Date of Award
Doctor of Philosophy
Lynn G. Clark
Gregory W. Courtney
John D. Nason
The temperate clade is a diverse but poorly understood major lineage of woody bamboos (Poaceae: Bambusoideae: Bambuseae). Ongoing work is needed to reconstruct evolutionary relationships and establish nomenclatural stability for this difficult but ecologically and economically important group. We present the first robust multilocus plastid phylogeny for the temperate bamboos, assess relationships among key genera with an emphasis on Arundinaria and its allies, and discuss evolutionary phenomena potentially responsible for the taxonomic complexity of this group. Utilizing a total of twelve cp DNA regions (1 coding, 10 intergenic spacers, 1 intron), the temperate bamboos were resolved to include six major lineages: the Bergbamboes Lineage, the African Alpine Bamboo Clade, the Chimonocalamus Clade, the Shibataea Clade, the Phyllostachys Clade, and the Arundinaria Clade. The resulting chloroplast phylogeny is incongruent with current morphological classifications, rendering subtribes and many genera poly- or paraphyletic. Within the Arundinaria Clade, several lineages were identified including the Sasa Clade, the Pleioblastus s.s. Clade, and a clade containing Chinese species currently classified in Acidosasa, Indosasa, Pleioblastus sect. Amari, and Pseudosasa subg. Sinicae (the Sinicae Clade). The analysis also recovered a monophyletic Arundinaria sensu stricto and indicated Sasa and Sasamorpha as possible close relatives of the North America species, although results were equivocal.;We also report the results of a molecular phylogenetic analysis of Arundinaria in North America, including estimates of genetic variation and evidence of natural hybridization and introgression among all three native species. The study involved a comparative analysis of amplified fragment length polymorphisms (AFLPs) and chloroplast DNA sequences representing diversity within and among all three species of Arundinaria sensu stricto plus accessions with intermediate or unusual morphological characteristics (putative hybrids). Molecular evidence demonstrates that A. tecta and A. appalachiana are sister species, forming a clade that is significantly divergent from A. gigantea. All three species retain the potential for cross-fertilization, albeit presumably rare due to allopatry and infrequent flowering. Detected patterns of hybridization were relatively shallow, with the majority of hybrids being the apparent direct (F1) product of crosses between A. gigantea and A. tecta.Several unusual genotypes were identified, presumably representing posthybridizational recombination and/or introgression. In conjunction with this molecular analysis, the newly recognized species from the southern Appalachian Mountains, Arundinaria appalachiana, is described, illustrated, and compared with the related species A. gigantea and A. tecta. This new species is distinguished by a combination of vegetative morphological characters including features of branching and leaf morphology, leaf anatomy, and ecology. A key for the identification of Arundinaria species in North America is included along with a comparative table based on morphology, leaf anatomy, and ecology.;Phylogenetic relationships among Arundinaria and its allies in East Asia were further explored using AFLP data in conjunction with a four-region plastid framework phylogeny, with an emphasis on species-level relationships in the genus Pleioblastus sensu stricto. Hybridization and introgression were detected both within and among genera, highlighting the significant role of reticulate evolution in temperate bamboo diversity. Molecular data confirmed the hybrid origin of Hibanobambusa, Semiarundinaria, and Sasaella, and also revealed the type species of Pseudosasa to be an intergeneric hybrid. Moreover, cryptic links were detected between Sasa and Sasamorpha, resulting in nothotaxa that have obscured the distinction between these genera. AFLP and chloroplast sequence data support the monophyly of Pleioblastus s.s. and reveal species-level resolution in section Pleioblastus, low genetic diversity among populations of the widespread P. simonii (section Medakea), and cryptic reticulation among species in sections Nezasa and Medakea. This analysis also provided additional evidence for the monophyly of North American genus Arundinaria, but failed to reveal its closest relative. A significant conclusion of this research is that reticulate evolution has had an important role in the evolution of the temperate bamboos, in spite of the rarity of flowering.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Jimmy K. Triplett
Triplett, Jimmy K., "Phylogenetic relationships among the temperate bamboos (Poaceae: Bambusoideae) with an emphasis on Arundinaria and allies" (2008). Retrospective Theses and Dissertations. 15723.