Patterns of growth in primates

A model is developed which demonstrates the pattern of the relationship between growth rate. body weight, proportion of adult weight attained, and time taken to mature in animals. The relationships of growth rate and time taken to mature, to body weight in primates are examined in relation to this model. Within each of the taxonomic groups: prosimians, New World monkeys, Old World monkeys and great apes, growth rate quite closely parallels the three-quarter power of weight. After accounting for size, growth rate clearly decreases through this taxonomic list. Man has the slowest growth rate of all primates in relation to his size. The model predicts that, after accounting for differences in size, the daily energy intake during growth may, like growth rate, decrease considerably through the taxonomic groups from prosimians to man. The results form a basis from which to account for the differences due to size and taxonomic position when using monkeys as models for human physiology or disease during growth.     

Patterns of paternal care in primates

An interspecific comparison was carried out to understand better the relationships among paternal care, paternal certainty, and reproductive burden in primates. Although monogamy is generally rare among mammals, a number of primate species are monogamous. Extensive paternal care is a related issue but is one that is not necessarily associated with monogamy or with paternal certainty. For example, despite paternal certainty, primate mothers in monogamous species with body weights over 2 kg still remain the primary infant caretakers, while males in the communally breeding tamarins carry infants more frequently than mothers do, even in the absence of paternal certainty. Several different tactics are used by small-bodied primates to cope with the energetic burden of raising proportionately large infants in an arboreal environment: (1) infant carrying by subadult and/or related nulliparous females (Saimiri, Lemur monogoz); (2) infant carrying by fathers and offspring (Aotus, Callicebus, Saguinus, Cebuella, Leontopithecus); (3) parking infants while family members forage (Tarsius, Galago, Microcebus, Cheirogaleus, Varecia); or (4) some combination of the above (Callithrix, Hapalemur, Loris). Lactation length and infant growth patterns appear to influence which of these tactics is employed by a given species. Moreover, although most small-bodied, mated, monogamous female primates spend no more than 9 months annually in gestation and lactation,Aotus andCallicebus mated females are either pregnant or lactating on a year-round basis. It is this heavy female reproductive burden that may be an important factor in selection for extensive paternal care in these monogamous cebids.     

Patterns of color and nectar variation across an Ipomopsis (Polemoniaceae) hybrid zone

Hybridization may uncouple adaptive trait combinations that are present in parental species. I studied variation in flower color and reward quality across a hybrid zone of Ipomopsis aggregata and I. tenuituba. Individuals from hybrid populations showed considerable variation in flower color using corolla reflectance measurements. Flower spectra of such individuals were either intermediate or else resembled those flowers from the parental species. Ipomopsis aggregata populations had consistently higher nectar production rates and higher nectar standing crops than either I. tenuituba or hybrids. Ipomopsis aggregata flowers also produced more dilute nectar than those of hybrids and I. tenuituba, but the actual concentration values were quite variable among populations of the same type. Overall, the nectar quality of hybrid flowers most resembled that of I. tenuituba flowers. Based on the observed interpopulation patterns of color-reward associations in this hybrid zone, pollinators should be able to discriminate against I. tenuituba and hybrid populations and against most individuals within hybrid populations. However, they may visit those hybrids that resemble the most rewarding flower type (I. aggregata). The results emphasize the need for studies that address how hybridization affects subsequent plant fitness and the evolutionary dynamics of the species involved.     

Genetic variation of aldehyde dehydrogenase in primates.

Genetic variation of aldehyde dehydrogenase has been demonstrated in catarrhine primates. The results are in accordance with the formal genetic interpretation: three alleles, AldDH1, AldDH2, AldDH3, at the gene locus AldDH. Obviously, the allele AldDH1 has undergone fixation in Homo and Hylobates, the allele AldDH2 in Macaca and Papio, and the allele AldDH3 in Cercopithecus.     

