Transcriptome data identifies signatures of divergence and gene flow in
pine trees (Pinaceae)
Abstract
Reconstructing the phylogeny of the pine family (Pinaceae) has
historically been problematic because analyses based on morphological
characters and genetic analyses using small numbers of sequences have
produced incongruent results. Such discrepancies may have resulted from
continuous gene flow or genome mixing events among certain pine species.
Here, we reconstructed a species-level tree of the Pinaceae using
genome-wide data from seven pine species. A multi-locus analysis of SNPs
from homologous fragments indicated that Pseudotsuga diverged
from Pinus and Picea 167.26–149.19 million years ago.
Analysis using the isolation-with-migration model identified significant
signals of two-way gene flow between Pinus taeda and Pinus
elliottii (P<0.001), while the
isolation-with-initial-migration model suggested that introgression did
not continue after this divergence. Gene flow has only ever occurred in
the initial period of species divergence. Further analyses highlighted
complex historical genome mixing and hybridization events over the
evolution of the pine family. Thus, the divergence and radiation of the
seven pines was a complex process accompanied by introgression and
historical admixture.