Tests for adaptive RAPD variation in population genetic structure of wild barley, Hordeum spontaneum Koch.

Abstract

We examined the adaptive importance of RAPD variation in the population genetic structure of wild barley, Hordeum spontaneum. The test involved (1) a nested sampling design with four population groups representing four distinct environments; and (2) a comparison of observed variation with that expected as a result of natural selection. Analyses of selection on fitness-related traits by reciprocal introductions served as guidelines for the expected pattern of RAPD variation. We found no concordance between the observed pattern of population genetic structure and that expected under the null hypothesis of environment-specific natural selection. There was no relationship between genetic distance and environmental similarity; none of 54 putative loci exhibited an allele distribution in accordance with that expected and no favoured epistatic allele combinations were detected across the four environments. The fact that environmentally induced adaptation, detected by fitness-related traits, was not reflected in inter-population RAPD structure (1) strongly enhances the neutralist viewpoint and (2) casts doubt on the notion that significant correlations between some environmental parameters and allele frequencies in one or more loci are evidence of selection on the latter. 100 Thermo Cycler under the following conditions: 94°C for 3 min, followed by 45 cycles of 94°C for 1 min, Van Rossum F, Vekemans X, Meerts P, Gratia E, Lefebvre C. 1997. Allozyme variation in relation to ecotypic differentiation and population size in marginal populations of Silene nutans. Heredity 7 8 552-560. Waser NM. 1987. Spatial genetic heterogeneity in a population of the montane perennial herb Delphinium nelsonii. Heredity 58: 249-256. Williams JGK, Kubelik AR, Livak KJ, Rafalski J A , Tingey SV. 1990. DNA polymorphisms amplified by arbitrary primers are useful as genetic markers. Nucleic Acid Research 18: 6531-6535. Zangerl AR, Bazzaz FA. 1984. Niche partitioning between two phosphoglucoisomerase genotypes in Amaranthus retmflexus. Ecology 65: 218-222. 6 1177-1187. 109: 511-528. 709-712.

Distinguishing adaptive from nonadaptive genetic differentiation: comparison of QST and FST at two spatial scales

“…The level of regional subdivision in two molecular markers was comparable with population subdivision within a region, while in quantitative traits it was significantly (almost 2 Â ) higher. Disagreement between the structure of variation at two scales (regions and populations within regions) in quantitative traits and two molecular markers, and the pattern of molecular variation reported here and in Volis et al (2001Volis et al ( , 2003 point at selective neutrality of overall allozyme and RAPD variation. However, effects of selection or gene hitch-hiking on allozyme and RAPD variation cannot be ruled out completely.…”

“…RAPD analysis was performed using DNA from 14 plants per population as described in Volis et al (2001).…”

“…The 20 sampled populations (five populations per region) were analyzed for allozyme and RAPD variation (Volis et al, 2001(Volis et al, , 2003 and quantitative traits (this paper). As a multiyear reciprocal introduction of seeds and seedlings conducted at one (pivot) location per region revealed local adaptation (Volis et al, 2002d), interpretation of the observed quantitative, allozyme and RAPD differentiation can be performed on the basis of a known effect of region-specific natural selection.…”

Fine-scale spatial genetic structure in a predominantly selfing plant: role of seed and pollen dispersal

“…This species has been intensively studied for the extent and structure of genetic diversity at a wide range of spatial scales from tens to hundreds and even thousands of kilometers (Brown et al, 1978a;Turpeinen et al, 2001Turpeinen et al, , 2003Volis et al, 2001bVolis et al, , 2002aVolis et al, , 2003Volis et al, , 2005Morrell et al, 2003). At large geographical scale, selection and colonization history are predominant evolutionary forces, and a great deal of information about these processes has been gained for wild barley.…”

Analysis of Genetic Diversity of Chukar Partridge (Alectoris chukar) Populations in Khorasan-e-Razavi Province of Iran by RAPD-PCR

“…In applying this method, it is assumed that populations are in Hardy-Weinberg equilibrium, that polymorphic bands segregate in the Mendelian way, and that marker alleles from different loci do not comigrate to the same position in the gel (D'Amato and Corach 1996). The problem of low reproducibility in early RAPD analyses can now be overcome through improved laboratory techniques and band scoring procedures (Nybom 2004;Volis et al 2001). RAPD markers, despite their limitations, provide a useful approach for evaluating a population's genetic differentiation, particularly in species that are poorly known genetically (Nybom 2004).…”