Grusz, Amanda L. , Windham, M. D. , Metzgar, Jordan S. , Pryer, Kathleen M. .
Polyploids and reticulate voids: the Cheilanthes fendleri complex revisited.
CHEILANTHES (Pteridaceae) is a xeric-adapted fern genus with about thirty species in North America. Relationships within the genus are poorly understood due to the prevalence of polyploidy, apomixis, and reticulate evolution. Here we explore the evolutionary history of the Cheilanthes fendleri complex -- a small group of species endemic to the southwestern United States. As circumscribed in Flora of North America, this group comprises two sexual diploids (C. covillei and C. fendleri), two apomictic triploids (C. lindheimeri and C. wootonii), and one apomictic tetraploid (C. yavapensis). Based on earlier studies, the apomictic tetraploid C. yavapensis was thought to have arisen through hybridization between C. covillei and C. lindheimeri; the evolutionary origins of the two triploids were unresolved. For this study, we sequenced four plastid loci (atpB-rbcL, trnS-rps4, trnG-trnR, and trnP-petG) and integrated this information with morphological, isozyme, and spore data to produce a clearer picture of the complex. The DNA sequence data contradicted earlier conclusions and suggested the existence of an undetected sexual diploid, which we subsequently located through spore analyses of herbarium specimens. The discovery of this diploid helps to explain the origin of tetraploids (C. yavapensis) and triploids (C. lindheimeri and C. wootonii) alike. Based on these results, we predict the existence of two additional apomictic triploids and an undetected sexual tetraploid. Our findings emphasize the importance of using multiple data sets to resolve species relationships in groups with a history of reticulate evolution and also demonstrate the vital role of herbarium specimens in filling the void in our understanding of polyploidy and apomixis.
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1 - University of North Carolina Wilmington, Department of Biology, 118 South Cardinal Drive, Wilmington, North Carolina, 28403, USA
2 - University of Utah,, Utah Museum of Natural History,, Salt Lake City,, Utah,, 84112,, USA
3 - Duke University, Department of Biology, 139 Biological Sciences Building, PO Box 90338, Durham, North Carolina, 27708, USA
Polymerase Chain Reaction
Presentation Type: Oral Paper:Papers for Sections
Date: Monday, July 31st, 2006
Time: 3:45 PM