Genotype Diversity of Salsola Tragus and Potential Origins of a Previously Unidentified Invasive Salsola From California and Arizona

Abstract

Various Salsola spp. have been introduced to the USA, and some of these are considered noxious or invasive in certain regions. The genus is taxonomically challenging, and recent morphological, cytological, and molecular work has shown that an unknown taxon, previously identified as S. tragus, but recently temporarily designated as Type B, with unknown origins, exists in California and Arizona. Type B's origins and identity are a point of concern for biological control efforts, as it is much less affected by fungal biological control agents than the sympatric invasive S. tragus. Initial studies in 2005 indicated that Type B is morphologically very similar to S. kali subsp. austroafricana which has been collected in southern Africa. Here we use DNA sequence data from a PEPC intron to compare USA and Old World specimens, and results indicate that S. kali subsp. austroafricana is genetically identical to Type B and distinct from S. tragus. It is unclear if 5'. kali subsp. austroafricana is native to southern Africa or to the northern hemisphere of the Old World, and further investigations in both regions are needed.

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

“…The resultant template was sequenced on a Beckman CEQ 2000XL DNA Analysis System using reagents and protocols supplied by the manufacturer and the same primers mentioned above. Heterozygotic genotypes were cloned and sequenced in an earlier study to determine the haplotypes involved (Gaskin et al 2006). The earlier study included 88 individuals from four taxa relevant to this study (S. tragus, S. kali subsp.…”

“…Known haplotypes from the earlier study were used to estimate haplotypes of the 11 heterozygotes in this study. Haplotype sequences were aligned by hand using SE-Al software (Rambaut 1996) and haplotype sequences are available in GenBank (accession numbers are in Gaskin et al 2006). Haplotypes from this study were combined with those from Gaskin et al (2006) and arranged manually into a most parsimonious network (Fig.…”

“…Collection information for other species is listed in Gaskin et al (2006). Following extraction of DNA by standard methods (Ryan and Ayres 2000), amplification of the intron between the fourth and fifth exon of the low copy PEPC gene utilized the primer pair ppcx4f (5 0 -ACTCCACAGGATGAGATGAG-3 0 ) and ppcx5r (5 0 -GCAGCCATCATTCTAGCCAA-3 0 ).…”

“…Young (1988) suggested that there might have been a second introduction to South Dakota during the early years of the infestation. Molecular comparison of S. tragus from California and Ukraine indicated that plants from the two regions were similar according to isoenzymic, RAPD and ISSR analyses (Ryan et al 2007) and phosphoenolpyruvate carboxylase intron DNA sequences (Gaskin et al 2006).…”

“…Recently, Type B was found to have the same DNA sequence as S. kali subsp. austroafricana Aellen from South Africa and Namibia (Gaskin et al 2006). Rilke (1999) considered S. kali subsp.…”