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Washington State University Molecular Plant Sciences

Associate Professor in the School of Biological Sciences Ph.D., 2000, Claremont Graduate University and Rancho Santa Ana Botanic Garden


The research in my lab focuses on several projects, particularly, (1) phylogenetic relationships, classification, and patterns of photosynthetic pathway diversification in Eleocharis (Cyperaceae); (2) phylogenetic patterns and processes of diversification in Carex subgenus Vignea (Cyperaceae); (3) diversification patterns in Hawaiian Cyrtandra (Gesneriaceae) and the influence of hybridization on the diversification process; and (4) genome structure and evolution in Carex (Cyperaceae). More details about all of these projects are available from the lab website, but here I will describe the Eleocharis research in more detail.

Central to the understanding of the diversification of organisms is understanding the evolution of critical physiological processes, the interaction of physiological processes and the environment, and the evolution of structure and form. Among plants, Eleocharis (Cyperaceae) is an excellent choice for studying photosynthetic pathway evolution and the associated changes in morphological and anatomical characteristics given multiple origins of C4 pathways from a C3 ancestral condition, as well as the presence of species in which individuals can utilize multiple photosynthetic pathways depending on their growing environment. Furthermore, their have been multiple adaptations to the submerged aquatic habit. Evolutionary relationships in Eleocharis are poorly understood at present, and preliminary phylogenetic evidence suggests that current classifications do not reflect evolutionary relationships in the genus.

In this project, we are pursuing intensive studies of Eleocharis and related genera such as Chillania, Egleria, and Websteria. In particular, we are in the process of: * generating multiple molecular phylogenies of Eleocharis and related genera using genes from the nuclear and chloroplast genomes to explore the number of C4 innovations in the genus and to compare obligate and facultative C4 and C3-C4 intermediates with their C3 progenitors or sister-species; * studying photosynthetic pathway development including exploring the changes in stem anatomy and carbon isotope ratios associated with changes from the C3 to the C4 pathway; * testing whether any species of Eleocharis other than E. vivipara are capable of changing photosynthetic pathway type under different growing conditions; and * exploring morphological variation in Eleocharis in light of the molecular phylogeny.

These studies particularly focus on understanding the connectivity of diversification processes, morphological, physiological, and ecological characteristics, and current and historical geographic distributions.

Selected Publications

Pillion, Y; Johansen, J; Sakishima, T; Chamala, S; Barbazuka W.B.; Roalson, E.H.; Price, D.K.; Stacy, E.A.  Potential use of low-copy nuclear genes in DNA barcoding:  A comparison with plastid genes in two Hawaiian plant radiations.  BMC Evolutionary Biology. 2013:13(1).

Hinchiff, C.E.; Roalson, E.H.  Using supermatrices for phylogenic inquiry:  An example using the sedges.  Systemic Biology, 2013, 62(2):205-219.

Jiwan, D; Roalson, E.H.; Main, D; Dhingra, A.  Antisense expression of peach mildew resistance locus O (PpMIo1) gene confers cross-species resistance to powdery mildew in Fragaria x ananassa.  Transgenic Research.  2013:1-13.

Pillon, Y; Johansen, J.B.; Sakishima, T; Roalson, E.H.; Price, D.K.; Stacy, E.A.  Gene discordance in phylogenomics of recent plant ratiations, an example from Hawaiian Cyrtandra (Gesneriaceae).  Molecular Phylogenetics and Evolution.  2013;69(1):293-298.

Voznesenskaya, E; Koteyeva, N.K.; Akhani, H; Roalson, E.H.; Edwards, G.E.  Structural and physiological analyses in Salsoleae (Chenopodiaceae) indicate multiple transitions among Ce, intermediate, and C4 photosynthesis.  Journal of Experimental Botany.  2013;64(12):3583-3604.

Roalson, E.H.  C 4 photosynthesis:  Need a gene?  Borrow one!  Current Biology.  2012;22(5)R161-163.

