Patterns of genetic diversity and structure of a threatened palm species (Euterpe edulis Arecaceae) from the Brazilian Atlantic Forest

The detection of distribution patterns of genetic diversity of plant and animal species has contributed to the understanding of biodiversity and evolutionary history of the Atlantic Forest. We used microsatellite markers to access the genetic diversity and structure of 26 populations and 527 adult individuals of Euterpe edulis, a native palm which is an important food resource for fauna and is intensively exploited due to economic reasons. We found high genetic diversity and inbreeding in all populations analyzed. We report highest rates of inbreeding for this species, which could reflect the anthropic impacts of selective cutting, fragmentation, and change in foraging behavior from pollinators and less availability and mobility of large dispersers. We detected by STRUCTURE, two genetic groups, Northern and Southern, which divide the Brazilian Atlantic Forest geographically. These groups have low genetic admixtures, but we found a region of lineage hybridization in the contact zone with low recent gene flow. Distribution pattern of this species corroborates results from previous studies reporting the Last Glacial Maximum (LGM) have shaped the structuring of the species through movements of forests' expansion and contraction. The STRUCTURE analysis of each group revealed the presence of genetic subgroups with low rates of recurrent gene flow. Southern subgroups have higher rates of admixtures than the Northern subgroups, revealing greater historical connectivity of forests in this region.

Plastid genome evolution in Amazonian açaí palm (Euterpe oleracea Mart.) and Atlantic forest açaí palm (Euterpe edulis Mart.)

The plastomes of E. edulis and E. oleracea revealed several molecular markers useful for genetic studies in natural populations and indicate specific evolutionary features determined by vicariant speciation. Arecaceae is a large and diverse family occurring in tropical and subtropical ecosystems worldwide. E. oleracea is a hyperdominant species of the Amazon forest, while E. edulis is a keystone species of the Atlantic forest. It has reported that E. edulis arose from vicariant speciation after the emergence of the belt barrier of dry environment (Cerrado and Caatinga biomes) between Amazon and Atlantic forests, isolating the E. edulis in the Atlantic forest. We sequenced the complete plastomes of E. edulis and E. oleracea and compared them concerning plastome structure, SSRs, tandem repeats, SNPs, indels, hotspots of nucleotide polymorphism, codon Ka/Ks ratios and RNA editing sites aiming to investigate evolutionary traits possibly affected by distinct environments. Our analyses revealed 303 SNPs, 91 indels, and 82 polymorphic SSRs among both species. Curiously, the narrow correlation among localization of repetitive sequences and indels strongly suggests that replication slippage is involved in plastid DNA mutations in Euterpe. Moreover, most non-synonymous substitutions represent amino acid variants in E. edulis that evolved specifically or in a convergent manner across the palm phylogeny. Amino acid variants observed in several plastid proteins in E. edulis were also identified as positive signatures across palm phylogeny. The higher incidence of specific amino acid changes in plastid genes of E. edulis in comparison with E. oleracea probably configures adaptive genetic variations determined by vicariant speciation. Our data indicate that the environment generates a selective pressure on the plastome making it more adapted to specific conditions.

Chemical composition and antioxidant capacity of açaí (Euterpe oleracea) genotypes and commercial pulps

BACKGROUND

Açaí has been reported to contain many bioactive compounds, including phenolic compounds such as anthocyanins. This study aimed to determine the chemical composition and antioxidant potential of pulps of three different açaí genotypes from the Active Germplasm Bank of Embrapa Eastern Amazon and three commercial açaí pulps from Belém, state of Pará, Brazil.

RESULTS

Anthocyanin 3-rutinoside was the major anthocyanin present in freeze-dried açaí pulp samples. The commercial sample C showed the greatest amounts of cyanidin 3-glucoside and cyanidin 3-rutinoside (18 942 and 34 397 µg g^-1 respectively). The content of phenolic compounds varied significantly among the commercial and genotype samples, and vanillic acid was found in the highest concentration in the samples studied. All açaí samples showed high DPPH, ORAC and TEAC values, confirming the exceptionally high radical-scavenging capacity of açaí pulp previously reported by other researchers.

CONCLUSION

The commercial samples showed higher antioxidant capacity and higher levels of anthocyanins and non-anthocyanic compounds than those of the genotype samples. Among the genotypes studied, L4P16 stood out for its higher contents of fibre and bioactive compounds and higher antioxidant capacity, indicating that this genotype has great potential for use in plant breeding programs that should be further explored. © 2016 Society of Chemical Industry.

Defaunation leads to microevolutionary changes in a tropical palm

Many large species have declined worldwide due to habitat fragmentation and poaching. The defaunation of large frugivores and the consequent reductions of seed dispersal services may have immediate effects on plant demography. Yet, the lasting effects of frugivore defaunation on microevolutionary processes of the plants they disperse remain understudied. We tested if the loss of large seed dispersers can lead to microevolutionary changes of a tropical palm. We show that frugivore defaunation is the main driver of changes in allelic frequency among populations. Turnover of alleles accounted for 100% of dissimilarity in allelic frequencies of individuals between defaunated and non-defaunated forests; and individuals from defaunated sites are 1.5 times more similar genetically than those found in pristine sites. Given that sizeable fractions of the palm fruit crops remain undispersed in defaunated sites due to lack of large-bodied frugivores, this distinct pattern of gene pool composition of early recruits may reveal strong dispersal limitation for specific genotypes, or collapses of gene flow between fragmented areas, or both. Because most of tropical tree species rely on seed dispersal by vertebrates, our results show that defaunation has a lasting effect on microevolutionary processes, with potential consequences for persistence under scenarios of environmental change.