Koontz, Jason , Segraves, Kari .
AFLP data refute hypothesis of hybrid speciation in Delphinium.
Hybrid speciation is thought to be an important process driving plant speciation. One of the classic examples of hybrid speciation is the California gypsum-loving larkspur, Delphinium gypsophilum (Ranunculaceae). Previous molecular studies of hybridization in D. gypsophilum using ITS DNA sequence and allozyme data are equivocal because few markers distinguish the purported parental and hybrid species. Here we use a combination of hyper-variable AFLP markers and chloroplast DNA sequences to test whether this classic example of hybrid speciation follows predictions. We examine multiple populations of D. gyposphilum, its hypothesized parents D. recurvatum and D. hesperium ssp. pallescens, and other geographically close species (D. hansenii ssp. ewanianum and ssp. hansenii, D. hesperium ssp. hesperium, D. parishii, and D. parryi). Chloroplast DNA sequences indicate that D. gypsophilum and D. recurvatum share identical cpDNA haplotypes and D. parishii and D. hesperium ssp. pallescens differ from each other by one nucleotide substitution. Although these data do not reject the hypothesis of hybrid speciation, they are also consistent with recent speciation. Over 1,700 AFLP markers, however, demonstrate monophyly of D. gypsophilum and its purported parental taxa and show only a close relationship between D. gypsophilum and D. recurvatum. There was no evidence supporting hybridization between D. recurvatum and D. hesperium ssp. pallescens as they were distantly related in the AFLP tree and substantially differentiated from the hypothesized hybrid species. We suggest that the sharing of chloroplast DNA haplotypes can readily be explained by incomplete lineage sorting in a recently derived group, and that hybridization was unlikely to have played a role in the evolution of D. gypsophilum.
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1 - Augustana College, Department of Biology, 639 38th Street, Rock Island, Illinois, 61201, USA
2 - Syracuse University, Biology, 130 College Place, Syracuse, NY, 13422, USA
Presentation Type: Oral Paper:Papers for Topics
Location: Williford A/Hilton
Date: Tuesday, July 10th, 2007
Time: 11:00 AM