Multiple introductions and population structure during the rapid expansion of the invasive Sahara mustard (Brassica tournefortii)

Abstract

The specific mechanisms that result in the success of any species invasion case are difficult to document. Reproductive strategies are often cited as a primary driver of invasive success, with human activities further facilitating invasions by, for example, acting as seed vectors for dispersal via road, train, air, and marine traffic, and by producing efficient corridors for movement including canals, drainages, and roadways. Sahara mustard ( Brassica tournefortii ) is a facultative autogamous annual native to Eurasia that has rapidly invaded the southwestern United States within the past century, displacing natives, and altering water‐limited landscapes in the southwest. We used a genotyping‐by‐sequencing approach to study the population structure and spatial geography of Sahara mustard from 744 individuals from 52 sites across the range of the species’ invasion. We also used herbaria records to model range expansion since its initial introduction in the 1920s. We found that Sahara mustard occurs as three populations in the United States unstructured by geography, identified three introduction sites, and combined herbaria records with genomic analyses to map the spread of the species. Low genetic diversity and linkage disequilibrium are consistent with self‐fertilization, which likely promoted rapid invasive spread. Overall, we found that Sahara mustard experienced atypical expansion patterns, with a relatively constant rate of expansion and without the lag phase that is typical of many invasive species.

Auto-taxonomy of Brassica tournefortii Gouan. (Brassicaceae) in Egypt

“…The results revealed low genetic similarity among the studied forms (Table 5). This genetic diversity is consistent with the results of Winkler et al (2019), who claimed that the low genetic diversity of B. tournefortii is a result of selffertilization. The retrieved molecular data from the ISSR tool reflect the presence of genotypic variation in the studied Forms (1-5), which is expressed as species morpho-plasticity.…”

Sahara mustard as a major threat to desert biodiversity in the southwest United States and the need to integrate contemporary methods to understand its biology

“…This metric allows heterozygosity to be measured on an identical scale for each subpopulation by accounting for sample sizes of individuals/subpopulations and number of loci typed within subpopulations (Coltman et al, 1999;Roberts et al, 2006). This is also the standard method for calculating F IS per the popular R packages adegenet and hierfstat, (Goudet, 2005;Jombart, 2008 (Winkler, 2017) to make claims about data and analyses in the related article published in Ecology and Evolution at the center of this discussion (Winkler et al, 2019). These claims are unsupported because the data mentioned were written in 2017, almost two years before Winkler et al (2019) was accepted for publication in Ecology and Evolution.…”

“…This is also the standard method for calculating F IS per the popular R packages adegenet and hierfstat, (Goudet, 2005;Jombart, 2008 (Winkler, 2017) to make claims about data and analyses in the related article published in Ecology and Evolution at the center of this discussion (Winkler et al, 2019). These claims are unsupported because the data mentioned were written in 2017, almost two years before Winkler et al (2019) was accepted for publication in Ecology and Evolution. Methods were revised, data were rescrutinized, and supplementary materials were all updated during the peer review process at two journals before being accepted by Ecology and Evolution.…”

Genetic and comparative mapping of Lupinus luteus L. highlight syntenic regions with major orthologous genes controlling anthracnose resistance and flowering time

“…This technology utilizes a Nextera (Illumina, Inc.) reaction to fragment genomic DNA and then amplification using modified primers which are complementary; therefore, only fragments containing this recognition site are amplified. The result is a randomized collection of DNA fragments that represents a sub-fraction of the tested genome 32,33 . Applications using NextRAD include studies of genetic diversity of the Andean lupin, Lupinus mutabilis 34 , and an insect 33,35 .…”

“…The result is a randomized collection of DNA fragments that represents a sub-fraction of the tested genome 32,33 . Applications using NextRAD include studies of genetic diversity of the Andean lupin, Lupinus mutabilis 34 , and an insect 33,35 . This, together with the phenotypic exploration of novel genetic variability for anthracnose resistance and flowering time genes, was used to go forward.…”