Abstract
PREMISE OF THE STUDY: Molecular genetic evidence can help delineate taxa in species complexes that lack diagnostic morphological characters.
Pinus ponderosa (Pinaceae; subsection
Ponderosae ) is recognized as a problematic taxon: plastid phylogenies of exemplars were paraphyletic, and mitochondrial phylogeography suggested at least four subdivisions of
P. ponderosa. These patterns have not been examined in the context of other
Ponderosae species. We hypothesized that putative intraspecific subdivisions might each represent a separate taxon. METHODS: We genotyped six highly variable plastid simple sequence repeats in 1903 individuals from 88 populations of
P. ponderosa and related
Ponderosae (
P. arizonica, P. engelmannii, and
P. jeffreyi). We used multilocus haplotype networks and discriminant analysis of principal components to test clustering of individuals into genetically and geographically meaningful taxonomic units. KEY RESULTS: There are at least four distinct plastid clusters within
P. ponderosa that roughly correspond to the geographic distribution of mitochondrial haplotypes. Some geographic regions have intermixed plastid lineages, and some mitochondrial and plastid boundaries do not coincide. Based on relative distances to other species of
Ponderosae, these clusters diagnose four distinct taxa. CONCLUSIONS: Newly revealed geographic boundaries of four distinct taxa (
P. benthamiana, P. brachyptera, P. scopulorum, and a narrowed concept of
P. ponderosa) do not correspond completely with taxonomies. Further research is needed to understand their morphological and nuclear genetic makeup, but we suggest that resurrecting originally published species names would more appropriately refl ect the taxonomy of this checkered classifi cation than their current treatment as varieties of
P. ponderosa.
Keywords
Pinaceae,
Pinus,
plastid microsatellites,
ponderosa pine,
Ponderosae
Citation
Willyard, Ann; Gernandt, David S.; Potter, Kevin; Hipkins, Valerie; Marquardt, Paula; Mahalovich, Mary Frances; Langer, Stephen K.; Telewski, Frank W.; Cooper, Blake; Douglas, Connor; Finch, Kristen; Karemera, Hassani H.; Lefler, Julia; Lea, Payton; Wofford, Austin. 2016.
Pinus ponderosa: A checkered past obscured four species. American Journal of Botany. 104 (1): 1-21.