Space and time as axes in intraspecific phylogeography

Abstract

Except in rare instances where DNA might be extracted from a well-preserved and well-dated fossil series, molecular genetic assays normally are confined to living organisms sampled from the present-day horizon in time. Nevertheless, temporal aspects of evolution can be recovered from extant organisms using genomic differences accumulated since shared ancestry. This temporal, phylogenetic dimension of evolution has traditionally been the province of macroevolutionary studies that deal with relationships among species and higher taxa. Phylogenetic perspectives were rarely applied, or even perceived as relevant, at the intraspecific level because of a lack of empirical approaches to assess historical relationships, and because of a widespread perception that phylogeny had no real meaning for potentially interbreeding assemblages of populations. In the last two decades, studies of mitochondrial (mt) DNA have changed this view dramatically by demonstrating that the matriarchal component of intraspecific phylogeny can be estimated empirically (Avise 1989).