Primate Dispersal Research Articles

Terrain Ruggedness and Canopy Height Predict Short-Range Dispersal in the Critically Endangered Black-and-White Ruffed Lemur.

Dispersal is a fundamental aspect of primates' lives and influences both population and community structuring, as well as species evolution. Primates disperse within an environmental context, where both local and intervening environmental factors affect all phases of dispersal. To date, research has primarily focused on how the intervening landscape influences primate dispersal, with few assessing the effects of local habitat characteristics. Here, we use a landscape genetics approach to examine between- and within-site environmental drivers of short-range black-and-white ruffed lemur (Varecia variegata) dispersal in the Ranomafana region of southeastern Madagascar. We identified the most influential drivers of short-range ruffed lemur dispersal as being between-site terrain ruggedness and canopy height, more so than any within-site habitat characteristic evaluated. Our results suggest that ruffed lemurs disperse through the least rugged terrain that enables them to remain within their preferred tall-canopied forest habitat. Furthermore, we noted a scale-dependent environmental effect when comparing our results to earlier landscape characteristics identified as driving long-range ruffed lemur dispersal. We found that forest structure drives short-range dispersal events, whereas forest presence facilitates long-range dispersal and multigenerational gene flow. Together, our findings highlight the importance of retaining high-quality forests and forest continuity to facilitate dispersal and maintain functional connectivity in ruffed lemurs.

The Influence of Seed Characteristics on Seed Dispersal Early Stages by Tibetan Macaques.

Simple SummarySeed dispersal by frugivores is critical to forest regeneration. However, the Tibetan macaque’s seed dispersal function and the effect of seed physical characteristics on seed dispersal effectiveness need to be confirmed. We not only demonstrated that Tibetan macaques could act as seed dispersers, but we also investigated the effect of seed physical characteristics on gut passage time and seed damage rates. Smaller seeds are less likely to be damaged and remain for longer periods of time, whereas larger and heavier seeds are defecated more quickly. In our experiments, the seed-to-shell investment rate had no effect on the damage rate. Understanding the role of seed dispersal in primates can aid in the understanding of seed dispersal symbiosis.There are numerous ecological and evolutionary implications for the ability of frugivores to predate on fruits and consume or disperse their seeds. Tibetan macaques, which are considered important seed predators, typically feed on fruits or seeds. However, systematic research into whether they have a seed dispersal function is still lacking. Endozoochory allows seeds to disperse over greater distances by allowing them to remain in the animal’s digestive tract. Consumption of fruit may not imply effective seed dispersal, and the physical characteristics of seeds (e.g., size, weight, specific gravity, etc.) may influence the dispersal phase’s outcome. We conducted feeding experiments with three captive Tibetan macaques (Macaca thibetana) and nine plant seeds to determine the influence of seed characteristics on Tibetan macaques’ early stages of seed dispersal. The results revealed that the percentage of seed destruction (PSD) after ingestion was 81.45% (range: 15.67–100%), with the PSD varying between plant species. Among the three passage time parameters, the transit time (TT) (mean: 18.8 h and range: 4–24 h) and the time of seed last appearance (TLA) (mean: 100.4 h and range: 48–168 h) differed significantly between seed species, whereas the mean retention time (MRT) (mean: 47.0 h and range: 32–70.3 h) did not. In terms of model selection, PSD was influenced by seed size, weight, volume, and specific gravity; TT was influenced by seed-to-shell investment rate, weight, volume, and specific gravity; and TLA was influenced only by seed size. These findings imply that seeds with a smaller size, specific gravity, volume, and greater weight pass more easily through the monkeys’ digestive tracts. Particularly, seeds with a mean cubic diameter (MCD) of <3 mm had a higher rate of expulsion, larger volume, and weight seeds pass faster, while smaller remained longer. Tibetan macaques, as potential seed dispersers, require specific passage time and passage rates of small or medium-sized seeds. Larger and heavier seeds may be more reliant on endozoochory. Tibetan macaques have the ability to disperse seeds over long distances, allowing for gene flow within the plant community.

