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Abstract Detail

Colloquia: Systematic and Evolutionary Perspectives on Apomixis

Lo, Eugenia [1].

Correlation of genome size with environment and its contribution to the ecological success of polyploid apomicts in the Pacific Northwest hawthorns (Crataegus; Rosaceae).

Apomixis is one mechanism that contributes to short-term reproductive success in polyploids. However, it is unclear how polyploid apomicts achieve ecological advantages under natural environments. To examine the possible influences of genome size (the 2C nuclear DNA content), reproductive system, and abiotic factors on the prevalence and success of polyploids, a total of 284 individuals of the black-fruited hawthorns collected from 27 localities in the Pacific Northwest were used to investigate three types of correlations: (1) genome size in leaf, endosperm (µend) and embryo (µemb), as to reflect the link between ploidy level and reproductive system in this group; (2) genome size with the distribution range of the samples as a proxy of dispersal limit; and (3) genome size with climate as a proxy for adaptive constraints. A significant and positive correlation was detected between the leaf DNA content and the µend to µemb ratio of our seed samples (r=0.67; p<0.001). In triploids and tetraploids, the megagametophytes appear to remain unreduced in the polar cells and fuse with the pollen nucleus, resulting in a higher DNA content in the endosperm. Samples of high endosperm DNA content show a significantly greater variance in geographical space (as described by the first principle component of the latitude, longitude, and elevation data) than those of low values (F2,36=5.13; p=0.005). These results suggest that polyploid apomicts have a wider dispersal range than diploid sexuals. Such a distributional pattern could also be explained by the significant differences detected in the variance of climate space (as described by the first principle component of seven climate variables) between samples of high and low endosperm DNA content (F2,36=5.13; p=0.005), implying a greater climatic tolerance. Given the known relationships among these individuals, the evolution of increased genome size resulting from polyploidy and apomixis could enhance adaptation and colonization within the species complex, probably through physiological adjustments particularly under adverse environment.

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1 - Yale University, Ecology & Evolutionary Biology, PO Box 208106, New Haven, CT, 06520

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Presentation Type: Symposium or Colloquium Presentation
Session: C4
Location: 551A/Convention Center
Date: Wednesday, August 4th, 2010
Time: 2:45 PM
Number: C4006
Abstract ID:393


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