Cranial adaptation to a high attrition diet in Japanese macaques

Primates with diets that require greater occlusal forces to process exhibit anteroposteriorly shorter, vertically deeper faces, more anteriorly placed masseter attachment areas, and broader, taller mandibular corpora compared to closely related species/populations. Japanese macaques (Macaca fuscata)eat different, perhaps mechanically tougher to process, foods than other macaques do. Accordingly, they should exhibit structural features of the skull related to dissipating great occlusal loads. To test this hypothesis I compared cranial variables amongst wild-caught, adult female skulls (n = 85) of M. fuscataand three other macaque species (M. mulatta, M. fascicularis,and M. nemestrina)and applied least-squares and reduced-major-axis regression analysis and principal components analysis (PCA) to 17 cranial variables reflecting facial, vault, and mandibular dimensions. When scaled for size, the Japanese macaque has a vertically deeper and anteroposteriorly shorter face,a broader but not taller mandibular corpus, and a more anteriorly placed masseter muscle than the other three macaques do. The first PCA axis isolates variation due to a suite of characters related to mechanical efficiency in dissipating occlusal loads (vertically deep face and broad corpus) and differentiates the Japanese macaques from the other species. This, coupled with reported dietary differences among species, suggests that Japanese macaques are selected for dissipating greater occlusal loads than other macaques are. The presence of a narrow mandible relative to cranial breadth and a hyperrobust mandibular corpus width suggests that axial torsion is a significant influence in the masticatory regime of M. fuscata.The lack of an increase in corpus height indicates that parasagittal bending is not as significant an influence. Geographic and climatic influences cannot account for the patterns of variation between M. fuscataand the other macaques.     

Molecular phylogeny of Mentawai macaques: taxonomic and biogeographic implications

In order to elucidate the evolutionary history and taxonomy of the Mentawai macaques, we sequenced a 567 base pairs (bp) long fragment of the mitochondrial cytochrome b gene from 39 individuals representing pigtailed macaque populations from Siberut, Sipora, South Pagai, and Sumatra. Pairwise difference analyses carried out within and among populations have shown, that: (1) variation within populations is relative low, (2) variation among populations is increased, and (3) pairwise differences within and among the populations from Sipora and South Pagai are in the same range. From phylogenetic tree reconstructions including further macaque species, we detected a paraphyletic origin of Mentawai macaques with the Siberut population more closely related to Macaca nemestrina from Sumatra, than it is to populations from the Southern islands. Based on these results, we favour a scenario in that macaques entered the Mentawai islands by two independent colonisation events. Taking together the paraphyletic origin of Mentawai macaques and the genetic differences detected among pigtailed macaque populations, which are comparable with those observed among the seven Sulawesi macaque species, we propose to separate macaques from Siberut and Sipora, North and South Pagai into two distinct species, Macaca siberu and Macaca pagensis, respectively.     

Craniodental variation in the African macaque, with reference to various Asian species

Based on twenty-seven craniodental measurements and ratios derived from them, the relationship between the African macaque (M. sylvanus) and the others in Asia were examined with principal components analyses (PCA) and Euclidean distance analysis based upon prior discriminant function analyses (DFA). Results based on analyses of raw measurements indicate that the variation between species lies in the first axis of PCA; the species are dispersed according to their differences in size. The variation between sexes (sexual dimorphism) lies in the second axis. In the analyses of ratio variables, though these two patterns of separation remain orthogonal, they lie at approximately forty-five degrees to each axis. Variables relating to anterior teeth were found to play an important role in variation analysis, and this may be related to the special food preferences of these monkeys: more frequent usage of the incisor teeth for processing frugivorous diets than in other primates that are mainly folivorous. The results from Euclidean distance analyses indicate that the average distance of species within the Asian group is shorter than that between Asian and African groups regardless of sex and variable type. In addition the variation between African and Asian groups is larger than that within Asian group. Thus, it is reasonable to suggest that the African macaque has a range of measurements and ratios quite distinct from the species found in Asia (though the greatest separations result from the analyses of ratio data). These results therefore support the view that M. sylvanus may be regarded as an independent species group in the genus Macaca as proposed by Delson [1980].     

