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Manipulation of Ploidy in Caenorhabditis elegans
Published on: March 15, 2018
Patterns of recurrent evolution and geographic parthenogenesis within apomictic polyploid Easter daises (Townsendia
Stacey Lee Thompson1, Jeannette Whitton
1Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada V6T 1Z4. st@ceythompson.com
Molecular Ecology
|September 14, 2006
Summary
Geographic parthenogenesis in Easter daisies is linked to glacial patterns, not latitude. Asexual polyploids evolved multiple times from sexual ancestors, with glaciation fragmenting sexual diploid ranges.
Area of Science:
- Evolutionary Biology
- Plant Science
- Genetics
Background:
- Parthenogenesis, or asexual reproduction, is common in plants, but its evolutionary origins and geographic distribution are not fully understood.
- Townsendia hookeri (Easter daisy) presents an opportunity to study the transitions from sexual reproduction to asexual polyploidy.
Purpose of the Study:
- To investigate the geographic patterns of parthenogenesis in Townsendia hookeri.
- To determine the number of independent origins of apomictic autopolyploidy from sexual diploid ancestors.
Main Methods:
- Pollen analysis (diameter and stainability) to distinguish sexual diploids from apomictic polyploids.
- Chloroplast DNA sequencing (ndhF gene and trnK intron) to identify haplotypes and infer phylogenetic relationships.
- Geographic distribution analysis of sexual and asexual populations in western North America.
Main Results:
- Sexual diploids were found in two refugia: Colorado/Wyoming and northern Yukon/Beringia.
- Apomictic polyploids inhabited formerly glaciated areas, with origins traced to both northern and southern sexual lineages.
- Phylogenetic analyses indicated at least four independent origins of apomictic polyploidy.
Conclusions:
- Glaciation patterns, rather than latitudinal trends, likely drove the geographic distribution of parthenogenesis in Townsendia hookeri.
- The fragmentation of sexual diploid ranges by glaciation facilitated the establishment of asexual polyploid lineages.
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