Genetic Variation in Invasive Populations of Yellow Toadflax (Linaria vulgaris) in the Western United States

Abstract

Intraspecific genetic variation may contribute significantly to invasiveness and control problems, but has been characterized to date in relatively few invasive weed species. We examined 56 intersimple sequence repeat (ISSR) loci in 220 individuals from 11 invading populations of yellow toadflax sampled across five western states. All populations showed high levels of genetic diversity. Estimated values for Shannon's diversity measure ranged from 0.217 to 0.388, and for expected heterozygosity from 0.178 to 0.260. Nei's total gene diversity index (HT), on the basis of all individuals across all populations, was 0.267. Partitioning of genetic variance using analysis of molecular variance revealed 1.7% of genetic variation among regional population groups, 29.1% among populations within groups, and 69.2% within populations, consistent with expectations for an outcrossing species but suggesting little geographic differentiation. Pairs of adjacent individuals identical at all ISSR loci that appeared to be ramets of a single clone were detected in only one population. This indicates that patch expansion in yellow toadflax is driven more by sexual reproduction via seed than by rhizomatous clonal spread, at least at the spatial scale of sampling for this study. Eight populations had significant values for Mantel's R at P = 0.05, suggesting some fine-scale positive genetic structuring, possibly from restricted gene flow. Population clustering on the basis of Nei's genetic distance between populations and unweighted pair group method with arithmetic mean did not reflect geographic location. It is likely that multiple introductions of this species have occurred across the Intermountain West, followed by extensive genetic recombination. High levels of genetic diversity within yellow toadflax populations pose management challenges, as already seen in reports of variable response to herbicide application and limited impacts of biocontrol agent releases.

Morphological, molecular and biological evidence reveal two cryptic species inMecinus janthinusGermar (Coleoptera, Curculionidae), a successful biological control agent of Dalmatian toadflax,Linaria dalmatica(Lamiales, Plantaginaceae)

“…In contrast, only rare and low‐density populations were reported on L. vulgaris in Canada (McClay & Hughes, 2007; R. De Clerck‐Floate, personal communication) and the U.S.A. (S. Sing, personal communication), some 20 years after the introduction. The limited establishment of M. janthinus on L. vulgaris in North America may be correlated with high levels of genetic diversity within and among invasive yellow toadflax populations in North America recently reported by Ward et al (2008). However, the limited establishment of the introductions on L. vulgaris and contrasting success on L. dalmatica raise the question of to what extent M. janthinus may be in need of taxonomic revision.…”

High genetic differentiation among wild populations of alien Medicago sativa in Lithuania

“…Population were defined as a contiguous distribution of alfalfa forming a patch with the length of transect through it at least 250 m [35,36]. Leaf samples were collected from flowering plants.…”

Genetic diversity and population structure in four Cirsium (Asteraceae) species

“…Various molecular markers have been used in genetic diversity studies of different plant species including Cirsium (e.g., Ayres & Ryan 1997;Balloux & Lugon-Moulin 2002;Hettwer & Gerowitt 2004;Ward et al 2008), but microsatellites (SSR) and Inter simple sequences repeat (SSR) markers are reported efficient markers for such investigations in Cirsium (Bodo Slotta et al 2006;Sheidai et al 2012). To our knowledge this is the first report of its kind from Iran.…”