Stillman, Amy , Robertson, Ian , Smith, James F. , Novak, Stephen J. .
Allozyme diversity in Lepidium papilliferum (Brassicaceae), a southwest Idaho endemic.
Lepidium papilliferum is a polyploid, insect pollinated, herbaceous annual or biennial endemic to the sagebrush steppe habitat of southwest Idaho. Occurring in specialized microsites called slick spots, populations naturally exhibit a patchy distribution. Habitat destruction and fragmentation due to overgrazing, invasive species, change in fire frequency, urban and agricultural development and off-road vehicle use has lead to a decline in this species. Enzyme electrophoresis was used to determine the amount and distribution of genetic variability within and among 15 populations of L. papilliferum, including 11 from the Snake River Plain and four disjunct populations from the Bruneau Desert. Enzyme banding patterns and a gene duplication are consistent with polyploid gene expression. Across all populations 10 of 11 (91%) loci were polymorphic, with an average of 4.1 alleles per locus. Compared to other endemic or narrowly distributed plant species, L. papilliferum exhibits high levels of percent polymorphism and allelic richness, most likely due to polyploidy. Within-population allozyme diversity differed for the two regions. On average, 82% of loci were polymorphic (%P) in the populations from the Bruneau Desert, whereas 59% of loci were polymorphic in the Snake River Plain populations. Disjunct populations also displayed slightly higher average number of alleles per locus (A=2.5) compared to Snake River Plain populations (A=2.2). Regional differences could be the result of historical events, habitat variability, or differences in the activity of insect pollinators. When analyzed separately, %P and A in the Snake River Plains populations were positively correlated with population size. Management of L. papilliferum should include preserving large tracts of sagebrush steppe habitat where slick spots are located and maintaining large populations sizes, especially in areas such as the Bruneau Desert region that still harbor high amounts of genetic diversity.
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1 - Boise State University, Department of Biology, 1910 University Drive, Boise, Idaho, 83725-1515, USA
2 - Department of Biology, Boise State University, 1910 University Drive, Boise, Idaho, 83725-1515, USA
Presentation Type: Oral Paper
Date: Monday, August 15th, 2005
Time: 10:45 AM