Independent evolution of ancestral and novel defenses in a genus of toxic plants ( < i > Erysimum < /i > , Brassicaceae)

Phytochemical diversity is thought to result from coevolutionary cycles as specialization in herbivores imposes diversifying selection on plant chemical defenses. Plants in the speciose genusErysimum (Brassicaceae) produce both ancestral glucosinolates and evolutionarily novel cardenolides as defenses. Here we test macroevolutionary hypotheses on co-expression, co-regulation, and diversification of these potentially redundant defenses across this genus. We sequenced and assembled the genome ofE. cheiranthoides and foliar transcriptomes of 47 additionalErysimum species to construct a phylogeny from 9,869 orthologous genes, revealing several geographic clades but also high levels gene discordance. Concentrations, inducibility, and diversity of the two defenses varied independently among species, with no evidence for trade-offs. Closely related, geographically co-occurring species shared similar cardenolide traits, but not glucosinolate traits, likely as a result of specific selective pressures acting on each defense. Ancestral and novel chemical defenses inErysimum thus appear to provide complementary rather than redundant functions.
Source: eLife - Category: Biomedical Science Tags: Evolutionary Biology Plant Biology Source Type: research