Abstract Detail

Colloquia: Systematic and Evolutionary Perspectives on Apomixis

Talent, Nadia [1].

Evolution and apomixis (agamospermy) in Crataegus (Rosaceae): Perhaps we should not discount the dihaploids.

We are studying the additional diversity center of Crataegus in southwestern Canada that was identified in 2002 by J.B. Phipps and R.J. O’Kennon. Results so far indicate a great diversity of tetraploid forms with near-obligate apomixis. The rare diploids appear to be dihaploids, derived from particular rare tetraploids that are only partially apomictic. These diploids are not yet known to be fertile. Hypotheses based on these data have profound implications for phylogenetic analysis of the tetraploids. One possibility is to dismiss the diploids and the partial apomicts as an aberration and unlikely to persist. The diversification of the apomictic lines may simply be due to antiquity, which is consistent with the pre-glacial extent of series Douglasianae. A second possibility is that an almost extinct diploid species interbreeds with polyploids, so that finding any ancestral genotypes would be enormously valuable. A third possibility, if the dihaploids are fertile, is that they cross with tetraploids to produce triploids, and hence tetraploids, an effect similar to increasing the rate of sexual reproduction. This raises the question of whether persistent dihaploids could be important, possibly including some of the widespread self-incompatible diploids elsewhere in the range of the genus, which we have so far assumed to be ancestral to the self-compatible polyploids. Although self-incompatible diploids probably never evolve from self-compatible diploid populations (Igic et al. 2007), there is probably little constraint with polyploid apomicts whose self-compatibility is due to single-locus gametophytic competitive-interference effects (de Nettancourt 2001; Huang et al. 2008). Genetic assortment from tetraploids that are probably allopolyploids would obscure the relationships among their diploid descendants. De Wet & Harlan (1970) found that similar dihaploids in Dichanthium promote hybridization at the diploid level, but this is not obvious in Crataegus. Further investigation of the partially apomictic tetraploids, their offspring and nearby diploids should thus be an important and immediate research priority.

Broader Impacts:

1 - University of Toronto and Royal Ontario Museum, Green Plant Herbarium (TRT), Department of Natural History, 100 Queen's Park, Toronto, ON, M5S 2C6, Canada

Keywords:
Apospory
hybridization
Rosaceae
Maloideae
Pyrinae.

Presentation Type: Symposium or Colloquium Presentation
Session: C4
Location: 551A/Convention Center
Date: Wednesday, August 4th, 2010
Time: 2:30 PM
Number: C4005
Abstract ID:341