Systematics Section / ASPT
Johnson, Leigh A. , Wilken, Dieter .
Are you my sister? Divergent and reticulate species relationships in a putatively monophyletic Collomia (Polemoniaceae).
Collomia is readily distinguished from other Polemoniaceae and circumscribes about 14 usually well-marked species. Collomia is also one of the few genera in the phlox family to be thoroughly sampled in chemical (flavonoid, anthocyanin) and micromorphological (pollen, seed) studies. Although, explicit phylogenetic analyses have not been conducted, sister relationships have been hypothesized for several species pairs, three sections have been erected, and diversification patterns are putatively strictly divergent within this genus. Against this background, representative sampling in family wide analyses of DNA sequence variation reveal a surprisingly close relationship between Collomia and Navarretia. This unexpected result includes a weak inference that Collomia is paraphyletic with respect to a monophyletic Navarretia. To test the several hypotheses outlined above and provide a robust framework for comparative studies, we sequenced the nuclear ITS region and plastid trnL intron – trnF spacer, matK, and 5’ trnK intron regions from all species of Collomia, two thirds of Navarretia, and four species of Allophyllum (outgroup). Independent parsimony analyses of the nuclear and chloroplast regions weakly fail to resolve Collomia as monophyletic. Combined analyses, however, reveal a monophyletic Collomia among the most parsimonious results. Addition to the data matrix of only one of several putative morphological synapomorphies for Collomia consistently resolves this genus as monophyletic. Within Collomia, several lineages that correspond with morphological groupings provide the basis for a revised sectional classification. Discordance between nuclear- and plastid-based genealogies indicates three unexpected instances of ancient hybrid speciation or introgression among species. Growing data sets from three single-copy nuclear regions also bear on these findings. For example, evidence for the allopolyploid origin of the single polyploid Collomia species is provided by the presence in its genome of divergent alleles with affinities to two different species.
1 - Brigham Young University, Department of Integrative Biology, P.O. Box 5181, Provo, Utah, 84602, USA
2 - Santa Barbara Botanic Gardent, 1212 Mission Canyon Road, Santa Barbara, California, 93105, USA
Presentation Type: Paper
Location: Cottonwood B (Snowbird Center)
Date: Tuesday, August 3rd, 2004
Time: 3:45 PM