RAPD Profiling in Detecting Genetic Variation in Endemic Coelonema (Brassicaceae) of Qinghai-Tibet Plateau of China

Random amplified polymorphic DNA (RAPD) markers were used to measure genetic diversity of Coelonema draboides (Brassicaceae), a genus endemic to the Qilian Mountains of the Qinghai-Tibet Plateau. We sampled 90 individuals in 30 populations of Coelonema draboides from Datong and Huzhu counties of Qinghai Province in P.R. China. A total of 186 amplified bands were scored from the 14 RAPD primers, with a mean of 13.3 amplified bands per primer, and 87% (161 bands) polymorphic bands (PPB) was found. Analysis of molecular variance (AMOVA) shows that a large proportion of genetic variation (84.2%) resides among individuals within populations, while only 15.8% resides among populations. The species shows higher genetic diversity between individuals than other endemic and endangered plants. The RAPDs provide a useful tool for assessing genetic diversity of rare, endemic species and for resolving relationships among populations. The results show that the genetic diversity of this species is high, possibly allowing it to adapt more easily to environmental variations. The main factor responsible for the high level of differentiation within populations and the low level of diversity among populations is probably the outcrossing and long-lived nature of this species. Some long-distance dispersal, even among far separated populations, is also a crucial determinant for the pattern of genetic variation in the species. This distributive pattern of genetic variation of C. draboides populations provides important baseline data for conservation and collection strategies for the species. It is suggested that only populations in different habitats should be studied and protected, not all populations, so as to retain as much genetic diversity as possible.     

Genetic Variation Within and Among Populations of Rhodiola alsia (Crassulaceae) Native to the Tibetan Plateau as Detected by ISSR Markers

Genetic variation of 10 Rhodiola alsia (Crassulaceae) populations from the Qinghai–Tibet Plateau of China was investigated using intersimple sequence repeat (ISSR) markers. R. alsia is an endemic species of the Qinghai–Tibet Plateau. Of the 100 primers screened, 13 were highly polymorphic. Using these primers, 140 discernible DNA fragments were generated with 112 (80%) being polymorphic, indicating pronounced genetic variation at the species level. Also there were high levels of polymorphism at the population level with the percentage of polymorphic bands (PPB) ranging from 63.4 to 88.6%. Analysis of molecular variance (AMOVA) showed that the genetic variation was mainly found among populations (70.3%) and variance within populations was 29.7%. The main factors responsible for the high level of differentiation among populations are probably the isolation from other populations and clonal propagation of this species. Occasional sexual reproduction might occur in order to maintain high levels of variation within populations. Environmental conditions could also influence population genetic structure as they occur in severe habitats. The strong genetic differentiation among populations in our study indicates that the conservation of genetic variability in R. alsia requires maintenance of as many populations as possible.     

Y-chromosome and mitochondrial DNA studies on the population structure of the Christmas Island community

Christmas Island is a remote Australian territory located close to the main Indonesian island of Java. Y-chromosome and mitochondrial DNA (mtDNA) markers were used to investigate the genetic structure of the population, which comprises communities of mixed ethnic origin. Analysis of 12 Y-chromosome biallelic polymorphisms revealed a high level of gene diversity and haplotype frequencies that were consistent with source populations in southern China and Southeast Asia. mtDNA hypervariable segment I (HVS-I) sequences displayed high levels of haplotype diversity and nucleotide diversity that were comparable to various Asian populations. Genetic distances revealed extremely low mtDNA differentiation among Christmas Islanders and Asian populations. This was supported by the relatively high proportion of sequence types shared among these populations. The most common mtDNA haplogroups were M* and B, followed by D and F, which are prevalent in East/Southeast Asia. Christmas Islanders of European descent were characterized by the Eurasian haplogroup R*, and a limited degree of admixture was observed. In general, analysis of the genetic data indicated population affinities to southern Chinese (in particular from the Yunnan Province) and Southeast Asia (Thailand, Malaysia, and Cambodia), which was consistent with historical records of settlement. The combined use of these different marker systems provides a useful and appropriate model for the study of contemporary populations derived from different ethnic origins.     

