Mating systems and population structure in two closely related species of the wheat group: II. Environmental factors and population structure

Correlations between environmental factors and means and variances of 36 quantitative characters were calculated for seven populations of a selfing species, Triticum longissimum, and five populations of the closely related outcrossing species T. speltoides. In T. longissimwn more characters were correlated with environmental factors than in T. speltoides. This was attributed to the high interpopulation differences in the means and environmental conditions among T. longissimum populations, presumably mediated by effective isolation between these selfing populations. Between the T. speltoides populations there are small differences in the population structure or local environmental conditions. This could be due to gene flow between populations. In T. longissimum, correlations between growth characteristics and environmental conditions suggest that selection for more economical growth and for smaller units has been mediated by harsher conditions. In those T. Ion gissimum populations where the annual fluctuations are smaller the variances within families are also smaller. On theoretical grounds this would be associated with decreased heterozygosity.