Abstract Detail

Systematics Section/ASPT

Sears, Chris [1], McGrath, Kate [1], Whitton, Jeannette [2].

Understanding the role of hybridization in the origin and spread of the North American Crepis agamic complex.

Despite the classic place that the North American Crepis agamic complex holds in the evolutionary literature, few of the hypotheses about the group presented by Babcock and Stebbins 1938 monograph have been tested. In particular, they hypothesized that the seven sexual diploids at the base of the array of auto- and allopolyploid apomicts had strong interfertility barriers that prevented the formation of diploid hybrids. These morphologically and ecologically distinct diploid species act as the progenitors for all polyploid derivatives in the complex and are distributed in two centers of diversity; a northern center of diversity occurring in central Washington State and a southern center, near the intersection of the California, Oregon, and Nevada borders. Here we present an analysis of all known diploids in the group, using molecular data obtained from both plastid and nuclear markers, in addition to data on pollen viability and flow cytometric analysis of DNA content. We infer evolutionary relationships among the diploid members of the complex and probe for the presence of homoploid hybridization using plastid and nuclear markers. Phylogenetic analysis of plastid sequence data from three regions (rpl16 and rps16 introns, and the trnS- trnfM intergenic spacer) support the monophyly of populations from the northern centre of diversity, and separate these from the remainder of diploids, in addition to finding support for the monophyly of most species overall. Additionally, two previously unrecognized diploid morphotypes in the California center of diversity belong to an unresolved clade with C. pleurocarpa and C. occidentalis may be the result of diploid x diploid hybridization. In order to further explore the results of the analysis of plastid sequences, and to clarify the origin of unresolved individuals, we are gathering bi-parentally inherited nuclear SNP markers using genotyping by sequencing.  We seek to determine if these individuals represent examples of stable homoploid hybrid derivatives, recent hybrids, or divergent lineages of non-hybrid ancestry through phylogenetic network and principal component analyses as well as population clustering methods.

1 - University of British Columbia, Department of Botany, 3529-6270 University Boulevard , Vancouver, BC, V6T 1Z4, Canada
2 - University Of British Columbia, Department Of Botany, 3529-6270 UNIV BLVD, VANCOUVER, BC, V6T 1Z4, Canada

Keywords:
Crepis
Genotyping by Sequencing
hybridization 
Agamic Complex.

Presentation Type: Oral Paper:Papers for Sections
Session: 44
Location: Firs North/Boise Centre
Date: Wednesday, July 30th, 2014
Time: 4:45 PM
Number: 44012
Abstract ID:863
Candidate for Awards:Margaret Menzel Award