Fertility and mortality differentials among the population groups of the Himalayas

Selection potential based on differential fertility and mortality has been computed for 24 Himalayan populations classified into four groups: Himalayan populations with Asian affinities (HPA), Brahmans, Rajputs, and Scheduled Castes (Shilpkars). Irrespective of the methodology followed, the total index of selection was found to be highest (0.794) in Barbatiyas (HPA) and lowest (0.428) in Rajputs. The relative contribution of fertility component (If) to the index of total selection (It) is higher than the corresponding mortality component (Im) in all 24 groups. An analysis of correlation and regression on different components of the indices of selection performed among these 24 Himalayan populations revealed that the contributions of If in determining It are stronger than Im. Further, both If and Im are strongly associated with It and account for 76% and 67% of total variability in It, respectively. Examination of the relationship of the selection potential with the differential altitude and social categories showed a decrease in the index from high altitude to low altitude. Similarly, an inverse relationship was found between various indices and social categories. Himalayan populations with Asian affinities (HPA) in the present study reveal higher values of selection potential. Interestingly, these populations invariably reside in high altitude areas where health and communication infrastructures are poorly developed. Thus, the differential pattern of fertility and mortality among the Himalayan populations indicates that they are passing through a stage of transition, as is evident from the decrease in various selection indices. It is also apparent that groups that are less developed socioeconomically, as well as those inhabiting high altitude regions, are lagging behind in this process.     

Natural selection among Kinnaura of the Himalayan highland: A comparative analysis with other Indian and Himalayan populations

The present investigation on fertility and mortality differential among Kinnaura of the Himalayan highland is based on data collected from 160 post-menopausal women belonging to the middle and high altitude region of Kinnaur district of Himachal Pradesh (Indian Himalayas). Selection potential based on differential fertility and mortality was computed for middle-and high-altitude women. Irrespective of the methodology, the total index of selection was found to be highest among middle-altitude women (0.386) as compared with high-altitude (0.370) women, whereas for the total population it is estimated to be 0.384. It was found that the Kinnaura of the Himalayan highland showing moderate index of total selection and relative contribution of the mortality component (Im) to the index of total selection is higher than the corresponding fertility component (If). The analysis of embryonic and post-natal mortality components shows that the post-natal mortality components are higher in comparison with the embryonic mortality components among highlanders and needs special intervention and health care. The present findings are compared with other Indian tribes as well as non-tribes of the Himalayan region and other parts of the country. It reveals that this index among Kinnaura is moderate than the other population groups; among the Himalayan population, the highest was reported for Galong (It = 1.07) of Arunachal, whereas the lowest was reported from Ahom (It = 0.218) of Manipur. The correlation and regression analysis between total index of selection (It) and fertility (If) and mortality (Im) components for pooled data of populations of the Indian Himalayan states show that If and Im account for 21.6 and 29.1% variability, respectively. In Crow's total index of selection (It) along with strong association, which is significant at the 1% level, this indicates that mortality plays a greater role in natural selection in comparison with fertility among populations of the Indian Himalayas.     

Significance of indices of potential selection for residents of the USSR

Crow's indices of the opportunity for selection and their components connected with differential mortality (Im) and differential fertility (If) were estimated for populations of Soviet Union republics and for a number of USSR ethnic groups on the basis of demographic statistics. More than 10-fold decrease in the Im value was revealed in the total population of the USSR during 1926-1987. At present, the Im values in republics vary from 0.020 to 0.094 for urban population and from 0.030 to 0.121 in rural population, the ratio of perinatal mortality in the whole structure of prereproductive mortality being higher in the republics with lower values of the Im. The range of the If values for different peoples (0.148-0.643) is wider than for the populations of the republics (0.326-0.578). Interethnic differences contribute 47% of the variance in fertility. The structure of Crow's indices is given for urban and rural populations of the republics. Genetic implications of the data presented are discussed with respect to possible manifestation of the effects of inter-group selection.     

Study on a Brazilian isolate. II. Opportunity for selection

The opportunity for selection, measured by prereproductive mortality and fertility, was calculated for a small and relatively isolated Brazilian population. The total index of selection opportunity (0.53) was low in comparison to those obtained for other isolated populations. The contribution of prereproductive mortality (Im = 0.28) was 40% higher than that of fertility (If = 0.20).     

