Gardner Hall 4111 (Office), 4201 (Lab)
Our research spans a wide range of topics in plant systematics and evolution, involving undergraduate and graduate students as well as international collaborations. Our general research goal is to test systematic and evolutionary hypotheses in a phylogenetic context. We use DNA sequences to reconstruct the phylogeny of plants and use the phylogeny as a framework to understand pattern and rate of diversification, biogeographic history, and evolution of morphology, genes, and genomes. We integrate phylogeny, development, and gene expression and functional analyses to understand the developmental genetics of inflorescence evolution in the dogwood family. We built a dogwood genetic transformation system for characterizing functions of genes regulating flowering and inflorescence development. Furthermore, we integrate populations genetics, phylogeography, and landscape ecology to understand how genetic variation responds to changes in landscape and environment in the state flower Cornus florida. Our focal plants for research have been the dogwoods and their close relatives (Cornales) as well as plants displaying a discontinuous distribution in eastern Asia and eastern North America.
Check out my YouTube video about Dogwoods, North Carolina’s State Flower and It’s Relatives.
Learn more about my “International Journey to a Botany Career“
The main course I teach is PB 403/503 Systematic Botany, which was offered every fall before 2015 and now every spring from 2016 onward, for undergraduate and graduate level students. I also teach a study abroad course in the summer Study Abroad Program: Plant Resources, Ecology and Culture in China (PB 495/595 – 501, 3 credits, S/U or graded; three weeks).
Other Teaching Efforts:
- PB 493 (undergraduate research) Contact Dr. Chad Jordan for details.
- Advising graduate students’ thesis research.
Ph.D. Botany-Plant Molecular Systematics Washington State University 1995
B.S. Plant Genetics Zhongshan (Sun Yat-sen) University 1982
Area(s) of Expertise
Plant systematics and evolution of flowering plants
- A New Pipeline for Removing Paralogs in Target Enrichment Data , SYSTEMATIC BIOLOGY (2022)
- Next Steps in Integrative Biology: Mapping Interactive Processes Across Levels of Biological Organization , INTEGRATIVE AND COMPARATIVE BIOLOGY (2022)
- Phylogenomics and biogeography of Torreya (Taxaceae) – Integrating data from three organelle genomes, morphology, and fossils and a practical method for reducing missing data from RAD‐seq , Journal of Systematics and Evolution (2022)
- Comprehending Cornales: phylogenetic reconstruction of the order using the Angiosperms353 probe set , AMERICAN JOURNAL OF BOTANY (2021)
- Genetic insights into the evolution of genera with the eastern Asia–eastern North America floristic disjunction: a transcriptomics analysis , American Journal of Botany (2020)
- In memory of Professor Tang Yan-Cheng: New perspectives in systematic and evolutionary biology , JOURNAL OF SYSTEMATICS AND EVOLUTION (2020)
- Phylogenomics, biogeography, and evolution of morphology and ecological niche of the eastern Asian-eastern North AmericanNyssa(Nyssaceae) , JOURNAL OF SYSTEMATICS AND EVOLUTION (2020)
- Phylogenomics, biogeography, and evolution of the blue‐ or white‐fruited dogwoods ( Cornus )—Insights into morphological and ecological niche divergence following intercontinental geographic isolation , Journal of Systematics and Evolution (2020)
- Phylogenomics, co-evolution of ecological niche and morphology, and historical biogeography of buckeyes, horsechestnuts, and their relatives (Hippocastaneae, Sapindaceae) and the value of RAD-Seq for deep evolutionary inferences back to the Late Cretaceous (vol 145, 106726, 2020) , MOLECULAR PHYLOGENETICS AND EVOLUTION (2020)
- Population structure, landscape genomics, and genetic signatures of adaptation to exotic disease pressure in Cornus florida L.—Insights from GWAS and GBS data , Journal of Systematics and Evolution (2020)
Overviewâ€”Collaborative Research: The Relative Roles of Historical Constraint, Local Adaptation, and Time in Shaping Diversity and Function of Co-distributed Plant and Microbial Communities Across an Ancient Biogeographic Disjunction. The mixed deciduous forests in eastern Asia (EA) and eastern North America (ENA) represent relics of once widespread Tertiary mesophytic forests that spanned the Northern Hemisphere; some of these relics are also present in western North America (WNA). As a result of this shared history, EA and ENA share many common floristic elements. Compared to eastern North America, eastern Asia has twice as many plant species, although the two areas are similar in size, geographic latitudes, and climate conditions. Accelerated net allopatric speciation in eastern Asia has been proposed to be a cause of this disparity. Intellectual merit â€” The disjunct forests in EA, ENA and WNA provide an excellent natural system to examine the link between biodiversity, within the context of a shared phylogenetic history, to ecological function. We have assembled an excellent international team with complementary expertise for the proposed research. A better understanding of biodiversity and ecosystem functioning requires knowledge from multiple spatial scales, multiple functions, and multiple measures of diversity. We address fundamental questions at the interface of plant and microbial phylogenetics and ecosystem function at multiple scales. For example, if historical constraint and local microevolutionary adaptation shape the phylogenomics of bacterial diazotrophs associated with plants across an ancient biogeographic disjunction, then the phylogenomic relationships between diazotrophs across the disjunction will reflect plant genotypesâ€. The corollary of this hypothesis is that divergence in soil edaphic variables associated with different regions will shape the genomic diversity of these bacterial taxa more so than plant genotype. Broader Impactsâ€” This project will provide modern interdisciplinary post-doc and graduate student training in next-generation sequencing, bioinformatics, large-scale phylogeny reconstruction, complex post-tree analyses including niche modeling and niche diversification, microbial phylogenomics. We will recruit underrepresented students and women. The project will enhance international collaboration with China in research and teaching through this project and reciprocal study abroad courses.
