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Abstract Detail


Colloquia: Systematic and Evolutionary Perspectives on Apomixis

Cushman, Kevin R. [1].

Frequency of apomixis in Amelanchier (Rosaceae).

Amelanchier can generate agamic complexes, wherein hybrid offspring of novel appearance are perpetuated via apomixis, thus leading to intricate patterns of diversity. Crucial to understanding these complex evolutionary pathways is discovery and systematic study of sexual diploids and documentation of ploidy-level variation and the occurrence of sexuality and apomixis. We used flow cytometric measurements of embryo and endosperm DNA to assess the frequency of apomixis across a wide taxonomic sample. All sampled diploids displayed a 2x embryo and 3x endosperm, which is the expected pattern of sexual reproduction. All tetraploids had 4x embryos, and all but three samples had endosperm within the 10x or 12x range. Amelanchier apomicts create chromosomally reduced pollen, and 10x and 12x endosperm values are consistent with fertilization of two polars by one or two sperm, respectively. We infer this pattern to represent apomictic, pseudogamous reproduction. The three samples not falling within a 10x or 12x range had 6x endosperm, which is the expected result of sexual reproduction. We also report for the first time apomictic triploids in Amelanchier, with 3x embryos and 8x endosperm. Flow-cytometry shows that apomixis in polyploid Amelanchier is nearly obligate, confirming our earlier findings for Amelanchier polyploids. Because of the efficiency of flow cytometry, we have greatly expanded our sample of the genus. The shift to polyploidy (at least allopolyploidy) is coincident with considerable reproductive versatility, with apomixis, self-fertility, and the retention of sexuality primarily via pollen. This shift, coupled with hybridization, also spawns the taxonomic complexity for which agamic complexes are known.

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Related Links:
Systematics and Evolution of Amelanchier


1 - University of Maine, School of Biology & Ecology, Orono, ME, 04469-5735, USA

Keywords:
none specified

Presentation Type: Symposium or Colloquium Presentation
Session: C4
Location: 551A/Convention Center
Date: Wednesday, August 4th, 2010
Time: 2:00 PM
Number: C4003
Abstract ID:672


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