Index Of Opportunity For Selection Research Articles

Index of opportunity for natural selection among the Gowdas of Kodagahalli village, Karnataka, India.

BACKGROUND:In order to understand how selection is operating in the Gowda population, the index of opportunity for selection was calculated and the present findings were compared with some related findings from other South Indian (SI) populations.MATERIALS AND METHODS:Crow (1958) and the modified method by Johnston and Kensinger (1971) were used for the present purpose.RESULTS AND DISCUSSION:The index of total selection intensity (I) was found to be moderate taking into consideration the range for many Indian populations. Considering certain differences in fertility and mortality heritable, it appears that natural selection play an important role in shaping the genetic constitution of the Gowda population. Analysis of data indicates that the index due to fertility seems to contribute more towards selection than mortality. This trend might be because of better living condition and health-care system among the Gowdas which have a positive impact on the lower contribution of mortality for the evolution mechanism of the Gowda population through natural selection.

Body size and sexual selection in the koala

Sexual selection is often characterized by polygynous breeding systems, size dimorphism, and skewed operational sex ratios. Koalas are sexually dimorphic in multiple domains, yet are absent from the literature on sexual selection and the structure of their mating system is unclear. We provide the first documentation of the strength of sexual selection in koalas by using microsatellite markers to identify sires. We combine the genetic data with morphological data in order to assess the role of body size in regulating reproductive output. During our 4-year study, 37% of males were identified as possible sires. Males were significantly larger than females, with sires heavier than non-sires. Male body mass correlated with annual reproductive output, with Crow’s Index of Opportunity for Selection revealing that variation in male reproductive success was threefold higher than that of females. Since it appears that male koalas rarely engage in physical confrontations over access to females, size dimorphism could be based upon non-agonistic competition and/or female mate choice. We propose that size dimorphism in koalas evolved as a consequence of endurance rivalry promoting vocal sexual advertisements that attract females. We suggest that female choice is a key mediator of male reproductive output.

Raji-A Food Gatherer and Hunter Primitive Tribe of Uttaranchal: A Study of Selection Intensity

The index of total opportunity for selection based on differential fertility and mortality have been calculated for the Raji – a primitive tribe of Central Himalayas of Uttaranchal State in Norther...

Demography and blood genetics of Argentinian Mapuche Indians

The whole Mapuche Indian community of Blancura Centro was covered by a demographic census, with special attention given to variables of genetic interest. Afterwards a sample of it was investigated in relation to 22 genetic systems. The community can be characterized as a young group, with high fertility, but moderate mortality and endogamy. The index of opportunity for selection is relatively low (0.46). The presence of variation at the ABO and Lutheran loci suggests some non-Indian admixture, calculated as 7% in the sample studied. Unusual findings were the absence of L*NS, low frequency (7%) of L*MS and high frequency (37%) of L*Ns. They also showed low frequencies of P*1 (28%) and DI*a (3%), but high of HP*1 (74%). Similarities, but also differences, were noted with previous results obtained in this tribe in Argentina and Chile.

Opportunity of Selection in the Khamti of Lakhimpur District, Assam, India

In the present communication an attempt has been made to measure the Index of Opportunity for selection in the Khamti, a migrant, endogamous, community of Narayanpur, Bihpuria areas in Lakhimpur district, Assam, based on data on pregnancy outcome of 29 Khamti ever-pregnant women aged 45 + years. The results of the present work were compared with those of the available data on the tribal populations of North Eastern India. It is observed from the present analysis that childhood death and embryonic death are very low but mean offspring size is high. The value of I and its mortality and fertility components are also low. I: is evident that selection is operating with low intensity in the Khamti of Lakhimpur district, Assam and the average general fitness of the population is high.

A Note on Selection Intensity Among the Muslims of a Calcutta Slum

In this study the value of the index of opportunity for selection with its mortality and fertility components are repotted; and have been compared with the published data on their rural counterpart...

New studies on the Macushi Indians of northern Brazil.

