Data from: Deep sequencing of amplicons reveals widespread intraspecific hybridization and multiple origins of polyploidy in big sagebrush (Artemisia tridentata)

PREMISE OF THE STUDY: Hybridization has played an important role in the
evolution and ecological adaptation in diploid and polyploid plants.
Artemisia tridentata (Asteraceae) tetraploids are extremely widespread and
of great ecological importance. These tetraploids are often taxonomically
identified as A. tridentata ssp. wyomingensis, or as autotetraploids of
diploid subspecies tridentata and vaseyana. Few details are available as
to how these tetraploids are formed or how they are related to diploid
subspecies. METHODS: We used amplicon sequencing to assess phylogenetic
relationships among three recognized subspecies: tridentata, vaseyana and
wyomingensis. DNA sequence data from putative genes were pyrosequenced and
assembled from 329 samples. Nucleotide diversity and putative haplotypes
were estimated from the high-read coverage. Phylogenies were constructed
from Bayesian coalescence and neighbor-net network analyses. KEY RESULTS:
Analyses support distinct diploid subspecies of tridentata and vaseyana in
spite of known hybridization in ecotones. Nucleotide diversity estimates
of populations compared to the total diversity indicate the relationships
are predominately driven by a small proportion of the amplicons.
Tetraploids, including subspecies wyomingenesis, are polyphyletic
occurring within and between diploid subspecies groups. CONCLUSIONS:
Artemisia tridentata is a species comprised of phylogenetically distinct
diploid progenitors and a tetraploid complex with varying degrees of
phylogenetic and morphological affinities to the diploid subspecies. These
analyses suggest tetraploids are formed locally or regionally from diploid
tridentata and vaseyana populations via autotetraploidy, followed by
introgression between tetraploid groups. Understanding the phylogenetic
versus ecological relationships of A. tridentata subspecies will have
bearing on how to restore these desert ecosystems.