicted, the forest fragments have fewer individuals with large seeds. The results suggest that forest fragmentation and local ateline extinctions affect plant communities, reducing diversity and affecting large-seeded plants.     

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.     

The evolution of brachiation in ateline primates, ancestral character states and history

This study examines how brachiation locomotion evolved in ateline primates using recently-developed molecular phylogenies and character reconstruction algorithms, and a newly-collected dataset including the fossils Protopithecus, Caipora, and Cebupithecia. Fossils are added to two platyrrhine molecular phylogenies to create several phylogenetic scenarios. A generalized least squares algorithm reconstructs ateline and atelin ancestral character states for 17 characters that differentiate between ateline brachiators and nonbrachiators. Histories of these characters are mapped out on these phylogenies, producing two scenarios of ateline brachiation evolution that have four commonalities: First, many characters change towards the Ateles condition on the ateline stem lineage before Alouatta splits off from the atelins, suggesting that an ateline energy-maximizing strategy began before the atelines diversified. Second, the ateline last common ancestor is always reconstructed as an agile quadruped, usually with suspensory abilities. It is never exactly like Alouatta and many characters reverse and change towards the Alouatta condition after Alouatta separates from the atelins. Third, most characters undergo homoplastic change in all ateline lineages, especially on the Ateles and Brachyteles terminal branches. Fourth, ateline character evolution probably went through a hindlimb suspension with tail-bracing phase. The atelines most likely diversified via a quick adaptive radiation, with bursts of punctuated change occurring in their postcranial skeletons, due to changing climatic conditions, which may have caused competition among the atelines and between atelines and pitheciines.     

Evolutionary renovation of L/M opsin polymorphism confers a fruit discrimination advantage to ateline New World monkeys

New World monkeys exhibit prominent colour vision variation due to allelic polymorphism of the long‐to‐middle wavelength (L/M) opsin gene. The known spectral variation of L/M opsins in primates is broadly determined by amino acid composition at three sites: 180, 277 and 285 (the ‘three‐sites’ rule). However, two L/M opsin alleles found in the black‐handed spider monkeys (Ateles geoffroyi) are known exceptions, presumably due to novel mutations. The spectral separation of the two L/M photopigments is 1.5 times greater than expected based on the ‘three‐sites’ rule. Yet the consequence of this for the visual ecology of the species is unknown, as is the evolutionary mechanism by which spectral shift was achieved. In this study, we first examine L/M opsins of two other Atelinae species, the long‐haired spider monkeys (A. belzebuth) and the common woolly monkeys (Lagothrix lagotricha). By a series of site‐directed mutagenesis, we show that a mutation Y213D (tyrosine to aspartic acid at site 213) in the ancestral opsin of the two alleles enabled N294K, which occurred in one allele of the ateline ancestor and increased the spectral separation between the two alleles. Second, by modelling the chromaticity of dietary fruits and background leaves in a natural habitat of spider monkeys, we demonstrate that chromatic discrimination of fruit from leaves is significantly enhanced by these mutations. This evolutionary renovation of L/M opsin polymorphism in atelines illustrates a previously unappreciated dynamism of opsin genes in shaping primate colour vision.     

