Abstract Detail

Population Genetics

Rushworth, Catherine [1], Windham, Michael D [2], Mitchell-Olds, Tom [3].

Apomixis and hybridization in the wild mustard Boechera retrofracta.

Classic evolutionary theory states that sexual and asexual reproduction cannot coexist. Yet apomixis (asexual reproduction via seed) is widespread, known from over 400 plant genera in 40 different plant families. In most of these groups, apomixis is strictly associated with hybridization and polyploidy. However, in the short-lived perennial mustard species Boechera retrofracta, apomixis occurs at the diploid level as well, co-existing with sexual reproduction in multiple populations. What evolutionary and ecological factors permit apomixis and sex to coexist in these populations? Results from a three-year, four-location reciprocal transplant show that fitness differences between the two groups do not maintain either reproductive mode across the landscape. Although sexually reproducing plants produce significantly more seeds per fruit than hybrid apomicts, the total seed output of each group does not differ. However, apomicts experience higher herbivory than sexually reproducing individuals, which may potentially impact the evolutionary trajectory of hybrid apomicts over long time scales. We also examined the hypothesis that apomixis, associated with hybridization in this largely self-fertilizing genus, may be maintained by heterosis. Results from a greenhouse experiment comparing fitness of F2 B. retrofracta x B. stricta hybrids and their self-fertilized parents show that, on average, parents enjoy higher survival to maturity and higher survival to reproduction. However, surviving hybrids have higher fecundity than their selfed parental genotypes. Although all hybrids display fecundity higher than the mean value of their progenitors, cumulative fitness deviates from this pattern in some hybrid lineages. This work suggests that apomixis may be maintained by heterosis in this group, but that the effect strongly depends on the identity of hybrid parents.

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

Keywords:
apomixis
hybridization 
Boechera
Brassicaceae
Heterosis
Evolutionary genetics
Asexual reproduction.

Presentation Type: Oral Paper:Papers for Topics
Session: 6
Location: Pines South/Boise Centre
Date: Monday, July 28th, 2014
Time: 10:45 AM
Number: 6009
Abstract ID:800
Candidate for Awards:Margaret Menzel Award