Germination success of large‐seeded plant species ingested by howler monkeys in tropical rain forest fragments

Primates are important seed dispersers, especially for large-seeded (>1 cm long) tropical species in continuous and fragmented rainforests. In three forest fragments within the Montes Azules Biosphere Reserve, southern Mexico, we investigated the effect of seed passage through the gut of howler monkeys (Alouatta pigra) on the germination rate and maximum germination (%) of native, large-seeded species. One group of howler monkeys, per fragment, was followed and fresh feces collected. Large seeds were removed to compare their germination success with non-ingested seeds of the same species collected underneath parent plants. Feces contained large seeds from seven tree species (Ampelocera hottlei, Castilla elastica, Dialium guianense, Garcinia intermedia, Pourouma bicolor, Spondias mombin, Trophis racemosa) and one liana species (Abuta panamensis). Except for G. intermedia, ingested seeds germinated significantly faster than non-ingested seeds, which had negligible germination. Ingested seeds of D. guianense, P. bicolor, S. mombin, T. racemosa, and A. panamensis had significantly greater germination, while G. intermedia had significantly lower germination and seed ingestion had no apparent effect for A. hottlei and C. elastica. In general, seed ingestion by howler monkeys confers faster germination compared with non-ingested seeds. Faster germination reduces predation probabilities and increases seedling establishment in forest fragments. Primate dispersal services contribute to germination heterogeneity within plant populations of old-growth forest species and to their persistence in forest fragments.

Roadside monkeys: anthropogenic effects on moor macaque (Macaca maura) ranging behavior in Bantimurung Bulusaraung National Park, Sulawesi, Indonesia.

A growing body of research focuses on how anthropogenic factors affect the behavior and ecology of primates and their ecosystems. Infrastructural development, such as roads, is an increasingly pervasive anthropogenic impact that destroys primate habitat, affects the distribution and dispersal of primates, and facilitates human-primate interactions. At our field site in Bantimurung-Bulusaraung National Park, Sulawesi, Indonesia, a major road bisects the habitat of the endangered moor macaque (Macaca maura). Beginning in 2015, we observed a behavioral shift by our main study group: they began spending more time along the road foraging in trash pits and waiting for provisions from vehicles. Our objective in this study was to examine how access to anthropogenic foods has affected the group's ranging behavior by comparing ranging data collected before (2010-2011) and after the shift (2016-2017). In contrast to what we expected, home ranges were significantly larger and daily travel distance was significantly longer after the shift compared to before. As predicted, mean distance to the road decreased after the shift. These results likely reflect the irregular and spatially dispersed nature of provisioning at this site. The macaques appear to be attracted to the road because it presents opportunities to obtain palatable and energy-dense foods. Our results indicate that moor macaques are able to flexibly adjust their ranging behavior in response to anthropogenic impacts. However, given the risks of being in proximity to roads and humans, management of this emerging human-macaque interface is needed.

Using strontium isotopes to determine philopatry and dispersal in primates: a case study from Kibale National Park.

Strontium isotope ratios (87Sr/86Sr) allow researchers to track changes in mobility throughout an animal's life and could theoretically be used to reconstruct sex-biases in philopatry and dispersal patterns in primates. Dispersal patterns are a life-history variable that correlate with numerous aspects of behaviour and socio-ecology that are elusive in the fossil record. The present study demonstrates that the standard archaeological method used to differentiate between ‘local’ and ‘non-local’ individuals, which involves comparing faunal isotopic ratios with environmental isotopic minima and maxima, is not always reliable; aspects of primate behaviour, local environments, geologic heterogeneity and the availability of detailed geologic maps may compromise its utility in certain situations. This study instead introduces a different methodological approach: calculating offset values to compare 87Sr/86Sr of teeth with that of bone or local environments. We demonstrate this method's effectiveness using data from five species of primates, including chimpanzees, from Kibale National Park, Uganda. Tooth-to-bone offsets reliably indicate sex-biases in dispersal for primates with small home ranges while tooth-to-environment offset comparisons are more reliable for primates with larger home ranges. Overall, tooth-to-environment offsets yield the most reliable predictions of species' sex-biases in dispersal.

