Abstract Detail

Molecular Ecology and Evolution

Plume, Olofron [1], Doyle, Jeff [2], Kessler, Andre [3].

Signatures of hybridization and polyploidy in the evolution of chemical diversity in Calendula (Asteraceae).

All angiosperms are ancestrally polyploid, with as many as 70% showing chromosomal evidence of polyploidy, and many of these are of hybrid origin (allopolyploids). Hybridization and polyploidy have genomic and evolutionary consequences including genome rearrangements, gene silencing and/or activation, and changes in location and time of gene expression, and these can generate diversity, including biochemical diversity. Calendula is a small genus of 12 species native to Macaronesia and the Mediterranean. It is notable for a wide range of chromosome numbers across species (2n = 14, 18, 30, 32, 44, and ~85) thought to reflect a history of hybridization and genome duplication. The best-known species, C. officinalis, has long been cultivated for its medicinal properties and there is a growing body of literature on its secondary chemistry, but studies focusing on chemical variation across species in the genus have not been published. The purpose of this study was to investigate phenolic and terpene diversity within the context of phylogenetic relationships in Calendula. Both types of compounds are known to be diverse in plants, they are physiologically, ecologically and economically important, and, being from different biosynthetic pathways, they have the potential to offer different perspectives on the effects of speciation, hybridization, and polyploidy on chemical diversification. Phenolic compounds (including caffeic acid derivatives and flavonoids) and mono- and sesquiterpenes were extracted from leaf and floral tissue of over 200 individuals representing ten Calendula species (including subspecific and geographical variation of some species) and analyzed by HPLC or GC-MS, respectively, in order to test the following hypotheses: 1) the chemical signature of Calendula plants will vary significantly between species; 2) terpenes will be poorer than phenolics at tracking speciation because of lower specificity of and much higher number of products produced by terpene synthases; 3) some compounds or mixtures of compounds will vary by tissue, potentially because of different selective forces on these tissues (e.g., herbivore resistance in the leaves and ray florets (female) vs. pollinator attraction in the disc florets (male)); and 4) hybrid and polyploid individuals will have more compounds, novel compounds, different ratios of compounds, and/or differences in chemical signatures between tissues, relative to their progenitor species. Here, phenolic and terpene diversity is characterized in Calendula both across species and tissues, and implications for the above hypotheses are discussed.

Broader Impacts:

1 - Cornell University, 412 Mann Library Bldg, Ithaca, NY, 14853, USA
2 - Cornell University, 412 Mann Library Building, ITHACA, NY, 14853-4301, USA
3 - Cornell University, E445 Corson Hall, Ithaca, NY, 14853, USA

Keywords:
Calendula
chemical diversity
chemical evolution
hybridization
Polyploidy.

Presentation Type: Oral Paper:Papers for Topics
Session: 46
Location: Newberry/Riverside Hilton
Date: Wednesday, July 31st, 2013
Time: 2:30 PM
Number: 46005
Abstract ID:453
Candidate for Awards:Margaret Menzel Award