Tumbleweed (Salsola, section Kali) species and speciation in California

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.

Speciation by genome duplication: Repeated origins and genomic composition of the recently formed allopolyploid speciesMimulus peregrinus

“…), and Salsola ryanii in the Amaranthaceae (Ayres et al. ). Generalizations of the evolutionary changes observed during polyploid speciation clearly will benefit from the study of additional young allopolyploids.…”

“…Recently formed allopolyploid species provide opportunities to investigate the earliest stages of speciation by genome duplication. Examples of recently formed allopolyploid species (< 200 years old) include only a handful of species in four families: Senecio cambrensis, S. eboracensis , Tragopogon mirus and T. miscellus (Soltis et al 2004) in the Asteraceae, Cardamine x insueta and C. x schulzii in the Brassicaceae (Mandakova et al 2013), Spartina anglica in the Poaceae (Ainouche et al 2004), and Salsola ryanii in the Amaranthaceae (Ayres et al 2009). Generalizations of the evolutionary changes observed during polyploid speciation clearly will benefit from the study of additional young allopolyploids.…”

Nomenclatural Notes on Some Alliances of the Halophytic Vegetation of Southern Ural and the Caspian Lowlands

“…was described in Australia, and as such it is different from European S. tragus subsp. tragus (see Borger et al 2008, Hrusa & Gaskin 2008, Ayers et al 2009, Chinnock 2010. The taxon reminiscent of S. australis, found in the Caspian deserts probably to the Salsola tragus s.…”

Does an expressed sequence tag (EST) library ofSalsola iberica(tumbleweed) help to understand plant responses to environmental stresses?

“…They are commonly found in disturbed areas, uncultivated grain fields and roadsides throughout the continental United States. 4 Thought to have Eurasian origins, this weed has become naturalized in North America, Australia and elsewhere. 5 For example, S. australis is a major weed in Australia.…”