Dickinson, Tim , Zarrei, Mehdi , Kuzmina, Maria , Stefanovic, Sasa .
Mixed success with DNA barcoding of hawthorns (Crataegus L., Rosaceae).
The genus Crataegus is one in which the promises of DNA barcoding make this technology extremely attractive. Crataegus species can be notoriously hard to identify on the basis of morphology. Both flowering and fruiting specimens from a given individual may be needed for a definitive identification, in addition to field observations of features that are not preserved in herbarium material (e.g.color of the undehisced anther, time course of fruit color development). We have drawn on a reference collection of voucher specimens and field-collected silica gel dried tissue of North American and Eurasian Crataegus taxa representing 50 species, and have used two standard barcode loci (rbcL and matK) and two supplementary markers (ITS2 and psbA-trnH) that have been proposed for plants. Our results suggest that routine DNA barcoding may have limited utility in Crataegus, and possibly also within Rosaceae subtribe Pyrinae (equivalently, the fleshy-fruited members of subfamily Maloideae). We were unable to get sequences of matK, but succeeded with psbA-trnH, rbcLa, and ITS2. Despite earlier successes using psbA-trnH together with three other cpDNA spacer regions in phylogenetic studies, psbA-trnH by itself (185 sequences for 49 species) yielded an NJ tree with virtually no resolution. Greater resolution was obtained using rbcLa (189 sequences for 49 species), as four species (18 accessions) were resolved in the NJ tree. These results with cpDNA loci are not surprising in view of how poorly these loci resolve genera in the Pyrinae, to say nothing of species in Crataegus. Fewer sequences (118, for 40 species) were obtained with ITS2 amplified from genomic DNA. Nevertheless, with ITS2 at least nine species were resolved as monophyletic, and other clades comprised members of a single series or section of the genus. However, one diploid species and a polyploid species complex were each polyphyletic on the NJ tree, suggesting the amplification of more than one ITS2 paralog.
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LO, E. Y. Y., STEFANOVIC, S., and DICKINSON, T. A. (2007). Molecular reappraisal of relationships between Crataegus and Mespilus (Pyreae, Rosaceae) - two genera or one? Syst. Bot. 32(3): 596-616.
1 - Royal Ontario Museum, Natural History, Green Plant Herbarium (TRT), 100 Queen's Park, Toronto, ON, M5S 2C6, Canada
2 - Biodiversity Institute of Ontario, University of Guelph, 50 Stone Rd East, Guelph, ON, N1G 2W1, Canada
3 - University Of Toronto At Mississauga, Department Of Biology, 3359 Mississauga Rd N, Mississauga, ON, L5L 1C6, Canada
Presentation Type: Oral Paper:Papers for Sections
Location: Lindell C/Chase Park Plaza
Date: Tuesday, July 12th, 2011
Time: 11:15 AM