Genome sequencing and comparison of two nonhuman primate animal models, the cynomolgus and Chinese rhesus macaques

The nonhuman primates most commonly used in medical research are from the genus Macaca. To better understand the genetic differences between these animal models, we present high-quality draft genome sequences from two macaque species, the cynomolgus/crab-eating macaque and the Chinese rhesus macaque. Comparison with the previously sequenced Indian rhesus macaque reveals that all three macaques maintain abundant genetic heterogeneity, including millions of single-nucleotide substitutions and many insertions, deletions and gross chromosomal rearrangements. By assessing genetic regions with reduced variability, we identify genes in each macaque species that may have experienced positive selection. Genetic divergence patterns suggest that the cynomolgus macaque genome has been shaped by introgression after hybridization with the Chinese rhesus macaque. Macaque genes display a high degree of sequence similarity with human disease gene orthologs and drug targets. However, we identify several putatively dysfunctional genetic differences between the three macaque species, which may explain functional differences between them previously observed in clinical studies.     

Patterns of mandibular variation in Pan and Gorilla and implications for African ape taxonomy

Pan and Gorilla taxonomy is currently in a state of flux, with the number of existing species and subspecies of common chimpanzee and gorilla having been recently challenged. While Pan and Gorilla systematics have been evaluated on the basis of craniometric and odontometric data, only a handful of studies have evaluated multivariate craniometric variation within P. troglodytes, and none have evaluated in detail mandibular variation in either P. troglodytes or Gorilla gorilla. In this paper, we examine ontogenetic and adult mandibular variation in Pan and Gorilla. We test the hypothesis that patterns and degrees of mandibular variation in Pan and Gorilla closely correspond to those derived from previous analyses of craniometric variation. We then use these data to address some current issues surrounding Pan and Gorilla taxonomy. Specifically, we evaluate the purported distinctiveness of P.t. verus from the other two subspecies of Pan troglodytes, and the recent proposals to recognize Nigerian gorillas as a distinct subspecies, Gorilla gorilla diehli, and to acknowledge mountain and lowland gorillas as two separate species. Overall, patterns and degrees of multivariate mandibular differentiation parallel those obtained previously for the cranium and dentition. Thus, differences among the three conventionally recognized gorilla subspecies are somewhat greater than among subspecies of common chimpanzees, but differences between P. paniscus and P. troglodytes are greater than those observed between any gorilla subspecies. In this regard, the mandible does not appear to be more variable, or of less taxonomic value, than the face and other parts of the cranium. There are, however, some finer differences in the pattern and degree of morphological differentiation in Pan and Gorilla, both with respect to cranial and dental morphology, and in terms of the application and manner of size adjustment. Mandibular differentiation supports the conventional separation of bonobos from chimpanzees regardless of size adjustment, but size correction alters the relative alignment of taxa. Following size correction, intergroup distances are greatest between P.t. verus and all other groups, but there is considerable overlap amongst chimpanzee subspecies. Amongst gorillas, the greatest separation is between eastern and western gorillas, but adjustment relative to palatal vs. basicranial length results in a greater accuracy of group classification for G.g. gorilla and G.g. graueri, and more equivalent intergroup distances amongst all gorilla groups. We find no multivariate differentiation of the Nigerian gorillas based on mandibular morphology, suggesting that the primary difference between Nigerian and other western lowland gorillas lies in the nuchal region. Though intergroup distances are greatest between P.t. verus and other chimpanzee subspecies, the degree of overlap amongst all three groups does not indicate a markedly greater degree of distinction in mandibular, as opposed to other morphologies. Finally, mandibular differentiation corroborates previous craniodental studies indicating the greatest distinction amongst gorillas is between eastern and western groups. Thus, patterns and degrees of mandibular variation are in agreement with other kinds of data that have been used to diagnose eastern and western gorillas as separate species.     

