Abstract Detail

Molecular Ecology and Evolution

Grusz , Amanda Lee [1], Windham, Michael D [2], Pryer, Kathleen M [2].

Is premeiotic chromosome duplication a significant source of genotypic diversity in apomictic ferns? .

Over the last century, our understanding of the evolution and maintenance of sex has improved exponentially. As a byproduct of this research, we are beginning to appreciate the complex and dynamic nature of asexual reproduction among eukaryotes. Nevertheless, asexual organisms remain burdened by a reputation for being “evolutionary dead ends”. They are portrayed as mere clones, lacking the genotypic diversity critical for adaption by natural selection. And while apomictic lineages often exhibit high levels of heterozygosity, the limited ability to generate recombinants has been considered fatal. Such generalizations fail to consider either the diversity of reproductive pathways involved, or the growing body of contradictory evidence. Recent genetic studies of several apomictic lineages have reported relatively high population-level genotypic diversity and revealed that such lineages often occupy broader ecological and geographical landscapes than their sexual relatives. This has led investigators to speculate on possible source(s) of genetic diversity in apomicts. While many hypothesize that multiple origins, accumulation of new mutations, and/or hybridization with sexual relatives might explain unexpectedly high levels of genetic variation in apomicts, others have suggested that some apomictic lineages may generate genetic variablity via subsexual processes involving the pairing of non-sister (homeologous) chromosomes. Few studies have investigated homeologous pairing in apomictic plants and those that do have focused on the offspring of single sporophytes. In this study, we assess the degree to which homeologous chromosome pairing is impacting genotypic diversity in the apomictic triploid fern Myriopteris lindheimeri (Pteridaceae). Our analyses focus on allelic variation at 8 newly-developed microsatellite loci for a broad geographic sampling of the species encompassing 41 sporophytes and 847 of their gametophytic offspring. The primary goals of this study were to 1) assess whether premeiotic chromosome doubling facilitates the pairing of homeologous chromosomes in apomictic ferns, leading to the production of genetically variable offspring, and 2) document the extent to which this phenomenon occurs in natural populations.

1 - Duke University, Box 90338, Durham, NC, 27708, USA
2 - Duke University, Department of Biology, Box 90338, Durham, NC, 27708, USA

Keywords:
apomixis
Döpp-Manton sporogenesis
genetic diversity
subsexual processes
cheilanthoid ferns.

Presentation Type: Oral Paper:Papers for Topics
Session: 11
Location: Firs North/Boise Centre
Date: Monday, July 28th, 2014
Time: 4:15 PM
Number: 11011
Abstract ID:816
Candidate for Awards:Margaret Menzel Award