Genetic structure and diversity of Copaifera langsdorffii Desf. in Cerrado fragments of the São Paulo State, Brazil

Abstract

-The loss of large areas of Cerrado (Brazilian savanna) in Brazil can lead to reduced biodiversity and to the extinction of species. Therefore, the present study aimed to investigate the genetic fragility of populations of Copaifera langsdorffii Desf exposed to different anthropic conditions in fragments of Cerrado in the state of São Paulo. The study was carried out in two Experimental Stations operated by the Forest Institute (Assis and Itirapina), in one fully protected conservation unit (Pedregulho) and in one private property (Brotas). Analyses were conducted using leaf samples from 353 adult specimens and eight pairs of microsatellite loci. The number of alleles per locus ranged from 13 to 15 in all populations, but the mean number of effective alleles was approximately half this value (7.2 to 9-1). Observed heterozygosity was significant and lower than the expected in all populations. Consequently, all populations deviated from Hardy-Weinberg expected frequencies. Fixation indexes were significant for all populations, with the Pedregulho population having the lowest value (0.189) and Itirapina having the highest (0.283). The analysis of spatial genetic structure detected family structures at distance classes of 20 to 65 m in the populations studied. No clones were detected in the populations. Estimates of effective population size were low, but the area occupied by each population studied was large enough for conservation, medium and long term. Recent reductions or bottlenecks were detected in all four populations. Mean Gst' (genetic divergence) indicated that most of the variation was within populations. Cluster structure analysis based on the genotypes detected K= 4 clusters with distinct allele frequencies patterns. The genetic differentiation observed among populations is consistent with the hypothesis of genetic and geographic isolation. Therefore, it is essential to adopt conservation strategies that raise the gene flow between fragments.Keywords: Copaíba; Gene flow; Microsatellites. ESTRUTURA E DIVERSIDADE GENÉTICA DE Copaifera langsdorffii Desf. EM FRAGMENTOS DE CERRADO NO ESTADO DE SÃO PAULO RESUMO -Considerando que a perda de grandes áreas de Cerrado no Brasil pode levar à diminuição da biodiversidade e, mesmo, à extinção de espécies, questiona-se a fragilidade genética de populações de Copaifera langsdorffii Desf. expostas a diferentes condições antrópicas em fragmentos de Cerrado do Estado de São Paulo. Foram consideradas duas áreas em Estações Experimentais do Instituto Florestal (Assis e Itirapina), uma área em unidade de conservação de proteção integral (Pedregulho) e outra área de propriedade particular (Brotas). As análises foram realizadas com amostras foliares de 353 indivíduos adultos e oito pares de locos microssatélites. O número de alelos por loco variou de 13 a 15 em todas as populações, porém o número médio de alelos efetivos foi aproximadamente a metade desse valor (7,2 a 9-1). As estimativas de heterozigosidade observada foram significativas e ficaram abaixo dos valore...

Gene flow affects the genetic diversity of Copaifera langsdorffii Desf. in Cerrado

“…All fragments (Assis, Itirapina, Pedregulho and Brotas) are located in the Cerrado biome in the State of São Paulo, Brazil. Criteria used for selection were the values of observed and expected heterozygosity (H O = 0.68; H E = 0.87) reported by Antiqueira et al (2014).…”

“…A spatial migration model was considered, with coordinates based on the geographic location (latitude and longitude) of the genotyped populations. Regarding the mutation settings, there were assumed eight loci evolving according to the single-step mutation model (SSM), with a proportion of 0.1 K-allele model (KAM) events, under 103 possible allelic states (Antiqueira et al 2014). We considered a mutation rate of 0.0001 mutations per locus per generation and assumed 100 generations.…”

“…Each combination of selfing and migration rates was replicated 100 times. The observed and expected heterozygosities from Antiqueira et al (2014) were used to select the model settings that presented values closest to the field observations. The two independent sample t-tests at a 5% level of probability were used to compare the observed and expected heterozygosities of the selected combination of selfing and migration rates with other combinations.…”

“…The main animal seed dispersers are monkeys and birds, which both swallow arils and eventually regurgitate the seeds close to the mother plant, limiting gene flow (Martins et al 2008;Sebbenn et al 2011). Assis and Pedregulho are the most distant fragments (460 km away), followed by Assis -Itirapina (350 km), Pedregulho -Itirapina (280 km), Pedregulho -Brotas (280 km), Assis -Brotas (275 km) and Itirapina -Brotas (24 km) (Antiqueira et al 2014). Thus, the long distances between the fragments and the dispersal syndrome in this species can justify the low gene flow obtained in our simulations.…”