Plume, Olofron .
Molecular systematics of Calendula (Asteraceae): evidence from the chloroplast and internal transcribed spacers (ITS).
The small pan-Mediterranean genus Calendula includes 12 currently recognized species, the best known of which is C. officinalis (pot marigold), cultivated for centuries for both medicinal and ornamental use. The genus is remarkable not only for the striking heterocarpy of its achenes and its disjunct distribution relative to the other genera in tribe Calenduleae (all of which are South African), but also for the wide range of chromosome numbers reported for different species (2n=14, 18, 30, 32, 44, and ~85). These numbers have been hypothesized to be the result of hybridization events between species with different chromosome numbers followed by genome duplication (allopolyploidy). In order to elucidate relationships in the genus and to begin testing hypotheses of polyploid parentage, total genomic DNA was extracted from over 70 wild-collected or cultivated individuals representing 10 of the 12 species of Calendula, eleven of 15 accepted subspecies from the C. incana and C. suffruticosa groups, and a range of form variants of the highly polymorphic C. arvensis, as well as from six outgroup species in three genera of the Calenduleae. Five non-coding chloroplast regions (atpI-atpH, petL-psbE, ndhF-rpl32, trnQ-rps16, and trnY-rpoB) and the internal transcribed spacers (ITS) 1 and 2 of nuclear ribosomal DNA were amplified and sequenced. Parsimony analyses of both the chloroplast and ITS datasets resolved the taxa into two major clades, a clade of species endemic to Morocco and a clade of all other taxa, casting doubt on previous hypotheses that these Moroccan species were involved in the parentage of some putative polyploid species.
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1 - Cornell University, L. H. Bailey Hortorium, Department of Plant Biology, 412 Mann Library, Ithaca, New York, 14853, USA
Presentation Type: Oral Paper:Papers for Sections
Location: 556A/Convention Center
Date: Tuesday, August 3rd, 2010
Time: 2:30 PM