Abstract Detail

Ecological Section

Garani, Alice [1], Whitton, Jeannette [2].

Evidence for reproductive interference between sexual and apomictic populations of the Easter daisy (Townsendia hookeri, Asteraceae).

Townsendia hookeri (Asteraceae) is a diminutive, perennial herbaceous species that thrives on the foothills of the Rocky Mountains, from central Colorado to British Columbia, with a disjunct distribution in Yukon Territory. Outside Yukon, sexual populations are only found in the southernmost portion of the species range (Colorado and southern Wyoming), whereas apomictic populations span from southern Wyoming to Canada. Moreover, in T. hookeri the reproductive strategy has been shown to be tightly coupled with ploidy level, where diploid plants are invariably outcrossers and polyploidy is always associated with asexuality in the form of apomixis. The goal of this study was to expand our understanding of the factors that have shaped and maintain the geographical distribution of sexual and apomictic populations of Townsendia hookeri along the Rocky Mountains. Having documented that polyploid plants retain the ability to produce some viable pollen, we were interested in understanding the potential effects of apomictic pollen grains on sexual seed-parents. We hypothesized that asymmetric reproductive interference could explain why different cytotypes never coexist at the population level, and it could also contribute to explaining the absence of polyploids in the southern portion of the species range. To test the effects of reproductive interference between cytotypes, we performed a crossing experiment involving six natural populations located in southern Wyoming, over the course of one season. We assessed reproductive success based on seed set (proportion of viable seeds per flower head), achene mass, germination success, as well as seedling survival. In addition, a subset of the seedlings obtained from sexual-asexual crosses was analyzed to detect the presence of polyploid offspring using flow cytometry. Our results indicate that apomictic pollen can successfully fertilize diploid mother plants, leading to a reduction in seed set and to the formation of progeny of varying ploidy levels, from diploid to tetraploid.

1 - The University of British Columbia , Botany, 6270 University Boulevard , room #3529 , Vancouver, BC, V6T 1Z4 , Canada
2 - University Of British Columbia, Department Of Botany, 3529-6270 UNIV BLVD, VANCOUVER, BC, V6T 1Z4, Canada

Keywords:
apomixis
polyploidy
Townsendia hookeri
Asteraceae
cross pollination
reproductive interference
flow cytometry.

Presentation Type: Oral Paper:Papers for Sections
Session: 1
Location: Firs South/Boise Centre
Date: Monday, July 28th, 2014
Time: 8:30 AM
Number: 1003
Abstract ID:748
Candidate for Awards:Ecological Section Best Graduate Student Paper