Ann Willyard1, David S Gernandt2, Kevin Potter3, Valerie Hipkins4, Paula Marquardt5, Mary Frances Mahalovich6, Stephen K Langer7, Frank W Telewski8, Blake Cooper9, Connor Douglas9, Kristen Finch9, Hassani H Karemera9, Julia Lefler9, Payton Lea9, Austin Wofford9. 1. Hendrix College, 1600 Washington Ave, Conway, Arkansas 72032 USA willyard@hendrix.edu. 2. Departmento de Botánica, Instituto de Biología, Universidad Nacional Autónoma de México, A.P. 70-233, Mexico City 04510 México. 3. Department of Forestry and Environmental Resources, North Carolina State University, Research Triangle Park, North Carolina 27709 USA. 4. National Forest Genetics Laboratory, USDA Forest Service, Placerville, California 95667 USA. 5. USDA Forest Service, Northern Research Station, Institute for Ecosystem Studies, 5985 Highway K, Rhinelander, Wisconsin 54501 USA. 6. Genetic Resource Program, Northern, Rocky Mountain, Southwestern, and Intermountain Regions, USDA Forest Service, Moscow, Idaho 83843 USA. 7. 301 North Main #214, Layton, Utah 84041 USA. 8. W. J. Beal Botanical Garden, Department of Plant Biology, Michigan State University, East Lansing, Michigan 48824 USA. 9. Hendrix College, 1600 Washington Ave, Conway, Arkansas 72032 USA.
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 reflect the taxonomy of this checkered classification than their current treatment as varieties of P. ponderosa.
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 reflect the taxonomy of this checkered classification than their current treatment as varieties of P. ponderosa.
Authors: Brian T Sullivan; Amanda M Grady; Richard W Hofstetter; Deepa S Pureswaran; Cavell Brownie; Daniel Cluck; Tom W Coleman; Andrew Graves; Elizabeth Willhite; Lia Spiegel; Dwight Scarbrough; Andrew Orlemann; Gerardo Zúñiga Journal: J Chem Ecol Date: 2021-01-06 Impact factor: 2.626