Estrutura genética populacional de Copaifera langsdorffii Desf. (Leguminosae - Caesalpinioideae) em fragmentos florestais no Pontal do Paranapanema, SP, Brasil

Abstract

-(Population genetic structure of Copaifera langsdorffii Desf. (Leguminosae -Caesalpinioideae) in forest fragments in "Pontal do Paranapanema", SP, Brazil). The "Pontal do Paranapanema" is the most recently deforested region of the state of São Paulo in Brazil. The effects of forest fragmentation on the population genetic structure of Copaifera langsdorffii Desf. were evaluated by genotyping with six microsatellite loci at least 30 adult and 30 sapling individuals of three populations in "Pontal do Paranapanema". The sampling areas comprised two fragments located in the rural settlements Tucano (800 ha) and Madre Cristina (300 ha); and one population located in a continuous forest, the "Parque Estadual do Morro do Diabo" (35,000 ha). High levels of genetic diversity were detected in saplings and adults, gene diversity (H e ) ranged from 0.718 to 0.835 and average number of alleles per locus (Â) ranged from 8.67 to 11.83, showing that the fragmentation has not caused loss of alleles yet. The high estimated fixation indexes (from 0.183 to 0.387) are due to null alleles in some loci and the occurrence of inbreeding within populations. Genetic divergence was low among adults (R ST = 0.035) but increased among saplings (R ST = 0.075). As expected, forest fragmentation has caused a decrease in gene flow among the populations, especially between the most distant fragment (Tucano -about 8 km from the "Parque Estadual do Morro do Diabo"). An alternative to promote gene flow among forest fragments of "Pontal do Paranapanema" would be the settle of agroforests, which would act as stepping-stones, favouring pollen and seed dispersion among fragments.Key words -Atlantic forest, forest fragmentation, gene flow, genetic diversity, microsatellites RESUMO -(Estrutura genética populacional de Copaifera langsdorffii Desf. (Leguminosae -Caesalpinioideae) em fragmentos florestais no Pontal do Paranapanema, SP, Brasil) O Pontal do Paranapanema é a região mais recentemente desflorestada do Estado de São Paulo. Os efeitos da fragmentação florestal na estrutura genética de Copaifera langsdorffii Desf. foram avaliados por meio da genotipagem, com seis locos microssatélites, de pelo menos 30 indivíduos regenerantes e 30 adultos em três áreas do Pontal do Paranapanema. A amostragem compreendeu dois fragmentos localizados em assentamentos rurais, Tucano (800 ha) e Madre Cristina (300 ha); e uma população localizada em floresta contínua, no Parque Estadual do Morro do Diabo (35.000 ha). Níveis elevados de diversidade genética foram detectados tanto nos regenerantes como nos adultos. A diversidade gênica (H e ) variou de 0,718 a 0,835 e o número médio de alelos por loco (Â) variou de 8,67 a 11,83, mostrando que a fragmentação ainda não causou perda de alelos. As estimativas elevadas dos índices de fixação (0,183 a 0,387) foram conseqüentes da ocorrência de alelos nulos em alguns locos e de endogamia nas populações. A divergência genética foi pequena entre os adultos (R ST = 0,035), mas aumentou entre os regenerantes (R ST = 0,075). C...

Genetic diversity and mating system of Copaifera langsdorffii (Leguminosae/Caesalpinioideae)

“…This pattern of genetic structure is expected for tree species with efficient mechanisms of gene flow, such as tropical tree species that are pollinated by animals and have seed dispersal. Previous studies with C. langsdorffii observed a similar pattern with low genetic differentiation among populations (Carvalho and Oliveira, 2004;Martins et al, 2008). The observed low genetic differentiation between the populations indicates the lack of isolation and intense gene flow between the populations, which homogenizes its genetic diversity.…”

Genetic diversity of Casearia sylvestris populations in remnants of the Atlantic Forest

“…The high genetic divergence observed between the populations of Santa Genebra and Tietê is most likely related to the low gene flow resulting from forest fragmentation (Frankham et al, 2008). Similar results were found for the Copaíba tree (Copaifera langsdorffii) by Martins et al (2008), whereby it was suggested that forest fragmentation restricts gene flow between populations of these species, possibly due difficulty in pollinator movement. The genetic isolation may also be related to the high number of private alleles found in this study (Karasawa, 2005).…”

Microsatellite diversity and chromosome number in natural populations of Trifolium riograndense Burkart

“…Null alleles have been found in more than 25 % of the microsatellite loci, reaching frequencies over 15 % (Jarne and Lagoda, 1996) and observed in other plants such as Allium cepa L. cultivars (Santos et al, 2010) and Copaifera langsdorffii Desf. (Martins et al, 2008), among others. Null alleles may be due mainly to the lack of a sequence for the initiatior annealing, due to point mutations.…”

“…In T. pratense, Dias et al (2008), also using SSR found high intrapopulational variability in a core collection of red clover (T. pratense), number of alleles per locus ranging from seven to 12. Null alleles, those alleles that are consistently not amplified (Martins et al, 2008) were observed in SSR ats 070, TM0133 and TM0256 (Table 2). Null alleles have been found in more than 25 % of the microsatellite loci, reaching frequencies over 15 % (Jarne and Lagoda, 1996) and observed in other plants such as Allium cepa L. cultivars (Santos et al, 2010) and Copaifera langsdorffii Desf.…”

“…Null alleles may be due mainly to the lack of a sequence for the initiatior annealing, due to point mutations. This fact can: (i) difficult parentage analysis interpretations (Dakin and Avise, 2004); (ii) provide an erroneous detection the amount of homozygote genotypes per locus (White et al, 1999); and (iii) cause deviations in Hardy-Weinberg balance leading to wrong conclusions on populations genetic diversity (Martins et al, 2008). PIC values, which reflects diversity and allelic frequency, varied among T. riograndense populations from 0.48 to 0.80, with an average of 0.68 (Table 2), outlining high intrapopulation variability.…”