The Cornales - which includes both dogwoods and hydrangea - is the sister lineage to all other asterids and a high quality dogwood genome assembly, together with the forthcoming blueberry genome (Vaccinum corymbosum, Ericaceae, Ericales; http://www.vaccinium.org) will elucidate gene content and genome structure in the ancestors of all asterids and in turn all core eudicots. The strategic position of the Cornales in the angiosperm phylogeny makes the dogwood genome an ideal catalyst for advancing comparative genomics across all angiosperm woody ornamentals. The specific aims of the proposed two-year project include resource development for genome-enabled research in the dogwoods, across the Cornales and among all woody ornamentals: 1. Establish a flowering dogwood (Cornus florida) reference genome assembly and annotation as a foundation for Cornales, asterid and eudicot comparative genomics. We will generate a reference genome sequence and deep transcriptome sequence for Appalachian Spring, the most important cultivar in the horticultural dogwood trade. We will also employ gene capture to assess genetic variation and structure among natural populations. In addition will generate gene-space genome assemblies and transciptomes for Conus kousa and Hydrangea macrophylla. 2. Characterize genes and gene interactions contributing to powdery mildew resistance within flowering dogwood. RNA Seq data generated from infected and uninfected plantlets from resistant (including the Appalachian Spring cultivar and C. kousa) and non-resistant dogwood accessions. 3. Initiate a consortium for genomics research on woody ornamental in the horticultural industry. We will launch a web portal and database for genomics data from/for woody ornamentals including development of a set of conserved orthologous genes (COGs) for eudicot and other angiosperm woody ornamentals. We are already cultivating interest in such a web site and database (see letters) and we will generate further interest by hosting a conference to discuss the state-of-the-art and future of genomics and transcriptomics research in woody ornamentals. Finally we will work with the organizers of the Ornamentals session at the Plant and Animal Genome Conference (PAG) to include a set of presentations and discussions focused on woody ornamentals.
The rapid loss of biodiversity due to human activities has adversely affected ecosystem functions and services around the world, and is a pressing concern to all nations. The importance of better understanding and protecting biodiversity cannot be overstated. The United States and China occupy large areas of North America and eastern Asia at similar temperate latitudes. While both are rich in biodiversity, China harbors more species. Unfortunately, China is also losing its diversity at a higher rate. . The two regions offer many opportunities for comparative studies of biodiversity at all levels and in different dimensions, from the origin, evolution, and distribution of species to the community assembly and ecological functions. Recent increases in research funding from the Chinese government have greatly enhanced the research capacity in China and led to an enhancement of biodiversity studies and training of a younger generation of investigators in China. This provides the right timing for large-scale collaboration between researchers in the US and China in support of innovative and integrative research to address questions about biodiversity that are unique to these geographic regions which can greatly benefit the two countries and other geographic regions. To promote more collaboration on biodiversity research between the US and China, we proposed to hold two 3-day US-China collaborative workshops, one in the US and the other in China, to bring biologists from China and the US together to foster new research partnerships via presentations, discussions, and field visits to research sites. Intellectual merits: The workshops will integrate keynote talks from invited speakers, mini-talks of all participants in topical groups, discussion periods and three field trips. The invited talks will present the state of the science in biodiversity studies, successful examples of collaborations, discuss frontier issues on US-China biodiversity, and innovative approaches and new opportunities for collaborative studies. The mini-talks in topical groups will communicate expertise and interest of the participants and facilitate seeking appropriate partners by participants. The workshops will target leading scientists, including some who have received NSF dimensions awards as invited speakers to share their cutting-edge research, and recruit junior PIs, graduate students, and postdoctoral researchers from diverse fields including evolutionary biology, ecology, systematics, and bioinformatics, as participants from both countries. The group discussion and field trips to the to coastal, Piedmont, and mountain research sites will foster broad interactions seeking new research directions and inspiring new collaboration. Broader Impacts: The workshops will expose the younger generation of biologists to cutting-edge research on biodiversity and will engage participants from across diverse disciplines and institutions. A wiki website will be constructed to post the talks and relevant information. With respect to the North American meeting, through local news report, NESCent and NC Natural History Museum, the workshop event can outreach to local communities and increase the awareness of biodiversity research and education.
