Changes in allozyme frequencies inFestuca ovinapopulations after a 9‐year nutrient/water experiment

Abstract

Summary 1The grass Festuca ovina is an important constituent of the species-rich`alvar' grasslands on the Baltic island of O È land. Levels of allozyme polymorphism are high and variation is known to be correlated with habitat variation (soil moisture, pH and depth). 2 A 9-year ®eld experiment on species diversity provided replicate plots (in three sites) that had been subjected to six di erent experimental treatments (control; N P K; P K; N K; K; water). 3 Samples of F. ovina were collected and analyses of deviance were used to investigate associations between allele frequencies, at each of four polymorphic loci, and the nutrient/water treatments. We also used the models to estimate predicted values for the alleles in di erent nutrient/water treatments and in interactions involving the nutrient/water treatments and additional explanatory variables (vegetation height and clipping). 4 There were signi®cant allozyme frequency di erences between samples of F. ovina from the six di erent nutrient/water treatments in the grassland experiment. Frequencies in the fertilized or watered plots had diverged from those in the control plots. There were also signi®cant allele±habitat associations (after the removal of site e ects), especially at the Pgi-2 locus. 5 Soil moisture was the only variable that was common to this study and an earlier study of variation in F. ovina in natural habitats. In natural populations, the Pgi-2-2 allele was signi®cantly associated with soil moisture and was more common in dry habitats. Our ®ndings that the frequency of the Pgi-2-2 allele was signi®cantly a ected by the nutrient/water treatments, and that it was rarest in the treatment that involved the addition of extra water, were therefore as predicted. 6 The study supports the conclusion, from an earlier study of populations in unmanipulated grassland habitats, that selection is contributing to the ®ne-scale patterning of genetic variation in the alvar populations of F. ovina.

Landscape genetics of alpine-snowbed plants: comparisons along geographic and snowmelt gradients

“…In addition to phenological segregation, differential natural selection along a snowmelt gradient might be important for the development of spatial patterns of genetic variation. Some allozyme studies at microgeographic scales suggest that changes in gene frequencies reflecting environmental gradients are indeed caused by natural selection (eg Allard et al, 1993;Linhart and Grant, 1996;Prentice et al, 2000). In our study, only species having excess homozygotes within populations showed a significant genetic structure along the phenological gradient.…”

The structuring of quantitative genetic variation in a fragmented population of Briza media (Poaceae)

“…Many grasses have been reported to evolve locally adapted populations as a response to spatially varying selection forces (Prentice et al 1995;Linhart and Grant 1996). For example, grazed populations of Poa pratensis have been found to be genetically shorter than ungrazed populations, indicating a selective advantage of short stature under grazing management (Kemp 1937).…”

Allozyme Variation in Diploid, Polyploid and Mixed-Ploidy Populations of the Pilosella alpicola Group (Asteraceae): Relation to Morphology, Origin of Polyploids and Breeding System

“…Indeed, the distributional and genetic pattern of many mountain species suggested biogeographical connections between the Bulgarian mountains and the Southern Carpathians (Reed et al 2004;Puşcaş et al 2008;Varga and Schmitt 2008;Schmitt 2009). It has been demonstrated that, despite the assumed selective neutrality of allozyme markers (e.g., Kimura 1968), environmental factors (temperature, humidity) can promote a shift in allele frequencies in populations through directional selection mechanisms (Koehn and Hilbish 1987;Karl and Avise 1992;Prentice et al 2000;Karl et al 2009). Thus, more similar environmental conditions between the southeastern Carpathians and the Balkans might be another reason of grouping of southeastern Carpathian P. ullepitschii and P. rhodopea populations.…”