FERGUSON, CAROLYN J.1* AND BARBARA A. SCHAAL2. 1Herbarium and Division of Biology, Kansas State University, Manhattan, KS 66506-4901, 2Department of Biology, Washington University, St. Louis, MO 63130-4899. - Genetic relationships and variation in populations of Phlox pilosa and P. divaricata (Polemoniaceae) in the Ozarks.
Phylogenetic relationships of eastern North American Phlox L.
are complicated, and many studies have suggested this may be due in
part to hybridization. Recently developed molecular phylogenies
(based on markers from the nuclear and chloroplast genomes) showed
patterns of incongruence consistent with hypotheses of hybridization,
although other causes of incongruence were not ruled out. To explore
the potential evolutionary role of hybridization in Phlox, we
are investigating genetic relationships and variation in populations
of two species, P. pilosa L. and P. divaricata L., in
and near the Ozark highlands of the central United States. Phlox
pilosa exhibits striking morphological variation in the Ozarks,
and a distinct subspecies is recognized, P. pilosa subsp.
ozarkana (Wherry) Wherry. Given that P. pilosa and
P. divaricata occasionally come into local contact and
hybridize, it is intriguing to ask whether introgression has occurred
between these species in the Ozark region, potentially contributing to
the variation observed within P. pilosa. A phylogeographic
approach to this question is presented, and preliminary gene trees
based on regions of low-copy number nuclear genes are discussed, along
with some of the challenges of developing and interpreting these
trees. In addition, development of microsatellite markers is
underway, and these methods are outlined. The microsatellite data
will yield information on population genetic structure for comparison
with the gene genealogies. Overall, this approach of carefully
examining genetic data at the population level and interpreting that
information within a larger phylogenetic context will provide insights
that lead to an improved understanding of the evolutionary processes
at play in Phlox.
Key words: hybridization, introgression, Phlox divaricata, Phlox pilosa, Polemoniaceae