SCHAAL, BARBARA A. Department of Biology, Washington University, St. Louis, MO 63130. - Plant population biology and systematics.
Traditionally population genetics and systematics have been separate
fields, with distinct conceptual frameworks, tools, and statistics.
Hennig drew a clear distinction between the reticulate genealogical
relationships among individuals and populations on one hand, and the
hierarchical phylogenetic relationships among divergent species or
taxa on the other. For many plant species, such distinctions blur.
The genetic structuring of plant populations is strongly affected by
phylogenetic history, and the phylogenetic relationships among species
are frequently confounded by gene migration between species. The
identification of molecular markers that vary within species, as well
as reductions in costs and time associated with DNA sequencing have
set the stage for a blending of the two fields. Haplotype variation
at a non-recombining locus can be historically ordered to produce a
gene genealogy. Genealogical analysis coupled with the theoretical
framework of coalescence theory can be used to estimate the roles of
migration, founder effects and range expansion during the formation
and subsequent establishment of species. Such studies hold great
promise for understanding the interplay of phylogenetic history and
population level process in shaping distinct evolutionary lineages.
Key words: gene genealogies, phylogeography, speciation