Patterns of tooth size variability in the dentition of primates

Published data on tooth size in 48 species of non-human primates have been analyzed to determine patterns of variability in the primate dentition. Average coefficients of variation calculated for all species, with males and females combined, are greatest for teeth in the canine region. Incisors tend to be somewhat less variable, and cheek teeth are the least variable. Removing the effect of sexual dimorphism, by pooling coefficients of variation calculated for males and females separately, reduces canine variability but does not alter the basic pattern. Ontogenetic development and position in functional fields have been advanced to explain patterns of variability in the dentition, but neither of these appears to correlate well with patterns documented here. We tentatively suggest another explanation. Variability is inversely proportional to occlusal complexity of the teeth. This suggests that occlusal complexity places an important constraint on relative variability within the dentition. Even when the intensity of natural selection is equal at all tooth positions, teeth with complex occlusal patterns must still be less variable than those with simple occlusion in order to function equally well. Hence variability itself cannot be used to estimate the relative intensity of selection. Low variability of the central cheek teeth ( \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm M}\frac{1}{1} $\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm M}\frac{2}{2} $\end{document}) makes them uniquely important for estimating body size in small samples, and for distinguishing closely related species in the fossil record.     

Taxonomic variation in the patterns of craniofacial dimorphism in primates

Understanding sexual dimorphism in living primates is important for interpreting the biological and taxonomic significance of variation in the primate fossil record. In the past two decades, there has been an increasing emphasis on the fact that sexual dimorphism varies in both magnitude and pattern among species. Several studies have suggested that distinct patterns of dimorphism may assist in species recognition and perhaps phylogenetic analysis. This study evaluates patterns of craniofacial dimorphism in samples of 82 anthropoid primates. Dimensions of the viscerocranium tend to be more dimorphic than those of the neurocranium and orbits. Principal components analysis of phylogenetically controlled data demonstrates a basic pattern of dimorphism in overall skull proportions, and a distinction between length and breadth measurements. For any given species there can be substantial variation in the magnitude of dimorphism among dimensions, and different species can show substantially different patterns of dimorphism within and between regions of the skull and jaws. Patterns of dimorphism are clearly associated with phylogeny. Pattern similarity is not dependent on the overall magnitude of craniofacial dimorphism, or body mass dimorphism. Among all anthropoids, there are few combinations of characters that consistently show greater or lesser degrees of dimorphism. Such "stability" of patterns increases within genera. Patterns of dimorphism are likely to be useful for interpreting the taxonomic significance of variation in the fossil record. However, phylogenetic propinquity alone is not reason to use an extant species as a model for variation in an extinct species. Rather, care must be taken to identify stable patterns of dimorphism within a group of closely related extant species.     

Patterns of allozyme variation in Nordic Pilosella

Patterns of allozyme variation have been investigated in 101 clones representing most of the morphological variation (and taxa) found in the amphi-apomictic genus Pilosella Hill. in the Nordic countries. Levels of variation were very high, both within narrowly defined taxa and within the whole data-set, but the correlation between a morphology-based taxonomy and patterns of allozyme variation was very weak. Almost all enzyme bands were found in more than one taxon and the differences between broadly defined species in terms of the frequency of bands were generally small. Cluster analyses did not perfectly recover any taxon but there were some tendencies for samples of some broadly defined taxa (e.g. P. officinarum s. l., and P. cymosa ssp. cymosa) to cluster together. It is concluded that there is considerable gene-flow among virtually all Nordic morpho-types of Pilosella and this is considered an argument for applying a very broad species concept in this genus.Financial support for the present study has been recieved from Stiftelsen Harald E. Johanssons minnesfond at the Royal Swedish Academy of Sciences.     

