Data from: Ancestral reconstruction of sunflower karyotypes reveals non-random chromosomal evolution

Mapping the chromosomal rearrangements between species can inform our
understanding of genome evolution, reproductive isolation, and speciation.
Here we present a novel algorithm for identifying regions of synteny in
pairs of genetic maps, which is implemented in the accompanying R package,
syntR. The syntR algorithm performs as well as previous methods while
being systematic and repeatable and can be used to map chromosomal
rearrangements in any group of species. In addition, we present a
systematic survey of chromosomal rearrangements in the annual sunflowers,
which is a group known for extreme karyotypic diversity. We build
high-density genetic maps for two subspecies of the prairie sunflower,
Helianthus petiolaris ssp. petiolaris and H. petiolaris ssp. fallax. Using
syntR, and we identify blocks of synteny between these two subspecies and
previously published high-density genetic maps. We reconstruct ancestral
karyotypes for annual sunflowers using those synteny blocks and
conservatively estimate that there have been 7.9 chromosomal
rearrangements per million years – a high rate of chromosomal evolution.
Although the rate of inversion is even higher than the rate of
translocation in this group, we further find that every extant karyotype
is distinguished by between 1 and 3 translocations involving only 8 of the
17 chromosomes. This non-random exchange suggests that specific
chromosomes are prone to translocation and may thus contribute
disproportionately to widespread hybrid sterility in sunflowers. These
data deepen our understanding of chromosome evolution and confirm that
Helianthus has an exceptional rate of chromosomal rearrangement that may
facilitate similarly rapid diversification.