Recalculating route: dispersal constraints will drive the redistribution of Amazon primates in the Anthropocene

Climate change will redistribute the global biodiversity in the Anthropocene. As climates change, species might move from one place to another, due to local extinctions and colonization of new environments. However, the existence of permeable migratory routes precedes faunal migrations in fragmented landscapes. Here, we investigate how dispersal will affect the outcome of climate change on the distribution of Amazon's primate species.We modeled the distribution of 80 Amazon primate species, using ecological niche models, and projected their potential distribution on scenarios of climate change. Then, we imposed landscape restrictions to primate dispersal, derived from a natural biogeographical barrier to primates (the main tributaries of the Amazon river) and an anthropogenic constraint to the migration of many canopy‐dependent animals (deforested areas). We also highlighted potential conflict zones, i.e. regions of high migration potential but predicted to be deforested.Species response to climate change varied across dispersal limitation scenarios. If species could occupy all newly suitable climate, almost 70% of species could expand ranges. Including dispersal barriers (natural and anthropogenic), however, led to range expansion in only less than 20% of the studied species. When species were not allowed to migrate, all of them lost an average of 90% of the suitable area, suggesting that climate may become unsuitable within their present distributions.All Amazon primate species may need to move as climate changes to avoid deleterious effects of exposure to non‐analog climates. The effect of climate change on the distribution of Amazon primates will ultimately depend on whether landscape permeability will allow climate‐driven faunal migrations. The network of protected areas in the Amazon could work as ‘stepping stones’ but most are outside important migratory routes. Therefore, protecting important dispersal corridors is foremost to allow effective migrations of the Amazon fauna in face of climate change and deforestation.

Comparison of forest regeneration in two sites with different primate abundances in Northwestern Ecuador

There is increasing evidence that large-bodied primates play important roles as seed dispersers and in the maintenance of tree diversity in forest ecosystems. In this study we compared forest regeneration at two sites with differing primate abundances in the Ecuadorian Chocoan rainforest. We predicted: (1) significant differences in primate abundance between the two sites; (2) higher understory tree species richness and density at the site with greater primate abundance; (3) the site with lower primate abundance characterized by tree species dispersed by non-primate biotic agents and/or abiotic factors. We compared two sites, Tesoro Escondido (TE) a campesino cooperative, and the El Pambilar (EP) wildlife refuge that both maintain populations of mantled howler monkey (Alouatta palliata), the brown-headed spider monkey (Ateles fusciceps fusciceps) and the capuchin monkey (Cebus capucinus). We characterized canopy structure by point-quadrant sampling, determined primate abundance and sampled seedlings/saplings in 1 m2 plots, classifying tree species based on three dispersal syndromes: adapted for primate dispersal, dispersed by other biological agents, and abiotic dispersal. We compared sites in terms of primate abundance (groups and individuals observed per day) and regeneration characteristics (overall density, species richness, and dispersal syndrome). We carried out within site comparisons and constructed understory tree species accumulation curves. Overall the forests were structurally similar - with significantly higher densities of A. f. fusciceps at TE. Encounter rates for the other two primate species were similar at both sites. Understory tree density and species richness was significantly higher in TE with no stabilization of tree species accumulation curves. The species accumulation curve for understory trees at EP stabilized. Higher densities and species richness of primate dispersed tree species were observed at TE, with non-primate biotically dispersed tree species the dominant dispersal syndrome at both sites. Our observations are consistent with those from other studies investigating the role of large-bodied frugivorous primates in forest regeneration, and point to a general pattern: future lowland tropical forest tree diversity depends on maintaining robust populations of large primate species in these systems. It is highly probable that the maintenance of high levels of tree diversity in Chocoan rainforests is dependent on the conservation of its largest resident primate, the critically endangered brown-headed spider monkey (A. f. fusciceps).

Microsatellite DNA suggests that group size affects sex-biased dispersal patterns in red colobus monkeys.

