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Patterns of genetic diversity and candidate genes for ecological divergence in a homoploid hybrid sunflower, Helianthus anomalus.

Abstract：

:Natural hybridization accompanied by a shift in niche preference by hybrid genotypes can lead to hybrid speciation. Natural selection may cause the fixation of advantageous alleles in the ecologically diverged hybrids, and the loci experiencing selection should exhibit a reduction in allelic diversity relative to neutral loci. Here, we analyzed patterns of genetic diversity at 59 microsatellite loci associated with expressed sequence tags (ESTs) in a homoploid hybrid sunflower species, Helianthus anomalus. We used two indices, ln RV and ln RH, to compare variation and heterozygosity (respectively) at each locus between the hybrid species and its two parental species, H. annuus and H. petiolaris. Mean values of ln RV and ln RH were significantly lower than zero, which implies that H. anomalus experienced a population bottleneck during its recent evolutionary history. After correcting for the apparent bottleneck, we found six loci with a significant reduction in variation or with heterozygosity in the hybrid species, compared to one or both of the parental species. These loci should be viewed as a ranked list of candidate loci, pending further sequencing and functional analyses. Sequence data were generated for two of the candidate loci, but population genetics tests failed to detect deviations from neutral evolution at either locus. Nonetheless, a greater than eight-fold excess of nonsynonymous substitutions was found near a putative N-myristoylation motif at the second locus (HT998), and likelihood-based models indicated that the protein has been under selection in H. anomalus in the past and, perhaps, in one or both parental species. Finally, our data suggest that selective sweeps may have united populations of H. anomalus isolated by a mountain range, indicating that even low gene-flow species may be held together by the spread of advantageous alleles.

journal_name

Mol Ecol

journal_title

Molecular ecology

authors

Sapir Y,Moody ML,Brouillette LC,Donovan LA,Rieseberg LH

doi

10.1111/j.1365-294X.2007.03557.x

subject

Has Abstract

pub_date

2007-12-01 00:00:00

pages

5017-29

issue

eissn

0962-1083

issn

1365-294X

pii

MEC3557

journal_volume

pub_type

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Patterns of genetic diversity and candidate genes for ecological divergence in a homoploid hybrid sunflower, Helianthus anomalus.