Diversidade GenÃtica Populacional nas espÃcies pioneiras Cyperus ligularis L. C. oduratus L. (Cyperaceae) e Miconia prasina (Sw.) dc. (Melastomataceae) ocorrentes em remanescentes da Floresta AtlÃntica de Pernambuco detectada pelos marcadores moleculares DAF e ISSR

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

The Atlantic Forests have suffered continuous reductions resulting in urgent need of new strategies for its preservation and for the understanding of the fragmentation consequences, especially aiming its preservation. Regarding this scenario, the plant families Cyperaceae and Melastomataceae play an important role, due to its function as pioneers and forest regenerators. The present work aimed to evaluate the genetic diversity and the gene flow among populations of Cyperus ligularis and C. odoratus (Cyperaceae) collected in a urban Atlantic Forest fragment in the Dois IrmÃos Reserve (Recife, Pernambuco, Brazil) and surrounding areas. Additionally, populations of Miconia prasina (Melastomataceae) occurring in three Atlantic Forest fragments in an area surrounded by sugarcane plantations (Usina SÃo JosÃ, USJ in the city of Igarassu, Pernambuco, Brazil) were also analyzed using DAF (DNA Amplification Fingerprinting) and ISSR (Inter Simple Sequence Repeats) markers. The generated phenogram using DAF for C. ligularis and C. odoratus separated both species in distinct branches, a segregation supported by 165 interspecific polymorphic marks. Additionally, significant genetic diversity was observed within populations according with Nei Gst index (Gst- 0.3632), correlated to a low gene flow tax, represented by the observed migrant number (Nm- 0.8766). C. odoratus specimens occurred exclusively inside the Dois IrmÃos Reserve, bearing larger genetic diversity than that observed among C. ligularis individuals, distributed in Dois IrmÃos Reserve as well as in adjacent areas under strong human influence, with a maximal distance of 3 km between collection points. Such results suggested the existence of higher intraspecific and intrapopulational variation for C. odoratus while the lower variability observed in C. ligularis suggested the influence of a possible founder effect as an explanation for its capacity to occupy urban areas subjected to stressing conditions of drought or pollution, limited to a specific combination of genetic factors. Additionally, these individuals have been grouped randomly, suggesting the formation of a metapopulation. For M. prasina 237 DAF and ISSR polymorphic loci have been detected with an estimated global genetic diversity (Dg%) of 91 and 85.5% for DAF and ISSR respectively, with the Macacos fragment (Mac) as the major contributor and the AÃude do Prata (Apr) and Pezinho (Pez) fragments as minor contributors, suggesting that Mac have major adaptability potential. The Mac fragment presented a higher intrapopulacional Dg% value, probably due to most effective pollination and dispersion. Considering Apr and Pez lower Dg values indicated that these fragments need additional attention due to their lower diversity and fragility. The generated phenograms indicated genetic structuring for the Apr population as compared to other here analyzed populations, a fact also indicated by the population analyses (Gst and Nm). The global Gst and Nm values for DAF and DAF/ISSR indicated considerable genetic divergence among the analyzed fragments, suggesting that this phenomenon would be consequence of past expansions and retractions of the Atlantic Forest during the Quaternary period, as well as of human pressure. The association of these data with field observations and reproductive biology shall bring a better understanding of the population dynamic in the studied area and also of the participation of these plants in the successive processes.

ASSUNTO(S)

cyperus ligularis l. gene flow genÃtica de populaÃÃes dna fingerprinting miconia prasina fragmentation population structure floresta atlÃntica genetica

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