Reconciling extremely strong barriers with high levels of gene exchange in annual sunflowers

Sambatti, Julianno B. M., Strasburg, Jared L., Ortiz-Barrientos, Daniel, Baack, Eric J. and Rieseberg, Loren H. (2012) Reconciling extremely strong barriers with high levels of gene exchange in annual sunflowers. Evolution, 66 5: 1459-1473. doi:10.1111/j.1558-5646.2011.01537.x

Author Sambatti, Julianno B. M.
Strasburg, Jared L.
Ortiz-Barrientos, Daniel
Baack, Eric J.
Rieseberg, Loren H.
Title Reconciling extremely strong barriers with high levels of gene exchange in annual sunflowers
Journal name Evolution   Check publisher's open access policy
ISSN 0014-3820
Publication date 2012-05
Sub-type Article (original research)
DOI 10.1111/j.1558-5646.2011.01537.x
Volume 66
Issue 5
Start page 1459
End page 1473
Total pages 15
Place of publication Oxford, United Kingdom
Publisher Wiley-Blackwell Publishing
Collection year 2013
Language eng
Formatted abstract
In several cases, estimates of gene flow between species appear to be higher than we might predict given the strength of interspecific barriers separating these species pairs. However, as far as we are aware, detailed measurements of reproductive isolation have not previously been compared with a coalescent-based assessment of gene flow. Here, we contrast these two measures in two species of sunflower, Helianthus annuus and H. petiolaris. We quantified the total reproductive barrier strength between these species by compounding the contributions of the following prezygotic and postzygotic barriers: ecogeographic isolation, reproductive asynchrony, niche differentiation, pollen competition, hybrid seed formation, hybrid seed germination, hybrid fertility, and extrinsic postzygotic isolation. From this estimate, we calculated the probability that a reproductively successful hybrid is produced: estimates of Phyb range from 10−4 to 10−6 depending on the direction of the cross and the degree of independence among reproductive barriers. We then compared this probability with population genetic estimates of the per generation migration rate (m). We showed that the relatively high levels of gene flow estimated between these sunflower species (Nem= 0.34-0.76) are mainly due to their large effective population sizes (Ne > 106). The interspecific migration rate (m) is very small (<10−7) and an order of magnitude lower than that expected based on our reproductive barrier strength estimates. Thus, even high levels of reproductive isolation (>0.999) may produce genomic mosaics.
Keyword Effective population size
Reproductive isolation
Species divergence
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: Official 2013 Collection
School of Biological Sciences Publications
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