Traditional medicinal use is linked with apparency, not specialized metabolite profiles in the order Caryophyllales

A better understanding of the relationship between plant specialized
metabolism and traditional medicine has the potential to aid in
bioprospecting and untangling of cross-cultural use patterns. However,
given the limited information available for metabolites in most plant
species, understanding medicinal use-metabolite relationships can be
difficult. The order Caryophyllales has a unique pattern of lineages of
tyrosine- or phenylalanine-dominated specialized metabolism, represented
by mutually exclusive anthocyanin and betalain pigments, making
Caryophyllales a compelling system to explore the relationship between
medicine and metabolites by using pigment as a proxy for tyrosine- vs
phenylalanine-dominant metabolism. We compiled a list of medicinal species
in select tyrosine- or phenylalanine-dominant families of Caryophyllales
(Nepenthaceae, Polygonaceae, Simmondsiaceae, Microteaceae,
Caryophyllaceae, Amaranthaceae, Limeaceae, Molluginaceae, Portulacaceae,
Cactaceae, and Nyctaginaceae) by searching scientific literature until no
new medicinal uses were recovered. We then tested for phylogenetic
clustering of uses using a “hot nodes" approach. To test potential
non-metabolite drivers of medicinal use, like how often humans encounter a
species (apparency), we repeated the analysis using only North American
species across the entire order and performed phylogenetic generalized
least squares regression (PGLS) with occurrence data from the Global
Biodiversity Information Facility (GBIF). We hypothesized families with
tyrosine-enriched metabolism would show clustering of different types of
medicinal use compared to phenylalanine-enriched metabolism. Instead,
wide-ranging, apparent clades in Polygonaceae and Amaranthaceae are
overrepresented across nearly all types of medicinal use. Our results
suggest that apparency is a better predictor of medicinal use than
metabolite profile, although metabolism type may still be a contributing
factor.