Comparative and functional myology of the prehensile tail in new world monkeys

The caudal myology of prehensile-tailed monkeys (Cebus apella, Alouatta palliata, Alouatta seniculus, Lagothrix lagotricha, and Ateles paniscus) and nonprehensile-tailed primates (Eulemur fulvus, Aotus trivirgatus, Callithrix jacchus, Pithecia pithecia, Saimiri sciureus, Macaca fascicularis, and Cercopithecus aethiops) was examined and compared in order to identify muscular differences that correlate with osteological features diagnostic of tail prehensility. In addition, electrophysiological stimulation was carried out on different segments of the intertransversarii caudae muscle of an adult spider monkey (Ateles geoffroyi) to assess their action on the prehensile tail. Several important muscular differences characterize the prehensile tail of New World monkeys compared to the nonprehensile tail of other primates. In atelines and Cebus, the mass of extensor caudae lateralis and flexor caudae longus muscles is more uniform along the tail, and their long tendons cross a small number of vertebrae before insertion. Also, prehensile-tailed monkeys, especially atelines, are characterized by well-developed flexor and intertransversarii caudae muscles compared to nonprehensile-tailed primates. Finally, Ateles possesses a bulkier abductor caudae medialis and a more cranial origin for the first segment of intertransversarii caudae than do other prehensile-tailed platyrrhines. These myological differences between nonprehensile-tailed and prehensile-tailed primates, and among prehensile-tailed monkeys, agree with published osteological and behavioral data. Caudal myological similarities and differences found in Cebus and atelines, combined with tail-use data from the literature, support the hypothesis that prehensile tails evolved in parallel in Cebus and atelines. © 1995 Wiley-Liss, Inc.     

Long‐term regeneration of a tropical plant community after sand mining

Sandy coastal plant communities in tropical regions have been historically under strong anthropic pressure. In Brazil, these systems shelter communities with highly plastic plant species. However, the potential of these systems to regenerate without human assistance after disturbances has hardly been examined. We determined the natural regeneration of a coastal sandy plain vegetation (restinga) in Brazil, 16 years after the end of sand removal. We inventoried 38 plots: 20 within a sand‐mined site and 18 in an adjacent undisturbed site. We expected lower diversity values in the sand‐mined site compared to the undisturbed site, but similar species composition between the two sites due to the spatial proximity of the two sites and the high plasticity of restinga species. Species were ranked using abundance and importance value index in both sites, and comparisons were performed using Rényi entropy profiles, rarefaction curves, principal component analysis, and redundancy analysis. Species composition and dominant species differed markedly between the two sites. Bromeliads and Clusia hilariana, well‐known nurse plants, dominated the undisturbed site but were almost absent in the regenerating site. Species richness did not differ between both sites, but diversity was higher in the undisturbed site. Within‐site composition differences in the mined area were associated with field characteristics. Interestingly, species classified as subordinate or rare in the undisturbed site became dominants in the regenerating site. These newer dominants in the sand‐mined site are not those known as nurse plants in other restingas, thus yielding strong implications for restoration.     

First evidence of epizoochorous seed dispersal by golden snub-nosed monkeys (<Emphasis Type="Italic">Rhinopithecus roxellana</Emphasis>) in temperate forest

Although many primates are identified as effective endozoochorous seed dispersers in forest ecosystems, epizoochorous seed dispersal by primates has generally been overlooked. In this study, we report epizoochorous seed dispersal in a group of free-ranging golden snub-nosed monkeys (Rhinopithecus roxellana) residing in the temperate forests of central China by identifying seeds carried by 12 well-habituated individuals. The results showed a total of 1920 seeds (five families, seven genera) belonging to eight plant species attached to the monkeys’ fur; the three most abundant species were Geum aleppicum (54% of the total), Torilis japonica (17%), and Agrimonia pilosa (14%). The majority of seeds (95.3%) that attached to the monkeys’ fur had special morphologies such as hairs, hooks, or awns. We also found that the quantity of seeds attached to the fur was not significantly different by age-sex class, even though adult males have very long fur. Our study provides the first empirical evidence of epizoochorous seed dispersal by primates and suggests the role of primates in seed dispersal may be greater than previously assumed.     