Genetic structure of an isolated group of the indigenous population of northern Siberia, the Nganasans (Tavginians) of Ta?mir

Demographic data of genetic interest were studied in presently living population in comparison with preseding generations of Nganasans. Decrease of sex ratio in the whole population has been revealed along with the reduction of reproductive and, possibly, effective size. The number and variance of livebirths per female were 7.29 and 9.86 respectively. Crow' index of the opportunity for selection (I) and its components (Im and If) were estimated. I was found to be 1.17, whereas Im and If--1.56 and 0.18 respectively. Linear pattern of settling in the past as well as the type of migration between adjoining subpopulations depended on culture and economy of arctic reindeer hunters as well as landscape character.     

Comparison of Chuvashs with Maris and Russians by vital statistics and the Crow index

Genetic demographic characteristics were calculated for Chuvash and Russian inhabitants of the Republic of Chuvashia. The generation lengths were 27.09 and 26.4 years and the sibship sizes were 2.54 and 1.82 for Chuvashes and Russians, respectively. Crow's indices and their components were as follows: Im = 0.05, If = 0.31, and Itot = 0.37 for Chuvashes and Im = 0.03, If = 0.43, and Itot = 0.46 for Russians. The genetic demographic characteristics obtained were compared with those for Highland and Meadow Maris.     

Genetical ESS-models. II. Multi-strategy models and multiple alleles

The problem of evolutionarily stable strategies (ESS) in sexual populations can be investigated by means of genetical ESS-models which link common sense, phenotypic ESS-models to an underlying genetical system. Thorough results are obtained for multi-strategy models in diploid, panmictic populations on the basis of multi-allelic, one-locus systems. A sexual population will be maintained at a phenotypic ESS if this can possibly be produced by the genotypes currently existing. If there is enough allelic variation, the corresponding gene pool may either be an ESS itself, or belong to an attracting, continuous set of states, which all determine the same evolutionarily stable population. The latter case allows new alleles to enter and spread in the gene pool without disturbing the phenotypic ESS. If a phenotypic ESS cannot be established, ESSs of the genetical model may be found which give rise to stable populations alternatively. Since these depend on the phenotypes determined by the currently existing genotypes, they may be destabilized by the occurrence of new mutations. In this sense, they are less durable than populations maintained at a phenotypic ESS and can be expected to evolve, in the long run, towards a phenotypic ESS.     

Assessing the genetic divergence of Pinus leucodermis Ant. endangered populations: use of molecular markers for conservation purposes

 In this study, 23 previously identified Mendelian RAPD markers and 16 polymorphic allozymic markers were used to assess divergence among two Greek populations and five Italian populations of Pinus leucodermis. Confidence intervals of observed genetic divergence were obtained using bootstrap analysis. Divergence among Italian populations was found to be about as large as that between Italian and Greek populations. Since it is likely that the split of two nuclei took place more than 10,000 years ago, a larger differentiation between, rather than within, the above nuclei was expected. If genetic drift was responsible for the larger divergence of Italian populations, large randomly generated disequilibrium between alleles at neutral, unlinked loci was expected. Indeed, the proportion of pairs of loci showing a non-random association of alleles within each of the Italian populations was larger than what was expected by pure chance (7.95–10.88%). Effective population size based on randomly generated disequilibrium was quite small for three out of the five populations considered (N _e =17.31±1.88, 16.57± 1.73, and 31.41±7.26, respectively). The implications of the results with respect to the conservation of endangered species of trees are discussed. Received: 27 April 1997 / Accepted: 14 June 1997     

Genetic and demographic structure of the yakut population: reproduction indices

Genetic and demographic information for the Yakut population living in the Republic of Sakha (Yakutia) is presented. The mean number of children per woman constituted 4.605. Crow's index and its components (Im and If) were 0.483, 0.104, and 0.343, respectively.     