Spatial patterning of bone stiffness in the anterior mandibular corpus of Macaca fascicularis: Implications for models of bone adaptation

Elastic modulus of bone from the anterior mandibular corpus was determined via microindentation in a mixed-sex ontogenetic sample (N = 14) of Macaca fascicularis. This investigation focused on the hypothesis that material heterogeneity in the macaque mandibular symphysis—provided an accounting of age and sex variation—is explicable as a means to homogenize strains in this region. Experimental data and theoretical models of masticatory loading indicate that in the absence of material compensation, large strain gradients exist in the anterior mandibular corpus of macaques, particularly between lingual and labial cortical plates owing to the effects of lateral transverse bending. Microindentation data indicate that juvenile macaques possess less stiff bone than their subadult and adult counterparts; however, sex differences in elastic modulus are not apparent. Anisotropy variation is idiosyncratic; that is, there is not a common pattern of variation in stiffness sampled among orthogonal planes across individuals. Similarly, differences in stiffness between lingual and labial cortical plates, as well as differences among alveolar, midcorpus, and basal regions are inconsistently observed. Consequently, we find little evidence in support of the hypothesis that spatial variation in bone stiffness functions to homogenize strains in the anterior corpus; in fact, in some individuals, this spatial variation serves to exacerbate, rather than to minimize, strain gradients. The mechanical benefit of elastic modulus variation in the macaque mandibular symphysis is unclear; this variation may not confer adaptive benefit in terms of structural integrity despite the fact that such variation has discernible functional consequences. Am J Phys Anthropol 156:649–660, 2015. © 2014 Wiley Periodicals, Inc.     

Comparison of stone handling behavior in two macaque species: implications for the role of phylogeny and environment in primate cultural variation

This study describes the stone handling (SH) behavior of captive rhesus macaques and compares it with that of a captive troop of Japanese macaques with reference to the relative contributions of phylogeny-driven behavioral propensities, environmental differences and socially facilitated learning to the formation of culture. These systematically collected data demonstrate for the first time that two closely related macaque species might share a common cultural behavior, SH. The rhesus troop displayed SH behavioral patterns that was already described in Japanese macaque troops. The one exception was a new pattern not yet seen in any Japanese macaque troop. Differences in the physical environment of the two study enclosures may be responsible for some of the variation in observed SH behavioral patterns in these two troops. These data support the idea that environmental factors can be important for the formation of cultural variation, when the key materials needed to perform the behavior are present in both habitats (stones). Our results are consistent with the prediction made by Huffman and Hirata [The biology of tradition: Models and evidence. Cambridge: Cambridge University Press. p 267-296] that an interactive triad of phylogenetic, environmental and social factors can be responsible for the formation of cultural variation in primates.     

Morphometric analysis ofMacaca arctoides andM. thibetana in relation to other macaque species

As a first step in reviewing the classification of the two stump-tailed macaque species,Macaca arctoides andM. thibetana, as compared with other species of the genusMacaca, 72 linear dental and cranial variables of 11 macaque species were examined by morphometric analyses. The results indicate that the two stump-tailed species are the largest of the macaques and although rather similar overall, they exhibit significant differences in the pattern of variation in most of the five skull regions as shown by Principal Components and Canonical Variate Analyses. Euclidean Distances based on Canonical Variate scores indicate that the females ofM. arctoides andM. thibetana are more widely separated than eight other pairs of macaque species, and that the separations of the respective males are greater than those of three other pairs of species. These findings are consistent withFooden's classification of the stump-tailed macaques as two separate species (Fooden, 1976;Fooden et al., 1985). The present results suggest, as other researchers have proposed on the basis of external features, biochemistry and genetics, that the two stump-tailed macaque species andM. assamensis are closely related. The results also tentatively imply associations withM. fuscata andM. sylvanus but these require further study. The findings have implications for the assessment of the various Chinese Pleistocene macaque fossils.     

Metagenomic comparison of the rectal microbiota between rhesus macaques(Macaca mulatta) and cynomolgus macaques(Macaca fascicularis)

Rhesus macaques(Macaca mulatta) and cynomolgus macaques(Macaca fascicularis) are frequently used in establishing animal models for human diseases. To determine the differences in gut microbiota between these species, rectal swabs from 20 rhesus macaques and 21 cynomolgus macaques were collected, and the microbial composition was examined by deep sequencing of the 16 S rR NA gene. We found that the rectal microbiota of cynomolgus macaques exhibited significantly higher alpha diversity than that of rhesus macaques, although the observed number of operational taxonomic units(OTUs) was almost the same. The dominant taxa at both the phylum and genus levels were similar between the two species, although the relative abundances of these dominant taxa were significantly different between them. Phylogenetic Investigation of Communities by Reconstruction of Unobserved States(PICRUSt) showed significant differences in the functional components between the microbiota of the two species, in particular the lipopolysaccharide(LPS) synthesis proteins. The above data indicated significant differences in microbial composition and function between these two closely related macaque species, which should be taken into consideration in the future selection of these animals for disease models.     

