A first complete phylogenomic hypothesis for diploid blueberries (Vaccinium section Cyanococcus)

The premise of the study: The true blueberries, (Vaccinium sect.
Cyanococcus; Ericaceae), endemic to North America, have been intensively
studied for over a century. However, with species estimates ranging from 9
to 24 and much confusion regarding species boundaries, this ecologically
and economically valuable group remains inadequately understood at a basic
evolutionary and taxonomic level. As a first step toward understanding the
evolutionary history and taxonomy of this species complex, we present the
first phylogenomic hypothesis of the known diploid blueberries. Methods:
We used flow cytometry to verify the ploidy of putative diploid taxa and a
target-enrichment approach to obtain a genomic dataset for phylogenetic
analyses. Results: Despite evidence of gene flow, we found that a primary
phylogenetic signal is present. Monophyly for all morphospecies was
recovered, with two notable exceptions: one sample of V. boreale was
consistently nested in the V. myrtilloides clade, and V. caesariense was
nested in the V. fuscatum clade. One diploid taxon, Vaccinium pallidum, is
implicated as having a homoploid hybrid origin. Conclusions: This
foundational study represents the first attempt to elucidate evolutionary
relationships of the true blueberries of North America with a phylogenomic
approach and sets the stage for multiple avenues of future study such as a
taxonomic revision of the group, the verification of a homoploid hybrid
taxon, and the study of polyploid lineages within the context of a diploid
phylogeny.