Kinematics of vertical climbing in lorises and Cheirogaleus medius

The type of climbing exhibited by apes and atelines is argued to have been important in the evolution of specialized locomotion, such as suspensory locomotion and bipedalism. However, little is known about the mechanics of climbing in primates. Previous work shows that Asian apes and atelines use larger joint excursions and longer strides than African apes and the Japanese macaque, respectively. This study expands knowledge of climbing mechanics by providing the first quantitative kinematic data for vertical climbing in four prosimian species: three lorisid species (Loris tardigradus, Nycticebus coucang, and Nycticebus pygmaeus) that share with apes and atelines morphological traits arguably related to climbing, and a more generalized quadruped, Cheirogaleus medius. Subjects were videotaped as they climbed up a wooden pole. Kinematic values, such as step length and limb excursions, were calculated and compared between species. The results of this study show that lorises, like Asian apes and spider monkeys, use relatively larger joint excursions and longer steps than does C. medius during climbing. These data lend further support to the idea that some primate species (e.g., lorises, atelines, and apes) are more specialized kinematically and morphologically for climbing than others. Pilot data suggest that such kinematic differences in climbing style across broad phylogenetic groups may relate to the energetics of climbing. Such data may be important for understanding the morphological and kinematic adaptations to climbing exhibited by some primates.     

Does restored plant diversity play a role in the reproductive functionality of Banksia populations?

Vegetation structure and plant species diversity of restoration sites are predicted to directly affect pollinator attraction, with potential impacts on gene flow, reproduction, genetic diversity of future generations, and ultimately restoration success. We compared Banksia attenuata R.Br. (Proteaceae) in a low species diversity restoration site and an adjacent natural remnant. We assessed fecundity genetic diversity in adult plants and their offspring, mating system parameters and pollen dispersal using paternity assignment. Results were compared to an earlier study of reproductive functionality within a high species diversity restoration site that was restored in a similar manner, enabling us to investigate any association between plant species diversity and fecundity. Seed set data indicated no significant differences between restored and adjacent natural sites; however, seed set data between restoration sites was significantly different (2.08 ± 0.39 and 6.89 ± 1.12, respectively). The mean number of fruits (follicles) per inflorescence was not significantly different between restoration sites. Genetic diversity of adult plants and their offspring were comparable in all sites. Higher allelic richness and genetic differentiation in one restored site reflected sourcing beyond local provenance. Low correlated paternity indicated high levels of multiple siring of seeds and paternity assignment demonstrated strong genetic connectivity between sites. Reproductive functionality, as measured by fecundity and genetic diversity in the offspring of B. attenuata, is resilient to low species diversity within a restored plant community. We consider our results in the context of establishing seed production areas (SPAs) that maximize the quantity and genetic quality of Banksia seeds for restoration.     

Assessing the Success of Restoration Plantings in a Temperate New Zealand Forest

The success of restoration plantings in restoring indigenous forest vascular plant and ground invertebrate biodiversity was assessed on previously grass-covered sites in the eastern South Island, New Zealand. The composition and structure of grassland, three different aged restoration plantings (12, 30, and 35 years old), a naturally regenerating forest (100 years old), and a remnant of the original old-growth forest of the area were measured. The restoration plantings are dominated by the native tree Olearia paniculata, which is not indigenous to the study area. Despite this, indigenous forest invertebrate and plant species are present in all three restoration sites and with increasing age the restoration sites become compositionally more similar to the naturally regenerating and mature forest sites. In particular the regenerating vegetation of the restoration sites is very similar floristically to the regenerating vegetation of the naturally regenerating and mature forest sites, despite marked differences in the current canopy vegetation reflecting the presence of the planted O. paniculata. The presence of regeneration in all three restoration sites indicates that the functional processes that initiate regeneration, such as dispersal, are present. The majority of regenerating tree species (71%) are bird dispersed and it is clear that birds play an important role in the recolonization of plant species at these sites despite the absence of edible fruit attractive to frugivorous birds on O. paniculata, a wind-dispersed species. The strong correlations between plant and invertebrate community composition and study-site age (r = 0.80, ?0.24, ?0.68 for plants, beetles, and spiders, respectively) suggest that the restoration site plant and invertebrate communities are undergoing change in the direction of the naturally regenerating and mature forest communities. Without restoration, colonization of grassland by forest plants is very slow in the study area and the restoration plantings studied here have been successful because they have considerably accelerated the return to forest at these sites.     

