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Abstract Detail

Conservation Biology

Schwabe , Anna L [1], Neale, Jennifer Ramp [2], McGlaughlin, Mitchell E. [3].

Hybridization or phenotypic plasticity? A genetic investigation of an endangered Colorado cactus (Sclerocactus glaucus) in the face of hybridization threats from a widespread congener (Sclerocactus parviflorus).

The genus Sclerocactus was first described in the early 20th Century and included only two species. Taxonomic circumscription has been fiercely debated for years with the most recent assessment defining 15 species and 17 subspecies that have been identified using morphological characteristics, which are variable within and between species. Sclerocactus glaucus (K. Schumann) L.D. Benson (Cactaceae), the Colorado hookless cactus, is rare and protected under the Endangered Species Act. It has a small range around Grand Junction, Colorado, where the few populations are under threat from oil and gas exploration, urbanization, trampling, off road vehicle damage, over-collecting, and hybridization. Due to the low numbers found in the wild along with anthropogenic pressures, the future of S. glaucus and the genetic integrity of the species have been questioned. Additionally, field biologists have frequently observed S. glaucus populations containing individuals with hooked spines. Hooked individuals in S. glaucus populations were thought to be either hybrids or individuals of a closely related species, S. parviflorus Clover and Jotter (Cactaceae). Sclerocactus parviflorus, smallflower fishhook cactus, has prominently hooked central spines and is distributed in Colorado, Utah, Arizona and New Mexico. We used nuclear microsatellites and chloroplast DNA sequence data to examine genetic diversity and structure within S. glaucus and potential hybridization between S. glaucus and S. parviflorus. The results showed that (1) Sclerocactus glaucus remains genetically diverse with low levels of hybridization and many populations show negligible genetic influx from S. parviflorus, (2) two putative S. parviflorus populations were previously misidentified based on morphology and are without question S. glaucus populations, (3) one population showed a high level of hybridization not indicative of typical S. glaucus populations where over 50% of individuals had a hybrid signal, and (4) S. glaucus was found to have a distinct southern genetic cluster located in the Gunnison River and eastern Grand Valley drainages, and a distinct north genetic cluster located in the Colorado River drainage.

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1 - Denver Botanic Gardens, Research and Conservation , 909 York Street, Denver, Colorado, 80206, USA
2 - Denver Botanic Gardens, Research & Conservation, 909 York Street, Denver, CO, 80206, USA
3 - University Of Northern Colorado, 501 20th St, Box 92, Greeley, CO, 80639, USA

gene flow
Genetic structure
population genetics

Presentation Type: Oral Paper:Papers for Topics
Session: 16
Location: Firs North/Boise Centre
Date: Tuesday, July 29th, 2014
Time: 11:15 AM
Number: 16013
Abstract ID:388
Candidate for Awards:None

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