Chung, K.S.; Hipp, A.L.; Roalson, E.H.  Chromosome number evolves independently of genome size in a clade with nonlocalized centromeres (carex:cyperaceae).  Evolution. 202;66(9):2708-2722.

Kappmeyer, L.S.; Thiagarajan, M; Herndon, D.R.; Ramsay, J.D.; Caler, E; Djikeng, A; Gillespie, J.J.; Lau, A.O.T.; Roalson, E.H.; Silva, J.C.; et al.  Comparative genomic analysis and phylogenic position of Theileria equi.  BMC Genomics. 2012;13(1).

Koteyeva, N.K.; Vozenenskaya, E.V.; Roalson, E.H.; Edwards, G.E.  Diversity in forms of C 4 in the genus Cleome (Cleomaceae).  Annals of Botany. 2011;107(2):269-283.

Clark, J.L.; Roalson, E.H.; Prichard, R.A.; Coleman, C.L.; Teoh, V.H.; Matos, J.  Independent origin of radial floral symmetry in the Gloxinieae (Gesnerioideae: Gesneriaceae) is supported by the rediscovery of Phinaea pulchella in Cuba.  Systematic Botany.  2011;36(3):757-767.

Skinner, M.K.; Rawls, A; Wilson-Rawls, J; Roalson, E.H.  Basic helix-loop-helix transcription factor gene family phylogenetics and nomenclature.  Differentiation.  2010;80(1):1-8.

Roalson, E.H.; Hinchliff, C.E.; Trevisan, R; Da Silva, C.R.M.  Phylogenetic relationships in eleocharis (cyperaceae):  C4 photosynthesis origins and patterns of diversification in the spikerushes.  Systemic Botany.  2010;35(2):357-271.
Feodorova, T., E. V. Voznesenskaya, G. E. Edwards, and E. H. Roalson. Biogeographic patterns of diversification and the origins of C4 in Cleome (Cleomaceae). Systematic Botany 2010;35(4):811-826.

Hinchliff, C. E., A. E. Lliully Aguilar, T. Carey, and E. H. Roalson. 2010.The origins of Eleocharis (Cyperaceae) and the phylogenetic position of Websteria, Egleria, and Chillania. Taxon 59: 709–719.

Roalson, E. H. 2010. Origins and transitions in photosynthetic pathway types in the monocots: a review and reanalysis. In: Raghavendra, A. S. and R. F. Sage (eds.), C4 Photosynthesis and Related CO2 Concentrating Mechanisms.

Roalson, E. H., C. E. Hinchliff, R. Trevisan, and C. R. M. da Silva. 2010. Phylogenetic relationships in Eleocharis (Cyperaceae): C4 photosynthesis origins and patterns of diversification in the spikerushes. Systematic Botany 35: 257–271.

Skinner, M. K.,A. Rawls, J. Wilson-Rawls, and E. H. Roalson. 2010. Basic helix-loop-helix transcription factor gene family phylogenetics and nomenclature. Differentiation 80: 1–8.

Besnard, G., A. M. Muasya, F. Russier, E. H. Roalson, N. Salamin, and P.-A. Christin. 2009. Phylogenomics of C4 photosynthesis in sedges (Cyperaceae): multiple appearances and genetic convergence. Molecular Biology and Evolution 26: 1909–1919.

Clark, J. R., W. L. Wagner, and E. H. Roalson. 2009. Patterns of diversification and ancestral range reconstruction in the Southeast Asian-Pacific angiosperm lineage Cyrtandra (Gesneriaceae). Molecular Phylogenetics and Evolution 53: 982–994.

Hinchliff, C. E. and E. H. Roalson. 2009.Evolution of stem architecture in Eleocharis subgenus Limnochloa (Cyperaceae): evidence of rapid dynamic evolution in a group of pantropical sedges. American Journal of Botany 96: 1487–1499.