Frugivory in Canopy Plants in a Western Amazonian Forest: Dispersal Systems,Phylogenetic Ensembles and Keystone Plants

Frugivory is a widespread mutualistic interaction in which frugivores obtain nutritional resources while favoring plant recruitment through their seed dispersal services. Nonetheless, how these complex interactions are organized in diverse communities, such as tropical forests, is not fully understood. In this study we evaluated the existence of plant-frugivore sub-assemblages and their phylogenetic organization in an undisturbed western Amazonian forest in Colombia. We also explored for potential keystone plants, based on network analyses and an estimate of the amount of fruit going from plants to frugivores. We carried out diurnal observations on 73 canopy plant species during a period of two years. During focal tree sampling, we recorded frugivore identity, the duration of each individual visit, and feeding rates. We did not find support for the existence of sub assemblages, such as specialized vs. generalized dispersal systems. Visitation rates on the vast majority of canopy species were associated with the relative abundance of frugivores, in which ateline monkeys (i.e. Lagothrix and Ateles) played the most important roles. All fruiting plants were visited by a variety of frugivores and the phylogenetic assemblage was random in more than 67% of the cases. In cases of aggregation, the plant species were consumed by only primates or only birds, and filters were associated with fruit protection and likely chemical content. Plants suggested as keystone species based on the amount of pulp going from plants to frugivores differ from those suggested based on network approaches. Our results suggest that in tropical forests most tree-frugivore interactions are generalized, and abundance should be taken into account when assessing the most important plants for frugivores.     

Diet and Feeding Ecology of Woolly Monkeys in a Western Amazonian Rain Forest

I investigated the diet and feeding ecology of two social groups of woolly monkeys (Lagothrix lagotricha poeppigii) in Yasuní National Park, Ecuador between April 1995 and March 1996. Woolly monkeys in Yasuní were predominantly frugivorous, with fruits comprising ca. 77% of the yearly diet; the next most common food type in the diet was insect and other animal prey. The fruit diet of woolly monkeys in Yasuní is the most diverse yet recorded for any ateline primate, including spider monkeys (Ateles), which are often regarded as ripe fruit specialists: 208 distinct morphospecies of fruits were consumed by woolly monkeys either during the study or during several preceding months of pilot work. Nonetheless, close to one-third of the yearly diet came from just 3 plant genera—Inga, Ficus, and Spondias—and only 20 genera each contributed to 1% of the diet. For one study group, the proportion of ripe fruit in the diet each month was correlated with the habitat-wide availability of this resource, a pattern evidenced by several other ateline species. However, the relationship was not apparent in the second study group. The modal party size for feeding bouts on all food types was a single monkey, and, contrary to reports for other atelines, neither feeding party size nor the total number of feeding minutes that groups spent in food patches was well predicted by patch size. Both results highlight the independent nature of woolly monkey foraging. Given that woolly monkeys and closely-related spider monkeys focus so heavily on ripe fruits, their very different patterns of social organization are intriguing and raise the question of just how their ecological strategies differ. Two important differences appear to be in the use of animal prey and in the phytochemical composition of the ripe fruits that they consume: spider monkeys rarely forage for animal prey, and woolly monkeys seldom consume the lipid-rich fruits that are an important part of spider monkey diets.     

