Convergent Evolution

Sources of Funding:

  1. National Geographic grant 7534-03: “Fragrance complexity in night-blooming flowers: convergence or character displacement?”
  2. Andrew W. Mellon Foundation: “Evolution and Historical Biogeography of Onagraceae Tribe Onagreae, a Major Lineage Derived from the Madro-Tertiary Flora”
  3. NSF grant DEB-9806840: “Pattern and Process in the Evolution of Hawkmoth Pollination”

Convergent Evolution

Observations

  1. Guilds of night-blooming flowers pollinated by hawkmoths have evolved across the world in subtropical grasslands, deserts and tropical rainforests.
  2. Members of sphingophilous guilds show strong convergent evolution in floral form, nectar tube length, color and timing of anthesis.
  3. The intensity and composition of floral scent is less strongly conserved among guild members, with some properties specific to plant lineage.

I originally studied the Sonoran Desert hawkmoth pollination guild as a postdoc at the University of Arizona. With Lucinda McDade and Rachel Levin, we had an NSF- funded study to address the gain and loss of sphingophily in three lineages (Onagraceae, Nicotiana (Solanaceae), and Nyctaginaceae. Rachel continued this work as a postdoc with Warren Wagner and Liz Zimmer at the Smithsonian, focusing on Onagraceae systematics. We added a fourth lineage (Echinopsis cacti) as part of Boris Schlumpberger’s postdoc with me at South Carolina. Finally, we compared similar guilds from the same Lattitudes in South Africa and Argentina, in a National Geographic study with Steve Johnson, Andrea Cocucci and Marcela Moré.

Convergent Evolution

Questions

  1. If scent is demonstrably necessary to attract hawkmoths to flowers, then why does its complexity and intensity vary so dramatically between guild members pollinated by the same moths?
  2. Can some of this variation be parsed into factors other than pollinator attraction, such as floral defense, biosynthetic artifacts and phylogenetic history?
  3. Once these other factors are accounted for, is there evidence for convergent evolution of scent components associated with “pollination syndrome”?
  4. Turning the question on its end, is scent chemistry useful as a phylogenetically informative set of characters?

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