Stillman, Amy J. , Robertson, Ian , Smith, James F. , Novak, Stephen J. .
Assessing allozyme diversity and polyploidy in the rare southwestern Idaho endemic, Lepidium papilliferum.
Rare plant species typically exhibit low levels of genetic diversity and high levels of genetic differentiation. However, habitat destruction and fragmentation can alter historic patterns of gene flow and increase the risk of genetic erosion in such species. Several mechanisms may counter the adverse genetic consequences of habitat destruction and fragmentation such as polyploidy or an outcrossing mating system, but the role of polyploidy in buffering against genetic erosion has only recently been assessed. Lepidium papilliferum, is a rare, herbaceous plant, endemic to sagebrush steppe communities of southwestern Idaho. The base haploid chromosome number of Lepidium is n=8. Previous studies have shown that North American species of Lepidium are apparently allopolyploids. The purpose of the current study was to determine the chromosome number of L. papilliferum, and to use enzyme electrophoresis to determine whether enzyme banding patterns are consistent with autopolyploid or allopolyploid gene expression. Chromosome counts were conducted on pollen mother cells using the acetocarmine staining technique. Haploid chromosome numbers of pollen mother cells among populations of L. papilliferum ranged from 15 to 17 (n = 15.96 + 0.16). Although not conclusive, preliminary observations on chromosome pairing behavior suggest multivalent formation at meiosis. Enzyme banding patterns and a gene duplication at TPI were consistent with polyploid gene expression. Both balanced and unbalanced heterozygotes were observed at all polymorphic loci except one. There was no evidence of fixed heterozygosity for any of the loci, but neither did we consistently detect multiple alleles (three or more) at any locus. These data are consistent with the available literature on L. papilliferum, and indicate that the species is probably an allotetraploid derived from closely related parental species. Based on the level of genetic diversity detected in L. papilliferum, polyploidy may be buffering against the adverse genetic consequences of habitat destruction and fragmentation.
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1 - Boise State University, Biology, 1910 University Drive, Boise, ID, 83725, USA
2 - Boise State University, Department of Biology, 1910 University Drive, Boise, Idaho, 83725-1515, USA
3 - Department of Biology, Boise State University, 1910 University Drive, Boise, Idaho, 83725-1515, USA
Presentation Type: Oral Paper:Papers for Sections
Location: Lake Huron/Hilton
Date: Monday, July 9th, 2007
Time: 2:45 PM