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Abstract Detail

Systematics Section/ASPT

Cacho, Natalia [1], Burrell, Millie [2], Pepper, Alan [3], Strauss, Sharon [4].

Systematics and evolution of serpentine tolerance in California Jewelflowers and allies (Streptanthoid complex, Brassicaceae).

Streptanthus is a genus of ca. 35 species in the tribe Thelypodieae with unique urn-shaped calyx and flowers that are strongly zygomorphic and vary widely in color, unlike the cruciform actinomorphic flowers typical of Brassicaceae. Ample morphological intergradation of Streptanthus with species assigned to allied genera in the tribe (e.g., Caulanthus, Thelypodium, Streptanthella, Sibaropsis, Stanleya) points to a complex evolutionary history leading some authors to treat a set of ca. 60 taxa within the Thelypodieae as the ‘Strepanthoid Complex’ based on affinity with the North American genus Streptanthus and a largely conserved chromosome number of n=14. Ecologically, Streptanthus exhibits a high degree of edaphic specialization, particularly associated with ultramafic or serpentine soils: about 30% of the recognized species are serpentine obligates and a few have been recognized as having serpentine and non-serpentine populations. While ecological research has shed some light regarding the adaptation to serpentine in Streptanthus, there have been few insights on the origins and evolution of serpentine tolerance in this group, largely due to limited success in resolving the phylogenetic relationships of the species in Streptanthus and allied genera of the Thelypodieae. We present a much improved phylogenetic hypothesis for Streptanthus and allied genera, based on six single copy nuclear regions, three of which are newly identified (AT4G34700, AT1G61620, and AT1G56590, and three that are widely used (ITS, PHYA, and PEPC). We also include data for two chloroplast regions (trnL and trnH-psbA). Taxonomically, our sampling is nearly complete in Streptanthus and Caulanthus, and includes closely allied genera in the Thelypodieae. Our results reveal that Streptanthus, Caulanthus, and possibly Thelypodium are not monophyletic as currently defined. The species of Streptanthus form two rather distantly related clades. One clade is comprised of species with urn-shaped calyces that occur mainly within the California Floristic Province hotspot; the other clade is composed of species with extant ranges mainly outside of such bioregion. Finally, we will discuss results the origin and evolution of serpentine tolerance and endemism in this group.

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1 - University of California-Davis, One Shields Ave, Davis, CA, 95616, USA
2 - Texas A&M University, Institute For Plant Genomics And Biotechnology, Department Of Horticultural Sciences, TAMU 2123, College Station, TX, 77843-2123, USA
3 - Department of Biology, Texas A&M University, TAMUS 3258, College Station, TX, 77843, USA
4 - University of California Davis, SECTION OF EVOLUTION AND ECOLOGY, One Shields Avenue, Davis, CA, 95616, USA

edaphic endemism

Presentation Type: Oral Paper:Papers for Sections
Session: 19
Location: Napoleon Ballroom/Riverside Hilton
Date: Tuesday, July 30th, 2013
Time: 10:45 AM
Number: 19009
Abstract ID:443
Candidate for Awards:George R. Cooley Award

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