Biochemical variation of hair keratins in man and non-human primates

Human hair from various racial groups was investigated using the following techniques: amino acid analysis, acrylamide gel electrophoresis, x-ray diffraction studies, stress-strain analysis. Each of these techniques yielded identical results for all samples, indicating that the variables producing phenotypic differences in human hair form are probably not on the level of primary or secondary biochemical structure. Hair samples of a variety of primates were examined electrophoretically, with each taxonomic family investigated exhibiting a different pattern. These biochemical results are consistent with accepted primate phylogeny.     

Patterns of sexual dimorphism in body weight among prosimian primates.

Many primatologists believe that there is no sexual dimorphism in body size in prosimian primates. Because this belief is based upon data that came from only a few species and were largely flawed in some aspect of sample quality, I re-examined the extent of sexual dimorphism in body weight, using weights of 791 adult prosimians from 34 taxa recorded over the last 17 years at the Duke University Primate Center. There was no significant sex difference in body weight in 17 species, but males were significantly larger in Nycticebus pygmaeus, Tarsius syrichta, Galago moholi, Galagoides demidovii, Otolemur crassicaudatus and Otolemur garnettii. Moreover, females were significantly larger in Microcebus murinus. Thus, the general lack of sexual dimorphism could be confirmed, notably for lemurs, but prosimians as a group show more variability in sexual size dimorphism than was previously thought. After including previously published data obtained in the wild from 8 additional species, I found significant heterogeneity in the degree of sexual dimorphism at the family level, but only the Indridae and Galagidae were significantly different from each other. Among the prosimian infraorders, the Lorisiformes were significantly more dimorphic than the Lemuriformes. Differences in dimorphism between higher taxonomic groups are discussed in the context of prosimian evolution, concluding that phylogenetic inertia cannot provide a causal explanation for the evolution of sexual dimorphism. The relative monomorphism of most prosimians may be related to allometric constraints and, especially in the Lemuriformes, to selective forces affecting male and female behavioral strategies.     

Three-dimensional finite element modelling of muscle forces during mastication

This paper presents a three-dimensional finite element model of human mastication. Specifically, an anatomically realistic model of the masseter muscles and associated bones is used to investigate the dynamics of chewing. A motion capture system is used to track the jaw motion of a subject chewing standard foods. The three-dimensional nonlinear deformation of the masseter muscles are calculated via the finite element method, using the jaw motion data as boundary conditions. Motion-driven muscle activation patterns and a transversely isotropic material law, defined in a muscle-fibre coordinate system, are used in the calculations. Time-force relationships are presented and analysed with respect to different tasks during mastication, e.g. opening, closing, and biting, and are also compared to a more traditional one-dimensional model. The results strongly suggest that, due to the complex arrangement of muscle force directions, modelling skeletal muscles as conventional one-dimensional lines of action might introduce a significant source of error.     

Patterns of variation within self-incompatibility loci

Diverse self-incompatibility (SI) mechanisms permit flowering plants to inhibit fertilization by pollen that express specificities in common with the pistil. Characteristic of at least two model systems is greatly reduced recombination across large genomic tracts surrounding the S-locus, which regulates SI. In three angiosperm families, including the Solanaceae, the gene that controls the expression of gametophytic SI in the pistil encodes a ribonuclease (S-RNase). The gene that controls pollen SI expression is currently unknown, although several candidates have recently been proposed. Although each candidate shows a high level of polymorphism and complete allelic disequilibrium with the S-RNase gene, such properties may merely reflect tight linkage to the S-locus, irrespective of any functional role in SI. We analyzed the magnitude and nature of nucleotide variation, with the objective of distinguishing likely candidates for regulators of SI from other genes embedded in the S-locus region. We studied the S-RNase gene of the Solanaceae and 48A, a candidate for the pollen gene in this system, and we also conducted a parallel analysis of the regulators of sporophytic SI in Brassica, a system in which both the pistil and pollen genes are known. Although the pattern of variation shown by the pollen gene of the Brassica system is consistent with its role as a determinant of pollen specificity, that of 48A departs from expectation. Our analysis further suggests that recombination between 48A and S-RNase may have occurred during the interval spanned by the gene genealogy, another indication that 48A may not regulate SI expression in pollen.     

