Abstract
Anthocyanin pigments are responsible for many of the vivid pink, purple, red, and blue flower colors across angiosperms and frequently vary within and between closely related species. While anthocyanins are well known to influence pollinator attraction, they are also associated with tolerance to abiotic stressors such as extreme temperatures, reduced precipitation, and ultraviolet radiation. Using a comparative approach, we tested whether abiotic variables predict floral anthocyanin in monkeyflowers (Phrymaceae) across western North America. Within two polymorphic species, we found that abiotic variables predicted flower color across their geographic ranges. In Erythranthe discolor, the frequency of pink flowered (anthocyanin producing) individuals was greater in populations with reduced precipitation. In Diplacus mephiticus, the frequency of pink flowered individuals was greater at higher elevations that had reduced precipitation and lower temperatures but less ultraviolet radiation. At the macroevolutionary scale, across two parallel radiations of North American monkeyflowers, species with floral anthocyanins (pink, purple, or red corollas) occupied areas with reduced precipitation in Erythranthe but not Diplacus. However, after accounting for phylogenetic relatedness, we found no evidence for the joint evolution of flower color and environmental affinity in either clade. We conclude that although abiotic stressors may play a role in the evolution of flower color within polymorphic species, we found no evidence that these processes lead to macroevolutionary patterns across monkeyflowers.
Highlights
Anthocyanin pigments cause the vivid red, blue, pink and purple colors in flowers, and are one of the most common flower color polymorphisms across angiosperms (Richards, 1986; Warren and Mackenzie, 2001)
Characterizing Environmental Conditions at Each Population We examined six environmental attributes relating to drought, temperature and UV stressors that vary across our study populations: mean annual temperature, mean annual precipitation, precipitation during peak flower, climatic water deficit, UV-B radiation and elevation
Polymorphic populations on the other hand occurred in areas that are both warmer than pink populations, with less precipitation than yellow populations, and had higher climatic water deficit than either pink or yellow populations
Summary
Anthocyanin pigments cause the vivid red, blue, pink and purple colors in flowers, and are one of the most common flower color polymorphisms across angiosperms (Richards, 1986; Warren and Mackenzie, 2001). Flower Color Evolution in Monkeyflowers radiation, with strong abiotic selection leading to traitenvironment correlations (e.g., Warren and Mackenzie, 2001; Coberly and Rausher, 2003; Schemske and Bierzychudek, 2007; Dick et al, 2011; reviewed in Strauss and Whittall, 2006). This raises the question: are abiotic stressors common drivers of flower color evolution and, if so, does this lead to macroevolutionary patterns such as the association between floral anthocyanin and abiotic stressors across species?. Floral anthocyanins may be directly selected on due to protection of flowers or flower buds from abiotic stressors (e.g., Dick et al, 2011; Koski and Galloway, 2018; Peach et al, 2020) or indirectly through selection in vegetative tissue where anthocyanins protect plants from a variety of biotic and abiotic stressors (Warren and Mackenzie, 2001; Coberly and Rausher, 2003)
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call