Demographic data and genetic information concerning 40 genetic systems are reported for three populations of Macushi Indians, and have been compared to those already obtained for three other communities of this tribe. These are young populations (mean age, 19 years), with a low sex ratio (90), low percentages of non-Indian ancestry (1-2%) and of marriages between locally born persons (34). Intertribal unions (14%) are less frequent than among their neighbours, the Wapishana. Fertility is high (average of 8.2 children per woman who completed reproduction), but the variance in family size and the frequency of premature deaths relatively low for populations at this cultural level. This conditions the lowest Index of Opportunity for Selection (0.45) calculated thus far among South American Indians. No variation was observed in 20 genetic systems, limited variation in 3, and larger variability in the remaining 17. In 13 of the 29 comparisons (45%), the Macushi gene frequencies present values in the middle third of the range observed among South American Indians. The previously reported private genetic polymorphism of esterase A was encountered in one of the three villages. A comparison of the genetic distances between villages with and without this polymorphism, and a similar comparison for the villages of the neighbouring Wapishana, yields no clue as to the tribe in which this polymorphism originated.

Opportunity for natural selection among three migrant groups of fishermen of Puri, India.

Abstract Pregnancy histories of 470 ever‐married women aged 40 years and older from three endogamous groups of marine fishermen of Puri, Orissa, are analyzed to estimate Crow's index of opportunity for selection. All these populations are migrants. The value of I ranges from 0.63 to 1.08. The results are interpreted in the light of their ethno‐historical, migratory backgrounds, degree of isolation, and population sizes. A comparison with published Indian data is also made.

Endogamy and Exogamy

Abstract Three populations of Cayapo Indians from southern Para and northern Mato Grosso, Brazil, show similar age distributions and endogamy rates, but low sex ratios and inbreeding rates, in comparison to those of other South American hunters and gatherers with incipient agriculture. Their fertility is moderate with a small variance, and mortality is low. The index of opportunity for selection is one of the lowest calculated so far for groups at this cultural stage. The pattern of exchange between the local groups can be described by the fission‐fusion model of genetic structure.

Reproductive life of Bhoksa women.

The paper discusses the reproductive life of 111 ever-married Bhoksa women. The mean age at marriage for women of all ages among Bhoksas, like other tribal populations, is high, unlike the caste populations. The mean ages at first birth of the pooled sample and of the completed fertility cases suggest late and early marriages of the older and younger generations. The maximum number of marriages occur between 15 and 19 years and of first births between 16 and 20 years. Percentage of reproductive wastage is high in both the lower and higher age groups. Young mothers with low birth orders and older mothers with high birth orders display a high frequency of reproductive wastage. Evidently, both birth order and the age of the mother have effects on reproductive wastage. Average number of children ever born (including stillbirth but not abortion or miscarriage) per mother of all ages is the highest among Bhoksas of all the studied ethnic groups of India. The Bhoksa, like caste populations, show a high number of children ever born per mother of completed fertility. Quite a high masculinity in the secondary sex ratio, like other mongoloid population is noticed. The contribution of mortality component to the Total Index of Opportunity for Selection is more than that of the fertility component. Bhoksas conform to the general low range of net reproductive index, which is however greater than unity, suggesting that they are in a growth stage.

Genetic demography of the amazonian Ticuna Indians

Abstract The Ticuna Indians of Brazil are now a largely acculturated and integrated tribe, situated for the most part in villages along the Solimoes river. Demographic information collected in eight of their villages is reported here. For five of them detailed data concerning migration, fertility and mortality were obtained. They are characterized by a relatively large mobility, high fertility (mean number of livebirths per female of age 40 or more: seven), low (2·5%) frequency of sterile couples, and relatively low mortality for groups living at this cultural stage (25% of deaths before the age of reproduction). This low mortality, and a relatively small variance in the number of live-born children in completed families, lead to the lowest index of opportunity for selection obtained thus far in populations of South American Indians (0·54).

Demographic and genetic relationships among Brazilian Wapishana Indians.

Demographic information is given and data on 25 genetic systems are reanalysed for six populations of Wapishana Indians living in northern Brazil. Despite 200 years of contact with non-Indians, the maximum amount of admixture that may be present in persons who claim 'pure' Indian ancestry is 3%. Historical sources mention considerable exchange with the Macushi, Taurepan and Atorai tribes, confirmed by our genealogies. Departures from the maximum amount of heterozygosity per locus are similar in putative 'full bloods' and admixed individuals, as well as among the first and members of other tribes. Demographically the Wapishana can be characterized as very mobile, with high fertility but moderate mortality for an agricultural group. The Index of Opportunity for Selection (0 x 57) is one of the lowest calculated so far among South American tribes. Despite the indicated high mobility, clustering of some alleles was observed in two localities.