Persistent Differences in Mortality Patterns across Industrialized Countries

The epidemiological transition has provided the theoretical background for the expectation of convergence in mortality patterns. We formally test and reject the convergence hypothesis for a sample of industrialized countries in the period from 1960 to 2008. After a period of convergence in the decade of 1960 there followed a sustained process of divergence with a pronounced increase at the end of the 1980''s, explained by trends within former Socialist countries (Eastern countries). While Eastern countries experienced abrupt divergence after the dissolution of the Soviet Union, differences within Western countries remained broadly constant for the whole period. Western countries transitioned from a strong correlation between life expectancy and variance in 1960 to no association between both moments in 2008 while Eastern countries experienced the opposite evolution. Taken together, our results suggest that convergence can be better understood when accounting for shared structural similarities amongst groups of countries rather than through global convergence.     

Patterns of morphological variation insesamum indicum

Cultivars of sesame from 20 countries were sampled for morphological variability. Taximetric methods, including factor, cluster, discriminant, and principal components analyses, established patterns of similarities and were used to generate groupings among the taxa. The complementary results of the analyses indicate that 8 major groups can be discerned. Plants with tetracarpellate capsules have a distinctive form and comprise the initial separation from the entire collection on the dendrogram. The second branch is a group of purple-tinged plants from India that also includes the proposed progenitor. A short, bushy, early maturing genotype consists of predominantly Turkish cultivars. Another group, composed primarily of Korean accessions, consists of unbranched plants with strap-shaped leaves. Other groups are less easily typified. This characterization of the genetic variation in sesame can be used to identify sources of genetic materials for crop improvement, as well as to provide information about the evolution and genetic differentiation of the crop.     

Patterns of genetic variation in anthropogenically impacted populations

Genetic variation is considered critical for allowing natural populations to adapt to their changing environment, and yet the effects of human disturbance on genetic variation in the wild are poorly understood. Different types of human disturbances may genetically impact natural populations in a predictable manner and so the aim of this study was to provide an overview of these changes using a quantitative literature review approach. I examined both allozyme and microsatellite estimates of genetic variation from peer-reviewed journals, using the mean number of alleles per locus and expected heterozygosity as standardized metrics. Populations within each study were categorized according to the type of human disturbance experienced (“hunting/harvest”, “habitat fragmentation”, or “pollution”), and taxon-specific, as well as time- and context-dependent disturbance effects were considered. I found that human disturbances are associated with weak, but consistent changes in neutral genetic variation within natural populations. The direction of change was dependent on the type of human disturbance experienced, with some forms of anthropogenic challenges consistently decreasing genetic variation from background patterns (e.g., habitat fragmentation), whereas others had no effect (e.g., hunting/harvest) or even slightly increased genetic variation (e.g., pollution). These same measures appeared sensitive to both the time of origin and duration of the disturbance as well. This suggests that the presence or absence, strength, type, as well as the spatial and temporal scale of human disturbance experienced may warrant careful consideration when conservation management plans are formulated for natural populations, with particular attention paid to the effects of habitat fragmentation.     

Patterns of genetic variation in Native America.

Allele frequencies from seven polymorphic red cell antigen loci (ABO, Rh, MN, S, P, Duffy, and Diego) were examined in 144 Native American populations. Mean genetic distances (Nei's D) and the fixation index FST are approximately equal for the North and South American samples but are reduced in the Central American geographic area. The relationship between genetic distance and geographic distance differs markedly across geographic areas. The correlation between geographic distance and genetic distance for the North and Central American data is twice as large as that observed for the South American samples. This geographic difference is confirmed in spatial autocorrelation analyses; no geographic structure is apparent in the South American data but geographic structure is prominent in North and Central American samples. These results confirm earlier observations regarding differences between North and South American gene frequency patterns.