Abstract Detail

Conservation Biology

Hay, Nikolai [1], Allphin, Loreen [2], Beck, James [3], Li, Fay-Wei [4], Windham, Michael [5].

Relationships and conservation status of the Fremont County rockcress (Brassicaceae).

Boechera pusilla (Rollins) Dorn, the Fremont County rockcress, is an extremely rare mustard species known from a single population on a large metamorphic rock outcrop in Fremont County, Wyoming, USA. It is currently a candidate for federal listing under the Endangered Species Act. The species was first described (as an Arabis) in 1982 by Reed Rollins, who commented that it most closely resembled the Colorado endemic A. oxylobula. To investigate the relationships and evolutionary history of B. pusilla, we conducted cytogenetic analysis of the species, as well as morphological and microsatellite studies of nearly all available collections. The cytogenetic analyses reveal additional differences between B. pusilla and the superficially similar B. oxylobula; the former is an apomictic triploid taxon (n = 2n = 21) whereas the latter is a sexual diploid (n = 7). Microsatellite analyses indicate that the three genomes of B. pusilla were each contributed by a different species. Not surprisingly, one genome is derived from B. oxylobula, a species restricted to west-central Colorado at elevations of 2000-3200 m. Another was contributed by B. lemmonii, a widespread alpine species generally occurring above 3000 m in the southern Rocky Mountains. The source of the third genome is B. “wyomingensis”, a previously undescribed sexual diploid largely confined to southern Wyoming at elevations ranging from 1600-2800 m. Given the current geographic distributions of these taxa, the most parsimonious explanation for the origin of B. pusilla involves 1) an initial hybridization event between B. oxylobula and B. lemmonii in western Colorado, forming an unnamed, apomictic diploid bridge taxon, 2) migration of this apomictic diploid north into Wyoming, followed by 3) a second hybridization between this apomict and B. “wyomingensis” to produce the Fremont County rockcress. Our data suggest that the rarity of B. pusilla is likely due to recency of origin rather than inherent genetic limitations. There are scores of such apomictic hybrids in Boechera and, in a world with limited conservation resources, the future may be better served by using these funds to protect the rarer sexual diploid taxa.

1 - Duke University, Biology, Campus Box 90338, Durham, NC, 27708, United States
2 - Brigham Young University, Department Of Plant And Wildlife Sciences, Byu,dept Plant And Wildlife Sciences, 4105 LSB, Provo, UT, 84602, United States
3 - Wichita State University, Biology, 1845 Fairmount, Box 26, Wichita, KS, 67260, United States
4 - Cornell University, Boyce Thompson Institute, Ithaca, NY, 14853, USA
5 - Duke University, Department Of Biology, Box 90338, Durham, NC, 27708, United States

Keywords:
Hybridization
apomixis
Boechera
Triploid
Brassicaceae
Microsatellite
Cytogenetic.

Presentation Type: Oral Paper
Session: 43, Conservation Biology II
Location: 106/Mayo Civic Center
Date: Wednesday, July 25th, 2018
Time: 2:30 PM
Number: 43005
Abstract ID:854
Candidate for Awards:None