Host and geographic structure of endophytic and endolichenic fungi at a continental scale

? Premise of the study: Endophytic and endolichenic fungi occur in healthy tissues of plants and lichens, respectively, playing potentially important roles in the ecology and evolution of their hosts. However, previous sampling has not comprehensively evaluated the biotic, biogeographic, and abiotic factors that structure their communities. ? Methods: Using molecular data we examined the diversity, composition, and distributions of 4154 endophytic and endolichenic Ascomycota cultured from replicate surveys of ca. 20 plant and lichen species in each of five North American sites (Madrean coniferous forest, Arizona; montane semideciduous forest, North Carolina; scrub forest, Florida; Beringian tundra and forest, western Alaska; subalpine tundra, eastern central Alaska). ? Key results: Endolichenic fungi were more abundant and diverse per host species than endophytes, but communities of endophytes were more diverse overall, reflecting high diversity in mosses and lycophytes. Endophytes of vascular plants were largely distinct from fungal communities that inhabit mosses and lichens. Fungi from closely related hosts from different regions were similar in higher taxonomy, but differed at shallow taxonomic levels. These differences reflected climate factors more strongly than geographic distance alone. ? Conclusions: Our study provides a first evaluation of endophytic and endolichenic fungal associations with their hosts at a continental scale. Both plants and lichens harbor abundant and diverse fungal communities whose incidence, diversity, and composition reflect the interplay of climatic patterns, geographic separation, host type, and host lineage. Although culture-free methods will inform future work, our study sets the stage for empirical assessments of ecological specificity, metabolic capability, and comparative genomics.     

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.     

Urbanization increases floral specialization of pollinators

Understanding how urbanization alters functional interactions among pollinators and plants is critically important given increasing anthropogenic land use and declines in pollinator populations. Pollinators often exhibit short‐term specialization and visit plants of the same species during one foraging trip. This facilitates plant receipt of conspecific pollen—pollen on a pollinator that is the same species as the plant on which the pollinator was foraging. Conspecific pollen receipt facilitates plant reproductive success and is thus important to plant and pollinator persistence. We investigated how urbanization affects short‐term specialization of insect pollinators by examining pollen loads on insects’ bodies and identifying the number and species of pollen grains on insects caught in urban habitat fragments and natural areas. We assessed possible drivers of differences between urban and natural areas, including frequency dependence in foraging, species richness and diversity of the plant and pollinator communities, floral abundance, and the presence of invasive plant species. Pollinators were more specialized in urban fragments than in natural areas, despite no differences in the species richness of plant communities across site types. These differences were likely driven by higher specialization of common pollinators, which were more abundant in urban sites. In addition, pollinators preferred to forage on invasive plants at urban sites and native plants at natural sites. Our findings reveal indirect effects of urbanization on pollinator fidelity to individual plant species and have implications for the maintenance of plant species diversity in small habitat fragments. Higher preference of pollinators for invasive plants at urban sites suggests that native species may receive fewer visits by pollinators. Therefore, native plant species diversity may decline in urban sites without continued augmentation of urban flora or removal of invasive species.     

Leaf-cutting ants negatively impact the regeneration of the Caatinga dry forest across abandoned pastures

The mechanisms affecting forest regeneration in human-modified landscapes are attracting increasing attention as tropical forests have been recognized as key habitats for biodiversity conservation, provision of ecosystem services, and human well-being. Here we investigate the effect of the leaf-cutting ants (LCA) Atta opaciceps on regenerating plant assemblages in Caatinga dry forest. Our study encompassed 15 Atta opaciceps colonies located in landscape patches with a gradient of forest cover from 8.7% to 87.8%, where we monitored regenerating individuals (seedlings and saplings of woody and herbaceous plants) in different habitats (nests, foraging areas, and control areas) over one year. We recorded 2,977 regenerating plant individuals, distributed among 55 species from 23 families. Herbaceous plants represented 82.1% and 58.2% of the total number of individuals and species, respectively. Species richness of both the whole and herbaceous plant assemblages increased along the forest cover gradient, but without difference between the habitats. Total plant abundance was highest in control areas followed by foraging areas and nests and this pattern held for both woody and herbaceous plants. Although forest cover did not influence the abundance of herbaceous plants and the whole plant assemblage, it positively affects woody plant abundance across control areas. Forest cover and habitat changed species composition of both the entire regenerating and the herbaceous assemblages. These results together indicate that LCA negatively impact regenerating plant assemblages, particularly in those sites with increased forest cover. As LCA proliferate in human-modified landscapes, they may prevent plant regeneration of disturbed areas.     