Body proportions in ancient Andeans from high and low altitudes

Living human populations from high altitudes in the Andes exhibit relatively short limbs compared with neighboring groups from lower elevations as adaptations to cold climates characteristic of high-altitude environments. This study compares relative limb lengths and proportions in pre-Contact human skeletons from different altitudes to test whether ecogeographic variation also existed in Andean prehistory. Maximum lengths of the humerus, radius, femur, and tibia, and femoral head breadth are measured in sex-specific groups of adult human skeletons (N = 346) from the central (n = 80) and the south-central (n = 123) Andean coasts, the Atacama Desert at 2,500 m (n = 102), and the southern Peruvian highlands at 2,000-3,800 m (n = 41). To test whether limb lengths vary with altitude, comparisons are made of intralimb proportions, limb lengths against body mass estimates derived from published equations, limb lengths against the geometric mean of all measurements, and principal component analysis. Intralimb proportions do not statistically differ between coastal groups and those from the Atacama Desert, whereas intralimb proportions are significantly shorter in the Peruvian highland sample. Overall body size and limb lengths relative to body size vary along an altitudinal gradient, with larger individuals from coastal environments and smaller individuals with relatively longer limbs for their size from higher elevations. Ecogeographic variation in relation to climate explains the variation in intralimb proportions, and dietary variation may explain the altitudinal cline in body size and limb lengths relative to body size. The potential effects of gene flow on variation in body proportions in Andean prehistory are also explored.     

F-81 skeleton from Wadi Mataha, Jordan, and its bearing on human variability in the Epipaleolithic of the Levant

The discovery of a Middle Epipaleolithic adult skeleton (F-81) at the site of Wadi Mataha in southern Jordan provides new insights into human variability in the Epipaleolithic of the Levant. This paper analyzes the skeletal morphology of Wadi Mataha F-81 in the context of other Epipaleolithic remains from Jordan and Israel to assess the current evidence for morphological variability throughout this period. The F-81 skeleton shares morphological features with earlier Epipaleolithic skeletons from Ohalo and Nahal Ein Gev, and later Natufian populations. Despite the morphological similarities, F-81 extends the range of known variability prior to the Natufian with its unusually small stature and unique combination of morphological characteristics. High levels of cranial and postcranial robusticity suggest that the F-81 individual was physically active and terrestrially mobile. Pronounced bilateral asymmetry in the upper limb suggests significant lateralization of habitual activity. In the context of Epipaleolithic remains, the F-81 skeleton provides preliminary evidence for greater morphological variability, terrestrial mobility, and lateralized habitual behavior prior to the Natufian, and skeletal gracilization between the Middle and Late Epipaleolithic in the Levant.     

Ontogenetic bases of canine dimorphism in anthropoid primates

This study tests hypotheses regarding the ontogeny of canine tooth size dimorphism in five anthropoid primate species (Saguinus fuscicollis, Macaca mulatta, Cercocebus atys, Papio hamadryas, and Mandrillus sphinx). Canine measurements and chronological age data are analyzed to determine if bimaturism, a sex difference in the age at which eruption ceases, accounts for canine tooth sexual dimorphism. Canine height measurements are evaluated through a variety of regression techniques. Results show a lack of sexual dimorphism in Saguinus. While size dimorphism is absent in the deciduous teeth of all species analyzed, the adult teeth in cercopithecines become increasingly dimorphic through ontogeny. Female adult tooth eruption regularly precedes male tooth eruption, and regression-based eruption trajectories for both sexes intersect at about the age at which the female tooth reaches adult size. Males erupt the tooth later and more rapidly than females. Males also reach a larger adult size than females by erupting the tooth for much longer periods of time. Bimaturism is primary in the production of dimorphism, but rates of eruption show modest variation. These results point to the scheduling of sexual selection through intermale competition as a primary factor determining male eruption timing, rates of eruption, and adult size. Life history factors may play a role in determining the relations between the scheduling of intrasexual competition and canine eruption. Female contributions to sexual dimorphism are apparent in these species, suggesting that similar levels of dimorphism can be attained through diverse ontogenetic pathways.     