Variation in floral display (inflorescence) affects the success of plant reproduction and the yield of a crop by influencing seed number and dispersal/harvest ability. Despite its importance, little progress has been made in understanding how developmental and genetic changes have shaped inflorescence architectures in angiosperm evolution, in part because existing model organisms exhibit little variation in these traits. Species of Dogwood (Cornus L.) are popular ornamental trees in American landscapes due to their spectacular inflorescences often associated with large showy (petaloid) bracts. The genus offers us a unique opportunity to tackle this important problem. Cornus exhibits a wide variation in inflorescence structure, including heads, umbels and compound cymes. A recent breakthrough in our laboratory has resulted in successful regeneration and transformation of a key species of the genus. This new ability along with our recent achievements in phylogenetic reconstruction and nearly completed comparative developmental studies, now provides a timely opportunity to develop a model for investigating the molecular mechanisms shaping inflorescence architectures in a non-model plant lineage. In this proposal, we aim to test four hypotheses to gain insights into the changes in developmental and genetic mechanisms that may have led to alteration of inflorescence forms in dogwoods. Hypotheses: 1. Differences in early development processes lay the ground for divergence of inflorescence architectures in dogwood species. 2. Spatial, temporal, and quantitative variation of expression of conserved key inflorescence regulatory genes are essential for the changes of inflorescence architecture. 3. Expression of petal identity genes in bracts is essential for the origin of the petaloidy of bracts in dogwoods. 4. Spatial, temporal, and quantitative variation of expression of other genes are essential for the modification of inflorescence architecture and origin of petaloid bracts in dogwoods. Objectives: 1. Complete the comparative developmental characterization of four Cornus inflorescence types. 2. Comparative characterization of the expression of conserved key inflorescence regulators and petal identity genes in different inflorescence types. 3. Identify new genes regulating inflorescence development and bract petaloidy in dogwood. 4. Optimize the existing transformation system of Cornus canadensis and test the function of conserved key inflorescence regulatory genes Intellectual merits: This project represents the first study investigating the molecular controls of inflorescence development and evolution using a comparative approach on multiple closely related woody species from a non-model plant lineage. Although the proposal has technical challenges, we have overcome the most significant hurdles and achieving of our objectives would offer novel insights into the genetic basis underlying the evolutionary transitions of floral display strategies, of which the knowledge is presently lacking. The transformation system has tremendous potentials for future research of genetic controls of other plant traits including resistance to fungal diseases and drought, and flowering time divergence among species. By providing a transformation system in a non-model plant, this study will potentially provide a new tool for genetic analysis in other plants that are more closely related to the dogwoods than to the few existing model species. Broader impact: The project will not only enhance our understanding of inflorescence development and evolution in angiosperms, but also hold promise in breeding and bioengineering of dogwoods. Biotechnological improvement of Cornus species in display, disease and drought resistance holds tremendous industrial potential. Thus the results of this project will have broad interests to the scientific, biotechnolgical, and industrial communities. Perfection of the transformation system will immediately benefit the research of identifying genes resistant to the dogwood anthracnose disease that
Fothergilla (Hamamelidacea) is a small genus of uncommon, deciduous shrubs found exclusively in the Southeastern United States. The objectives of this research are to: 1) complete a taxonomic/systematic assessment of Fothergilla including molecular, cytogenetic, morphological, and ecological approaches, and 2) establish a representative germplasm collection for long-term ex situ conservation. These efforts will elucidate the diversity and evolutionary relationships among species within Fothergilla, providing essential data to help guide future conservation efforts. On a broader scale, this study will provide further insights into the phytogeoraphic patterns and history of Southeastern flora.