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Abstract Detail

Conservation Biology

ALLPHIN, LOREEN [1], Li, Fay-Wei [2], Windham, Michael D. [3].

Systematics and conservation status of the Hells Canyon rock cress (Brassicaceae).

Boechera hastatula (Greene) Al-Shehbaz, the Hells Canyon rock cress, is a critically imperiled plant species known only from the rim of Hells Canyon in the Wallowa-Whitman National Forest of Wallowa County, Oregon, USA. Originally described as a new species of Arabis based on a single plant collected in 1907, similar plants were not collected again until 1952. Harvard-based brassicologist Reed Rollins encountered the latter specimen while working on his 1993 synopsis of North American Cruciferae, and he concluded that it did, indeed, represent a distinct species. Intent to learn more about this rare plant, botanists from the Oregon Natural Heritage Program and U.S. Forest Service conducted a field survey in 1996 that identified ten “occurrences” of the species, amounting to fewer than a thousand individuals “along a single band of cliffs.” The taxon is currently globally ranked as G2 (globally imperiled) and as S1 (state critically imperiled) according to the Natural Heritage Program in Oregon. The taxon is also maintained on the US Forest Service sensitive species list. Despite its rarity, the few available specimens of B. hastatula suggest that the species, like many other members of the genus, exhibits variation in both ploidy level and reproductive mode. To investigate the sources of this diversity, we conducted morphological, palynological, cytogenetic and microsatellite DNA analyses on all available herbarium specimens as well as a new series of collections from more intense sampling obtained during the 2012 field season. Our studies reveal that B. hastatula, as currently defined, includes three genetic entities: a sexual diploid, an apomictic diploid, and an apomictic triploid. Microsatellite data indicate that both apomictic entities arose through hybridization involving the sexual diploid taxon and the widespread species now known as B. retrofracta (Graham) Löve & Löve. The type specimen of Boechera hastatula belongs to the triploid entity, which contains two genomes of the apparently unnamed sexual diploid and one of B. retrofracta. Based on these results, we propose to circumscribe B. hastatula as a hybrid nothospecies, encompassing the two apomictic entities, and recognize the newly discovered sexual diploid as a new species. Regardless of the taxonomic approach taken, however, B. hastatula sensu stricto appears to be considerably rarer than previously anticipated.

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1 - Brigham Young University, Department of Plant and Wildlife Sciences, Provo, Utah, 84602, United States
2 - Cornell University, Boyce Thompson Institute, Ithaca, NY, 14850, USA
3 - DUKE UNIVERSITY, Department Of Biology, BOX 90338, DURHAM, NC, 27708, USA


Presentation Type: Oral Paper
Session: 38, Conservation Biology
Location: Sundance 1/Omni Hotel
Date: Wednesday, June 28th, 2017
Time: 1:45 PM
Number: 38002
Abstract ID:299
Candidate for Awards:None

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