Tumbleweed (Salsola, section Kali) species and speciation in California |
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Authors: | Debra Ayres Frederick J Ryan Eva Grotkopp John Bailey John Gaskin |
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Institution: | (1) Department of Evolution and Ecology, University of California, Davis, CA, USA;(2) 3625 No. Van Ness Blvd., Fresno, CA 93704, USA;(3) Department of Biology, University of Leicester, Leicester, UK;(4) United States Department of Agriculture, Agricultural Research Service, Northern Plains Agricultural Research Laboratory, 1500 North Central Avenue, Sidney, MT, USA |
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Abstract: | Tumbleweeds (Salsola species, section Kali) are road side and rangeland pest plants throughout the 48 contiguous states in the US. Three described tumbleweed species
and two undescribed Salsola taxa occur in California. The known species are Russian thistle, Salsola tragus, introduced from Eurasia in the 1800s, Russian barbwire thistle, S. paulsenii, which grows in the desert regions of California, and is also native to Eurasia, and the recently identified S. kali subspecies austroafricana, possibly native to South Africa. Our goals were to investigate karyology, genome size, and molecular genetic affinities
of the described species and the other taxa within their ranges in California using recently developed microsatellite loci,
dominant nuclear DNA markers (RAPD and ISSR), and DNA sequence data. Chromosome counts and genome size assessments made with
flow cytometry were compared. These analyses indicated that one undescribed taxon is a new allopolyploid hybrid between S. tragus and S. kali subspecies austroafricana, and the other undescribed taxon appears to be a complex hybrid involving all three described species. The invasion potentials
for the hybrid taxa are unknown. Tumbleweeds are the focus of biological controls efforts but the identification of suitable
agents for the hybrid taxa may be problematic because of the large amount of genetic variability encompassed within this evolving
Salsola complex. |
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Keywords: | Allopolyploid speciation Invasive hybrids Salsola tragus |
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