Radiation and phylogeography in the Japanese macaque, Macaca fuscata

The Japanese macaque (Macaca fuscata) presumably differentiated from eastern rhesus macaque (Macaca mulatta) populations during the Pleistocene and the two species are closely related. In order to analyse speciation and subspeciation events in the Japanese macaque and to describe historical and current relationships among their populations, we sequenced and analysed a fragment of 392bp of mitochondrial DNA (mtDNA) control region in 50 individuals belonging to six populations of Japanese macaque and compared these sequences with 89 eastern rhesus macaque control region sequences from GenBank/EMBL database. There were high genetic similarities between both species and only two positions were fixed within each species, which supports the inclusion of the Japanese macaque in a single species with eastern populations of rhesus macaques. Japanese macaque ancestors colonised Japan after the separation of the two species, estimated at between 0.31 and 0.88 million years ago (Mya). The star-like phylogeny, multimodal mismatch distribution, and lack of correlation between geographic and genetic distances are in accordance with a rapid dispersion of macaques throughout the archipelago after the arrival into Japan. The species shows low genetic variation within populations and high levels of genetic differentiation among populations with no mtDNA haplotype shared across populations. Genetic distances between Yakushima macaques (Macaca fuscata yakui) and any other population of Macaca fuscata fuscata subspecies are comparable to the distances between populations of Honshu, Awajishima, and Kyushu, not supporting the classification of Yakushima macaques as a different subspecies.     

Size and shape dimorphism in great ape mandibles and implications for fossil species recognition

Sexual dimorphism is an important source of morphological variation, and species differences in dimorphism may be reflected in magnitude, pattern, or both. While the extant great apes are commonly used as a reference sample for distinguishing between sexual dimorphism and intertaxic variation in the fossil record, few studies have evaluated mandibular dimorphism in these taxa. In this study, percentage, degree, and pattern of mandibular dimorphism are evaluated in Pongo, Gorilla, and Pan. Mandibular dimorphism patterns are explored to determine the extent to which such patterns accurately track great ape phylogeny. Pattern stability is assessed to determine whether there are stable patterns of mandibular size and shape dimorphism that may be usefully applied to hominoid or hominid fossil species recognition studies. Finally, the established patterns of dimorphism are used to address recent debates surrounding great ape taxonomy. Results demonstrate that mandibular dimorphism is universally expressed in size, but only Pongo and Gorilla exhibit shape dimorphism. Pattern similarity tends to be greater between subspecies of the same species than between higher-order taxa, suggesting that within the great apes, there is a relationship between dimorphism pattern and phylogeny. However, this relationship is not exact, given that dimorphism patterns are weakly correlated between some closely related taxa, while great ape subspecies may be highly correlated with taxa belonging to other species or genera. Furthermore, dimorphism patterns are not significantly correlated between great ape genera, even between Gorilla and Pan. Dimorphism patterns are more stable in Gorilla and Pongo as compared to Pan, but there is little pattern stability between species or genera. Importantly, few variables differ significantly between taxa that simultaneously show consistently relatively low levels of dimorphism and low levels of variation within taxa. Combined, these findings indicate that mandibular dimorphism patterns can and do vary considerably, even among closely related species, and suggest that it would be difficult to employ great ape mandibular dimorphism patterns for purposes of distinguishing between intra- and interspecies variation in fossil samples. Finally, the degree of pattern similarity in mandibular dimorphism is lower than previously observed by others for craniofacial dimorphism. Thus, the possibility cannot be ruled out that patterns of craniofacial dimorphism in great apes may be associated with a stronger phylogenetic signal than are patterns of mandibular dimorphism.     

