Data from: Parallel Pleistocene amphitropical disjunctions in a parasitic plant and its host

PREMISE OF THE STUDY: Aphyllon is a clade of holoparasites that includes
closely related North American and South American species parasitic on
Grindelia. Both Aphyllon (Orobanchaceae) and Grindelia (Asteraceae) have
amphitropical disjunctions between North America and South America;
however, the timing of these patterns and the processes to explain them
are unknown. METHODS: Chronograms for the Orobanchaceae and Grindelia and
their relatives were constructed using fossil and secondary calibration
points, one of which was based on the inferred timing of horizontal gene
transfer from a papilionoid legume into the common ancestor of Orobanche
and Phelipanche. Elevated rates of molecular evolution in the
Orobanchaceae have hindered efforts to determine reliable divergence time
estimates in the absence of a fossil record. However, using a horizontal
gene transfer event as a secondary calibration overcomes this limitation.
These chronograms were used to reconstruct the biogeography of Aphyllon,
Grindelia, and relatives using a DEC+J model implemented in RevBayes. KEY
RESULTS: Aphyllon had two amphitropical dispersals from North America to
South America, while Grindelia had a single dispersal. The dispersal of
the Aphyllon lineage that is parasitic on Grindelia (0.40 Ma) took place
somewhat after Grindelia began to diversify in South America (0.93 Ma).
Using a secondary calibration based on horizontal gene transfer, we infer
more recent divergence dates of holoparasitic Orobancheae than previous
studies. CONCLUSIONS: Parallel host–parasite amphitropical disjunctions in
Grindelia and Aphyllon illustrate one means by which ecological
specialization may result in nonindependent patterns of diversity in
distantly related lineages. Although Grindelia and Aphyllon both dispersed
to South America recently, Grindelia appears to have diversified more
extensively following colonization. More broadly, recent Pleistocene
glaciations probably have also contributed to patterns of diversity and
biogeography of temperate northern hemisphere Orobancheae. We also
demonstrate the utility of using horizontal gene transfer events from
well-dated clades to calibrate parasite phylogenies in the absence of a
fossil record.