Dispersal is a major life history trait of social organisms influencing the behavioral and genetic structure of their groups. Unfortunately, primate dispersal is difficult to quantify, because of the rarity of these events and our inability to ascertain if individuals dispersed or died when they disappear. Socioecological models have been partially developed to understand the ecological causes of different dispersal systems and their social consequences. However, these models have yielded confusing results when applied to folivores. The folivorous red colobus monkey (Procolobus rufomitratus) in Kibale National Park, Uganda is thought to exhibit female-biased dispersal, although both sexes have been observed to disperse and there remains considerable debate over the selective pressures favoring the transfers of males and females and the causes of variation in the proportion of each sex to leave the natal group. We circumvent this problem by using microsatellite DNA data to investigate the prediction that female dispersal will be more frequent in larger groups as compared to smaller ones. The rationale for this prediction is that red colobus exhibit increased within-group competition in bigger groups, which should favor higher female dispersal rates and ultimately lower female relatedness. Genetic data from two unequally sized neighboring groups of red colobus demonstrate increased female relatedness within the smaller group, suggesting females are less likely to disperse when there is less within-group competition. We suggest that the dispersal system is mediated to some degree by scramble competition and group size. Since red colobus group sizes have increased throughout Kibale by over 50% in the last decade, these changes may have major implications for the genetic structure and ultimately the population viability of this endangered primate.

‘Out‐of‐Africa’ dispersal of tropical floras during the Miocene climatic optimum: evidence fromUvaria(Annonaceae)

AbstractAim African–Asian disjunctions are common in palaeotropical taxa, and are typically explained by reference to three competing hypotheses: (1) ‘rafting’ on the Indian tectonic plate, enabling Africa‐to‐Asia dispersal; (2) migration via Eocene boreotropical forests; and (3) transoceanic long‐distance dispersal. These hypotheses are tested usingUvaria(Annonaceae), which is distributed in tropical regions of Africa, Asia and Australasia. Recent phylogenetic reconstructions of the genus show a clear correlation with geographical provenance, indicating a probable origin in Africa and subsequent dispersal to Asia and then Australasia. Ancestral areas and migration routes are inferred and compared with estimates of divergence times in order to distinguish between the prevailing dispersal hypotheses.Location Palaeotropics.Methods Divergence times inUvariaare estimated by analysing the sequences of four DNA regions (matK,psbA–trnH spacer,rbcL andtrnL–F) from 59Uvariaspecies and 77 outgroup species, using a Bayesian uncorrelated lognormal (UCLD) relaxed molecular clock. The ancestral area ofUvariaand subsequent dispersal routes are inferred using statistical dispersal–vicariance analysis (s‐diva).Results Uvariais estimated to have originated in continental Africa 31.6 Ma [95% highest posterior density (HPD): 38.4–25.1 Ma] between the Middle Eocene and Late Oligocene. Two main migration events during the Miocene are identified: dispersal into Madagascar around 17.0 Ma (95% HPD: 22.3–12.3 Ma); and dispersal into Asia between 21.4 Ma (95% HPD: 26.7–16.7 Ma) and 16.1 Ma (95% HPD: 20.1–12.1 Ma).Main conclusions Uvariafruits are widely reported to be consumed by primates, and are therefore unlikely candidates for successful long‐distance transoceanic dispersal. The other biogeographical hypotheses, involving rafting on the Indian tectonic plate, and dispersal via the European boreotropical forests associated with the Eocene thermal maximum, can be discounted due to incongruence with the divergence time estimates. An alternative scenario is suggested, involving dispersal across Arabia and central Asia via the tropical forests that developed during the late Middle Miocene thermal maximum (17–15 Ma), associated with the ‘out‐of‐Africa’ dispersal of primates. The probable route and mechanism of overland dispersal between Africa and Asia for tropical plant groups during the Miocene climatic optimum are clarified based on theUvariadata.

Molecular identification of the causative agent of human strongyloidiasis acquired in Tanzania: Dispersal and diversity of Strongyloides spp. and their hosts

In order to identify the causative agent of imported strongyloidiasis found in a Japanese mammalogist, who participated in a field survey in Tanzania, the hyper-variable region IV (HVR-IV) of 18S ribosomal DNA and partial mitochondrial cytochrome c-oxidase subunit 1 gene ( cox1) were analyzed and compared with Strongyloides fuelleborni collected from apes and monkeys of Africa and Japan, and S. stercoralis from humans, apes and dogs. The HVR-IV and cox1 of the patient's worms were identical to or only slightly differed from those of worms parasitic in Tanzanian chimpanzees and yellow baboons, demonstrating that the patient acquired the infection during her field survey in Tanzania. Phylogenetic analysis with the maximum-likelihood method largely divided isolates of S. fuelleborni into three groups, which corresponded to geographical localities but not to host species. Meanwhile, isolates of S. stercoralis were grouped by the phylogenetic analysis into dog-parasitic and primate-parasitic clades, and not to geographical regions. It is surmised that subspeciation has occurred in S. fuelleborni during the dispersal of primates in Africa and Asia, while worldwide dispersal of S. stercoralis seems to have occurred more recently by migration and the activities of modern humans.