Changes of selection opportunities with a changing environment: regional heterogeneity in Italy.

The mortailty and fertility components of the index of opportunity for selection (the Crow index) have been studied in the various Italian regions during the last century. To estimate the relevance of environmental factors on both components, their trends and those of their interregional variances have been compared with illiteracy. The results show that the selection opportunities due to mortality have decreased in a smiliar way in all the regions with a trend parallel to that of the national percentage of illiteracy, suggesting that this component is directly affected by the general socio-cultural level. As to the component due to fertility differentials, the regions, though scattered in the time scale, show a characteristic cycle of rise and fall. Moreover, the interregional variances of this component and of illiteracy are quite parallel, thus supporting the hypothesis that the reproductive pattern is strongly influenced by the individual cultural level.

Demografia genética dos índios Ticuna da Amazônia

Resumo Os índios Ticuna do Brasil são atualmente uma tribo bastante aculturada e integrada, que habita, na sua maioria, aldeias localizadas ao longo do rio Solimões. São aqui apresentados dados demográficos coletados em oito destas aldeias, sendo que para cinco delas foram obtidas informações minuciosas quanto à migração, fertilidade e mortalidade. Os Ticuna caracterizam-se por uma mobilidade relativamente grande, fertililidade alta (número médio de filhos nascidos vivos por mulher com > 40 anos :7), baixa freqüência de casais estéreis (2,5%) e uma mortalidade relativamente pequena para grupos que vivem neste estágio cultural (25% de mortes antes da idade de reprodução). A mortalidade baixa e uma variância também pequena no número de nascidos vivos em irmandades completas levaram a um índice de oportunidade para seleção igual a 0.54 o menor obtido até agora em populações de índios sul-americanos.

The effects of demographic transition on the opportunity for selection: changes during the last century in Italy

The index of opportunity for selection proposed by Crow has been calculated for the Italian population during the last century. The evolution of its two components, the pre-reproductive mortality and the variance in fertility, has been also analysed and compared with similar data for the United States. The results clearly show the relevance of socio-economic changes to the evolution of selective patterns in our species; in particular the relative incidence of mortality and fertility to selection intensity: the total index has in fact been reduced by 75% during the last century, the relative amount due to fertility increasing from 57 to 89%. The probable different relevance of genetic factors in the two components has also been discussed.

Evolutionary implications of the ethnography and demography of Ayoreo Indians

The Ayoreo Indians of southern Bolivia and northern Paraguay are still a relatively unacculturated tribe whose members live at present in association with nine missions. Five of these populations were studied by us. Previously they were semi-nomadic hunters and gatherers. Their world is completely classified according to seven clans; exogamy rules are highly respected, only 5% of the marriages studied showing violations of them. There is also extensive exogamy among local groups. Marriage is generally monogamous, but there are no practices that would assure great marriage stability. Child adoptions, infanticide and violent deaths are relatively common. Demographically, they can be characterized as a very young population, with a sex-ratio above 100. The average number of live births per woman who completed her reproductive period is relatively high for groups living at this cultural level, but this is compensated by the above-mentioned high incidence of infanticide. The rate of mortality when infanticides are not considered and the number of sterile women are relatively low, in accordance with previous studies in hunters and gatherers. Historical evidence suggests demographic stability, but their ecological adapation and social organization indicate the possibility of a high impact of the acculturation process among them, with population disruption. The index of opportunity for selection is one of the highest obtained thus far in any human population.

Demography and H-Lea salivary secretion of the Macá Indians of Paraguay.

AbstractThe Macá Indians living at Fray Bartolomé de las Casas show a high rate of endogamy, high mortality (36% of them die before the age of reproduction), low fertility (average of 3.6 livebirths per female who completed her reproductive performance) and low variance in family size. The index of opportunity for selection (0.88) is lower than the one obtained in other populations of agriculturalists and in industrialized communities. The frequency of H secretors (N = 143) is 97% and that of Lea secretors (N = 123) is 78%.