0737-B2

The population Structure of Gmelin Larch in The Central Evenkia.

A. Ya. Larionova, N. V. Yakhneva ¹

Abstract

On the basis of 17 genes, coding allozyme diversity MDH, IDH, G-6-PD, ME, 6-PGD, GDH, LAP, SKDH, EST, AAT, the values of principal parameters of genetic variation were determinated in three stands of Gmelin larch (Larix gmelinii (Rupr.) Rupr) occurring near the settlement Tura (Evenkia). It was established that 50.98% of gene loci assayed were polymorphic at 95% and 78.43% at 99% polymorphism criterions.

The mean number of alleles per locus, the mean observed and expected heterozygosities, effective number of alleles per locus were 2.000, 0.0915, 0.1246 and 1.179, respectively. More than 98% of total genetic variation resides within stand and only 1.66% among stands. The mean value of Nei's genetic distance (D) between stands of L. gmelinii was 0.0035. The data obtained point to a very low differentiation in the Evenkia Gmelin larch stands.

Intruduction

Material and Methods.

Seed material for electrophoretic analysis was collected from 76 trees in three stands of Gmelin larch in Central Evenkia near the settlement Tura. The stand I is situated at right bank of Kochechum River (64^˚ 19^' N, 100^˚ 07^' E). The stand II is located at left bank of Kochechum River (64^˚ 19^' N, 100^˚ 13^' E). The stand III is placed in the of Nizhnyaya Tunguska River valley (64^˚ 17^' N, 100^˚ 14^' E).

Individual trees were genotyped using 8 to 50 megagametophytes. The megagametophytes were sampled randomly from each tree a set extracted from minimum of 20 cones. The gomogenates were electrophoresed in horizontal chamber on 13-14 % starch gels. For electrophoresis of enzymes two buffer systems were used: A) tris-citrate, pH 6.2 (Adams, Joly, 1980), B) tris-citrate, pH 8.5 / LiOH-borate, pH 8.1 (Ridgway et al., 1970). Enzyme extraction, electrophoresis, histochemical staining followed standart methods (Brewer, 1970; Vallejos, 1983; Goncharenko et al., 1989) with insignificant modifications. The enzymes assayed, their abbreviations, the buffer systems used are given in Table 1.

To estimate level of genetic variation in the populations studied the values of principal parameters (P - percentage of polymorphic loci, A - number of alleles per locus, H_o - observed and H_e - expected heterozygosities, n_e - effective number of alleles) were determinated. The percentage of polymorphic loci was estimated at 95% (the frequency of the most common allele was not greater than 95%) and 99% polymorphism criterions. The mean number of alleles per locus was calculated for all the alleles revealed. To measure gene diversity in natural stands of Gmelin larch the parameters of Wright's F-statistics were used (Guries, Ledig, 1982). The genetic distance coefficient (D) among the stands was estimated by Nei's method (Nei, 1972). The effective number of alleles was calculated, using following formula:

n_e=1/(1-H_e).

Results and Discussion

The electrophoretic analysis revealed 40 allelic variants at 17 loci. The most variable loci in the Evenkia stands of Gmelin larch were Est-1, Mdh-3 and G-6-pd. The Mdh-4, Skdh, Aat-1, Aat-2, Aat-3, Idh, Me-2, 6-Pgd loci showed an intermediate level of variability. Five loci (Lap-1, Lap-2, Mdh-2, Me-1, Gdh) were less polymorphic and one locus (Mdh-1) was monomorphic in all stands (Table 2).

On the basis of allelic frequencies for 17 loci the principal parameters of genetic variation were computed (Table 3). The values of all parameters vary among the stands. The most high level of genetic variation was revealed in the oldest stand III, situated in the Nizhnyaya Tunguska River valley. On average in L. gmelinii stands from Evenkia 50.98% of the loci assayed were polymorphic at 95% and 78.43% at 99% polymorphism criterions, the mean number of alleles per locus was 2.000, the average observed and expected heterozygosities, effective number of alleles were 0.0915 and 0.1246, 1.179 respectively. In all stands studied of Gmelin larch the mean values of observed heterozygosity were lesser than those expected under Hardy-Weinberg conditions.

Obtained values of observed heterozygosity were lower than values of H_o established by Semerikov et al. (1999) at 15 loci in the populations of L. gmelinii from Eastern Siberia and than those determinated by Potenko, Rasumov (1996) at 21 loci in two populations from Khabarovsk Territory (Far East). The values of expected heterozygosity, mean number of alleles per locus, effective number of alleles were over the range of values established in other populations studied of this species.

