Antagonistic pleiotropy and the evolution of alternate generations

Despite some general patterns, it is difficult to guess the genetic basis of morphological differences between closely related species or varieties of plants from the magnitude or pattern of the differences between them (Gottlieb, 1984). Sometimes little or no morphological differentiation occurs among taxa that appear from other evidence to represent different phylogenetic or reproductive entities (Shaw, 2001). Alternatively, sometimes substantial morphological differences turn out to be conditioned by one or a few genes (Clausen et al., 1947). Only careful - sometimes tedious - genetic research can reveal the true basis of morphological differences. McHaffie et al. (see pp. 491-500 in this issue) investigated the genetic basis of such differences between two varieties of the fern Athyrium distentifolium, hoping also to clarify ecological reasons for the curious distribution of the two varieties. Their findings have implications for both conservation and basic evolutionary biology.