Lipid profiles and DNA barcoding markers reveal the genetic delimitation between species of the Carapa genus native from the Amazon

Abstract

Authentic identification of Amazonian tree species is important for conservation and their sustainable exploitation. This work aimed to characterize the inter- and intraspecific divergence in two taxonomic units of the genus Carapa using the lipidomic profile of the seed oils, analyzed by gas chromatography-mass spectrometry (GC-MS) and DNA barcoding molecular markers to identify and discriminate differences between Carapa species. Seeds and leaves of 53 individuals were collected and morphologically grouped into Carapa guianensis and Carapa vasquezii. The oils extracted from seeds were esterified, and their lipidomic profiles were analyzed. Two chloroplast genome regions (psbA-trnH and rbcL) were amplified for genetic diversity analyses and the barcoding-gap test. The lipidomic profile allowed the identification of 40 substances present in the C. guianensis and C. vasquezii oils, with 20 shared among the species independent of the region of collection, two occurring only in the oil of C. guianensis from Acre, four in samples of C. guianensis and C. vasquezii from Amazonas, and 16 substances occurring only in samples of C. vasquezii oil. C. vasquezii presented a greater diversity of terpenoids. The genome regions made it possible to obtain 16 distinct haplotypes for the two species (C. guianensis and C. vasquezii), 999 conserved sites, and 32 polymorphic sites. The species presented significant molecular divergence (FST=0.87), and the rbcL region was considered promising for barcode studies at levels ranging from 0.1 to 0.2% of genetic distance. The results suggest that the two species morphologically identified C. guianensis and C. vasquezii constitute genetically divergent biological groups.