Diet and feeding behavior of Rhinopithecus brelichi at Yangaoping, Guizhou

Expectations of increases in human population growth and accelerated habitat loss, along with the realization that efforts to provide protection for ecosystems that sustain primates have met with limited success, make it critical that conservation plans are grounded firmly in scientific observation. Studies of the diet breadth and feeding behavior of endangered species, therefore, are critical for understanding ecological adaptations and developing a conservation strategy. The diet and feeding ecology of gray snub-nosed monkeys (Rhinopithecus brelichi) were studied in the Fanjingshan National Nature Reserve, Guizhou, China. The monkeys were found to consume 107 different species of trees, shrubs, and ground plants from 58 genera and 28 families. Food items included young leaves, mature leaves, flowers, fruits/seeds, buds, and insects. Among these food items, there were at least 13 evergreen species of tree and liana, 3 species of grasses, and at least 2 kinds of invertebrates collected from decayed wood. Diet varied markedly throughout different seasons. Overall, diet composition (based on feeding records) was 15.3% buds, 25.5% young leaves, 21.8% mature leaves, 9.4% flowers, 21.6% fruits/seeds, and 6.3% other items. The monkeys feed mainly on young leaves and flowers in spring, unripe fruits/seeds and young leaves in summer, ripe fruits/seeds in autumn, and mature leaves and buds in winter. We propose that when inhabiting forests of lower elevation and greater vegetation complexity, R. brelichi is characterized by expanded diet breadth and includes a greater diversity of food types and plant species in its diet. One food type that appears critical to the diet of this species, especially during the winter, are the buds of Magnolia sprengeri. To protect this resource we advocate working with local communities to limit the collection of M. sprengeri, which is used in traditional Chinese medicine and has high economic value for people in the reserve.     

Birth seasonality and offspring production in threatened neotropical primates related to climate

Given the threatened status of many primate species, the impacts of global warming on primate reproduction and, consequently, population growth should be of concern. We examined relations between climatic variability and birth seasonality, offspring production, and infant sex ratios in two ateline primates, northern muriquis, and woolly monkeys. In both species, the annual birth season was delayed by dry conditions and El Niño years, and delayed birth seasons were linked to lower birth rates. Additionally, increased mean annual temperatures were associated with lower birth rates for northern muriquis. Offspring sex ratios varied with climatic conditions in both species, but in different ways: directly in woolly monkeys and indirectly in northern muriquis. Woolly monkeys displayed an increase in the proportion of males among offspring in association with El Niño events, whereas in northern muriquis, increases in the proportion of males among offspring were associated with delayed onset of the birth season, which itself was related, although weakly, to warm, dry conditions. These results illustrate that global warming, increased drought frequency, and changes in the frequency of El Niño events could limit primate reproductive output, threatening the persistence and recovery of ateline primate populations.     

Primate Community Structure in Guyana: A Biogeographic Analysis

Studies of primate community structure increase our understanding of behavior, adaptation, and evolution. However, there are few biogeographic data on specific composition and association patterns in primate communities. I conducted a biogeographic analysis of the community structure of primate species at 16 sites in Guyana. I used data from 1725 km of line-transect censuses to determine specific composition and association patterns of 220 primate groups . Of the 18 polyspecific groups, 94.1% (N = 16) included squirrel monkeys. There was an overall trend towards positive specific associations among Guyanese primates. The only species that exhibited a negative pattern of interspecific associations were brown and wedge-capped capuchins. The sighting rate for wedge-capped capuchins at sympatric sites was particularly depressed compared to that for brown capuchins. Low plant productivity in Guyanese forests may reduce the diversity of feeding niches and result in a low incidence of polyspecific associations and scramble competition between wedge-capped and brown capuchins.