Fruit size, crop mass, and plant height explain differential fruit choice of primates and birds

Seed dispersal by animals is an important ecological process shaping plant regeneration. In general, seed dispersers are highly variable and often opportunistic in their fruit choice. Despite much research, the factors that can explain patterns of fruit consumption among different animal groups remain contentious. Here, we analysed the interactions between 81 animal species feeding on the fruits of 30 plant species in Kakamega Forest, Kenya, during 840 h of observations. Our aim was to determine whether plant characteristics, fruit morphology, fruit colours and/or fruit compounds such as water, sugar, phenols and tannins explained the relative importance of fruit consumption by the two most important consumer groups, primates and birds. We found significant differences in fruit choice between both groups. Primates fed on larger fruits and on higher trees that had larger fruit crops, whereas birds were observed feeding on smaller fruits and on smaller plants producing fewer fruits. Fruit colours did not differ between fruits consumed by primates and those consumed by birds. However, differences in the fruit choice among frugivorous birds were associated with differences in fruit colours. Smaller plants with smaller fruits produced red fruits which contrasted strongly with the background; these fruits were dispersed by a distinct set of bird species. The contents of water, sugar, phenols and tannins did not differ between fruits eaten by primates and those eaten by birds. Some phylogenetic patterns were apparent; primates fed preferentially on a phylogenetically restricted subsample of large plants with large fruits of the subclass Rosidae. We discuss why the observed primate dispersal syndrome is most likely explained by a process of ecological fitting.

What traits promote male parallel dispersal in primates?

Summary Parallel dispersal occurs when individuals emigrate together with peers or close kin, or immigrate into groups containing familiar or closely related individuals. To understand the evolution of parallel dispersal in male primates, we explore if parallel dispersal co-occurs with male coalitions, or with other traits that may facilitate coalition formation. We conducted a meta-analysis using phylogenetic comparative methods to test for an association between male parallel dispersal and male coalition formation, multi-male social groups, male-biased dispersal, high paternity concentration, and breeding seasonality. These traits were predicted to be correlated with parallel dispersal because they increase the availability of potential dispersal partners, increase individual competitive ability, or provide inclusive fitness benefits for cooperating relatives. Pairwise comparisons revealed that coalitions in general were significantly associated with male parallel dispersal. However, neither intergroup nor intragroup coalitions were associated with parallel dispersal when examined separately, though there was a trend towards significance for intergroup coalitions. Male-biased dispersal was equivocally associated with parallel dispersal, while multi-male social groups, paternity concentration, and breeding seasonality were not. These results suggest that the evolution of male parallel dispersal may be linked with the propensity of males to form coalitions and the need to retain coalition partners.

Dispersal in primates: advancing an individualized approach

Dispersal in primates: advancing an individualized approach

Dispersal patterns in sympatric woolly and spider monkeys: integrating molecular and observational data

Dispersal is a behavioral process that shuffles genes across the physical and social landscapes. Analysis of how genetic variation is structured hierarchically and among males versus females can provide insights into underlying dispersal processes, even when direct observations of dispersal events are lacking, but application of these techniques in primate studies has been limited. We investigated dispersal patterns in two South American primates — woolly and spider monkeys — using a combination of multilocus genotype data from > 150 animals sampled at two sites in Amazonian Ecuador and opportunistic field observations that shed light on likely dispersal events. Molecular analyses revealed considerable gene flow by females, but substantial male-mediated gene flow was also detected, particularly for woolly monkeys. In both taxa, the extent of population differentiation between the two study sites was greater for males than for females, indicating that gene flow by males has been more restricted historically. Additionally, in one group of spider monkeys, the average relatedness among adult males was significantly greater than that among females, consistent with strong male philopatry, and assignment tests for that group likewise suggest female-biased dispersal. However, for another group of spider monkeys — and for all groups of woolly monkey surveyed — these patterns were not observed. Our molecular results are concordant with field observations of immigrations by female spider monkeys, disappearances (likely emigrations) involving females of both species, and multiple sightings of solitary males and small bachelor groups in woolly monkeys, as well as with the specific dispersal histories of a few woolly monkey individuals discernable through longitudinal molecular sampling. Overall, the results demonstrate the utility of molecular approaches to studying dispersal in primates as a complement to observational studies, but also suggest that further evaluation of dispersal patterns among these primates is needed.