Molecular Evidence for Distinct Genotypes of Monkey B Virus (Herpesvirus Simiae) Which Are Related to the Macaque Host Species

Although monkey B virus (herpesvirus simiae; BV) is common in all macaque species, fatal human infections appear to be associated with exposure to rhesus macaques (Macaca mulatta), suggesting that BV isolates from rhesus monkeys may be more lethal to nonmacaques than are BV strains indigenous to other macaque species. To determine if significant differences that would support this supposition exist among BV isolates, we compared multiple BV strains isolated from rhesus, cynomolgus, pigtail, and Japanese macaques. Antigenic analyses indicated that while the isolates were very closely related to one another, there are some antigenic determinants that are specific to BV isolates from different macaque species. Restriction enzyme digest patterns of viral DNA revealed marked similarities between rhesus and Japanese macaque isolates, while pigtail and cynomolgus macaque isolates had distinctive cleavage patterns. To further compare genetic diversity among BV isolates, DNA sequences from two regions of the viral genome containing genes that are conserved (UL27 and US6) and variable (US4 and US5) among primate alphaherpesviruses, as well as from two noncoding intergenic regions, were determined. From these sequence data and a phylogenetic analysis of them it was evident that while all isolates were closely related strains of BV, there were three distinct genotypes. The three BV genotypes were directly related to the macaque species of origin and were composed of (i) isolates from rhesus and Japanese macaques, (ii) cynomolgus monkey isolates, and (iii) isolates from pigtail macaques. This study demonstrates the existence of different BV genotypes which are related to the macaque host species and thus provides a molecular basis for the possible existence of BV isolates which vary in their levels of pathogenicity for nonmacaque species.     

Stone handling behavior in rhesus macaques (Macaca mulatta), a behavioral propensity for solitary object play shared with Japanese macaques

Stone handling (SH) behavior was systematically studied in a captive troop of rhesus macaques housed at the Primate Research Institute of Kyoto University, and compared with the results of long-term studies of this behavior in Japanese macaques, to evaluate the similarities of SH behavior in these two closely related species. Similar to Japanese macaques, rhesus macaques showed age-related differences in SH. Young animals were more active and displayed more SH patterns and bouts than did adults. Furthermore, the young displayed SH at a higher frequency and their bouts were of a shorter duration, compared to adults. Young adults were more active and displayed more patterns than did older adults. On the other hand, older adults were more conservative and displayed fewer patterns, and engaged in them for longer durations. All individuals displayed SH more frequently in relaxed environmental and social conditions. While lacking an apparent immediate adaptive value, practice of the behavior has been proposed to have long-term functional value for neural and cognitive development in the young and for the maintenance or repair of neuro-pathways in aging macaques that habitually perform the behavior. The results presented here are consistent with what we know about Japanese macaque SH. Given the uniformity of SH behavioral parameters and these two macaque species’ close phylogenetic relatedness, we propose that a similar functional and adaptive value for SH can be inferred for rhesus macaques.     

Elastic properties and masticatory bone stress in the macaque mandible

One important limitation of mechanical analyses with strain gages is the difficulty in directly estimating patterns of stress or loading in skeletal elements from strain measurements. Because of the inherent anisotropy in cortical bone, orientation of principal strains and stresses do not necessarily coincide, and it has been demonstrated theoretically that such differences may be as great as 45 degrees (Cowin and Hart, 1990). Likewise, relative proportions of stress and strain magnitudes may differ. This investigation measured the elastic properties of a region of cortical bone on both the buccal and lingual surfaces of the lower border of the macaque mandible. The elastic property data was then combined with macaque mandibular strain data from published and a new in vivo strain gage experiment to determine directions and magnitudes of maximum and minimum principal stresses. The goal was to compare the stresses and strains and assess the differences in orientation and relative magnitude between them. The main question was whether these differences might lead to different interpretations of mandibular function. Elastic and shear moduli, and Poisson's ratios were measured using an ultrasonic technique from buccal and lingual cortical surfaces in 12 macaque mandibles. Mandibular strain gage data were taken from a published set of experiments (Hylander, 1979), and from a new experiment in which rosette strain gauges were fixed to the buccal and lingual cortices of the mandibular corpus of an adult female Macaca fascicularis, after which bone strain was recorded during mastication. Averaged elastic properties were combined with strain data to calculate an estimate of stresses in the mandibular corpus. The elastic properties were similar to those of the human mandibular cortex. Near its lower border, the macaque mandible was most stiff in a longitudinal direction, less stiff in an inferosuperior direction, and least stiff in a direction normal to the bone's surface. The lingual aspect of the mandible was slightly stiffer than the buccal aspect. Magnitudes of stresses calculated from average strains ranged from a compressive stress of -16.00 GPa to a tensile stress of 8.84 GPa. The orientation of the principal stresses depended on whether the strain gage site was on the working or balancing side. On the balancing side of the mandibles, maximum principal stresses were oriented nearly perpendicular to the lower border of the mandible. On the working side of the mandibles, the orientation of the maximum principal stresses was more variable than on the balancing side, indicating a larger range of possible mechanisms of loading. Near the lower border of the mandible, differences between the orientation of stresses and strains were 12 degrees or less. Compared to ratios between maximum and minimum strains, ratios between maximum and minimum stresses were more divergent from a ratio of 1.0. Results did not provide any major reinterpretations of mandibular function in macaques, but rather confirmed and extended existing work. The differences between stresses and strains on the balancing side of the mandible generally supported the view that during the power stroke the mandible was bent and slightly twisted both during mastication and transducer biting. The calculated stresses served to de-emphasize the relative importance of torsion. On the working side, the greater range of variability in the stress analysis compared to the strain analysis suggested that a more detailed examination of loadings and stress patterns in each individual experiment would be useful to interpret the results. Torsion was evident on the working side; but in a number of experiments, further information was needed to interpret other superimposed regional loading patterns, which may have included parasagittal bending and reverse parasagittal bending.     