Genetic-demographic characteristics of the rural population of the Republic of Tuva: reproductive indicators and the structure of Crow's indices]

The age limits of the female reproductive function, vital statistics, and Crow's indices were estimated in populations of three districts of the Tuva Republic that were remote from one another. These were the Kyzyl (the Shinaan population), Todzhinskii, and Bai-Taiginskii raions. The monoethnic Shinaan population was characterized by the longest reproductive period (15.88 years) but the lowest average number of pregnancies throughout the reproductive period (5.77); childbirth was an outcome of 86.72% of pregnancies. In the Bai-Taiginskii population, which was also monoethnic but lived in an industrial area of Tuva, these parameters were 12.99 years, 7.06 pregnancies, and 81.97%, respectively. The Todzhinskii population, which was ethnically mixed, exhibited the shortest actual reproductive period (10.72 years) and the greatest average number of pregnancies throughout the reproductive period (7.29), with the proportion of pregnancies ending in childbirth as low as 48.30%. The indices of potential selection and their components related to differential mortality and differential fertility were the following: in the Shinaan population, Itot = 0.59, Im = 0.19, and I(f) = 0.34; in the Bai-Taiginskii population, Itot = 0.48, Im = 0.18, and I(f) = 0.26; and in the Todzhinskii population, Itot = 0.90, Im = 0.23, and I(f) = 0.55. Thus, reproductive parameters in the studied populations of the Tuva Republic were largely determined by the ethnic composition of the population and social factors.     

Opportunity for natural selection in a Basque population and its secular trend: evolutionary implications of epidemic mortality

Analysis of the interaction between mortality patterns and opportunity for natural selection could help to elucidate potential evolutionary implications of epidemic mortality. In this paper secular trends are studied in relation to Crow's index (It) and its components of mortality (Im) and fertility (If), using parish records for family reconstitution in a Basque population. A principal components analysis (91% of the variance accounted for) showed marked quantitative and qualitative variations of Im and If depending on the stage of demographic transition of the population analyzed: In pretransitional societies the opportunity for natural selection is determined mainly by differential prereproductive mortality, whereas in posttransitional societies selection resulting from differential fertility plays a key role. The highest values for the mortality component (range 0.81-1.26) and for the relative contribution of Im, to It (range 47.1-57.2%) were observed in periods with a high incidence of infectious diseases and when the most severe mortality crises were detected (1830-1859, 1860-1889, and 1890-1919). A differential incidence of epidemic mortality was also found at prereproductive ages (before 16 years) and at reproductive ages (16-45 years), which provides strong support for the idea of the long-term genetic consequences of mortality crises.     

Hierarchical order of critical residues on the immunity-determining region of the Im7 protein which confer specific immunity to its cognate colicin.

The directed mutagenesis study of the Im7 protein of colicin E7 revealed that three residues, D31, D35, and E39, located in the loop 1 and helix 2 regions of the protein were critical for initiating the complex formation with its cognate colicin E7. Interestingly, the importance of these three critical residues in conferring specific immunity to its own colicin was exhibited in a hierarchical order, respectively. Moreover, we found that existence of the three critical residues was common among the DNase-type Im proteins. Most likely the three residues of the DNase-type immunity proteins are critical for initiating the unique protein-protein interactions with their cognate colicin. In addition, replacement of the helix 2 of Im7 by the corresponding region of Im8 produced a phenotype of the mutant protein very similar to that of Im8. This result suggests that the DNase-type Im proteins indeed share a "homologous-structural framework" and evolution of the Im proteins may be engendered by minor amino acid changes in this specific immunity-determining region without causing structural alteration of the proteins.     

The rapid transmembrane movement of cholesterol in small unilamellar vesicles.

The exchange of cholesterol between two populations of small unilamellar vesicles has been investigated using a new system. Uniformly sized egg lecithin-cholesterol vesicles containing [3H]cholesterol and the glycolipid N-palmitoyl-DL-dihydrolactocerebroside were used as donors, whereas similar vesicles containing unlabelled cholesterol and no glycolipid were used as cholesterol acceptors. The two populations of vesicles were separated with the castor bean lectin Ricinus communis. It was found that greater than 90% of the cholesterol in the donor vesicle could be exchanged with a single time constant, the half-time for the completion of this exchange process being 1.5 h at 37 degrees C. Therefore, the rate of transmembrane movement or flip-flop of cholesterol in these vesicles must be at least as fast as the intermembrane exchange process. Similar results were obtained using hemoglobin-free human erythrocyte ghosts as the acceptor membrane. If the molecular-sieve chromatography step used to fractionate the vesicles was omitted, a non-exchangeable pool of cholesterol was detected which was shown not to be due to the presence of multilamellar vesicles.     

Catalysis of the disproportionation of superoxide by metalloporphyrins.