A NEW MICROCHOERINE OMOMYID (PRIMATES, MAMMALIA) FROM THE ENGLISH EARLY EOCENE AND ITS PALAEOBIOGEOGRAPHICAL IMPLICATIONS

Abstract: A new genus and species of omomyid primate, Melaneremia bryanti, is described from the Early Eocene Blackheath Beds of Abbey Wood, London, UK. It shares unique derived characters with the European subfamily Microchoerinae and is its most primitive member. It is nevertheless more derived than the primitive omomyid Teilhardina belgica from the beginning of the European Eocene. Cladistic analysis shows that the Microchoerinae are sister group to a clade comprising subfamilies Omomyinae and Anaptomorphinae, but excluding Teilhardina belgica and T. asiatica, which are stem omomyids. The Mammalian Dispersal Event (MDE), which marks the beginning of the Eocene (55·8 Ma), saw the dispersal of primates, perissodactyls and artiodactyls into the Northern Hemisphere. At this time similar species of Teilhardina lived in Europe, Asia and North America. The Abbey Wood microchoerine lived about 1 million years later. It co‐occurs with non‐primate species identical or very similar to those that lived in North America. The latter were ground‐dwellers, whereas the microchoerine and others that show distinct differences from North American relatives were tree‐dwellers. Land‐bridges connected North America and Europe via Greenland at the beginning of the Eocene, but 2 million years later these had been severed by submarine rifting. North American species at Abbey Wood indicate that a land connection still remained at c. 55 Ma. However, the forest belt that must have been continuous during the MDE to allow tree‐dwellers to disperse between the continents is likely by this time to have been disrupted, perhaps by volcanic eruption.

Female dispersal, inbreeding avoidance and mate choice in Thomas langurs (Presbytis thomasi)

AbstractFemale social dispersal in primates differs from the general mammalian pattern of locational dispersal. Both nulliparous and parous females may disperse to another group. Several hypotheses can explain female social dispersal: reduction of predation risk, inbreeding avoidance, and offspring protection through mate choice. We tested these hypotheses with an extended data set of Thomas langurs (Presbytis thomasi) and investigated parameters of male behaviour that females may use in their dispersal decisions. Data were collected over a 12.5-year period from a wild population in Sumatra, Indonesia, allowing for some critical tests of the hypotheses. Females dispersed to a group smaller than their original one, thereby refuting the predation risk hypothesis. Maturing nulliparous females only dispersed when their father was resident. Therefore, dispersal by nulliparous females was best explained through inbreeding avoidance. Parous females transferred to young, adult males. These males provided better protection to offspring against predation and infanticide than the old, late tenure males. Therefore, females transfer to better protector males. The male behavioural cues that females use to assess male quality were unclear. Females, however, may use proxies of male age, such as group composition and acoustical characteristics of loud calls, as indicators of male quality. The results suggest that female mate choice is an important function of social dispersal by parous females. Its importance in locational dispersal remains to be investigated.

Molecular estimates of primate divergences and new hypotheses for primate dispersal and the origin of modern humans.