Metric dental variation of major human populations

Mesiodistal and buccolingual crown diameters of all teeth recorded in 72 major human population groups and seven geographic groups were analyzed. The results obtained are fivefold. First, the largest teeth are found among Australians, followed by Melanesians, Micronesians, sub-Saharan Africans, and Native Americans. Philippine Negritos, Jomon/Ainu, and Western Eurasians have small teeth, while East/Southeast Asians and Polynesians are intermediate in overall tooth size. Second, in terms of odontometric shape factors, world extremes are Europeans, aboriginal New World populations, and to a lesser extent, Australians. Third, East/Southeast Asians share similar dental features with sub-Saharan Africans, and fall in the center of the phenetic space occupied by a wide array of samples. Fourth, the patterning of dental variation among major geographic populations is more or less consistent with those obtained from genetic and craniometric data. Fifth, once differences in population size between sub-Saharan Africa, Europe, South/West Asia, Australia, and Far East, and genetic drift are taken into consideration, the pattern of sub-Saharan African distinctiveness becomes more or less comparable to that based on genetic and craniometric data. As such, worldwide patterning of odontometric variation provides an additional avenue in the ongoing investigation of the origin(s) of anatomically modern humans.     

DOES GENE FLOW CONSTRAIN ADAPTIVE DIVERGENCE OR VICE VERSA? A TEST USING ECOMORPHOLOGY AND SEXUAL ISOLATION IN TIMEMA CRISTINAE WALKING‐STICKS

Population differentiation often reflects a balance between divergent natural selection and the opportunity for homogenizing gene flow to erode the effects of selection. However, during ecological speciation, trait divergence results in reproductive isolation and becomes a cause, rather than a consequence, of reductions in gene flow. To assess both the causes and the reproductive consequences of morphological differentiation, we examined morphological divergence and sexual isolation among 17 populations of Timema cristinae walking-sticks. Individuals from populations adapted to using Adenostoma as a host plant tended to exhibit smaller overall body size, wide heads, and short legs relative to individuals using Ceonothus as a host. However, there was also significant variation in morphology among populations within host-plant species. Mean trait values for each single population could be reliably predicted based upon host-plant used and the potential for homogenizing gene flow, inferred from the size of the neighboring population using the alternate host and mitochondrial DNA estimates of gene flow. Morphology did not influence the probability of copulation in between-population mating trials. Thus, morphological divergence is facilitated by reductions in gene flow, but does not cause reductions in gene flow via the evolution of sexual isolation. Combined with rearing data indicating that size and shape have a partial genetic basis, evidence for parallel origins of the host-associated forms, and inferences from functional morphology, these results indicate that morphological divergence in T. cristinae reflects a balance between the effects of host-specific natural selection and gene flow. Our findings illustrate how data on mating preferences can help determine the causal associations between trait divergence and levels of gene flow.     

Enzyme Activities and Alcohol Tolerance in Isofemale Lines of Drosophila melanogaster Originating from Different Habitats

Enzyme activity variation was studied in a Drosophila melanogaster population from two villages (Tiszafüred and Tiszaszolos) in Hungary. Two habitats (distillery and farmyard) were sampled in both villages and 8-9 isofemale lines were established from each sample with a total of 35 lines. The activities of ADH, alphaGPDH, IDH and 6PGDH were determined on starch gel after electrophoresis in 10 F1 females of each of the 35 isofemale lines. Three sublines were established from three selected isofemale lines of all four samples (altogether 36 sublines). Alcohol tolerance of the adult flies was assayed in these sublines. The activity of ADH was similar in the two habitats; so was the sensitivity to ethanol. Accordingly, no differences in adaptation to environmental ethanol were detected between the two habitats. The deviations between the two habitats in average activities and in the total variation of enzyme activities were not consistent in the two villages. These results suggest that founder effects and genetic drift are more pronounced in distilleries than selection. The association among enzyme activities varied greatly both between the two villages and between the two habitats. The two parameters of alcohol tolerance were not significantly different between the two habitats in any of the two villages.