Hemicastration in the skink induces change in the electrophoretic pattern of some enzymes like LDH, MDH, acid phosphatase and esterases

Murali, S.

Prasad, D. T.

Rajendra, M.

Sarkar, H. B. D.

University of Mysore - Digital Repository of Research, Innovation and Scholarship (ePrints@UoM)

© Kamla-Raj 2005 J. Hum. Ecol., 18(3): 199-201 (2005)Selection Intensities and Effective Population Size and VarianceDue to Drift Among the Madigas in Andhra PradeshK. Rajasekhara ReddyDepartment of Anthropology, University of Mysore, Manasagangotri,Mysore 570 006, Karnataka, IndiaKEYWORDS Selection Intensity. Variance. Madigas. Consanguineous. Non-consanguineous.ABSTRACT  The total index of selection computed for Madigas of Cuddapah (MDCDP) and Chittoor (MDCTR) districts ofAndhra Pradesh, inhabiting in two different geographical areas, show the value is relatively higher in former group than in latter.The value of intensity in the pooled Madigas falls within the range of Indian Populations. Breeding size (N) is more or less samein MDCDP and MDCTR. But the effective population size (Ne) is relatively lower in the former group than the latter. When thefrequency of an allele is 0.5, the estimated random genetic drift in the pooled Madigas is 0.0000711, the effect of which isnegligible in the two groups.INTRODUCTIONSelection is one of the major evolutionaryfactors that brings about changes in the genefrequency in a population. Crow (1958) devisedan index that facilitates quantitative estimationof the selective pressure, given the reproductivepattern of a population. This is a generation ana-logue of Fisher’s (1930) fundamental theoremof natural selection and measures the proportionby which fitness would increase with specificbirth and death rates if they were all selectiveand the heritability of fitness were complete(Crow, 1972). But, in reality, the geneticcomponent in differential fertility and mortalityis rather small, as the reproductive outcome ofan individual and/or a population is a result ofthe interaction of a variety of socio-culturalfactors (Crow, 1966; Cruz-Coke et al., 1966).Therefore, the index sets only an upper limit forthe potential action of natural selection and isaccordingly renamed as Opportunity for NaturalSelection (Crow, 1966). It can be divided intotwo components – one due to differential fertilityand the other due to differential mortality – anddoes not reveal more than that which is containedin vital statistics. It is therefore descriptive andnot analytical (Crow, 1972).Number of studies has been made to explorethe relationship between the indices of selectionand socio-economic conditions (Rajanikumari etal., 1985; Suri Babu and Bhasin, 1991) and otherpopulation structural measures like populationsize (Chengal Reddy and Lakshmanudu, 1979)and inbreeding (Barua, 1976; Rao and Murty,1984). Few studies have implicated the note offamily planning programmes in imposingcharacteristic differential fertility. In India,Rajnikumari et al. (1985) found a lower indexof total selection among the women who hadcompleted their fertility by family planningmethods than in women who completed theirfertility by attaining menopause. The presentstudy was attempted to estimate the index ofselection potential among the two groups ofMadigas i.e. Madigas of Cuddapah district(MDCDP) and Madigas of Chittoor district(MDCTR) in Andhra Pradesh.MATERIAL AND METHODSThe study sample was collected fromCuddapah and Chittoor districts of AndhraPradesh and comprised of 108 MDCDP and 128MDCTR mother who have completed theirreproductive life span. The fertility and mortalitydata were collected on different aspects of socio-economic variables and reproductive perfor-mance of the women by using the questionnaires.The methodology of Crow (1958) and Johnstonand Kensinger (1971) were used to compute theindex of total selection.The effective population size was computedfor both Madiga populations according toWright’s formulae (Sen, 1976). The variance dueto random drift has been computed according tothe Wright’s formula (Wright, 1940).RESULTS AND DISCUSSIONSelection Potential:  The indices of mortality,fertility and total selection potential in both200 K. RAJASEKHARA REDDYconsanguineous (C) and non-consanguineous(NC) matings of both groups of Madigasaccording to Crow’s Original (1958) andModified (Johnston & Kensinger, 1971) methodswere furnished in table 1. A higher value of totalselection intensity index(I) is found in Modifiedmethod(0.8433) than the Original method(0.6837) among the pooled Madigas, which isdue to the contribution of a very high proportionof prenatal mortality component (Ped) to totalselection intensity index(I) in the Modifiedmethod. A great deal of disparity is also observedin the consanguineous and non- consanguineousmatings of two groups of Madigas.The total selection intensity index (0.8443)for the pooled Madigas shows smaller selectiondue to fertility (If = 0.2067) component than themortality component particularly childhoodmortality (Imc = 0.4183). This is very unusualfeature of this population indicating that theselection is more due to mortality than thefertility component. The value of total selectionintensity is relatively lower in consanguineous(0.8262) than in non-consanguineous (0.8626)marriages due to higher value of the differentialmortality of the former one than the latter one.Thus higher differential mortality value in theconsanguineous group suggests that averagegeneral fitness of a population may be lowereddue to consanguineous matings.The value of total intensity index is relativelyhigher in MDCDP (0.8831) than in MDCTR(0.8123), which may be due to the relativelylower incidence of consanguineous marriages,higher differential fertility as well as mortalitycomponents that increase the average generalfitness