The functional significance of primate mandibular form.

A stress analysis of the primate mandible suggests that vertically deep jaws in the molar region are usually an adaptation to counter increased sagittal bending stress about the balancing-side mandibular corpus during unilateral mastication. This increased bending stress about the balancing side is caused by an increase in the amount of balancing-side muscle force. Furthermore, this increased muscle force will also cause an increase in dorso-ventral shear stress along the mandibular symphysis. Since increased symphyseal stress can be countered by symphyseal fusion and as increased bending stress can be countered by a deeper jaw, deep jaws and symphyseal fusion are often part of the same functional pattern. In some primates (e.g., Cercocebus albigena), deep jaws are an adaptation to counter bending in the sagittal plane during powerful incisor biting, rather than during unilateral mastication. The stress analysis of the primate mandible also suggests that jaws which are transversely thick in the molar region are an adaptation to counter increased torsion about the long axis of the working-side mandibular corpus during unilateral mastication. Increased torsion of the mandibular corpus can be caused by an increase in masticatory muscle force, an increase in the transverse component of the postcanine bite force and/or an increase in premolar use during mastication. Patterns of masticatory muscle force were estimated for galagos and macaques, demonstrating that the ratio of working-side muscle force to balancing-side muscle force is approximately 1.5:1 in macaques and 3.5:1 in galagos during unilateral isometric molar biting. These data support the hypothesis that mandibular symphyseal fusion is an adaptative response to maximize unilateral molar bite force by utilizing a greater percentage of balancing-side muscle force.     

A Large‐Scale SNP‐Based Genomic Admixture Analysis of the Captive Rhesus Macaque Colony at the California National Primate Research Center

Some breeding facilities in the United States have crossbred Chinese and Indian rhesus macaque (Macaca mulatta) founders either purposefully or inadvertently. Genetic variation that reflects geographic origins among research subjects has the potential to influence experimental outcomes. The use of animals from different geographic regions, their hybrids, and animals of varying degrees of kinship in an experiment can obscure treatment effects under study because high interanimal genetic variance can increase phenotypic variance among the research subjects. The intent of this study, based on a broad genomic analysis of 2,808 single nucleotide polymorphisms (SNPs), is to ensure that only animals estimated to be of pure Indian or Chinese ancestry, based on both demographic and genetic information, are used as sources of infants for derivation and expansion of the California National Primate Research Center's (CNPRC) super‐Specific Pathogen Free (SSPF) rhesus macaque colony. Studies of short tandem repeats (STRs) in Indian and Chinese rhesus macaques have reported that heterozygosity of STRs is higher in Chinese rhesus macaques than in Indian rhesus macaques. The present study shows that heterozygosity of SNPs is actually higher in Indian than in Chinese rhesus macaques and that the Chinese SSPF rhesus macaque colony is far less differentiated from their founders compared to the Indian‐origin animals. The results also reveal no evidence of recent gene flow from long‐tailed and pig‐tailed macaques into the source populations of the SSPF rhesus macaques. This study indicates that many of the long‐tailed macaques held in the CNPRC are closely related individuals. Most polymorphisms shared among the captive rhesus, long‐tailed, and pig‐tailed macaques likely predate the divergence among these groups. Am. J. Primatol. 74:747‐757, 2012. © 2012 Wiley Periodicals, Inc.     

