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 populatio ns is strongly affected by phylogenetic history, and the phylogenetic relat ionships 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, hav e 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 genealo gy. Genealogical analysis coupled with the theoretical framework of coalesc ence theory can be used to estimate the roles of migration, founder effects and range expansion during the formation and subsequent establishment of s pecies. Such studies hold great promise for understanding the interplay of phylogenetic history and population level process in shaping distinct evolu tionary lineages.