Madrinan, S. | Search bioRxiv

bioRxiv2023

Cultural use of tropane alkaloids of Brugmansia species and cultivars in Colombia depends on local plant growth environment rather than genetic diversity

Borracheros or Angel Trumpets (Brugmansia spp.) of the Solanaceae plant family are known for producing scopolamine and other tropane alkaloids and are widely used by indigenous communities in the Andes for medicinal and ritual purposes. Growing different varieties has increased the popularity of Brugmansia species in recent years, leading to the promotion of hybridization to get new morphotypes. However, so far no medical or cultural use of plant extracts could be linked to selected Brugmansia species or cultivars. Moreover, until now there is only limited knowledge about the effect of hybridization on tropane alkaloid contents and/or diversity of Brugmansia species or cultivars. Here, a liquid chromatography-mass spectrometry (LC-MS) approach was applied to identify and characterize secondary metabolite contents in various Brugmansia species and hybrids from different geographic origins in Colombia. The analysis of the metabolic data sets revealed that tropane alkaloids and other secondary metabolites accumulate in a leaf and flower specific manner. Although some minor differences were found between Brugmansia subgroups, the only significant difference exists between plants collected in the Sibundoy Valley, where they have been domesticated by indigenous communities since a long time and those, which so far have not been used by humans at all. The different genetic constitutions of Brugmancia species and cultivars are not the dominating reason for their differences in tropane alkaloid contents and medical and cultural usages, as there is no clear taxonomical signature based on the metabolite properties for species segregation. Instead, their use by indigenous communities during ceremonies and for medical treatment such as wound healing, infection control, rheumatism and arthritis is rather caused by the plasticity of the individual plants to react to the local abiotic and biotic environments by the variation of secondary metabolite composition and by the differences in the bioavailability of the active compounds as result of the extraction method.

plant biology↗

bioRxiv2020

The Nature of Espeletia Species

Species are often regarded as basic units of study in biology, following the presumption that they are real and discrete natural entities. But several biologists wonder if species are arbitrary divisions that do not correspond to discrete natural groups of organisms. Two issues must be addressed to solve this controversy, but few studies seem to do so. The first is whether organisms form sympatric and synchronic groups that are distinct in terms of phenotypes and genome-wide allele frequencies, often called "good species." Alternatives to "good species" include "cryptic species," syngameons and, more generally, cases in which phenotypes and genome-wide allele frequencies reflect contrasting evolutionary histories. The second issue is the degree to which species taxa (i.e., taxonomic classification at the species level) reflect natural groups of organisms or constitute arbitrary divisions of biological diversity. Here, we empirically addressed both issues by studying plants of the Andean genus Espeletia (Asteraceae). We collected a geographically dense sample of 538 specimens from the paramo de Sumapaz, in the Cordillera Oriental of Colombia. Additionally, we examined 165 herbarium specimens previously collected by other researchers in this region, or from taxa known to occur there. We tested for the existence of phenotypic groups using normal mixture models and data on 13 quantitative characters. Among 307 specimens with all 13 measurements, we found six distinct phenotypic groups in sympatry. We also tested for the existence of groups defined by genome-wide allele frequencies, using ancestry models and data on 2,098 single nucleotide polymorphisms. Among 77 specimens with complete genomic data, we found three groups in sympatry, with high levels of admixture. Concordance between groups defined by phenotype and genome-wide allele frequencies was low, suggesting that phenotypes and genome-wide allele frequencies reflect contrasting evolutionary histories. Moreover, the high levels of admixture suggest that Espeletia plants form a syngameon in the paramo de Sumapaz. To determine the extent to which species taxa corresponded to phenotypic and genomic groups, we used data on 12 phenotypic characters to assign 307 specimens to species taxa, according to descriptions of species taxa in the most recent monograph of Espeletia. This sample included 27 specimens cited in the monograph. Remarkably, only one out of 307 specimens in our sample fell inside any of the phenotypic ranges reported in the monograph for the species taxa known to occur in the paramo de Sumapaz. These results show that species taxa in Espeletia are delineations of largely empty phenotypic space that miss biological diversity.

evolutionary biology↗