Spatial Autocorrelation Analysis of Genetic Structure Within White Clover Populations

Abstract

White clover (Trifolium repens L.) populations exhibit high genetic and clonal diversities, while existing for many decades in grazed swards at northern midlatitudes. Genetic structure might exist within rapidly changing populations and might be a factor in creating genetic diversity. Trifoliate leaf samples were taken monthly for two years from up to 37 specific stolon points in quadrats from May to September on three central Pennsylvania farm sites. Random amplified polymorphic DNA (RAPD) profiles for individuals within populations in quadrats were tested by analysis of molecular variance (AMOVA) and spatial autocorrelation. Genetic variance by quadrat population dates in the three pastures ranged from 15 to 74 % and 46 to 80% in 1997 and 1998, respectively. Significant (P < 0.05) overall spatial autocorrelation was found in 26 populations that had clones and in seven populations without clones. No significant autocorrelation was found in 27 and seven populations with and without clones, respectively. The estimated patch size did not change significantly over two growing seasons. Number of clones and patch size was less important in determining genetic structure than variable existence of spatial autocorrelation.Key wordsgenetic diversityclonal diversitypopulation dynamicsDNA markersRAPD markers