Neighboring genes predictably share similar evolutionary histories to an extent delineated by recombination. This correlation
should extend across multiple linked genes in a selfing species such as
Arabidopsis thaliana due to its low effective recombination rate. To test this prediction, we performed a molecular population genetics analysis
of nucleotide polymorphism and divergence in chromosomal regions surrounding four low-diversity loci. Three of these loci,
At1g67140, At3g03700, and
TERMINAL
FLOWER1 (
TFL1), have been previously implicated as targets of selection and we would predict stronger correlations in polymorphism between
neighboring loci due to genetic hitchhiking around these loci. The remaining locus, At1g04300, was identified in a study of
linkage disequilibrium surrounding the
CRYPTOCHROME2 (
CRY2) locus. Although we found broad valleys of reduced nucleotide variation around two of our focal genes, At1g67140 and At3g03700,
all chromosomal regions exhibited extreme variation in the patterns of polymorphism and evolution between neighboring loci.
Although three of our four regions contained potential targets of selection, application of the composite-likelihood-ratio
test of selection in conjunction with a goodness-of-fit test supports the selection hypothesis only for the region containing
At3g03700. The degree of discordance in evolutionary histories between linked loci within each region generally correlated
with estimates of recombination and linkage disequilibrium for that region, with the exception of the region containing At1g04300.
We discuss the implications of these data for future population genetics analyses and genomics studies in
A. thaliana.
Keywords Plant - Population genetics - Nucleotide diversity -
TFL1
- Genomics