Population structure of L. gmelinii in the Evenkia was analysed by means of Wright's F-statistics (Guries, Ledig, 1982). Data on the correlation between uniting gametes within stands (F_is), among stands (F_st), for the species as a whole (F_it) were calculated on the basis of analysis for 17 loci (Table 4).

The F_is values ranged from - 0.0780 at Aat-2 to +0.5218 at Est-1 and averaged 0.2658. Obtained value is positive. This indicates to a deficiency of heterozygotes within L. gmelinii stands studied relative to Hardy-Weinberg expections. As a whole in L. gmelinii from Evenkia deficiency of heterozygotes was 0.2781. Value of F_st for polymorphic loci ranged from 0.0022 (Lap-1) to 0.0267 (Aat-3). The average value of F_st for all the 17 loci assayed was equal to 0.0166 (1.66%). This means that more than 98% of the total genetic diversity resides within stands of L. gmelinii from Evenkia and only 1.66% among stands. F_st value point to low extent genetic differentiation between the stands studied.

Genetic similarity among L. gmelinii stands in Central Evenkia was quantified using Nei's genetic distance coefficient (Nei, 1972). The values D obtained for three stands are listed in Table 5.

It is obvious that genetic differences between stands are insignificant. The values of D range from 0.0025 to 0.0037 and averaged - 0.0035. These values D are typical for stands within one population and for very closely related geographically connected populations of conifers. The most genetic similarity (D=0.0025) was revealed between stands I, situated at right bank of Kochechum River, and III, placed in the of Nizhnyaya Tunguska River valley.

References

Abaimov A.P., Zyryanova O.A., Prokushkin S.G., Koike T., Matsuura Y., 2000. Forest Ecosystems of the Cryolithic Zone of Siberia; Regional Features, Mechanisms of Stability and Pyrogenic Changes. Eurasian J. For. Res., 1: 1 - 10.

Adams W.T., Joly R.I., 1980. Genetics of Allozyme Variants in Loblolly Pine. Heredity, 71: 33 - 40.

Brewer G.J., 1970. Introduction to isozyme techniques. N.Y.-L. Academ press: 186 p.

Goncharenko G.G., Padutov V.E., Potenko V.V., 1989. Guide to conifer species research by isozymes methods. Gomel.: 164 p. (In Russian).

Guries R.P., Ledig F.T., 1982. Genetic diversity and population structure in Pitch pine (Pinus rigida Mill.). Evolution, 36: 387 - 402.

Milyutin L.I., Vishnevetskaia K.D., 1995. Larch and larch forests of Siberia. Ecol. and Manag. of Larix Forests: A Look Ahead, Ogden, USA: 50 - 53.

Nei M., 1972. Genetic distance between populations. Amer. Natur., 106: 283 - 291.

Potenko V.V., Rasumov P.N., 1996. Genetic variability and population structure in Gmelin larch at territory of Khabarovsk region. Lesovedenie, 5: 11 - 18. (In Russian).

Pozdnyakov L.K., 1975. Larix dahurica. Moscow, Russia, Nauka: 312 p. (In Russian).

Ridgway G.J., Sherburne S.W., Lewis R.D., 1970. Polymorphism in the Esterases of Atlantic Harring. Trans. Am. Fish. Soc., 99: 147 - 151.

Semerikov V.L, Matveev A.V., 1995. Investigation of geneticvariability in Siberian larch (Larix sibirica Ldb.) at isozyme loci. Genetika, 31: 1107 - 1113.(In Russian)

Semerikov V.L., Semerikov L.F., Lascoux M., 1999. Intra and interspecific allozyme variability in Eurasian Larix Mill. species. The Genetical Society of Great Britain. Heredity, 82: 193 - 204.

Shurchal A.V., Podogas A.V., Semerikov V.L., Zhivotovskii L.А., 1989. Allozyme polymorphism in Siberian larch (Larix sibirica Ledeb.). Genetika, 25: 1899 - 1901. (In Russian).

Vallejos G.E., 1983. Enzyme activity staining. Isozymes in plant genetics and breeding. Amsterdam: Elsevier Sci. Publ. B.V.: 469 - 516

Table 1. Enzymes, their Abbreviations (Abbr.), Enzyme Commission numbers (EC) and buffer systems used for electrophoresis.

Table 2. Allele frequencies for 17 loci in three stands of Gmelin larch in Evenkia

Table 3. Genetic variation in natural stands of L. gmelinii.

Table 4. Estimates of F_is, F_it, F_st- in Gmelin larch

Table 5. Estimates of Nei's genetic distance coefficient (D), based upon data from 17 loci

¹ V.N. Sukachev Institute of Forest, SB RAS, Akademgorodok, Krasnoyarsk, Russia, 660036
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