Hipp, A. L., P. E. Rothrock, and E. H. Roalson. 2009. The evolution of chromosome arrangements in Carex (Cyperaceae). The Botanical Review 75: 96–109.

King, M. G. and E. H. Roalson. 2009. Discordance between phylogenetics and coalescent-based divergence modeling: exploring phylogeographic patterns of speciation in the Carex macrocephala species complex. Molecular Ecology 18: 468–482.

King, M. G., M. E. Horning, and E. H. Roalson. 2009.Range persistance during the last glacial maximum: Carex macrocephala may have been unrestricted to glacial refugia. Molecular Ecology 18: 4256–4269.

Lau, A. O. T., T. F. McElwain, K. A. Brayton, D. P. Knowles, and E. H. Roalson. 2009. Babesia bovis: A comprehensive phylogenetic analysis of plastid-encoded genes supports green algal origin of apicoplasts. Experimental Parasitology 123: 236–243.

Christin, P.-A., N. Salamin, M. Muasya, E. H. Roalson, F. Russier, and G. Besnard. 2008. Evolutionary switch and genetic convergence on rbcL following the evolution of C4 photosynthesis. Molecular Biology and Evolution 25: 2361–2368.

Clark, J. R., R. H. Ree, M. E. Alfaro, M. G. King, W. L. Wagner, and E. H. Roalson. 2008.A comparative study in ancestral range reconstruction methods: Retracing the uncertain histories of insular lineages. Systematic Biology 57: 693–707.

Roalson, E. H. 2008. C4 Photosynthesis: differentiating causation and coincidence. Current Biology 18: R167–R168.

Roalson, E. H. 2008. A synopsis of chromosome number variation in the Cyperaceae. The Botanical Review 74: 209–393.

Roalson, E. H., L. E. Skog, and E. A. Zimmer. 2008. Untangling Gloxinieae (Gesneriaceae). II. Reconstructing biogeographic patterns and estimating divergence times among New World continental and island lineages. Systematic Botany 33: 159–176.

Rodgers, B. D., E. H. Roalson, and C. Thompson. 2008. Phylogenetic analysis of the insulin-like growth factor binding protein (IGFBP) and IGFBP-related protein gene families. General and Comparative Endocrinology 155: 201–207.

Stevens, J. D., E. H. Roalson, and M. K. Skinner. 2008. Phylogenetic and expression analysis of the basic helix-loop-helix transcription factor gene family: genomic approach to cellular differentiation. Differentiation 76: 1006–1022.

Voznesenskaya, E. V., H. Akhani, N. K. Koteyeva, S. D. X. Chuong, E. H. Roalson, O. Kiirats, V. Franceschi, and G. E. Edwards. 2008. Structural, biochemical and physiological characterization of photosynthesis in two C4 subspecies of Tecticornia indica and the C3 species Tecticornia pergranulata (Chenopodiaceae). Journal of Experimental Botany 59: 1715–1734.

Akhani, H., G. E. Edwards, and E. H. Roalson. 2007. Diversification of the Old World Salsoleae s.l. (Chenopodiaceae): Molecular phylogenetic analysis of nuclear and chloroplast datasets and a revised classification. International Journal of Plant Sciences 168(6): 931–956.

Garikipati, D. K., S. A. Gahr, E. H. Roalson, and B. D. Rodgers. 2007. Characterization of rainbow trout myostatin-2 genes (rtMSTN-2a & -2b): Genomic organization, differential expression and psuedogenization. Endocrinology 148(5): 2106–2115.

Murphy, L. R., J. Barroca, V. R. Franceschi, R. Lee, E. H. Roalson, G. E. Edwards, and M. S. B. Ku. 2007. Diversity and plasticity of C4 photosynthesis in Eleocharis (Cyperaceae). Functional Plant Biology 34(7): 571–580.

Roalson, E. H. 2007. C4 photosynthesis: convergence upon convergence upon… . Current Biology 17: R776–R778.