Systematics Section / ASPT
Barnes, Donna M. , Johnson, Leigh A. .
Comparative Micromorphology of the Kelloggioid Navarretias (Polemoniaceae).
The three species of Gilia section Kelloggia have been removed from this traditionally heterogeneous genus and placed in either Allophyllum or Navarretia. Affinity with Allophyllum was argued based on suggested similarity between these groups in pollen pore distribution and exine patterning, trichomes, and seed shape and color. Affinity with Navarretia was inferred from comparative DNA sequence analysis of both chloroplast and nuclear genes. Differences in these hypotheses of relationship may be attributable to one or more of the following factors: 1) real discordance between morphological and DNA-based inferences; 2) inaccuracies in generalizations of morphological similarity; 3) differences in methods of taxonomic inference; and 4) breadth of taxa considered when inferring relationship. Real discordance between morphology and DNA sequences has important implications for character evolution and therefore this explanation merits critical examination. As a step toward explicit tests of discordance across a range of morphological features, we report our study of pollen, seed, and trichome characters surveyed from Allophyllum, Collomia, Navarretia, and the species formerly placed in Gilia section Kelloggia. Our results show pollen exine patterns in Navarretia similar to both types found in section Kelloggia, and greater morphological variation in trichome and seed features than previously reported. These findings underscore the importance of broad taxonomic consideration when inferring relationship with either morphology or DNA. Accurate characterization of morphological similarity is also critical. Other features, such as the lack of spinescent leaves in section Kelloggia, may indeed show discordance with DNA-based inferences. However, the characters expressly used to support affinities with Allophyllum do not do so. Rather, these features either support or are equivocal regarding the placement of these former gilias in Navarretia.
1 - Brigham Young University, Department of Integrative Biology, P.O. Box 5181, Provo, Utah, 84602, USA
comparative plant morphology
Presentation Type: Poster
Location: Special Event Center (Cliff Lodge)
Date: Tuesday, August 3rd, 2004
Time: 12:30 PM