The efficiencies of several metalloporphyrin complexes at catalyzing the disproportionation of superoxide have been determined at pH 10 in both carbonate and borate buffer systems. Catalytic rate constants were obtained for the iron(III) and cobalt(III) derivatives of tetrakis(4-N-methylpyridyl) porphine, for tetraphenylporphinesulfonatoferrate(III) and for hemin. In addition, the effects of added bovine serum albumin and imidazole were studied. The order of catalytic efficiency is FeTMpyP greater than FeTMpyP(Im)2 greater than FeTPPS(Im)2 approximately FeTPPS approximately FeTPPS.BSA approximately Fe(EDTA) greater than or approximately CoTMpyP greater than hemin(Im)2 greater than or approximately hemin.     

河北木蓝的叶表型可塑性研究

以中国分布最广、形态变异复杂且分类上存在争议的木蓝属植物河北木蓝(Indigofera bungeana Walp.)为研究对象,运用GIS技术从较大尺度上(17省28县29个居群)进行叶表型可塑性分析,利用表型可塑性指数和变异系数对叶表型可塑性进行评价,并对叶表型性状与环境因子的相关性进行分析。结果显示:河北木蓝叶表型性状在居群间的变异大于居群内;叶长、叶柄长、最少小叶数、最多小叶数、小叶长、小叶宽6个叶表型性状均具有可塑性,其中叶长的可塑性最大,小叶数目的可塑性最小;年均降水量是对叶表型可塑性影响最大的环境因子;6个叶表型性状与海拔均呈负相关,与年均气温呈正相关。研究结果可为河北木蓝的分类、适应性进化和开发利用奠定基础。     

Genetic diversity in Leavenworthia populations with different inbreeding levels.

Levels of neutral genetic diversity within and between populations were compared between outcrossing (self-incompatible) and inbreeding populations in the annual plant genus Leavenworthia. Two taxonomically independent comparisons are possible, since self-incompatibility has been lost twice in the group of species studied. Within inbred populations of L.uniflora and L.crassa, no DNA sequence variants were seen among the alleles sampled, but high diversity was seen in alleles from populations of the outcrosser L. stylosa, and in self-incompatible L. crassa populations. Diversity between populations was seen in all species. Although total diversity values were lower in the sets of inbreeding populations, between-population values were as high or higher, than those in the outcrossing taxa. Possible reasons for these diversity patterns are discussed. As the effect of inbreeding appears to be a greater than twofold reduction in diversity, we argue that some process such as selection for advantageous mutations, or against deleterious mutations, or bottlenecks occurring predominantly in the inbreeders, appears necessary to account for the findings. If selection for advantageous mutations is responsible, it appears that it must be some form of local adaptive selection, rather than substitution of alleles that are advantageous throughout the species. This is consistent with the finding of high between-population diversity in the inbreeding taxa.     

Expression of differentiation and age-related antigens on chicken erythroleukemia cells transformed by avian erythroblastosis virus (AEV)

Immature circulating chicken red cells express on their surface two antigenic molecules referred to as Im 48 kD and Im 140 kD antigens. The Im 140 kD antigen is not present beyond the erythroblast stage while the expression of Im 48 kD antigenic molecule remains detectable on circulating erythrocytes of embryos and young chickens, but not on erythrocytes of adult animals. In addition to Im 48 kD and Im 140 kD antigens, the avian erythroblastosis virus (AEV)-transformed erythroid cells express two novel high molecular weight (MW) immature antigens referred to as Im 150 kD and Im 160 kD. Since the transformed erythroid cells are apparently blocked at a stage close to the colony-forming units erythrocytic (CFU-E), these molecules might be expressed on these progenitor cells. The age-related antigenic molecules referred to as E1 48 kD and A 40 kD/A 85 kD antigens are detected on erythrocytes of embryos (and young chickens) and adult animals respectively. The E1 48 kD antigen as well as an antigen related to the A 40 kD were also detected on AEV-transformed erythroid cells deriving from both young chicken bone marrow and yolk sac. The presence of an adult antigen on the embryonic cells might well be related to the transformation by AEV, since the yolk sac CFU-E progenitor cells do not bear the adult antigenicity.     

The molecular mechanism and potential dependence of the Na+/glucose cotransporter.