The concept of recent hominoid divergences has been a mainstay in molecular primatology since the 1970's. However, the ages allocated to the calibration points used to establish these divergence times and the estimates resulting from their application, notably the commonly accepted divergence between Pan (chimpanzees) and Homo 5 million years before present (MYBP), are now palaeontologically refutable. Here we estimate the ages of various primate divergences using three references with a more detailed fossil record than any of the traditional primate calibration points. Our findings suggest that the latter yield datings that are too recent by a factor of about two. For example, our estimates place the divergence between Pan and Homo 10.5-13 MYBP. The revised estimates of primate divergence times suggest a new hypothesis for primate evolution and dispersal: that the divergence between strepsirhines (lorises, lemurs) and anthropoids was contemporary with the break-up of Southern continents about 90 MYBP, with strepsirhines becoming isolated on Madagascar and later dispersing to Africa (and Asia) and anthropoids evolving in South America and subsequently colonizing Africa (and Asia), or possibly North America. In addition we present a new hypothesis, which accommodates the strikingly similar coalescence times for human mitochondrial DNA and the Y-chromosome. This hypothesis posits a common mitochondrial and Y-chromosome bottleneck about 400,000 years ago, associated with the origination of the human 2n = 46 karyotype, obstructing genetic exchange with the 2n = 48 Homo contemporaries.

Linking dispersal and marriage in humans: Life history data from Oakham, Massachusetts, USA (1750–1850)

Despite the emphasis on inbreeding avoidance and competition for mates in explaining primate dispersal, little is known about how dispersal and mating interconnect in humans. I examine the link between dispersal and marriage using life history data from Oakham, MA (1750–1850). I find that dispersal status, timing, and destination were linked to marital status, timing, and spouse's place of origin. Men, unmarried individuals, and individuals with spouses from Oakham were less likely to disperse than their counterparts. Individuals with spouses from Oakham also married earlier than others. For women, dispersal and marriage often coincided, and women were more likely to disperse to their spouses' town of origin than were men. Although dispersal coincided with marriage in at least two-thirds of dispersal events, the majority of cases were inconsistent with both inbreeding avoidance and mating competition explanations. Where one of these explanations was still plausible, dispersal seemed more likely linked to competition for mates than to inbreeding, with resource availability also likely shaping dispersal, and male control of resources contributing to sex biases in dispersal.

Character Convergence, Diversity, and Disturbance in Tropical Rain Forest in Guyana

The level of tree diversity varies greatly between sites in Guyana and decreases along a gradient from south to north. We conducted a study to understand what controls this gradient of diversity using data from country-wide forest inventories. Analysis of tree diversity on the basis of soil and rainfall effects in an area of 15 × 106 ha showed that soil exerts a strong local effect on tree diversity, whereas rainfall, potential evapotranspiration, and length of the dry season do not. Community averages of disturbance-sensitive attributes of trees, such as seed mass or wood density, were not correlated with variation in either rainfall or soil, but were strongly correlated with tree diversity. As such, the forests in central Guyana were characterized by generally a high average wood density, large seeds, and rodent or unassisted dispersal. These forests also displayed the highest single dominance, thus lowest diversity and low percentages of pioneers in the community. The more highly diverse forests in south Guyana showed much lower average community wood density and seed mass, and bird and primate dispersal were more common than in central Guyana. Large-scale spatial variation in diversity and community averages of life history characteristics are here considered the product of local convergence of species with similar characteristics. Characteristics bestowing competitive superiority in environments with little disturbance ultimately lead to a decline in diversity through competitive exclusion, much as that predicted by the intermediate disturbance hypothesis and dynamic equilibrium theory. The more diverse communities are associated with characteristics of superior colonizers: low wood density, small seeds, and good dispersal. Variation in diversity at smaller spatial scales is strongly affected by soils.

Phylogenetic and biogeographic significance of the tarsiiform primate Asiomomys changbaicus from the eocene of Jilin Province, people's Republic of China

AbstractA newly discovered Paleogene mammal locality in Jilin Province, People's Republic of China has yielded a dentary fragment of the tarsiiform primate Asiomomys changbaicus. Unlike most other Eocene primates from Asia, the phylogenetic position of A. changbaicus is well resolved: it represents the sister taxon of Stockia powayensis, a probable washakiin omomyid from the early Uintan of southern California. The phylogenetic position and geographic provenance of A. changbaicus demonstrate the feasibility of primate dispersal between North America and Asia during middle Eocene time. This finding establishes a biogeographic link between the most diverse known radiation of tarsiiform primates, which occurred in the Eocene of North America, and the present range of the genus Tarsius. Accordingly, biogeographic considerations no longer detract from the hypothesis of a close phylogenetic relationship between Tarsius and a clade of North American Omomyidae.