Genetic variation between and within populations of a perennial grass: Arrhenatherum elatius

Abstract

Three pairs of adjacent populations of Arrhenatherum elatius were studied both for their genetic diversity and for their genotypic structure. Each pair consisted of one population on a normal soil type and the other on spoil from mining.Using morphological characters as well as allozyme markers, the genetic diversity in populations on toxic soils (mining spoil) was found to be higher than in populations in normal pasture. This suggests that the tolerant populations have been built up from a large number of tolerant genotypes emanating from normal pasture populations in which tolerance genes are not uncommon. The higher genetic diversity of the tolerant population has then been maintained by the spatial heterogeneity of toxic habitats, or less intense selective forces of biotic origin (e.g. intraspecific competition) or by a more open breeding system. Variations in allozymes gave interesting clues. No clear cut differences in the genetic structure between pairs of populations were found, but there was a higher heterozygote deficit in denser populations.This might arise from inbreeding because of a more limited gene flow in dense populations. The higher genetic diversity of sparse populations on toxic soil might partly result from the effectively greater gene flow into these populations in which individuals must trap pollen from longer distances than do individuals in dense populations.

The effects of heavy metal pollution on genetic diversity in zinc/cadmium hyperaccumulator Sedum alfredii populations

“…Mengoni et al (2000) found that the genetic diversity of the uncontaminated population was the same as that of the contaminated population in Silene paradoxa. Similar results were also reported in other metal-tolerant species such as Agrostis stolonifera (Wu et al 1975) and Arrhenatherum elatius (Ducousso et al 1990). However, the reduction of genetic diversity was also found in some other tolerant populations such as Deschampsia cespitosa (Bush and Barrett 1993) and Armeria maritima (Vekemans and Lefèbvre 1997).…”

Genetic structure of Suillus luteus populations in heavy metal polluted and nonpolluted habitats

“…Although some studies report the detection of bottleneck effects in recently established tolerant populations (Bush & Barrett 1993; Vekemans & Lefèbvre 1997; Nordal et al . 1999), most exposed populations appear to be at least as variable as nonexposed populations (Ducousso et al . 1990; Lefèbvre & Vernet 1990; Mengoni et al .…”

Human influences on evolution, and the ecological and societal consequences

“…Some contexts that generate strong selection were discussed in §2a, especially hunting/harvesting and some coevolutionary arms races. However, even exceptionally strong selection does not always deplete relevant genetic variation [73,74], especially when the selection is variable in time and space. Some contexts that can greatly reduce population size include habitat loss (e.g.…”