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Systematics of Penstemon section Ericopsis, a group of plant species native to the Intermountain West

Wenzel, Aaron
http://rave.ohiolink.edu/etdc/view?acc_num=osu1471533204

Abstract Details

2016, Doctor of Philosophy, Ohio State University, Evolution, Ecology and Organismal Biology.
Penstemon Mitchell (Plantaginaceae) is the largest plant genus endemic to North America with approximately 280 species. Most species are only relatively recently diverged from one another, which has left questions about taxonomy and systematics in Penstemon unanswered. This dissertation considered one section in the genus, Ericopsis Keck, a group of 15 species from the Intermountain Region in western USA. Evolutionary and ecological frameworks were used to investigate phylogenetic relationships, population demographic history, polyploidy, and niche divergence. Chapter 1 presents the results of a phylogenetic study of section Ericopsis. Using a total of 39 nuclear and chloroplast loci obtained from high-throughput targeted sequencing and Sanger sequencing the exact membership of section Ericopsis was able to be determined. This included two taxa not currently classified in section Ericopsis, P. pinifolius and P. dolius var. dolius. It was also determined that three current Ericopsis species, P. acaulis, P. yampaensis, and P. laricifolius, group in a clade with species from section Cristati with high support. Within the Ericopsis clade, however, nodal support for relationships among species was low, so strong conclusions about exact relationships are difficult to ascertain. There was support for a clade comprising the species of subsection Linarioides, as well as groups consisting of the varieties of P. caespitosus and P. crandallii. It is likely that incomplete lineage sorting and hybridization are causing gene tree incongruence in these analyses, which may be alleviated by adding additional sequence data from informative loci. Chapter 1 also provides the context for questions asked in subsequent chapters of the dissertation. Chapters 2 and 3 use a population genetics framework to study evolutionary dynamics in two widespread species from section Ericopsis. In chapter 2 the variable P. linarioides Gray is considered. This population genetics study included 299 individuals from 22 populations (representing four of the five subspecies) using seven microsatellite loci. Overall genetic structure was limited, with the majority of genetic variation distributed within individuals. However, clustering methods found that populations of the same subspecies grouped with one another, and that the subspecies linarioides and coloradoensis share a close relationship. In addition there was evidence of hypothesized cryptic diversity within subsp. sileri, with populations forming three distinct clusters representing the Markagunt Plateau of southern Utah, the Beaver Dam/Bull Valley mountains of southern Utah, and the Kaibab Plateau of northern Arizona. Finally, an historical demographic study using approximate Bayesian computation found that a lineage most likely diverged from subsp. sileri and then split again into subspecies linarioides and coloradoensis. The timing of this event is estimated to be around the end of the Pleistocene. Chapter 3 is a population genetics study of P. caespitosus Nutt. ex. Gray, a species with three varieties from Utah, northern Arizona, and western Colorado. Penstemon caespitosus is an interesting case study because one of its varieties, desertipicti, is a tetraploid while varieties caespitosus and perbrevis are diploid. A total of 222 individuals from nine populations were considered in this study with the same microsatellite loci from chapter 2. Genetic structure was much greater in P. caespitosus than in P. linarioides. Results from clustering analyses revealed a close relationship between var. perbrevis (from central Utah) and var. desertipicti (from southwest Utah and northern Arizona). Tetraploid var. desertipicti also contained many unique alleles, consistent with a pattern of allotetraploidy. Although one of the parent progenitors is likely var. perbrevis, the other parent is most likely another species from section Ericopsis that shares a close geographic range with var. desertipicti (such as P. thompsoniae or a subspecies of P. linarioides). Chapter 4 builds on the results of the first three chapters by exploring niche divergence between sister taxa using ecological niche modeling (ENM). ENMs were constructed in MaxEnt using presence-only data collected from herbarium records. A total of four comparisons were made between sister species and subspecies/varieties. Most comparisons showed a situation of incomplete niche divergence, where niches of sister taxa were similar but not identical to one another. The comparisons made between varieties of P. laricifolius (laricifolius vs. exilifolius) and subspecies of P. linarioides (linarioides vs. coloradoensis) revealed that the two niches were more different than would be expected at random. The largest amount of niche divergence was between diploid P. caespitosus var. perbrevis and tetraploid var. desertipicti. These results support a scenario where sister taxa are diverging along environmental gradients (mostly precipitation and temperature during certain times of the year), and where polyploidy has lead to even greater niche divergence.
Andrea Wolfe (Advisor)
John Freudenstein (Committee Member)
Laura Kubatko (Committee Member)
Stephen Matthews (Committee Member)
204 p.
Biology; Plant Biology
Penstemon; systematics; phylogenetics; population genetics; polyploidy; ecological niche modeling

Recommended Citations

Citations

  • Wenzel, A. (2016). Systematics of Penstemon section Ericopsis, a group of plant species native to the Intermountain West [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1471533204

    APA Style (7th edition)

  • Wenzel, Aaron. Systematics of Penstemon section Ericopsis, a group of plant species native to the Intermountain West. 2016. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1471533204.

    MLA Style (8th edition)

  • Wenzel, Aaron. "Systematics of Penstemon section Ericopsis, a group of plant species native to the Intermountain West." Doctoral dissertation, Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1471533204

    Chicago Manual of Style (17th edition)

osu1471533204
764
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