Activity of the Na+/glucose cotransporter endogenously expressed in LLC-PK1 cells was measured using whole cell recording techniques under three different sodium concentration conditions: 1) externally saturating, zero trans; 2) 40 mM external, zero trans; and 3) externally saturating, 50 mM trans. Activity of the transporter with increasing concentrations of sugar was measured for each set of conditions, from which the maximal current for saturating sugar, Im, was determined. The Im measured shows substantial potential dependence for each set of conditions. The absolute Im and the relative potential dependence of Im compared among the various solute conditions were used to identify which loci in the transport cycle are responsible for potential-dependent changes in function. The experimental data were compared with the predicted Im values calculated from an eight-state, sequential, reversible model of a transport reaction kinetic scheme. Predictions derived from assignment of rate limitation and/or potential dependence to each of the 16 transitions in the transport pathway were derived and compared with the measured data. Most putative models were dismissed because of lack of agreement with the measured data, indicating that several steps along the transport pathway are not rate limiting and/or not potential dependent. Only two models were found that can completely account for the measured data. In one case, translocation of the free carrier must be rate limiting, and both extracellular sodium-binding events as well as translocation of both free and fully loaded carrier forms must be potential-dependent transitions. In the second case, translocation of the free carrier and dissociation of the first sodium to be released intracellularly must be equivalently rate limiting. In this case only the two translocation events are required to be potential dependent. The two external sodium-binding events might still be potential dependent, but this is not required to fit the data. Previous reports suggest that the first model is correct; however, no direct experimental data compel us to dismiss the second option as a feasible model.     

Contrasting genetic diversity and differentiation of populations of two successional stages in a Neotropical pioneer tree (Eremanthus erythropappus, Asteraceae)

Eremanthus erythropappus, commonly known as "candeia", is an abundant pioneer tree species, forming dense populations known as "candeial", but it is also found in forests at middle stages of succession. Trees from forests are bigger and occur in lower density than in the "candeial". The objectives of the present study were to investigate if the decrease in population density during successional process is accompanied by 1) changes in within-population genetic diversity, and 2) differentiation of populations. Eight populations, four of early successional stage ("candeial") and four of middle successional stages (forest), were analyzed with RAPD markers. The genetic diversity found was high compared to other tree species analyzed with RAPD markers. AMOVA revealed that most of the genetic variations of E. erythropappus were found within populations (85.7%), suggesting that this species is predominantly outcrossing. The relatively low differentiation among the populations can be attributed to small distances among the populations analyzed (0.2 to 10.8 km). No indication that populations from middle successional habitats show lower genetic variation than populations from early successional stages was found. The percentage of polymorphic fragments (82.8 and 84.8%) and the Shannon indexes (0.442 and 0.455) were similar in "candeial" and forest, respectively. These results suggest that if an increase in selection intensity occurred during succession, it did not result in a decrease in genetic diversity or that the selection effect was balanced by other factors, such as gene flow. Higher significant differentiation among E. erythropappus populations from "candeial" in relation to that among populations from forest was also not detected.     

Structural analysis of the rate-limiting transition states in the folding of Im7 and Im9: similarities and differences in the folding of homologous proteins

The bacterial immunity proteins Im7 and Im9 fold with mechanisms of different kinetic complexity. Whilst Im9 folds in a two-state transition at pH 7.0 and 10 degrees C, Im7 populates an on-pathway intermediate under these conditions. In order to assess the role of sequence versus topology in the folding of these proteins, and to analyse the effect of populating an intermediate on the landscape for folding, we have determined the conformational properties of the rate-limiting transition state for Im9 folding/unfolding using Phi(F)-value analysis and have compared the results with similar data obtained previously for Im7. The data show that the rate-limiting transition states for Im9 and Im7 folding/unfolding are similar: both are compact (beta(T)=0.94 and 0.89, respectively) and contain three of the four native helices docked around a specific hydrophobic core. Significant differences are observed, however, in the magnitude of the Phi(F)-values obtained for the two proteins. Of the 20 residues studied in both proteins, ten have Phi(F)-values in Im7 that exceed those in Im9 by more than 0.2, and of these five differ by more than 0.4. The data suggest that the population of an intermediate in Im7 results in folding via a transition state ensemble that is conformationally restricted relative to that of Im9. The data are consistent with the view that topology is an important determinant of folding. Importantly, however, they also demonstrate that while the folding transition state may be conserved in homologous proteins that fold with two and three-state kinetics, the population of an intermediate can have a significant effect on the breadth of the transition state ensemble.