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

Abstract

The structuring of quantitative genetic variation can have a significant impact on the adaptive potential and long-term viability of species in changing landscapes. The present study of the grass Briza media investigated the relationships between patterns of heritable variation in phenotypic characters and descriptors of landscape structure, land-use history and local habitat conditions in a landscape known to have undergone a progressive and massive loss of semi-natural grassland habitat over the past 300 years. Our analyses revealed significant levels of heritable variation for characters related to overall plant size and spikelet size-number ratio, with estimates of broad-sense heritability ranging between 29 and 34%. Differences between demes accounted for a minor fraction of the total variation. In contrast to previous allozyme results from the same plant material, which suggest significant impacts of both neutral and selective processes, neither the deme-specific means nor the heritabilities for the phenotypic characters were consistently associated with landscape structure or land-use history. The results of the study indicate that the structuring of quantitative variation has been relatively insensitive to habitat fragmentation, at least over the time frame considered in this study system.