in the former group than the latter.Effective Population Size and Variance Dueto Drift:  Effective population size is animportant parameter of population structure. Itis a measure of the reproductive potential of apopulation in which the number of individualsreally contributes to the genetic composition ofthe next generation. Due to a series of factorssuch as extreme differences of fertility amongindivi-duals, high distortions of the sex-ratio andhigh inbreeding rate (Freire-Maia, 1974),estimates of breeding size for the Madigas maybe some-what biased. Therefore, effective size(Ne) has been calculated correcting the breedingsize (N) for the said reproductive situations byapplying Wright’s (Sen, 1976) formula amongthe Madigas (Table 2). Table 1: Indices of selection potential along with the basic data among the Madiga groupsBasic dataIndices of selection potentialMadiga-TypeMothersPreg-Survivorsgroupsagednan-uptoLive births(Crow,1958)(Johnston & Kensinger,1971)40 yrs andcies15 yrsaboveof ageNX_V fI m(Pd/Ps)I f (V f /X_2 )I(Im+I f /P s)I meI mcI fIMDCDPC432671732545.90706.36340.46820.18240.73600.05120.46820.18240.8249NC653952553675.64627.70560.43930.24170.78720.07630.43930.24170.9235T1086624286215.75007.18750.45100.21740.76640.06600.45100.21740.8331MDCTRC775523264696.09095.19950.43860.14020.64030.11300.43860.14020.8256NC5223092072735.35295.29410.31890.18480.56260.13190.31890.18480.7688T1288315337425.79695.45870.39220.16240.61830.11990.39220.16240.8123PooledC1207894997236.02505.62440.44890.15490.67330.09130.45890.15490.8262NC1167044626405.51726.76690.38530.22230.69320.10000.38530.22230.8626T236149396113635.77546.23940.41830.18710.68370.09540.41830.20670.8443201SELECTION INTENSITIES AND EFFECTIVE POPULATION SIZE AND VARIANCEThe number of parents or Breeding size (N)among the pooled Madigas is 39.09% of theiractual (sample) population size, with a slightlylesser proportion in MDCDP (38.81%) than inMDCTR (39.36%). The effective population size(Ne) of the pooled Madigas is 33.20% of thepopulation size, which is smaller than thebreeding size (N) due to the larger variance ofthe mean number of chi1dren per couple (4.21)than the mean number of children (2.8l).Effective population size is relatively lower inMDCDP (31.79%) than in MDCTR (34.39%).Thus an overall 6% of the reduction is observedfrom breeding size to effective size.The effect of ‘drift’ on gene frequencies isbased on the product of effective size andmigration rate of the population (Wright, 1940).As there appears to be no migration among theMadigas, the operation of drift on geneticdiversity will be solely dependent upon theireffective sizes. Assuming the allele frequency as0.5 variance due to random drift in a singlegeneration has been calculated as σ2dq = q (1 -q)/2Ne. The estimate of Random genetic driftamong the pooled Madigas is 0.0000711. It’sdifference between MDCDP (0.0001510) andMDCTR (0.0001350) is negligible. From thesevalues it is known that the large effective size ofthe population will lead to small drift effects.REFERENCESBarua, S.: Selection intensity among the consanguineous andnon- consanguineous groups of a Muslim population of24 Paraganas, W.B.  Man in India, 56:  359 – 364 (1976).Chengal Reddy, P. and Lakshmamudu, M.: Indices ofopportunity of selection in Mala, Madiga and other Indianpopulations.  J. Ind. Anthrop. Soc., 14: 245-252 (1979).Crow, J.F.:  Some possibilities of measuring selection intensitiesin man. Hum. Biol., 30: 1-13 (1958).Crow, J. F.: The Quality of people: Human evolutionarychanges. Bioscience, 16:  863 (1966).Crow, J. F.: Some effects of relaxed selection and mutation.Proc. 4th Int. Cong. Hum. Genet. J. De Grouchy, F.J.E.Ebling and I.W. Henderson (Eds.). Excerpta Medica,Amsterdam (1972).Cruz-Coke, R., Christofannini, A.P., Aspillaga, M. andBiancani, F.: Evolutionary forces in human populationsin an environmental gradient in Africa, Chile. Hum. Biol.,38:  421-438 (1966).Fisher, R.A.: The Genetical Theory of Natural Selection.Oxford University Press, London (1930).Freire- Maia, N.: Population genetics and demography. Hum.Hered., 24: 105-113 (1974).Johnston, F.E. and Kensinger, K.M.:  Fertility and mortalitydifferentials and their implications for micro evolutionarychange among the Cashinahua. Hum. Biol., 43: 356-364(1971).Rajanikumari, J., Srikumari, C. R. and Rao, T.V.:    Variabilityof selection opportunities with changing socio-culturalenvironments. Hum. Hered., 35: 218-222 (1985).Rao, V.V and Murthy, J.S.: Selection intensities and inbreedingamong some caste groups of Andhra Pradesh, India. Soc.Biol., 31: 114 (1984).Sen, D.K.: Prospects of population genetical work in India: In:Anthropology in India, Vol.2, Physical Anthropology. H.K. Rakshit (Ed.). Anthropological survey of India,Calcutta (1976).Suri Babu, K and Bhasin, M.K.: Selection intensities amongoccupationally different communities: Yadavas andKammas in Andhra Pradesh. J. Hum. Ecol., 2(1):  77-79(1991).Wright, S.: Breeding structure of populations in relation tospeciation. Am. Natur., 74: 232 (1940).Table 2: Effective population size and variance due to drift among the Madiga groupsMadiga Sample No. of parents No. of children Effective Variance duegroups size or Breeding per parent population to random geneticsize(N) Size (Ne) drift (σ2 dq)No. % Mean variance No. %MDCDP 2605 1101 38.81 2.73 4.38 828 31.79 0.0001510MDCTR 2693 1060 39.36 2.87 4.06 926 34.39 0.0001350Pooled 5298 2071 39.09 2.81 4.21 1759 33.20 0.0000711

Hemicastration-induced changes in the electrophoretic pattern of some enzymes in the brain of the skink, Mabuya carinata

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Hemicastration-induced changes in the electrophoretic pattern of some enzymes in the brain of the skink, Mabuya carinata

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