Burgess, Michael B. , Campbell, Christopher S. , Talent, Nadia , Frye, Christopher .
Variation in ploidy level in Amelanchier (Rosaceae).
Agamic complexes are likely to be initiated through the evolution of apomixis in allopolyploids. The diploid progenitors of these allopolyploids can be thought of as pillars of agamic complexes. Diploids also serve as new genetic backgrounds for apomixis genes when diploids cross with unrelated polyploid apomicts. It is therefore of great importance to understand ploidy variation and reproductive mode (apomixis or sexuality) within agamic complexes. The identity of the plant for many early Amelanchier chromosome counts is uncertain because of the lack of vouchers. Chromosome counts in Amelanchier are difficult to obtain because meiosis occurs rapidly. In contrast, flow cytometry provides a proven and rapid means of determining nuclear DNA amounts from leaf and overwintering bud tissue. We sampled a broad taxonomic diversity within the genus, including 18 species and 10 entities that do not match formally described taxa. We found tetraploidy to be the most common ploidy level, occurring in 12 species and six undescribed entities. We determined diploidy in six species and one undescribed entity and triploidy in one species and two undescribed entities. Amelanchier pallida, a locally distributed taxon of the western United States, has both diploid and tetraploid individuals that differ in small ways, suggesting autotetraploidy. Most tetraploids do not closely resemble a diploid, and DNA sequence data confirms allotetraploidy in several cases. To infer reproductive mode, we are using flow cytometric DNA measurements of the embryo and endosperm of mature seeds. In Amelanchier, as in Crataegus, there are three genomes in the endosperm to two in the embryo in sexuals, whereas tetraploid apomicts often have 10 or 12 genomes in the endosperm and four in the embryo.
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Amelanchier Systematics and Evolution
1 - University of Maine, School of Biology & Ecology, Orono, ME, 04469-5735, USA
2 - University of Maine, School of Biology and Ecology, Orono, ME, 04469-5735, USA
3 - Royal Ontario Museum - Green Plant Herbarium (TRT), Department of Natural History, 100 Queen's Park, Toronto, Ontario, M5S 2C6, CANADA
4 - Maryland Department of Natural Resources, Natural Heritage Program, 909 Wye Mills Road, Wye Mills, MD, 21679, USA
Presentation Type: Oral Paper:Papers for BSA Sections
Location: Alpine C/Snowbird Center
Date: Monday, July 27th, 2009
Time: 8:45 AM