ESTRUTURA GENÉTICA POPULACIONAL E FLUXO GÊNICO EM Dipteryx alata VOGEL (FABACEAE) NO CERRADO
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2009-01-22
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Universidade Federal de Goiás
Resumo
The goal of this study was to evaluate the genetic structure and the spatial
pattern of intra and interpopulational gene flow of Dipteryx alata Vogel, based on nuclear
and chloroplastidial microsatellite markers. Primers were developed based on sequencing
of random fragments from a shotgun genomic library for detection of microsatellite
regions. 12 microsatellites regions were obtained from 688 sequences, which allowed the
construction of pairs of primers. These regions are composed of motifs with two to six
nucleotides, ranging from 136 to 380 base pairs. This shows that the random sequencing
strategy from shotgun libraries is interesting because it allows the achievement of primers
for repetitive regions with different motifs. Two of these loci (Da_E06 e Da_E12) were
polymorphic with three alleles each. He estimation for these loci showed satisfactory values
(0.2946 and 0.2879, respectively), considering the number of alleles. Also, we used a
transferred primer from the species Phaseolus vulgaris (BM164) for D. alata. Moreover,
other two chloroplastidials microsatellite primers were used for molecular analyses of
georeferenced subpopulations, totalizing 775 plants distributed over the natural occurrence
area of Cerrado. 210 of these plants were collected and georeferenced one by one along the
margins of the Araguaia River in the states of Mato-Grosso (RAMT) and Goiás (RAGO)
for spatial distribution of genetic variability in local scale analysis. The relationship
between estimations of genetic diversity parameters with patterns of potential distribution
of species was evaluated. This was used to test the hypothesis that the genetic variability of
D. alata populations is distributed according to the central-periphery model. D. alata
subpopulations showed considerable high levels of genetic variability that was
significantly structured among subpopulations and well structured in space, both for
nuclear and chloroplastidial data. The estimation of the apparent cross-fertilization rate (ta
= 1.0575) indicates that the species is allogamous. Estimations of migration rates by pollen
and by seeds were lower than one, indicating that seed dispersal contributes more effectively for total gene flow. Estimates of the genetic diversity parameters from the
Araguaia River population showed similar values between both margins. The estimation of
the apparent cross-fertilization rate (0.9434) indicated that the Araguaia River is not a
physical barrier to effective gene flow. The effective size of the neighborhood, i.e., the
mean number of individuals in an area where panmixia occurs was 85.64 and 22.99 for
nuclear and chloroplastidial data, respectively, indicating that seed dispersal is more
restricted. The correlogram generated with chloroplastidial data presented a cline pattern of
variance more evident than with nuclear data, suggesting that the presence of spatial
genetic structure is being more influenced by seed dispersal. We observed that the genetic
parameters do not follow a classical central-periphery model, because peripheral
population (according to geographical distribution of sampling locations) tended to
demonstrate higher values for these estimations, mainly the South and Western
subpopulations. The relationship found between the fixation index (f) with human impact
indicated that the subpopulations evaluated can be affected by fragmentation process and
land use, probably caused by the recent human colonization in Cerrado biome.
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Citação
SOARES, Thannya Nascimento. Populational genetic structure and gene flow in Dipteryx alata Vogel (Fabaceae) from Brazilian Cerrado. 2009. 120 f. Tese (Doutorado em Ciências Agrárias) - Universidade Federal de Goiás, Goiânia, 2009.