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Abstract Detail

Systematics Section

Windham, Michael [1], Beck, James [2], Alexander, Patrick [3], Allphin, Loreen [4], Bailey, C. Donovan [5], Call, Christina [4], Li, Fay-Wei [6], Rushworth, Catherine [7], Al-Shehbaz, Ihsan [8].

Is the glass half-empty or half-full?: the current state of Boechera (Brassicaceae) systematics.

With upwards of 60 sexual diploid species originating within the last four million years, Boechera (Brassicaceae) is among the most rapidly diversifying genera of flowering plants. Pre-zygotic reproductive isolating mechanisms have failed to keep pace with diversification in the group, and recurrent hybridization among geographically proximate species has given rise to hundreds of hybrid lineages that persist and reproduce through polyploidy and/or apomixis. This makes Boechera (formerly Arabis) one of the most intractable species complexes in North America, with patterns of morphological variability that monographer Reed Rollins conceded "nearly defy taxonomic resolution." In the past few years, significant progress has been made toward understanding the systematics of Boechera by focusing on the sexual diploids that lie at the heart of the complex. Implementation of this "diploids-first" approach in Boechera is facilitated by pollen differences between sexual diploids and polyploids/apomicts observable using a dissecting microscope. A critical reexamination of overall morphology has shown that the 60+ sexual diploids are rather easily distinguished from one another, and a newly developed 15-locus microsatellite data set provides critical genetic markers for each of these diploid genomes. The microsatellite data set currently comprises ca. 2400 samples, including nearly every sexual diploid Boechera recognized in the recently published Flora of North America treatment. Range-wide sampling of many species has been facilitated by extracting DNA from herbarium specimens, which provided more than 95% of the data. Microsatellites provide an effective barcode allowing determination of the genomic make-up (and usually the ploidy level and reproductive mode) of almost any Boechera specimen collected within the last 125 years.These successes are tempered by the discovery that the taxonomy of Boechera is even more complex than previously thought. The great diversity of apomictic triploids in the genus have been interpreted as either autopolyploids or digenomic hybrids (e.g., AAB or ABB). Instead, the majority appear to be trigenomic (ABC) hybrids that are much more difficult to diagnose morphologically.

Broader Impacts:

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1 - DUKE UNIVERSITY, Department Of Biology, BOX 90338, DURHAM, NC, 27708, USA
2 - University Of Wisconsin, Milwaukee, Lapham Hall S394, P.O. Box 413, Milwaukee, WI, 53201-0413, USA
3 - New Mexico State University, Biology Department, 248 Foster Hall, Las Cruces, NM, 88003, USA
4 - Brigham Young University, Department of Plant and Wildlife Sciences, Provo, UT, 84602, USA
5 - New Mexico State University, Department Of Plant Sciences, P.O. Box 30001 Msc 3AF, Las Cruces, NM, 88003, USA
6 - Duke University, Department of Biology, Durham, NC, 27708, USA
7 - Duke University, PO Box 90338, Durham, NC, 27708, USA
8 - Missouri Botanical Garden, Department of Asian Botany, P.O. Box 299, St. Louis, MO, 63166, USA


Presentation Type: Oral Paper:Papers for Sections
Session: 29
Location: Lindell B/Chase Park Plaza
Date: Tuesday, July 12th, 2011
Time: 10:45 AM
Number: 29009
Abstract ID:516

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