Uso de marcadores microssatélites para avaliação genética de populações de Melipona mandacaia Smith, 1863 (Hymenoptera, Apoidea) no Estado da Bahia / Microssatellites markers applied to genetic evaluation of populations of Melipona mandacaia Smith, 1863 (Hymenoptera, Apoidea) in Bahia State, Brazil

Margarete do Valle Werneck

Melipona mandacaia, is an indigenous stingless bee (Meliponini Tribe), an endemic species of the semi-arid of the northeast of Brazil. The original flora of the caatinga has been altered by the human action. This alteration reduces the food resources and the places available for nesting, so this affects the dispersion and the genetic flow of the populations of those organisms. The objective of this work was to evaluate the job of the markers microssatélites in the genetic evaluation of populations of Melipona mandacaia in Bahia sate, Brasil. Adult workers from Paulo Afonso, Macururé, Central Uibaí, São Gabriel, Irecê, Lapão and Serra do Ramalho were used. The extraction of genomic DNA was accomplished according to Waldschmidt et al. (1997) modified. The amplification was performed using primers microssatellites specific for Melipona bicolor to evaluate seven locos (Peters et al.1998). The amplification products were submitted to electrophoresis in poliacrilamide gel under 100v for 14 hours. Three of the seven appraised locos were monomorfic: Mbi 259, Mbi 219 and Mbi 088. The locos that presented polymorphism were Mbi 233 with 6 alleles, Mbi 278 with 4 alleles, Mbi 028 and Mbi 215 with 2 alleles. Because of the deficit in heterozygosis and alleles in low frequency showed in homozygosis lifted the suspicion for subestruturation and isolation by distance. The absence of amplification products in some samples lifted the suspicion also of the presence of null alleles. To satisfy the subestruturation condition, the samples were joined in three areas according to the geographical proximity of the places where they were collected. To verify the presence of null alleles the data were submitted to a null alleles estimator and further adjustment of the alleles frequencies. To evaluate the structuring the F coefficient of Wright was used in three extreme sceneries. In the first sceneries the absence of null alleles was considered, in the second the presence of infinite null alleles with the lowest possible frequencies was considered and in the third sceneries the presence of a single null allele with the highest possible frequency was considered. In the sceneries 2 (FST = 0,21) and 3 (FST = 0,26) we obtained the values for FST minimum and maximum for a population in Hardy-Weinberg equilibrium. The value obtained in the scenery 1 (FST = 0,16) was lower than the established interval for the minimum (2) and maximum (3) values. The strip of values of FST considering the presence of null alleles is compatible with high or very high structuration. The values of FST allow us to infer that the studied population of Melipona mandacaia is subestruturated and there is high genetic differentiation among the considered geographical groups. Additional studies are necessary to evaluate the endogamic matches that are happening in those subpopulations. The presence of null alelles commits the use of the microssatelites markers for genetic studies of populations.

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