Systematics Section / ASPT
Meyer, Therese , Windham, M. D. .
Distinct species or hybrid swarm?: Investigating the taxonomic status of Cronquist’s Woodyaster.
Xylorhiza cronquistii Welsh & Atwood is a rare Woodyaster from southern Utah that has been proposed for federal listing. Its recognition as a distinct species is not without controversy. Several authors have noted that X. cronquistii is morphologically intermediate between X. confertifolia (Cronq.) T. J.Watson and X. tortifolia (Torr. & Gray) Greene var. imberbis (Cronq.) T. J.Watson, and all known populations occur where these species are sympatric. In order to determine the appropriate taxonomic status of Xylorhiza cronquistii, this taxon and its near congeners were analyzed using morphology, cytogenetics, enzyme electrophoresis, nrDNA sequences, reproductive studies and artificial hybridization. Morphological intermediacy, isozyme and DNA additivity, and evidence of homoploid gene flow indicate recent and ongoing hybrid origins for Xylorhiza cronquistii. In addition, artificial hybrids between the putative parents X. confertifolia and X. tortifolia var. imberbis are easily formed and essentially identical to X. cronquistii. Nearly all individuals of X. cronquistii show extensive segregation of genetic traits in progeny arrays. However, a single, isolated plant from Wahweap Creek produced progeny arrays that were morphologically stable and showed fixed heterozygosity at PGI. This suggests that at least some of the hybrids are true breeding, a critical step in the evolution of X. cronquistii as a distinct species.
1 - University of Utah, Utah Museum of Natural History, 1390 E. President's Circle, Salt Lake City, Utah, 84112-0050, USA
Presentation Type: Paper
Location: Cottonwood A (Snowbird Center)
Date: Wednesday, August 4th, 2004
Time: 4:15 PM