Systematists and molecular phylogeneticists study the patterns and processes of organismal diversity, from the gene to the organism to the clade level, and ask questions focused on how the diversity we see has originated, and how different processes have led to these diversification patterns. Integration of studies across these different hierarchical levels is important to understand not only how lineages have diversified, and how they might be classified, but also what processes might have been important. My research has focused on two general questions: (1) what are the patterns of angiosperm diversity, from species boundaries to clade classifications to historical biogeography; and (2) what are the evolutionary dynamics of morphological and physiological traits (and their underlying genes) important to diversification, particularly floral structural changes and photosynthetic pathway modification. Current projects focus on the Cyperaceae, Gesneriaceae, and Cleomaceae, with studies exploring a variety of phylogenetic, cytogenetic, morphological, and physiological questions.
Patterns of Angiosperm Diversification
Understanding the patterns of lineage diversification is critical to understand the tempo and mode of diversification at all spatial scales. Only through robust phylogenetic hypotheses can the different processes of diversification be tested for their influence on lineage diversification. My lab has been focusing on understanding lineage diversification in a variety of groups, particularly the Cyperaceae, Gesneriaceae, and Cleomaceae.
Current Research and Future Plans:
Carex (Cyperaceae)
Recent collaborations with Andrew Hipp, Marcia Waterway, Pedro Jiménez-Mejías, Santi Martín-Bravo, Daniel Spalink, Isabel Larridon, and numerous other collaborators, has revised the sectional classification of Carex to reflect clades, and updated phylogenetic and biogeographic hypotheses in the genus. Many of these collaborations on Carex and Cyperaceae were recently published in a 2021 special issue of the Journal of Systematics and Evolution (JSE) (https://onlinelibrary.wiley.com/toc/17596831/2021/59/4).
Abildgaardieae (Cyperaceae)
The Abildgaardieae is a tribe that traditionally included two large genera (Bulbostylis and Fimbristylis) and six small genera. Phylogenetic studies to date have suggested that all multispecies genera are para- or polyphyletic. Recent collaborations have redefined generic limits (see Publications and the JSE special issue: https://onlinelibrary.wiley.com/toc/17596831/2021/59/4). The group also has several cases of adaptation to fire disclimax communities and a complex biogeographic history with multiple movements among Africa, Australasia, and South America. This project is a collaboration with Daniel Spalink (Texas A&M University), Isabel Larridon (Royal Botanic Gardens, Kew), and other collaborators, and is exploring the biogeographic and ecological diversification patterns in the group.
Eleocharis (Cyperaceae)
Past work on Eleocharis in my lab (Hinchliff and Roalson 2009; Hinchliff et al. 2010a, 2010b; Roalson et al. 2010) has primarily focused on defining major lineages in the clade. However, resolution of many of the species-level relationships and species boundaries remain unclear, and this is one of our current foci.
Cyrtandra (Gesneriaceae)
In the Gesneriaceae, my lab continues to focus on the Pacific diversification of Cyrtandra, particularly in the Hawaiian Islands. Efforts are underway to use hyb-seq high throughput sequencing approaches to understand lineage diversififcation, hybridization, species boundaries, and conservation of this diverse Hawaiian clade.
Cleomaceae
Cleomaceae generic concepts have had a troubled history, with few genera as traditionally or currently recognized being monophyletic. Current studies are starting to better understand clade relationships, and most of the genera have been recircumscribed to reflect lineages (see Publications). A major effort is underway to exhaustively sample all species in each clade of the family and finish the revision of generic concepts to reflect monophyletic groups that are morphologically diagnosable.
Current Research and Future Plans:
Carex (Cyperaceae)
Recent collaborations with Andrew Hipp, Marcia Waterway, Pedro Jiménez-Mejías, Santi Martín-Bravo, Daniel Spalink, Isabel Larridon, and numerous other collaborators, has revised the sectional classification of Carex to reflect clades, and updated phylogenetic and biogeographic hypotheses in the genus. Many of these collaborations on Carex and Cyperaceae were recently published in a 2021 special issue of the Journal of Systematics and Evolution (JSE) (https://onlinelibrary.wiley.com/toc/17596831/2021/59/4).
Abildgaardieae (Cyperaceae)
The Abildgaardieae is a tribe that traditionally included two large genera (Bulbostylis and Fimbristylis) and six small genera. Phylogenetic studies to date have suggested that all multispecies genera are para- or polyphyletic. Recent collaborations have redefined generic limits (see Publications and the JSE special issue: https://onlinelibrary.wiley.com/toc/17596831/2021/59/4). The group also has several cases of adaptation to fire disclimax communities and a complex biogeographic history with multiple movements among Africa, Australasia, and South America. This project is a collaboration with Daniel Spalink (Texas A&M University), Isabel Larridon (Royal Botanic Gardens, Kew), and other collaborators, and is exploring the biogeographic and ecological diversification patterns in the group.
Eleocharis (Cyperaceae)
Past work on Eleocharis in my lab (Hinchliff and Roalson 2009; Hinchliff et al. 2010a, 2010b; Roalson et al. 2010) has primarily focused on defining major lineages in the clade. However, resolution of many of the species-level relationships and species boundaries remain unclear, and this is one of our current foci.
Cyrtandra (Gesneriaceae)
In the Gesneriaceae, my lab continues to focus on the Pacific diversification of Cyrtandra, particularly in the Hawaiian Islands. Efforts are underway to use hyb-seq high throughput sequencing approaches to understand lineage diversififcation, hybridization, species boundaries, and conservation of this diverse Hawaiian clade.
