Pollution and Genetic Structure of North American Populations of the Common Dandelion (Taraxacum Officinale)

Abstract

Assessing the genetic structure of natural populations differentially impacted by anthropogenic contaminants can be a useful tool for evaluating the population genetic consequences of exposure to pollution. In this study, measures of genetic diversity at variable-number-tandem-repeat loci in six dandelion populations (3 urban and 3 rural) showed patterns that may have been influenced by exposure to environmental contaminants. Mean genetic similarity among individuals within a population was significantly and positively correlated with increasing levels of airborne particulate matter (< or = 10 microm, PM10) and soil concentrations of four metals (Cd, Fe, Ni and Pb). In addition, mean genetic similarity was always significantly higher at the urban sites compared to rural sites. There was a significant negative correlation between the number of genotypes at a site and increasing amounts of PM10, concentrations of five soil metals (Cd, Cu, Fe, Ni and Pb), leaf tissue levels of Fe and a significant positive correlation between the extent of clonality at a site and levels of PM10 and soil concentrations of five metals (Cd, Cu, Fe, Ni and Pb). Although, this study does not directly establish a causal link between the specific contaminants detected at the study sites and differences in genetic diversity, our data are consistent with the hypothesis that pollution-induced selection has contributed in some fashion to the lower genetic diversity found at the urban sites.

Comparison of remote consequences in Taraxacum officinale seed progeny collected in radioactively or chemically contaminated areas

“…Allozyme analysis for T. officinale coenopopulations showed an increased phenotypic diversity in the gradient of the chemical or radioactive contamination that is due to the growing proportion of rare morphs in the buffer and impact populations along with decreased clonal diversity. This agrees well with previously reported observation of genetic structure alterations under HM -Glowacki et al 1999), spruce, silver fir and beech (Longauer et al 2004) and the dandelion (Rogstad et al 2003;Keane et al 2005). In the Chernobyl accident area, nonlinear dependence between intensity of the mutation process in herbaceous plant populations and doses of chronic radiations was found (Abramov et al 1992;Geraskin et al 2003;Beresford et al 2005).…”

“…The seeds of this species are easy to cultivate because they are large in size, have high germination rates and rest period is absent. This species was previously widely used as a test object in the field of ecology and genetics (Rogstad et al 2003;Kashin et al 2005;Keane et al 2005).…”

Patterns of genetic variation in anthropogenically impacted populations

“…Thus, I suggest that pollution can have both positive and negative effects through different mechanisms. On the one hand, pollution may decrease population size (Posthuma and Van Straalen 1993) or increase selection for homozygous genotypes (Keane et al 2005), which would decrease genetic variation. Indeed, some studies have clearly found reductions in genetic variation because of pollution (e.g., Ma et al 2000;Belfiore and Anderson 2001).…”

“…On the one hand pollution might decrease genetic variation owing to genetic drift and inbreeding, particularly in cases of increased mortality that decrease population size (Posthuma and Van Straalen 1993;Belfiore and Anderson 2001). Genetic variation may also decrease owing to selection for pollutiontolerant genotypes (Keane et al 2005). On the other hand, populations chronically exposed to chemical pollutants may experience an increase in genetic variation due to increased mutation rates (Yauk and Quinn 1996;Baker et al 2001) or selection for heterozygotes (i.e., overdominant hypothesis; see Bickham et al 2000).…”

Effect of fluoride pollution on genetic variability ofLarix gmelinii(Pinaceae) in East Siberia

“…The effects of heavy metals on the genetic diversity of plant populations are well known. In particular, heavy metals were assumed to contribute to the lower genetic diversity found at the urban sites (Keane et al 2005). It has been shown that some plant species had lower values of genetic diversity in the heavy metal-tolerant ecotypes compared with non-tolerant ones (Bush and Barrett 1993;Vekemans and Lefèbvre 1997;Nordal et al 1999;Mengoni et al 2001).…”