Evolutionary history and ecology shape the diversity and abundance of phytochemical arsenals across monkeyflowers

Abstract

We examine the extent to which phylogenetic effects and ecology are associated with macroevolutionary patterns of phytochemical defence production across the Mimulus phylogeny. We grew plants from 21 species representing the five major sections of the Mimulus phylogeny in a common garden to assess how the arsenals (NMDS groupings) and abundances (concentrations) of a phytochemical defence, phenylpropanoid glycosides (PPGs), vary across the phylogeny. Very few PPGs are widespread across the genus, but many are common to multiple sections of the genus. Phytochemical arsenals cluster among sections in an NMDS and are not associated with total concentration of PPGs. There is a strong phylogenetic signal for phytochemical arsenal composition across the Mimulus genus, whereas ecological variables such as growing season length, latitude, and elevation do not significantly influence arsenal. In contrast, there is little phylogenetic signal for total PPG concentration, and this trait is significantly influenced by several ecological factors. Phytochemical arsenals and abundances are influenced by plant life history form. Both phylogenetic effects and ecology are related to phytochemical patterns across species, albeit in different ways. The independence of phytochemical defence concentrations from arsenal compositions indicates that these aspects of defence may continue to evolve independently of one another.

Climate and the biotic community structure plant resistance across biogeographic groups of yellow monkeyflower

“…At least some of these correlations also have strong associations with climate; for example, in annual monkeyflower populations, the length of the growing season (defined by both precipitation and temperature) is positively correlated with concentrations of phytochemical defense (Kooyers et al, 2017). This intra-specific pattern is similar to macroevolutionary patterns across the monkeyflower phylogeny, whereby PPG concentrations are significantly influenced by mean annual temperature, amount of precipitation, and growing season length (Holeski et al, 2021). There are thus likely indirect effects of climate on monkeyflower resistance arsenals mediated through plant life history strategy.…”

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

“…The specialized metabolite profile of a species tends to be influenced by phylogeny—while some SMs are relatively widespread, such as anthocyanins, others are more lineage specific, such as the glucosinolates, which outside Brassicales are only known in the family Putranjivaceae (Rodman et al, 1998). Overall, closely related plants tend to produce similar classes and abundances of SMs, being constrained by the SM biosynthetic pathways of their common ancestor (Wink, 2003; Holeski et al, 2021; Youssef et al, 2023).…”