Cleomaceae
Cleomaceae generic concepts have had a troubled history, with few genera as traditionally or currently recognized being monophyletic. Current studies are starting to better understand clade relationships, and most of the genera have been recircumscribed to reflect lineages (see Publications). A major effort is underway to exhaustively sample all species in each clade of the family and finish the revision of generic concepts to reflect monophyletic groups that are morphologically diagnosable.
Morphological and Physiological Evolution
Understanding the drivers of and consequences of lineage diversification are important components of understanding the broader patterns of lineage diversification. The morphological and physiological components of these processes (and their underlying genetics) are significant areas of research in my lab.
Current Research and Future Plans:
My lab is currently focused on the importance of the origins of photosynthetic pathway changes and the importance of floral developmental evolution to lineage diversification. These are two major adaptive pathways that have a long history of study in angiosperms. Morphological, physiological, and genetic origins of C4 photosynthesis have been under study for 80+ years (whether the original authors knew they were describing C4 photosynthesis or not; e.g., Kranz anatomy). The last decade has seen an increased understanding of the genetic adaptive aspects of C4 evolution, to which my lab has made some significant contributions for the Cheniopodiaceae (Kapralov et al. 2006; Akhani et al. 2007; Voznesenskaya et al. 2008; Voznesenskaya et al. 2013), Cleomaceae (Feodorova et al. 2010; Koteyeva et al. 2011), and Cyperaceae (Murphy et al. 2007; Christin et al. 2008; Besnard et al. 2009; Roalson et al. 2010; Roalson 2011). Current projects are delving more deeply into the genetic components of C4 evolution in the Suaedoideae and Salsoloideae clades of Chenopodiaceae (Rosnow et al. 2014, in prep.). Current results suggest that some of the genetic characteristics of the PEPC gene in other C4 lineages might not be necessary for suaedoid C4 function. In the Salsoloideae, it is possible that some of the C3 species might be reversions from the C4 condition, which would be the first discovery of a C4 to C3 reversion in the angiosperms. As with the Suaedoideae, we are exploring this through anatomical, physiological, and genetic characteristics of these clades (Rosnow et al. unpublished data; Voznesenskaya et al. unpublished data).
Floral evolution has been a theme of angiosperm diversification research from the time of Darwin. The Gesneriaceae, along with several other angiosperm families, are important clades for understanding patterns of floral evolution (Roalson et al. 2002; Zimmer et al. 2002; Roalson et al. 2003; Roalson et al. 2005a, 2005b; Roalson et al. 2008; Clark et al. 2011). My lab is exploring floral evolutionary genetics in Achimenes through the analysis of comparative gene expression data among developmental stages within species and between closely related species with different floral morphologies. From this, we are applying forward genetic approaches using transformed Achimenes to test a variety of candidate genes developed from the comparative gene expression data for specific function (Roberts et al. unpublished data). The ability to transform multiple species for different candidate genes should allow us to better characterize the contributions of these genes to the different morphological characteristics we see.
Current Research and Future Plans:
My lab is currently focused on the importance of the origins of photosynthetic pathway changes and the importance of floral developmental evolution to lineage diversification. These are two major adaptive pathways that have a long history of study in angiosperms. Morphological, physiological, and genetic origins of C4 photosynthesis have been under study for 80+ years (whether the original authors knew they were describing C4 photosynthesis or not; e.g., Kranz anatomy). The last decade has seen an increased understanding of the genetic adaptive aspects of C4 evolution, to which my lab has made some significant contributions for the Cheniopodiaceae (Kapralov et al. 2006; Akhani et al. 2007; Voznesenskaya et al. 2008; Voznesenskaya et al. 2013), Cleomaceae (Feodorova et al. 2010; Koteyeva et al. 2011), and Cyperaceae (Murphy et al. 2007; Christin et al. 2008; Besnard et al. 2009; Roalson et al. 2010; Roalson 2011). Current projects are delving more deeply into the genetic components of C4 evolution in the Suaedoideae and Salsoloideae clades of Chenopodiaceae (Rosnow et al. 2014, in prep.). Current results suggest that some of the genetic characteristics of the PEPC gene in other C4 lineages might not be necessary for suaedoid C4 function. In the Salsoloideae, it is possible that some of the C3 species might be reversions from the C4 condition, which would be the first discovery of a C4 to C3 reversion in the angiosperms. As with the Suaedoideae, we are exploring this through anatomical, physiological, and genetic characteristics of these clades (Rosnow et al. unpublished data; Voznesenskaya et al. unpublished data).
Floral evolution has been a theme of angiosperm diversification research from the time of Darwin. The Gesneriaceae, along with several other angiosperm families, are important clades for understanding patterns of floral evolution (Roalson et al. 2002; Zimmer et al. 2002; Roalson et al. 2003; Roalson et al. 2005a, 2005b; Roalson et al. 2008; Clark et al. 2011). My lab is exploring floral evolutionary genetics in Achimenes through the analysis of comparative gene expression data among developmental stages within species and between closely related species with different floral morphologies. From this, we are applying forward genetic approaches using transformed Achimenes to test a variety of candidate genes developed from the comparative gene expression data for specific function (Roberts et al. unpublished data). The ability to transform multiple species for different candidate genes should allow us to better characterize the contributions of these genes to the different morphological characteristics we see.
Floristics in the Pacific Northwest
There are numerous areas of the Pacific Northwest where our understanding of plant diversity and distributions is lacking. To address this, and in collaboration with the Marion Ownbey Herbarium and other rights holders and interested parties, we are working on doing targeted floristics studies, particularly as Master's projects, to address these issues. Specific areas are open to discussion.