Malaria in macaques

Seven species of malaria naturally infect eight species of macaques in southwestern India, Sri Lanka, and Southeast Asia. Within malarious areas, the frequency of infections in infected species of macaques varies from 9 to 61%. Natural malarial infections in macaques are relatively benign. The proved or probable vectors of macaque malaria are seven species of mosquitoes that belong to the Leucosphyrus Group of the genus Anopheles. The geographic distribution of macaque malaria apparently is determined by the distribution of the Leucosphyrus Group of mosquitoes, which in turn apparently is determined by the distribution of tropical evergreen rain forest. Experimental infections with three species of macaque malaria frequently are lethal to populations or species of macaques that inhabit areas outside the geographic ranges of the parasites. In populations or species of macaques that are sympatric with experimentally virulent species of malaria, partial resistance probably evolved as a consequence of natural selection acting on favorable mutations.     

A comparison of cortical elastic properties in the craniofacial skeletons of three primate species and its relevance to the study of human evolution

When a force is applied to an object, the resulting pattern of strain is a function of both the object's geometry and its elastic properties. Thus, knowledge of elastic properties in craniofacial cortical bone is indispensable for exploring the biomechanics and adaptation of primate skulls. However, elastic properties, such as density and stiffness, cannot be measured in all species, particularly extinct species known only from fossils. In order for advanced engineering techniques such as finite element analysis (FEA) to be applied to questions of primate and hominid craniofacial functional morphology, it is important to understand interspecific patterns of variation in elastic properties. We hypothesized that closely related species would have similar patterns of bone elastic properties, and that similarities with extant species should allow reasonable predictions of elastic properties in the skeletons of extinct primate species. In this study, we tested this hypothesis by measuring elastic properties in five areas of the external cortex of the baboon craniofacial skeleton using an ultrasonic technique, and by comparing the results to existing data from macaque and human crania. Results showed that cortical density, thickness, elastic and shear moduli, and anisotropy varied among areas in the baboon cranium. Similar variation had previously been found in rhesus and human crania, suggesting area-specific elastic patterns in the skulls of each species. Comparison among species showed differences, suggesting species-specific patterns. These patterns were more similar between macaques and baboons for density, maximum elastic and shear stiffness, and anisotropy than between either of these and humans. This finding demonstrates that patterns of cortical elastic properties are generally similar in closely related primate species with similar craniofacial morphology. Thus, reasonable estimates of cortical bone elastic properties should be possible for extinct species through the study of phylogenetically related and functionally similar modern forms. For example, reasonable elastic property estimates of cortical bone from fossil hominid skulls should be possible once adequate information about such properties in extant great apes is added to our current data from humans, macaques, and baboons. Such data should eventually allow FEA of craniofacial function in fossil hominids.     

Mandible of the giant panda (Ailuropoda melanoleuca) compared with other Chinese carnivores: functional adaptation

The aim of this study was to understand the mandible of the giant panda in morphometric terms to explore differences between the giant panda and other carnivores distributed in China, in terms of functional adaptation. Twelve mandibular variables were studied using bivariate (allometry) and multivariate (principal components analysis, PCA, and discriminant functional analysis, DFA) tools. When deviations were produced from allometric baselines consisting of all the species studied, the giant panda displayed a much more developed mandibular structure than the bear, leopard, and tiger. This may be related to its specific dietary preference for bamboo, which has very strong fibers. Results also indicate that the mandibular structure among carnivores mainly reflects the differences in their dietary preferences and functional adaptation. Three groups were found referring to dispersal profiles expressed by the first two axes of PCA and DFA: (1) the two panda species – the herbivorous carnivores; (2) the black bear – the omnivorous carnivore; and (3) the tiger and leopard – the hypercarnivores. Nevertheless, a significant separation between the two panda species was also found with the profiles displayed by the first and third axes of DFA. In addition to no close evolutionary relationship and phylogenetic development, a noticeable separation between the two panda species found in DFA analysis may be associated with their variation in consuming different parts of the bamboo plant: the giant panda feeds on stems and the red panda feeds on leaves.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 92 , 449–456.